US 5716834

I'll verify the CAFC 2026 docket status and try to pin down the issued claims, which the authoritative text above omits.

No CAFC docket surfaced. Let me try to retrieve the issued claim text from a source that reproduces it.

Let me run one final check for any 2026 appellate activity tied to this patent or its owner.

US Patent 5,716,834 — Verified Summary and Claim Overview

Prepared: April 26, 2026. This section builds on the litigation, PTAB, assignment, prior-art, and obviousness sections already generated; it does not repeat them. Where this pass contradicts an earlier section, I flag it explicitly (see §5).

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1. Docket check — USPTO and CAFC 2026

No Court of Appeals for the Federal Circuit docket for 5,716,834 was found. I searched the Federal Circuit's public 2026 materials and general docketing sources and retrieved zero hits tying patent number 5,716,834 (or any of its family members as appellant-side patents-in-suit) to a 2026 Federal Circuit appeal number.

Specifically:

• The Federal Circuit July 2026 oral-argument calendar (revised June 1, 2026, cafc.uscourts.gov/wp-content/uploads/OralArguments/PublicCalendar-July2026.pdf) lists roughly 40 scheduled cases — none involves 5,716,834, the National University of Singapore, Ding, Ho, or Factor C.
• The only 2026 Federal Circuit docketing notices my searches returned were unrelated matters (e.g., Contour IP Holding LLC v. GoPro, Inc., Fed. Cir. No. 2026-2012; Headwater Research; Rare Breed Triggers).

Caveat, stated plainly: my access was web-search only. I did not query PACER/CM-ECF or the Federal Circuit's own docket system directly, and I was cut off by a search-step limit before I could query CourtListener exhaustively. So the correct characterization is "none found," not "none exists." If you need a negative that binds, run a name-and-number query in the Federal Circuit's CM-ECF docket (https://ecf.cafc.uscourts.gov) and CourtListener (https://www.courtlistener.com).

This is consistent with the earlier sections: the only litigation signal on record remains District of Maryland, case 1:12-cv-00602 reported second-hand via Unified Patents, with parties and outcome unverified, and no PTAB proceeding ever filed against '834.

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2. Identification (from the authoritative full text; no auto-correction of identifiers)

One corroborating detail on the correspondent of record (which the earlier assignment section flagged as unretrieved): the front page of the sibling US 5,985,590 lists "Birch, Stewart, Kolasch & Birch, LLP" as attorney/agent of record. I retrieved this from the sibling's face, not from '834's own front page, so treat it as a strong lead rather than a confirmed entry for '834. It is worth checking against PatentCenter for application 08/296,014.

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3. Abstract (reproduced from the patent record)

"Full-length and deletion subclones of cDNAs for Factor C of Carcinoscorpius rotundicauda are provided. These cDNAs have been cloned into lambda gt 22 and pGEM 11Zf(+). Further manipulations of the 5' and 3' ends of these cDNAs have been carried out, and these cDNAs have been further subcloned into other expression vectors such as pGEMEX-1, pET 3b, and the yeast shuttle vectors YEpsec 1 and pEMBLyex 4, and pPIC 9 and pHIL D2. Also provided are host cells transformed with expression vectors containing DNA molecules encoding proteins having Factor C-like enzymatic activity, methods of producing such proteins, methods for purifying Factor C zymogens, and methods for protecting Factor C zymogens from autoactivation by Gram negative bacterial endotoxin while the proenzyme is being purified and/or processed from amoebocyte lysates or from recombinant clones, or during storage or subsequent handling. This protection is afforded by the addition of 5-30% Me2SO, which reversibly inhibits the Factor C zymogen."

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4. The issued claims in plain language

Sourcing warning: the authoritative full text supplied for this analysis is truncated — it breaks off inside the Detailed Description at FIG. 15 and omits the printed claims and the front-page References Cited list. The claim set below therefore comes from a third-party transcription (Justia's company-profile rendering at companyprofiles.justatic.com/patent/5716834), which I have cross-checked against the independent claim listing generated in the earlier PTAB section. The two agree on claim structure. Nevertheless, verify against the certified PatentCenter text before relying on any single claim's wording.

Twelve claims are reported. They fall into five groups.

Group A — Isolated DNA (claims 1–3)

• Claim 1 (independent). An isolated DNA molecule encoding a protein whose amino acid sequence is SEQ ID NO:2 or SEQ ID NO:4. In plain terms: DNA coding for either of the two C. rotundicauda Factor C proteins disclosed — CrFC 26 (SEQ ID NO:2) and CrFC 21 (SEQ ID NO:4). As rendered, claim 1 is limited to those two amino acid sequences; it is not a functional/hybridization genus.
• Claim 2 (dependent). The DNA of the preceding claim, having the nucleotide sequence SEQ ID NO:1 or SEQ ID NO:3 (the cloned CrFC 26 and CrFC 21 cDNAs).
• Claim 3 (dependent). The DNA of the preceding claim having the sequence of SEQ ID NO:1 with nucleotides 1 to 568 deleted — i.e., the 5′ untranslated leader (the 568-bp region containing seven false-start ATGs) removed.

Group B — Recombinant vectors (claims 4, 5, 9)

• Claim 4 (independent). A recombinant vector comprising DNA encoding an amino acid sequence of SEQ ID NO:2 or SEQ ID NO:4.
• Claim 5 (dependent). The vector wherein the DNA has the nucleotide sequence of SEQ ID NO:1 or SEQ ID NO:3.
• Claim 9 (dependent on claim 4). The vector wherein the vector portion is one of λgt 22, pGEM 11Zf(+), pGEMEX-1, pET 3b, YEpsec 1, pEMBLyex 4, pIC 9, and pHIL D2.

Group C — Transformed host cells (claims 6, 7, 10, 11)

• Claim 6 (independent in substance; depends on claim 5). A host cell transformed with the recombinant vector.
• Claim 7 (dependent). The host cell selected from E. coli, a mammalian cell, an insect cell, and a yeast.
• Claim 10 (independent in substance; depends on claim 4). A host cell transformed with the claim-4 vector.
• Claim 11 (dependent). Same host-cell genus as claim 7.

Group D — Methods of producing the protein (claims 8, 12)

• Claim 8 (independent in substance). A method of producing a protein having the enzymatic activity of Factor C protein in assays for Gram negative bacterial endotoxin, comprising culturing the claim-6 host cell under conditions such that the DNA is expressed, and recovering the protein.
• Claim 12 (independent in substance). The same method practiced on the claim-10 host cell.

Net effect. Every claim is anchored to the two C. rotundicauda Factor C amino acid sequences (SEQ ID NO:2 / SEQ ID NO:4) or the two cDNAs (SEQ ID NO:1 / SEQ ID NO:3). The claim set is a DNA / vector / host-cell / expression-method set. It contains no assay or kit claim, no purified-protein claim, no purification-process claim, and no DMSO-method claim.

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5. Explicit contradiction to flag against the earlier-generated sections

This is the most consequential finding of this pass, and it contradicts prior-art Grounds 5, 6 and 7 of the obviousness section.

As rendered:

Two consequences:

1. The earlier obviousness section's "highest risk in the patent" grounds (Ground 6, purification process — Navas 1990 + Ding 1993; Ground 7, Me₂SO zymogen maintenance — Navas 1990 alone) do not map onto '834's issued claims as rendered. Those grounds read the Summary of Invention as if it were the claim set. They are real §103 attacks on the family, and they transfer to whichever sibling actually carries those claims (US 5,712,144 is the demonstrated candidate) — but as against '834 itself, the live claim families are only Groups A–D above. The obviousness section did flag a version of this in its §0.3; this pass confirms it and sharpens it.

2. Ground 1 is weaker than the earlier section assumed. The obviousness section attacked an F1a "functional genus" DNA claim. As rendered, issued claim 1 recites the amino acid sequences SEQ ID NO:2 and SEQ ID NO:4 as such, with claims 2–3 adding the specific cDNA sequences and the 5′-deletion. That is the F1b "species" claim the earlier section itself characterized as the claim that survives — where In re Deuel controls and where the patent's documented 5′-UTR / seven-false-ATG unpredictability is genuine nonobviousness evidence. If the rendered claim 1 is accurate, the KSR/Kubin attack on '834's DNA claims has materially less traction than the earlier section implied, because there is no genus claim to reach Muta 1991 by anticipation.

Do not treat this as settled. The transcription is third-party and internally defective (see §6). If any claim was amended or if a claim reproduces the "hybridizes … 5×SSC, 42 °C" language, Ground 1 revives.

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6. Uncertainty — what I do not have authoritative confirmation of

1. The certified printed claim text of US 5,716,834. Not present in the supplied full text and not retrievable as a USPTO source in this pass. The renderings I have are third-party.
2. The third-party transcription is demonstrably garbled. As retrieved, claim 2 reads "The DNA molecule of claim 3" while claim 3 reads "The DNA molecule of claim 2" — a circular dependency that cannot exist in a granted patent. Claim 4 is also truncated mid-limitation ("…selected from the group consisting of SEQ ID NO:"). The sensible reconstruction is: claim 2 depends on claim 1 (SEQ ID NO:1/3), and claim 3 depends on claim 2 (568-nt deletion) — which is what I have written above — but I am reconstructing, and I say so. The dependency numbers, not the substance, are what is in doubt.
3. Claim 9's dependency is rendered as depending on claim 4; the earlier PTAB section described claims 4/5 as vectors and 9 as a vector claim — consistent. Not independently verified.
4. The Box 56 citation list for '834 remains unretrieved (noted in the earlier prior-art section, and still true).
5. No CAFC 2026 docket found — but "not found" ≠ "does not exist." My coverage was web-search only, not PACER/CM-ECF.

Corroborating note on '834's role going forward (none of this contradicts the earlier sections): the patent remains live citation currency as prior art. Seikagaku's Factor C family labels the C. rotundicauda sequence "834CrID4" — an apparent reference to this patent — and US 5,716,834 appears in the "Referenced Cited" lists of US 10,982,202 / US 11,236,318 / US 11,959,109 (Mizumura et al.), in JP 6927993 B2, in EP 1 224 299 B1, and in EP 3 530 670 B1. It is also cited in the PTAB papers where it is used as prior art against another party's Factor C claims.

Verify at: USPTO PatentCenter, application 08/296,014 — https://patentcenter.uspto.gov (front page, Box 56, printed claims); Federal Circuit CM-ECF — https://ecf.cafc.uscourts.gov; Google Patents — https://patents.google.com/patent/US5716834/en.

I'll start with targeted searches on the patent number and the reported case.

Let me drill into the specific 2012 case number and the patent's technology-space litigation.

Major find. Let me confirm the parties and track the outcome.

Litigation Involving US 5,716,834 — Findings

Prepared: April 26, 2026 · Patent: US 5,716,834 A (Ding & Ho; National University of Singapore) · Filed/priority 1994-08-19 · Issued 1998-02-10 · Expired 2015-02-10

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Bottom line

One (1) litigation involving US 5,716,834 is affirmatively identified:

Lonza Walkersville, Inc. v. Hyglos GmbH — District of Maryland, Case No. 1:12-cv-00602, filed February 4, 2012 — patent infringement — settled and dismissed pursuant to a global settlement including a patent licence to Hyglos.

That is the entirety of the identified record. This resolves the open litigation question flagged in the earlier-generated sections, and it resolves it in a way that contradicts part of the earlier framing (see §4).

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1. Case table

Accused instrumentalities: Hyglos products containing endotoxin detection assays — expressly EndoLISA® — and affinity matrices for endotoxin removal from solutions — expressly EndoTRAP®.

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2. Case detail — Lonza Walkersville, Inc. v. Hyglos GmbH

Nature of the action. Complaint for patent infringement alleging Hyglos's "manufacture, use, offers for sale, sale, and importation of products that contain endotoxin detection assays, including EndoLISA®, or that contain an affinity matrix for removal of bacterial endotoxins from solutions, including EndoTRAP®." Five patents were asserted, with '834 among them:

• US 5,716,834 — Cloned factor C cDNA of the Singapore horseshoe crab, Carcinoscorpius rotundicauda and purification of factor C proenzyme (issued 1998-02-10) — the patent at issue here
• US 5,712,144 — same title (issued 1998-01-27) — the sibling that carries the Me₂SO-method and protein claims discussed in the earlier sections
• US 5,858,706 — Expression of Carcinoscorpius rotundicauda Factor C in Eukaryotes (issued 1999-01-12)
• US 5,985,590 — same title (issued 1999-11-16)
• US 6,645,724 — Assays for Endotoxin (issued 2003-11-11)

Standing / ownership note (consistent with the earlier assignment analysis). The plaintiff of record is Lonza Walkersville, Inc., not the patent owner, National University of Singapore. That is exactly what the earlier-generating assignment section predicted: NUS licensed (never assigned) the rFC technology to BioWhittaker, Inc. in March 2000; that business passed to Cambrex and then to Lonza, and Lonza Walkersville is the operating rFC entity (PyroGene™). The suit was therefore brought by the exclusive licensee/practising entity, which is also why the earlier NPE-pattern scoring came out as it did (signals 1, 2, 4, 5, 6, 8 = not present). This litigation does not indicate a troll or privateer chain.

Outcome. The parties reached a "global settlement which includes a license agreement for Hyglos under certain Lonza patents in the area of endotoxin detection," permitting Hyglos "to use recombinant factor C technology under Lonza's patents to produce Hyglos' endotoxin products." Press coverage states the agreement "also includes the dismissal of the lawsuit Lonza previously filed against Hyglos." Terms confidential.

Practical reading. This was a practising-entity-vs-practising-entity rFC market dispute that ended in a licence, not a judgment. There is no merits ruling, no invalidity holding, and no claim construction of '834 on the public record from this case.

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3. Search coverage and negative results

I searched the patent number directly, the reported case number, party names, and the technology space (Factor C / recombinant factor C / endotoxin detection).

Not found — reported as negative, with the caveat that my coverage was web-search only:

• No second US district court case naming '834 as an asserted patent.
• No Court of Appeals for the Federal Circuit appeal. Consistent with a pre-judgment settlement dismissal — there was nothing to appeal. No 2026 CAFC docket tying this patent to an appeal number was found (as the earlier-generated summary also concluded).
• No PTAB/AIA trial against '834 — no IPR, PGR, or CBM, consistent with the earlier PTAB section.
• No ITC (Section 337) investigation naming '834.
• No foreign court litigation naming '834. The EP oppositions to Factor C-family patents (EP '466 / EP '670) that surfaced in the earlier section are EPO proceedings against different patents, not litigation, and not against '834.

Tool-limitation caveat, stated plainly: I did not query PACER/CM-ECF or CourtListener directly (my search budget was exhausted). The identification above rests on a contemporaneous court-report entry and multiple independent press releases that agree on parties, patents, accused products, and disposition. To make the negative binding, run the number in CourtListener RECAP (https://www.courtlistener.com/?q=%225716834%22) and PACER for D. Md. 1:12-cv-00602, and check the Unified Patents caselist (https://portal.unifiedpatents.com/litigation/caselist).

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4. Explicit contradiction / correction to the earlier-generated sections

Two corrections are required, and I flag them as instructed.

(a) The 2012 case is no longer "unverified" — and its parties were not identified in the earlier sections. The earlier summary, assignment, and PTAB sections all described the litigation as: "District of Maryland, case 1:12-cv-00602 reported second-hand via Unified Patents, with parties and outcome unverified." That is now resolved. The case is Lonza Walkersville, Inc. v. Hyglos GmbH, D. Md. 1:12-cv-00602, filed 2012-02-04, asserting five patents — including '834 — against Hyglos, and it settled with a licence and dismissal. Correct the "parties and outcome unverified" statements.

(b) The "D. Del. 1:12-cv-00602-SLR conflation" flag is now resolvable — and it was a false lead. The earlier sections flagged a possible conflation between a Maryland 1:12-cv-00602 and a Delaware 1:12-cv-00602-SLR (from an SEC filing in which discovery was consolidated across 1:12-cv-00070-SLR, -00298-SLR, -00301-SLR, -00448-SLR, and -00602-SLR). These are different matters. The Maryland case is a single-defendant action filed February 4, 2012 against Hyglos. The Delaware -SLR group (Judge Sue L. Robinson, D. Del.) comprises cases filed March 13, 2012 against multiple defendants. The shared "00602" is a docket-number coincidence, not the same case, and the Google Patents flag expressly points to the Maryland court. I could not verify the plaintiff in the Delaware group, but it should not be attributed to '834 on the present record.

(c) Consistency check on the PTAB section. The earlier PTAB section stated that the only Factor C PTAB activity found was IPR2025-00440, in which '834 is used as prior art against another party's claims — not challenged. Nothing in this litigation search contradicts that. It also corroborates the earlier statement that '834 expired 2015-02-10 and therefore could not attract a modern IPR.

(d) One thing the earlier sections got right and this search confirms. The earlier assignment section identified Lonza Walkersville as the practising commercial vehicle for the NUS rFC technology (via BioWhittaker → Cambrex → Lonza) and concluded the ownership chain shows no NPE signals. The fact that Lonza Walkersville is the plaintiff in the only identified suit confirms, rather than contradicts, that conclusion.

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5. What I could not verify

1. The settlement/dismissal date for Lonza v. Hyglos. Press coverage confirms the settlement and dismissal; the articles I retrieved did not carry a dateline in the retrieved text, and I did not reach the Maryland docket to read the dismissal order. I am not assigning a date.
2. The presiding judge, docket entries, whether Hyglos counterclaimed for invalidity, whether any stay or transfer motion was filed, and whether any terminal disclaimer was filed between '834 and '714 (a point the earlier obviousness section flagged as a double-patenting question).
3. Whether any other patents were added by amendment to the Maryland complaint beyond the five reported.
4. The plaintiff in the Delaware -SLR consolidated group — unrelated to '834 on the present record, but unresolved.
5. Whether any pre-suit licence demand or post-suit licensing programme touched other accused parties — no other case was found.

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6. Sources

• PatentDocs, "Court Report Supplement" (Nov. 1, 2012) — Lonza Walkersville, Inc. v. Hyglos GmbH, 1:2012-cv-602, D. Md., filed Feb. 4, 2012; identifies all five asserted patents including 5,716,834 and the accused EndoLISA® / EndoTRAP® products: https://patentdocs.org/2012/11/01/court-report-16/
• Contract Pharma, "Lonza, Hyglos Settle Patent Lawsuit" — settlement, licence, dismissal, confidential terms: https://www.contractpharma.com/breaking-news/lonza-hyglos-settle-patent-lawsuit/
• Genetic Engineering & Biotechnology News, "Lonza and Hyglos Reach Agreement Settling Patent Dispute" — https://www.genengnews.com/topics/drug-discovery/lonza-and-hyglos-reach-agreement-settling-patent-dispute/
• European Pharmaceutical Review, "Lonza and Hyglos reach agreement for endotoxin detection patents" — https://www.europeanpharmaceuticalreview.com/news/17700/lonza-and-hyglos-gmbh-reach-agreement-for-endotoxin-detection-patents/
• Cleanroom Technology, "Lonza and Hyglos reach agreement for endotoxin detection products" — https://www.cleanroomtechnology.com/lonza-and-hyglos-reach-agreement-for-endotoxin-detection-products-87102
• Google Patents legal events / Unified Patents litigation flag for US 5,716,834 (Maryland District Court, 1:12-cv-00602) — https://patents.google.com/patent/US5716834/en
• Unified Patents litigation caselist — https://portal.unifiedpatents.com/litigation/caselist

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One-line answer

One known litigation involves US 5,716,834: Lonza Walkersville, Inc. v. Hyglos GmbH, No. 1:12-cv-00602 (D. Md., filed February 4, 2012), asserting '834 alongside US 5,712,144, 5,858,706, 5,985,590 and 6,645,724 against Hyglos's EndoLISA® and EndoTRAP® products — resolved by a confidential global settlement and licence, with the action dismissed. No other case, no CAFC appeal, no ITC action, and no PTAB proceeding against '834 was found.

I'll start by searching for any PTAB proceedings involving this patent, since the structured ODP block shows none.

The search surfaced a Factor C IPR (IPR2025-00440) but it appears to involve Ding '834 as prior art, not as the challenged patent. Let me verify by searching more specifically.

Let me dig into the litigation referenced in the patent record and check for any PTAB filings tied to this patent number directly.

Proceedings overview

Zero AIA trial proceedings are on file against US 5,716,834. The canonical USPTO Open Data Portal list supplied in the structured block returns no IPR, PGR, or CBM for this patent, and my web searches surfaced none either — no petition, no institution decision, no Final Written Decision, no PTAB appeal. The only Factor C-related PTAB activity I found is a proceeding against a different patent in which US 5,716,834 (Ding et al.) is used as prior art, not as the challenged patent (details and caveats below). Bottom line for a defendant: there is no IPR estoppel, no claim-cancellation ruling, and no PTAB record to mine — but the reason is not that the patent is "hardened." It is that US 5,716,834 expired on 2015-02-10 and any AIA window closed years ago, so the operative defense is expiration/§ 286 damages limitation, not PTAB art.

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Proceedings on file

None. No AIA trial proceeding (IPR / PGR / CBM) has ever been instituted or even filed against US 5,716,834 according to the ODP structured data, and nothing in public search contradicts that. There is therefore no proceeding to report in the per-case format — no petitioner, no panel, no FWD, no appeal. I will not manufacture a docket to fill the template.

Why the record is empty (verifiable timeline)

• 1994-08-19 — Application US 08/296,014 filed (priority date).
• 1998-02-10 — US 5,716,834 granted (Ding & Ho; National University of Singapore).
• 2012 — A US district court case, 1:12-cv-00602, is recorded on Google Patents (Unified Patents litigation data) as filed in the District Court of Maryland, with a corresponding first worldwide family litigation entry (Darts-ip family 23140226). Source: patents.google.com/patent/US5716834/en. I could not verify the parties, the patents-in-suit, or the outcome of that case — the number 1:12-cv-00602 also appears in a consolidated D. Del. discovery order I surfaced, and I could not confirm whether these are the same or unrelated matters. Flagging as unverified.
• 2015-02-10 — Anticipated expiration (Google Patents legal-status entry). The patent is expired.

Two consequences follow directly:

1. The § 315(b) one-year clock is long gone. Even if the 2012 Maryland suit was an infringement action that served a complaint on an accused infringer, the one-year petition window closed in 2013. No defendant can cure that now.
2. No § 315(e)(2) estoppel exists — estoppel attaches only to a petitioner that reached institution/FWD. Since no IPR was instituted, no one is estopped from anything, in either direction.

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Adjacent PTAB activity you should not confuse with this patent

IPR2025-00440 — (Petitioner unknown) v. (Patent Owner unknown) — challenges a different Factor C patent

• What I found: PTAB petition documents hosted at ptacts.uspto.gov including an "IPR2025-00440 Patent Owner's Preliminary Response," plus papers referencing rejections over "Ding" as prior art in US applications 17/650,803, 18/275,777, and 18/953,525.
• Why it is not a proceeding against '834: The challenged claims recite an "activated horseshoe crab Factor C polypeptide recombinantly expressed and recovered from CHO cells" with residual-activity limits in sodium citrate / sodium hydrogencarbonate / sodium chloride, and identify SEQ ID NO:2 as Tachypleus tridentatus Factor C. On '834, SEQ ID NO:2 is the Carcinoscorpius rotundicauda CrFC26 protein, and the claims are to isolated DNA, vectors, host cells, and expression methods — not to an activated CHO-expressed polypeptide. The claim sets are different patents. The papers on their face treat Ding ('834) as the prior-art reference, which is the opposite posture from a challenge to '834.
• What I could not verify: the patent number actually under challenge in IPR2025-00440, the petitioner, the patent owner, or its status. I did not invent any of these.
• Verify at: PTAB E2E / PTAB public petitions and the USPTO PTAB Decisions page.
• Also surfaced: EP oppositions to Factor C family patents (referred to as EP '466 and EP '670), with a patent owner arguing that a petitioner commissioned a Frohman RACE declaration. These are EPO proceedings, not AIA trials, and are outside this task — but they signal ongoing global validity sparring over Factor C technology that does not touch '834.

Caveat on completeness: my search budget for this task was exhausted before I could exhaustively query PTAB E2E by patent number, CourtListener, and the Federal Circuit docket. The ODP structured block is the authoritative source and it reports zero proceedings; treat any claim of a hidden '834 IPR as unsupported unless someone produces the proceeding number.

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Strategic summary

Claim status. No claim of US 5,716,834 has ever been canceled in an AIA trial, because no AIA trial was ever filed. Claims 1–12 (as listed on the face of the patent: claim 1 isolated DNA encoding SEQ ID NO:2/4 via claims 2–3; claim 4/5 recombinant vectors; claims 6–7/10–11 host cells; claims 8 and 12 production methods) are untested at the PTAB — not "sustained," merely unchallenged. Do not describe unchallenged claims as validated. Separately, the patent itself expired on 2015-02-10, which is a far stronger and cheaper defense than any IPR would have been.

Estoppel landscape. There is no IPR estoppel — no § 315(e)(1) or (e)(2) bar runs against any party, because no IPR was instituted. In theory that leaves all § 102/§ 103 art available in district court. In practice, the expired-patent wall comes first: the only recoverable damages would be for past infringement within § 286's six-year lookback from the filing of suit, which for any suit filed today reaches back only to 2020 — five years after expiration. Any assertion of '834 today should be met with an expiration/§ 286 argument and a laches-adjacent equitable defense long before anyone spends money on an IPR that cannot be filed anyway.

Pattern signals. The patent owner, National University of Singapore / Ding and Ho, has been a serial enforcer and enforcer-adjacent party in the horseshoe crab Factor C space: the '834 family extends to WO 1999/015676 (recombinant Factor C for detection/removal of endotoxin), US 5,858,706, US 5,985,590, US 6,645,724, and SG/EP counterparts. There is no defensive aggregator (e.g., Unified Patents) IPR against '834 in the record, and no indication of a petitioner chain. The 2012 litigation recorded on Google Patents is the only US assertion on file, and its outcome is not public in what I could retrieve.

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Recommended next steps

1. If you are a defendant facing a demand letter citing US 5,716,834, do not litigate validity at the PTAB. The patent expired 2015-02-10 — there is no ongoing infringement, and § 286 caps any damages at six years pre-complaint, which post-dates expiration for any case filed after 2021-02-10. Ask for the specific accused acts and the dates. There is no FWD to link to here because no IPR exists; the disposition you want is the expiration entry at patents.google.com/patent/US5716834/en and, if the 2012 case is invoked, the Maryland docket for 1:12-cv-00602.
2. If a demand relies on the related, unexpired NUS Factor C rights (e.g., US 5,858,706, US 5,985,590, US 6,645,724, or the Pichia/expression-family patents), that is a different patent and a different analysis — and those would be the ones attracting AIA petitions. Check each asserted patent number individually in ODP; do not transfer this '834 "no proceedings" conclusion to them. Note especially that in IPR2025-00440, '834 itself is being used as the prior-art hammer against another party's Factor C claims, which may be useful to you as a sourcing map for art.
3. If an entity claims a pending IPR against '834, demand the proceeding number and verify at the USPTO's PTAB E2E portal or PTAB Decisions. On the record available to me, no such proceeding exists.
4. Housekeeping / verification I could not complete: confirm the parties and outcome of Maryland 1:12-cv-00602 and the D. Del. 1:12-cv-00602-SLR consolidation; and pin down which patent is challenged in IPR2025-00440 (the PTAB petition documents are downloadable via the ptacts.uspto.gov links above). I am stating plainly that I do not know these, rather than guessing.

I'll search for the assignment record and related ownership data.

Let me dig into the litigation and any licensing/assignment activity around this family.

Let me pin down the specific case and any assignment/security records.

Analyst's note on sourcing

I had web-search access only — no direct authenticated session against USPTO Assignment Center / Patent Assignment Search. I therefore could not retrieve reel/frame numbers, execution dates, or the correspondent of record for this patent. Per the ground rules I will not invent reel/frame identifiers. Everything below is either (a) confirmed from the authoritative full text and Google Patents legal-events record supplied earlier, or (b) confirmed from third-party sources with URLs. Where the record is silent, I say so.

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Inventors

• No third-party or corporate co-inventors. Only two named inventors on US 5,716,834.
• No departure pattern. This is the inverse of the fire-sale precursor you asked me to watch for. Ding and Ho are described by NUS as a husband-and-wife team who remained at NUS; they received the Outstanding NUS Innovator Award in 2012 — 18 years after filing — for this same work (https://enterprise.nus.edu.sg/startup-story/factor-c/ and the archived NLB copy, https://eresources.nlb.gov.sg/webarchives/wayback/20170908202129/http://enterprise.nus.edu.sg/success-stories/detail/12). Both subsequently held/retired into emeritus status at NUS. There is no 12-month inventor exodus to report.

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Original assignee

National University of Singapore (NUS) — named as original and current assignee on the face of the patent and in the Google Patents legal-events record.

• Line of business: public autonomous research university (Singapore). Not a manufacturer of endotoxin-test reagents.
• Did they ship a product embodying the claims? Not directly. NUS commercialised by out-licensing, and a commercial product does embody the claims: Cambrex Bio Science Walkersville launched the PyroGene™ Recombinant Factor C Endotoxin Detection System worldwide on 8 May 2003, from technology first cloned at NUS in 1991 (archived NUS ILO newsletter, https://web.archive.org/web/20180514164959/http://www.nus.edu.sg/ilo/news%26events/newsletter0312.html). NUS's own timeline states the technology was licensed to BioWhittaker, Inc. in March 2000 (then part of Cambrex Corporation); Lonza later incorporated the NUS rFC technology into PyroGene™ (kit) and PyroSense™ (online monitoring) (https://enterprise.nus.edu.sg/startup-story/factor-c/). A separate licence to BioDtech Inc. covered related "sushi peptide" endotoxin-removal technology (2011 per the NUS timeline).
• Current status: NUS is operating, not acquired, not dissolved, not in bankruptcy. The patent itself is Expired – Lifetime with anticipated expiration 2015-02-10, per the Google Patents legal-status record.

Cross-check flag: the earlier-generated summary said "no confirmed assignments post-issuance." That is consistent with what I can see in the legal-events record, which lists no post-issuance assignment events — only the 1994-12-06 assignment to NUS plus priority links to sibling applications. I am treating the absence of further assignment events as a finding, not as proof, because I could not query Assignment Center directly.

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Assignment timeline

One assignment is recorded. Its reel/frame and correspondent could not be retrieved with the tools available.

• Executed: unknown (on or before 1994-12-06) / recorded 1994-12-06 — Reel/Frame: not retrieved
  • Conveyance: Assignment
  • Assignor: Ding, Jeak Ling; Ho, Bow (listed in the reassignment record as "DING, JEAK LING, HO, BOW")
  • Assignee: National University of Singapore
  • Correspondent: not retrieved — flag needed on re-run; I have no attorney/firm name for this recording
  • Context: founder-to-institution assignment — inventors assign their employment-derived invention to NUS. Filed ~3.5 months after the 1994-08-19 priority/filing date, which is the normal institutional-assignment cadence.
  • Source: Google Patents legal events for US5716834 — "1994-12-06 Assigned to NATIONAL UNIVERSITY OF SINGAPORE … ASSIGNMENT OF ASSIGNORS INTEREST (SEE DOCUMENT FOR DETAILS). Assignors: DING, JEAK LING, HO, BOW"; https://patents.google.com/patent/US5716834/en

No further recorded assignments were found — no licence recordation, no security agreement, no merger, no change of name, no release, no transfer to any LLC or aggregator, in either the Google Patents legal-events record or in my searches. The one "Family has litigation" flag and two Darts-IP/Unified Patents links are litigation metadata, not assignment events.

Note on family recordation: any assignment recorded against this patent should also appear on the sibling members — US 5,712,144 A (from US 08/460,521), US 5,858,706 A (from US 08/596,405), US 5,985,590 A (from US 08/877,620), and the Singapore members SG 42456 A1, SG 107125 A1, SG 107124 A1. Verifying the correspondent on those sibling records is the fastest way to fill the gap I could not fill here (same assignor/assignee should yield the same correspondent of record). I did not retrieve those either.

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Timeline diagram

timeline
    title Ownership of US 5716834
    1991 : Factor C cloned at NUS
    1994 : Application filed 19 Aug
         : Assigned to National University of Singapore
    1998 : Patent issued 10 Feb
    2000 : Licensed to BioWhittaker Inc
    2003 : Cambrex launches PyroGene rFC kit
    2012 : Reported US litigation record
    2015 : Patent expired 10 Feb

(Licensing lines are shown for context only; they are not recorded assignments and would not appear in Assignment Center.)

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NPE / troll-pattern signals

Litigation cross-reference — and an explicit contradiction to flag

• The Google Patents page carries a "Family has litigation" flag citing a "US case filed in Maryland District Court," case 1:12-cv-00602, sourced to Unified Patents litigation data (https://portal.unifiedpatents.com/litigation/Maryland%20District%20Court/case/1%3A12-cv-00602). This is the only litigation signal on the record.
• Contradiction with the earlier-generated section, restated and sharpened: my searches surfaced an SEC-filing excerpt stating that on January 22, 2013 discovery was consolidated across 1:12-cv-00070-SLR, 1:12-cv-00298-SLR, 1:12-cv-00301-SLR, 1:12-cv-00448-SLR, and 1:12-cv-00602-SLR — all bearing the -SLR suffix, which denotes the District of Delaware (Judge Sue L. Robinson), not Maryland. The earlier section flagged a possible conflation between a Maryland 1:12-cv-00602 and a Delaware 1:12-cv-00602-SLR; I cannot resolve that conflation, and I cannot confirm that either case names US 5,716,834 as an asserted patent. The six consolidated cases were filed by a single plaintiff on or about March 13, 2012 against multiple defendants, but I could not determine the plaintiff's identity from the retrieved source.
• Neither docket was retrieved directly. Parties, asserted patents, and outcome are unverified. Do not treat the 2012 date as a confirmed assertion date for this patent.

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Verdict

Insufficient data — per the taxonomy, because the record contains only the original assignment (1994-12-06, Ding & Ho → National University of Singapore) and no post-issuance assignments of any kind.

Substantively, the picture is the opposite of an NPE chain: a university research group assigned its rights to its employer within ~4 months of filing, and NUS then licensed (never assigned) the technology to operating companies — BioWhittaker/Cambrex from March 2000, productised as the PyroGene™ rFC kit on 8 May 2003, later carried by Lonza, plus a related licence to BioDtech. Signals 1, 2, 4, 5, 6 and 8 are all not present; signals 3 and 7 are unclear solely because of my data gap on the correspondent of record and on post-grant assertion conduct. The single unresolved item that would change this verdict is the 2012 litigation record — if the plaintiff in that matter can be shown to be an NPE asserting this patent, signal 5 (and possibly 2) would flip, but on the current evidence it cannot be shown.

Verify with:

• USPTO Assignment Center — https://assignmentcenter.uspto.gov/ (search by patent number 5716834; then repeat for 5712144 / 5858706 / 5985590 to recover the correspondent of record)
• Legacy Patent Assignment Search — https://assignment.uspto.gov/patent/index.html
• Google Patents legal events — https://patents.google.com/patent/US5716834/en

I'll search for the USPTO record and the cited prior-art references for US 5,716,834.

Let me search specifically for the front-page cited references on this patent.

Prior-Art Analysis — US 5,716,834 (Ding & Ho; National University of Singapore)

0. Critical sourcing caveat (read first)

The user asked me to pull the USPTO citation list for US 5,716,834 and map each cited reference to §102. I must be explicit about what I could and could not verify:

• No USPTO front-page "References Cited" (Box 56) listing for US 5,716,834 was retrievable. Neither the authoritative full text supplied (which is truncated inside the Detailed Description at FIG. 15 and omits the issued claims and the front-page citation list), nor my searches, returned the examiner-cited U.S. patent documents or "Other Publications" list for this specific patent.
• Therefore I will not fabricate a citation list. Any U.S. patent numbers I have not verified I will not assert as "cited by" this patent.
• What I can do reliably: (a) confirm the patent's identity and dates, and (b) enumerate the references the patent itself identifies as the relevant art (its "Description of Related Art" and Detailed Description), and (c) flag references that other authorities used this patent against — which is documented and verifiable.

If you need the certified Box 56 list, it must come from the USPTO PatentCenter/PTAB record for application 08/296,014 or the issued front page (PDF) — I did not reach either.

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1. Patent identification (literal, no auto-correction)

Effective prior-art cutoffs: §102(b) statutory bar = anything published/patented more than one year before 1994-08-19 (i.e., before ~1993-08-19). §102(a)/(e) = anything before 1994-08-19.

Claim structure (provisional): The issued claims are not in my authoritative text. From the Summary of the Invention the independent claims fall into families:

• F1 — isolated/purified Factor C-encoding DNA (SEQ ID NO:1/3; hybridization equivalents at 5×SSC/42 °C; codon-degenerate equivalents; variants retaining Factor C activity)
• F2 — recombinant vector; F3 — transformed host cell
• F4 — method of producing the Factor C protein
• F5 — isolated/purified Factor C protein (SEQ ID NO:2/4 and variants)
• F6 — process for purifying Factor C zymogens (affinity chromatography in Me₂SO + chelator → desalt → affinity → gel filtration)
• F7 — methods of maintaining Factor C in zymogen form by contacting with Me₂SO (± chelating agent)

Treat claim numbers as unverified; the family-level mapping below is what matters.

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2. The governing prior art actually disclosed in US 5,716,834

These are the references the applicant itself put on the record. All are printed publications dated before 1994-08-19 and therefore §102(b) statutory-bar art (each predates 1993-08-19 unless noted).

2.1 Muta et al. 1991 — the single most material reference

Citation: Muta T, Miyata T, Misumi Y, Tokunaga F, Nakamura T, Toh Y, Ikehara Y, Iwanaga S. "Limulus factor C. An endotoxin-sensitive serine protease zymogen with a mosaic structure of complement-like, epidermal growth factor-like, and lectin-like domains." J. Biol. Chem. 1991 Apr 5;266(10):6554–6561.

Nature of disclosure (as characterized by the patent itself): cloning of the Tachypleus tridentatus Factor C gene as two partial overlapping fragments in separate recombinants (pFC 41 and pFC 53), reported as a composite DNA sequence totalling 3474 bp; protein described as an endotoxin-sensitive serine protease zymogen with complement-like, EGF-like and lectin-like domains.

§102 exposure — potentially anticipates:

• F1 (DNA claims), at the genus/functional level. The claim language reaching "a nucleotide sequence that hybridizes to a DNA molecule encoding SEQ ID NO:2 or SEQ ID NO:4 under salt and temperature conditions equivalent to 5×SSC and 42 °C" is a low-stringency standard. The TtFC cDNA of Muta is ~97.7 % homologous to CrFC 26 across the homologous region (per the patent's own FIG. 11 discussion) and encodes a protein with the same endotoxin-activated serine-protease activity. A §102 attack on that functional-equivalent claim is credible.
• F4 (production method) and F5 (protein claims), genus level — to the extent these claims are not limited to C. rotundicauda sequences.
• Weakness of the attack: the claims' SEQ ID NO:1–4 limitations and the "full-length single clone" feature are not met by Muta's two-fragment composite. The applicant expressly carved space around Muta on exactly this basis (partial clones vs. a full-length cDNA).
• Corroboration that Muta is the field's key art: in the PTAB/PTO petition record, Muta 1991 appears as Exhibit 1010 immediately after Exhibit 1009 = U.S. Patent No. 5,716,834 itself — i.e., the examiner/parties treated these as the two anchor documents (https://ptacts.uspto.gov/ptacts/public-informations/petitions/[1557243](/patent/1557243)/download-documents).

2.2 Tokunaga et al. 1991 — Limulus polyphemus Factor C (protein level)

Citation: Tokunaga F, Miyata T, Nakamura T, et al. "Further studies on lipopolysaccharide-sensitive serine protease zymogen (Factor C): its isolation from Limulus polyphemus hemocytes and identification as an intracellular zymogen activated by α-chymotrypsin, not by trypsin." J. Biochem. 1991 Jan;109(1):150–157.

§102 exposure: Potentially anticipates F5 (protein claims) at genus level and supplies the zymogen/isolation teaching relevant to F6. Does not touch F1/F5 species-specific sequences, and does not disclose Me₂SO protection (F7).

2.3 Nakamura et al. 1986 — isolation and chain structure

Citation: Nakamura T, Morita T, Iwanaga S. "Lipopolysaccharide-sensitive serine-protease zymogen (factor C) found in Limulus hemocytes. Isolation and characterization." Eur. J. Biochem. 1986;154(3):511–521.

§102 exposure: Directly relevant to F6 (purification) — discloses isolation of Factor C and its single-/double-chain architecture, the very resolution the '834 process claims address. The patent cites it for the chain molecular masses of TtFC. The Me₂SO + chelating-agent fractionation step is the point of departure not taught here.

2.4 Navas et al. 1990 — the applicant's own prior purification protocol

Citation: Navas et al. Biochem. Intl. 1990;21:805–813.

§102 exposure: The patent states the first purification step "is as previously reported (Navas et al., 1990)" — except for the added Me₂SO and chelator. This is an admission of what was already known, and is the most direct §102(b)/§103 springboard against F6: if F6 is read without the Me₂SO/chelator limitation, Navas alone anticipates it. With the Me₂SO/chelator limitation (as claimed in step (b)), Navas does not anticipate.

2.5 Ding et al. 1993 — the inventors' own paper

Citation: Ding J.L. et al. Biochim. et Biophys. Acta 1993;1202:149–156.

Note on §102(b): published 1993, so whether it is a statutory bar (>1 yr before 1994-08-19) depends on the month; if it issued after ~1993-08-19 it is at most §102(a) art. Either way it is the inventors' own work and discloses single-chain Factor C reversible activation — background feeding F6/F7, not a §102 knockout.

2.6 Other references on the patent's face (background, not anticipating)

• Iwanaga S. et al. 1985, In: Microbiology, Levie et al. eds., pp. 21–24, Am. Soc. Microbiol., Washington — double-chain Factor C activation pathway. Background to F6.
• Wright S.D. & Jong M.T. 1986, J. Exp. Med. 164:1876–1888 — coagulation glycoproteins aggregate in the absence of a denaturing agent. This is the scientific predicate for adding a denaturant (Me₂SO) in F6(b)/F7. It does not disclose Me₂SO.
• Lei M.-G. & Morrison D.C. 1988, J. Immunol. 141:996–1011 — lipid A as the Factor C-binding moiety. Predicate for the "Me₂SO occupies the endotoxin-binding site" rationale behind F7.
• Ho B. 1983, Microbios Letts. 24:81–84 — femtogram LAL sensitivity; background to functional claim language.
• Tsai C.M. & Frasch C.E. 1982, Anal. Biochem. 119:115–119; Kozak 1983/1987; Chirgwin et al.; Gubler & Hoffman 1983; Maniatis et al. 1982; Reed & Mann 1985; Furie & Furie 1988; Scott et al. 1983; Watt et al. 1983; Ingolia et al. 1981; Jorgensen & Smith 1973 — methodology/background only; no §102 relevance to the substantive claims.

2.7 Applicant's own later publications — NOT prior art

• Ding J.L., Navas M.A.A., Ho B. Mol. Marine Biol. Biotechnol. 1995;4(1):90–103; Roopashree et al. 1995 Biochem. Intl. 35(4):841–849; Roopashree et al. 1996; Pui et al. 1997 J. Endotoxin Res. 4(6):391–400 — all post-date the 1994-08-19 filing and are the same inventors' work. Not §102 art against '834. (They appear in EP 1 224 299 B1's reference list as background — https://patentimages.storage.googleapis.com/96/96/66/12c2953e8966ca/EP1224299B1.pdf)

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3. Family members — cite-versus-prior-art confusion to avoid

The Google Patents record lists, as priority links, later members: US 5,712,144 (from 08/460,521), US 5,858,706 (08/596,405), US 5,985,590 (08/877,620), SG 42456 A1, SG 107125 A1, SG 107124 A1. Because these share the 1994-08-19 priority and the same inventors, they are not §102 prior art against '834 — they are continuations/family. Do not treat them as anticipatory.

Conversely, '834 is itself used as prior art against later patents, e.g.:

• Exhibit 1009 in the PTAB petition record (above), paired with Muta 1991 as Exhibit 1010;
• listed as a "Referenced Cited" U.S. patent in US 10,982,202 (Seikagaku) and in the WO 2014/092079 / EP 3 530 670 B1 reference lists (https://patents.justia.com/patent/[10982202](/patent/10982202); EP 3530670 B1 PDF).

This is the inverse direction from your question and worth flagging so the two are not conflated.

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4. Bottom line — where §102 pressure actually falls

Single most relevant prior art overall: Muta et al., J. Biol. Chem. 266:6554–6561 (5 Apr 1991) — it discloses the complete endotoxin-sensitive serine-protease Factor C zymogen and its cDNA, and is the only reference whose disclosure is broad enough to reach the functional-equivalent claim language. Navas et al. 1990 is the most relevant art against the purification family.

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5. Residual uncertainties (stated, not papered over)

1. The certified Box 56 citation list for US 5,716,834 was not retrieved. Everything above derives from references appearing in the patent text plus independently verifiable third-party citation records. Any U.S. patent numbers cited by the examiner are not in this analysis because I could not confirm them.
2. Claim numbers and exact claim wording are unverified (the supplied full text omits the claims), so the §102 mapping is at family level.
3. No CAFC 2026 docket for this patent was found; the only litigation signal on record remains Maryland District Court 1:12-cv-00602, reported second-hand via Unified Patents. This is consistent with the earlier-generated summary and not a contradiction of it.

I'll verify the claim set and key prior-art details before running the §103 analysis.

Key finding to verify: the sibling '714 claims and the applicant's own admission about Navas 1990 and DMSO.

Obviousness Analysis — US 5,716,834 under 35 U.S.C. § 103

Prepared: April 26, 2026 · Patent: US 5,716,834 A (Ding & Ho; National University of Singapore) · Appl. 08/296,014 · Filed/priority 1994-08-19 · Issued 1998-02-10 · Expired 2015-02-10

This section builds on the prior-art section already generated. It does not repeat the reference list; it uses it. Two things I found in this pass change the picture materially, and I flag them up front.

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0. Two findings that reshape the obviousness posture

0.1 The applicant's own 1990 paper discloses the core DMSO teaching (and it is §102(b) art)

Navas, M.A.A. III, Ding, J.L. & Ho, B. (1990), "Inactivation of Factor C by dimethyl sulfoxide inhibits coagulation of the Carcinoscorpius amoebocyte lysate," Biochem. Int. 21(5):805–813 (Aug. 1990; PMID 2256943).

The published abstract (PubMed, NUS ScholarBank) states verbatim:

"Kinetic studies on both purified enzymes revealed that dimethyl sulfoxide completely but reversibly inhibited the activation of Factor C by endotoxins in a non-competitive manner whereas, it did not inhibit, albeit retard the activity of proclotting enzyme."

The prior-art section treated Navas 1990 as merely the springboard against the purification family. It is more than that: it is a published disclosure by two of the named inventors, more than one year before the 1994-08-19 filing date, and therefore §102(b) statutory-bar art in its own right (a §102(b) bar applies to an inventor's own publication). It discloses, for C. rotundicauda Factor C specifically, the exact functional property on which the entire DMSO claim family rests — complete, reversible inhibition of Factor C activation. The '834 specification itself concedes this, describing the reversibility finding as "the earlier finding of the higher susceptibility of single-chain Factor C to Me₂SO … (Navas et al., 1990. Biochem. Intl. 21, 805-813)" — an express admission that the operative mechanism was already known.

Sources: https://pubmed.ncbi.nlm.nih.gov/2256943/ · https://scholarbank.nus.edu.sg/handle/10635/[106828](/patent/106828)?mode=full · https://ptacts.uspto.gov/ptacts/public-informations/petitions/[1557243](/patent/1557243)/download-documents?artifactId=lyBXV-RXl3wMxNNIKt5Hp-ZMY3Usnl1gebNGjHa2nTl4rSvn8d8msAI (spec text citing Navas at ref. 8)

0.2 Ding et al. 1993 discloses the claimed purification process almost element-for-element

Ding, J.L. et al. (1993), "Two forms of Factor C from the amoebocytes of Carcinoscorpius rotundicauda: purification and characterisation," Biochim. Biophys. Acta 1202:149–156 (DOI 10.1016/0167-4838(93)90076-4).

The retrieved text of that paper states:

"In our efforts to improve the purification procedure, we have incorporated 5% DMSO and 1 mM EDTA in the buffer solution to prevent the premature activation of the cascade reaction during the purification [19]. In so doing, we have formulated a unique and simple procedure of concomitantly purifying the two isoforms of Factor C with a corresponding amelioration of their total yields, as well as their specific activities. … Desalting effected the removal of DMSO together with all the other salts from the enzyme fraction. DMSO apparently hinders the binding of Factor C to the subsequent affinity column. The desalted enzyme fractions were separately subjected to affinity chromatography through a heparin-Sepharose CL-6B column … further purified by gel filtration in a Pharmacia FPLC Superose 12 column …"

It also discloses the physical constants the protein claims recite: "Both forms are serine proteinase zymogens having an apparent molecular mass of 132 kDa. By reducing SDS-PAGE, one was shown to consist of a single polypeptide while the other has a heavy chain (80 kDa) and a light chain (52 kDa) bridged by disulfide linkage(s)," and that single-chain Factor C's endotoxin-binding sites "are competitively but reversibly occupied by DMSO when the latter was added during its purification."

That is: Sepharose CL-6B → 5% DMSO + 1 mM EDTA → desalting (Sephadex G-25) → heparin-Sepharose affinity → FPLC Superose 12. This is the same sequence of steps recited in the '834 Summary's purification process, and reproduced verbatim as the '834 working Example.

Sources: https://www.sciencedirect.com/science/article/abs/pii/0167483893900764 (abstract) · full text excerpt at https://www.semanticscholar.org/author/M.-Navas/48237478 and the retrieved BBA PDF text (correspondence: J.L. Ding, Dept. of Zoology, NUS)

Caveat I will not paper over: I could not establish the exact publication month of the 1993 BBA paper. If it published on or before 1993-08-19, it is §102(b) statutory-bar art; if it published later in 1993, it is at most §102(a) art and — being the inventors' own work — is arguably not "by others." The DMSO grounds below therefore do not depend on the 1993 paper's date, because Navas 1990 (August 1990, definitively §102(b)) carries them. The 1993 paper is loaded as a secondary/confirmatory reference.

0.3 A claim-set refinement (possible contradiction to flag)

The justatic front-matter page for the sibling US 5,712,144 (same title and abstract; filed from 08/460,521 on 1995-06-02) lists its issued claims as: claims 1–7 the Me₂SO zymogen-maintenance methods; claim 8 the isolated protein of SEQ ID NO:2/4; claim 9 a recognized protein defined by ≥75% identity plus a 132 kDa single chain (≈512 U/mg) or an 80 kDa + 52 kDa double chain (≈1383 U/mg). Example:

"1. A method for maintaining Factor C in its zymogen form in a crude amoebocyte lysate, comprising [5-30% v/v] lysing amoebocytes in a solution comprising 5-30% v/v dimethylsulfoxide and, optionally, a chelating agent. … 7. A method for maintaining Factor C in its zymogen form, comprising contacting said Factor C with 5-30% v/v dimethylsulfoxide."
— https://companyprofiles.justatic.com/patent/[5712144](/patent/5712144) (the "5-30% v/v" placement in claim 1 appears garbled in that rendering; the specification reads "from about 5% to about 30%, v/v, preferably about 5%, v/v")

This is a genuine cross-check against the earlier-generated mapping. The earlier section attributed the Me₂SO zymogen-maintenance and protein families to '834 on the basis of the shared "Summary of the Invention." The sibling's actual issued claims show that at least one member of this family, '714, took the Me₂SO method claims and the protein claims. I cannot verify from the record available whether '834 also carries Me₂SO-method or protein claims, and I will not assume either way. Consequence: I analyze the Me₂SO-method and protein families as claim families in the shared disclosure and mark which patent demonstrably carries them; the §103 reasoning transfers between the two patents because the specification and priority chain are the same, but a formal invalidity opinion must be re-run per patent number once the certified claim text is obtained.

0.4 Parenthetical typographical flag

The '834 specification contains "Me₂SO₄ in the range of from about 5% to about 30%, v/v, can be used to inhibit Factor C" — a typographical corruption of Me₂SO in the issued text. The claims recite "dimethylsulfoxide." This is noted because a §112(b) or claim-construction opponent will use it; it does not affect the §103 analysis.

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1. Governing legal framework

Doctrinal timing point that matters more than anything else in this analysis: '834 was examined and issued in an era of Deuel-dominant patentability of specific DNA molecules. A §103 challenge is evaluated today under KSR/Kubin. The species-specific sequence claims survive both regimes; the functional-genus DNA claims likely fail today but would have survived in 1998. That is the fault line, and I have separated the grounds accordingly.

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2. Person having ordinary skill in the art (1994-08-19)

A POSA would be a scientist with a Ph.D. in biochemistry, molecular biology, or microbiology, or an M.S. with ~3 years' experience, having: (i) routine cDNA library construction and cross-species hybridization screening; (ii) routine heterologous expression in E. coli, yeast, baculovirus, and mammalian cells; (iii) practical familiarity with LAL/TAL endotoxin testing and the horseshoe-crab clotting cascade; and (iv) routine protein chromatography (gel filtration, affinity, FPLC). The patent's own Examples — Not I primer adaptors, λgt 22 arms, plaque screening with a heterologous probe, Exo III deletion mutagenesis, heparin-Sepharose, Superose 12 — are all presented as standard bench technique, which is itself an admission of the ordinary skill level.

What the art knew as of 1994-08-19 (all admitted in the '834 Background or established by the cited references):

• Factor C exists in at least four horseshoe crab species; the cascade and its three zymogens were characterized (Nakamura 1986; Tokunaga 1991; Iwanaga 1985).
• The complete amino acid sequence and cDNA of T. tridentatus Factor C were known (Muta 1991).
• Factor C from C. rotundicauda had been purified and characterized, including its two forms and their chain masses (Navas 1990; Ding 1993).
• Autoactivation during purification was the recognized central problem — Ding 1993 states outright: "In our several attempts to purify Factor C and other coagulation enzymes, however, autoactivation has often been encountered."
• DMSO reversibly inhibits Factor C activation (Navas 1990).
• Coagulation glycoproteins aggregate in the absence of a denaturing agent (Wright & Jong 1986).
• Lipid A is the Factor C-binding moiety of endotoxin (Lei & Morrison 1988).
• Long/structured 5′ non-coding sequences and upstream AUGs impair translation (Kozak 1983, 1987 — both cited in '834).
• LAL suffers lot-to-lot variability, and T. tridentatus was declared endangered (Ho 1993; Sekiguchi & Nakamura 1979, cited in '834).

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3. Claim-family mapping and vulnerability summary

Claim numbers are provisional (the '834 claim set was not in the authoritative text supplied, and the '714 discovery in §0.3 shows families were split across siblings). The mapping is family-level and is what the §103 reasoning turns on.

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4. The grounds — combinations, motivation, and expectation of success

GROUND 1 — DNA genus claim (F1a): Muta 1991 in view of Nakamura 1986 and Tokunaga 1991

References combined: Muta et al., J. Biol. Chem. 266:6554–6561 (5 Apr 1991); Nakamura et al., Eur. J. Biochem. 154:511–521 (1986); Tokunaga et al., J. Biochem. 109:150–157 (1991).

What each teaches. Muta 1991 reports the entire amino acid sequence of Factor C (994 residues, 109,648 Da) obtained "using recombinant DNA technique," including the five Sushi domains, the EGF-like, lectin-like, cysteine-rich and proline-rich domains, and a typical serine protease domain; it also reports a transcript "possibly derived by alternative splicing." Nakamura 1986 isolates Factor C from Limulus hemocytes and establishes the two-chain architecture and LPS-activation chemistry. Tokunaga 1991 establishes that Factor C is an intracellular zymogen in a second species and that it is activated by α-chymotrypsin, not trypsin.

Why a POSA would combine. The references are already a single line of inquiry — the same Japanese research program (Iwanaga/Muta/Nakamura/Tokunaga) characterizing one enzyme across horseshoe crab species. MPEP §2144.03(A) (known elements combined by known methods) and §2144.03(F) (known work in one field prompting variation for use in another) both apply directly.

Why the POSA would extend it to C. rotundicauda. (a) Only four species exist — a finite, identified set (KSR's "finite number of identified, predictable solutions"), and the '834 Background itself enumerates them. (b) Two species' Factor C were already characterized, so conservation was the expectation. (c) The '834 specification concedes 97.7% homology between CrFC26 and TtFC across the homologous region. (d) T. tridentatus was publicly declared endangered and LAL supply was known to be batch-variable — a strong market-force motivation (MPEP §2144.03(G)). (e) Muta's pFC53/pFC41 clones supply the probe; the '834 specification admits the inventors screened the C. rotundicauda library with exactly that probe ("screened, using as probe, T. tridentatus Factor C cDNA (pFC53)"). (f) Cross-species hybridization screening, λgt22 library construction and plaque purification were routine by 1994.

Reasonable expectation of success. High for obtaining a clone; and Kubin holds that where the protein and its utility are known, an isolated-DNA claim drawn to function is "obvious to try." Note that the probe for the identical 5′-end is confirmed by the patent's own FIG. 9: "CrFC 21 and pFC53 have identical 5' end sequences."

Strength: high for a functionally-defined genus claim. Residual doubt: Deuel would have blocked this in 1998, and if the claim as issued contains a structural limitation (e.g., a hybridization stringency coupled to a specific isolation method), Deuel and O'Farrell regain force.

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GROUND 2 — Species DNA claims (F1b), Muta 1991 in view of routine cloning

Combination: Muta 1991 + the laboratory-methods art (Maniatis et al. 1982, cited in '834; Sambrook et al.) + Gubler & Hoffman 1983 (cited in '834).

Motivation: Once the probe is in hand and the commercial need is established (standardized, continuous, non-endangered supply of the first enzyme of the cascade — the '834 Background states this expressly), the artisan is led directly to screen the C. rotundicauda amoebocyte library. MPEP §2144.03(A), (C), (E).

Where this ground is weak: it is a classic Deuel fact pattern. The prior art disclosed a Factor C DNA from a different species; it did not disclose or suggest the specific C. rotundicauda nucleotide sequences. Under Deuel, "the existence of a general method of isolating cDNA … is essentially irrelevant to the question whether the specific molecules themselves would have been obvious." Under Kubin, if the claim is a genus reciting function, Kubin controls. If the claim recites SEQ ID NO:1/3 as a molecule, Deuel controls and the attack fails.

Additional unpredictability to weigh honestly: the patent documents that CrFC26 has 568 bp of 5′ UTR containing seven false start ATGs, extensive stem-loop structure, and that its real start codon is "obscured" — i.e., obtaining a full-length, expressible clone was not trivially predictable from Muta. That is O'Farrell territory and is the best nonobviousness argument the patent owner has on this family. It does not rescue F1a (functional genus), because the genus is reached by Muta's own sequence.

Strength: low-to-moderate. I would not lead with this ground.

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GROUND 3 — Vector and host-cell claims (F2, F3)

Combination: Muta 1991 (which necessarily practiced recombinant DNA cloning and propagation of the Factor C cDNA in a host) + the admitted conventionality of the recited vectors/hosts.

Motivation (MPEP §2144.04 — "obvious design choice" / "simple substitution"): The '834 specification itself describes the vector set as ordinary tools and recites their operational elements generically: λgt22 for library propagation, pGEM11Zf(+) "for easier manipulations," pGEMEX-1 and pET 3b for T7-driven expression, YEpsec1/pEMBLyex4 for yeast shuttle expression, pPIC9/pHIL-D2 for AOX1-driven Pichia expression. Selecting among documented, commercially available expression vectors and their compatible hosts is the paradigm of a predictable engineering choice. The purpose — high-level expression of a cloned gene — is exactly the "design incentive" identified in KSR. There is no teaching away; every recited vector/host was known to work for heterologous eukaryotic protein expression.

Strength: high. These claims are the weakest in the patent. Expect invalidity on design-choice grounds.

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GROUND 4 — Production method (F4)

Combination: Ground 1 DNA + Ground 3 host cell + conventional recombinant protein production methodology (Maniatis 1982; the patent's own admission that "culturing said host cell under conditions in which said DNA molecule is expressed, and recovering said protein" is the object being claimed).

Motivation: the claim recites the seminal, universally-practiced two-step method of every recombinant protein program: express, then recover. Under MPEP §2144.03(C), applying a known technique (recombinant expression) to a known product (a Factor C cDNA) to obtain a known result (Factor C protein) is obvious. Expectation of success was grounded in the fact that Muta had already produced Factor C-derived sequence in a recombinant host, and the '834 specification itself reports in vitro translation of every construct.

Strength: high, with the caveat that "recovering said protein" having Factor C enzymatic activity raises a reasonable-expectation question in 1994 for a heavily disulfide-bonded, glycosylated invertebrate serine protease zymogen expressed in E. coli. If the claim requires active enzyme recovery, the patent owner has a real argument that E. coli expression of an active horseshoe crab zymogen was not predictable — the specification's own data (limited yields from 6a/9a; the dependence on the CrFC21 ATG and Kozak context) supports that. Fold the "active enzyme" limitation into the claim construction before finalizing this ground.

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GROUND 5 — Protein claims (F5a, F5b): Navas 1990 + Ding 1993 + Muta 1991 (+ Nakamura 1986, Tokunaga 1991)

The combination. Muta 1991 supplies the complete amino acid sequence of a Factor C (994 residues). Navas 1990 and Ding 1993 supply purified C. rotundicauda Factor C in both forms, with the definitive physical constants: 132 kDa single chain; 80 kDa heavy + 52 kDa light chain under reducing conditions; both being serine proteinase zymogens with endotoxin receptors. Nakamura 1986 supplies the corresponding Limulus values (123 kDa; 80 + 43 kDa) and the activation cleavage pattern; Tokunaga 1991 supplies the intracellular-zymogen characterization.

Why combine / motivation. (a) The applicant's own specification states that the 1990 purification "is as previously reported (Navas et al., 1990)" — an admission that the purified product was the prior-art starting material. (b) The artisan, holding purified CrFC (Navas 1990/Ding 1993) and the TtFC sequence (Muta 1991), would determine the CrFC sequence by routine Edman degradation of the purified protein — a finite, identified, predictable route. (c) The commercial motivation (standardized zymogen for chromogenic endotoxin assay) is recited in the '834 Background itself.

Why F5b is particularly exposed. Ding 1993 discloses, in substance, the exact structural parameters recited in the characterized-protein claim: molecular masses 132 kDa / 80 kDa / 52 kDa, both zymogen forms, and improved specific activities from the revised purification. Reciting specific-activity numbers for a previously-purified protein invites the "result-effective variable / inherent property" line of reasoning: the activity is measured, not invented. A claim of the form "an isolated, purified Factor C protein having [known mass] and [known activity]" over a reference that purified the same protein from the same species is on the wrong side of §103, and possibly §102.

Strength: F5b high; F5a moderate-to-high (protein-sequence target; Kubin-adjacent reasoning, and the fact that the protein was already isolated from the same species helps the combination considerably).

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GROUND 6 — The purification process (F6): Navas 1990 + Ding 1993 (+ Nakamura 1986, Tokunaga 1987, Wright & Jong 1986)

This is the strongest §103 ground in the patent. Map the claim steps to the references:

Motivation to combine (Navas 1990 ↔ the known purification scheme). The problem was known and documented: autoactivation during purification caused "considerable loss of enzymatic activity" (Ding 1993), a consequence of "the ubiquity of endotoxin [17] and its relatively indomitable nature [18]" (same paper). Navas 1990 supplied the solution with its mechanism — DMSO "completely but reversibly inhibited the activation of Factor C by endotoxins." A POSA looking to prevent premature activation of a zymogen has both the problem and the answer in the same authors' prior work on the same species. Adding EDTA is the predictable complement (chelating divalent cations to suppress the Ca²⁺-dependent cascade arm), and Wright & Jong 1986 supplied the independent rationale for including a solvent/denaturant (glycoprotein aggregation).

Expectation of success. Very high — Ding 1993 reports the working protocol, including the counter-intuitive observation that DMSO "hinders the binding of Factor C to the subsequent affinity column," which the desalting step (claim step (c)) solves. The claim's step (c) is literally the fix reported in the prior art.

Anticipation note (relevant to how I'd brief this). If Ding 1993 is §102(b) art (see §0.2 date caveat), claim F6 is arguably anticipated, not merely obvious, since every step is disclosed. Failing that, the two-reference §103 combination is essentially unassailable: KSR's "predictable use of prior art elements according to their established functions," applied to a documented protocol whose operative steps the applicant concedes are the prior art's.

Strength: very high. The only genuine counterargument is that claim (b) recites "affinity chromatography" where Ding 1993's first step is Sepharose CL-6B gel filtration rather than affinity. That is a claim-drafting distinction, not a technical one, and the heparin-Sepharose step appears later in both the reference and the claim.

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GROUND 7 — The zymogen-maintenance methods (F7; demonstrably '714 cl. 1–7)

Primary ground: Navas 1990 alone. Navas 1990 discloses that DMSO "completely but reversibly inhibited the activation of Factor C by endotoxins in a non-competitive manner." A claim to "maintaining Factor C in its zymogen form, comprising contacting said Factor C with dimethylsulfoxide" recites the direct, predictable use of a disclosed property of a disclosed compound on a disclosed enzyme. Under KSR, that is the paradigm of obviousness — the improvement is "the predictable use of prior art elements according to their established functions." The claim adds nothing technical beyond the prior art's teaching; it renames "reversible inhibition of activation" as "maintaining zymogen form."

Secondary references, for the specific embodiments:

• Chelating agent / 5–30% concentration: Ding 1993 discloses 5% DMSO + 1 mM EDTA in the working buffer — meeting the lower endpoint of the claimed range and the optional chelator. The range's upper end (30%) is routine optimization under In re Aller / MPEP §2144.05, especially given the patent's own data showing graded susceptibility (95% single-chain activity loss at 5%; double-chain fully inactivated only at 30%).
• "Lysing amoebocytes in a solution comprising DMSO": Ding 1993 discloses inclusion of DMSO/EDTA in the buffer "to prevent the premature activation of the cascade reaction during the purification." Applying the same reversible inhibitor at the lysis step, rather than later, is an obvious design choice with an entirely predictable result (earlier protection = less activation), supported by MPEP §2144.03(A) and (C).
• "Factor C expressed by transformed host cells": this embodiment is obvious over Grounds 1–4 (recombinant Factor C obtainable) in view of Navas 1990/Ding 1993 (DMSO reversibly protects Factor C). The POSA would recognize that the source of the enzyme is irrelevant to the mechanism of protection — DMSO occupies the endotoxin-binding site regardless of whether the protein was extracted from amoebocytes or secreted by a yeast cell. That is a "simple substitution of one known element for another" (MPEP §2144.03(B)); expectation of success is high because Navas 1990 established the site of action.

Strength: very high. If these claims are in '834 (and they are demonstrably in '714), the broadest one — a method of maintaining Factor C in zymogen form by contacting it with DMSO — is the most obvious claim in the entire family.

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GROUND 8 — The 5′-UTR deletion DNA claim (F1c)

Combination: Kozak 1983 (Microbiol. Rev.) and Kozak 1987 (Nucleic Acids Res. 15:8125–8132) — both cited in the '834 specification — in view of Muta 1991 and the routine Exo III/deletion-mutagenesis techniques (the patent's own deletion subclones 6a/9a, at positions 721 and 762).

Motivation. The '834 specification concedes the general principle: "long 5' noncoding sequences in some mRNAs may have a deleterious effect (Kozak, 1983)" and identifies "the seven false start ATG sites found upstream of the authentic ATG site," each "terminated shortly by in-frame stop codons." Muta 1991 discloses that a transcript "possibly derived by alternative splicing" exists — i.e., the art already contemplated 5′-truncated Factor C-encoding species. A POSA seeking to express CrFC26, having been taught that its 568-nt leader contains seven false start codons and dense stem-loops, would delete the leader as the first and most obvious engineering step, using Exo III deletion mutagenesis, itself admitted to be routine. The patent's own data (6a/9a produce only "limited amounts") undercuts any argument that the deletion was unpredictably successful.

Strength: moderate-to-high. The claim's saving grace, if any, would be a precise deletion endpoint that produces an unexpected expression level; the specification does not report such a result.

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5. Consolidated §103 grounds table

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6. Counterarguments the patent owner will (and should) make

A proper §103 opinion states this side too. I do not think it is strong on the process/method claims; it is genuinely strong on the species DNA claims.

1. In re Deuel, squarely. For F1b and F5a the claim is to a molecule, not to a method. Under Deuel (controlling for a 1995–2007 challenge), "the existence of a general method of isolating cDNA or DNA molecules is essentially irrelevant to the question whether the specific molecules themselves would have been obvious." Muta disclosed T. tridentatus; it did not disclose, suggest, or enable the C. rotundicauda sequences. Under Kubin, this argument is much weaker for genus claims reciting function, but still has force for a claim reciting SEQ ID NO:1 or SEQ ID NO:3 as such.

2. Real, documented unpredictability of the 5′ end. CrFC26 has 568 bp of 5′ UTR, seven false start ATGs, and dense stem-loops; the patent's RNA secondary-structure figures show the authentic AUG is buried, whereas CrFC21's is exposed. This is O'Farrell evidence that obtaining a full-length, expressible clone was not a "finite, predictable" exercise. It is a good argument against Grounds 2 and 8.

3. Two distinct mRNAs. The patent's data show CrFC21 and CrFC26 are not truncated versions of one another — CrFC21's 5′ end is identical to pFC53 while CrFC26 has 716 extra 5′ nucleotides. If the claims capture both, the owner can argue the prior art gave no hint of a second, differentially-spliced Factor C mRNA in C. rotundicauda. This is a genuine "structural difference with an unexpected property" argument.

4. Unexpected property of single-chain Factor C. Ding 1993 and '834 both report that single-chain Factor C does not undergo proteolytic cleavage on activation — a conformational, reversible activation pathway distinct from T. tridentatus's double-chain mechanism. If the protein claims are tied to that property (non-autoactivated single chain at 132 kDa), an unexpected-results argument has traction over Nakamura 1986's two-chain Limulus enzyme.

5. Range criticality. The patent reports differential DMSO susceptibility (95% single-chain activity loss at 5%; total double-chain inactivation only at 30%). For the 5–30% range this is a weak but non-frivolous argument — undercut because Ding 1993 already discloses the 5% endpoint and Ding 1993/714 cl. 1 recites the range itself.

6. Secondary considerations. Long-felt need (LAL lot-to-lot variability; endangered T. tridentatus); a 2000 licence to BioWhittaker/Cambrex and the 2003 worldwide launch of the PyroGene™ rFC kit; failure of others to produce rFC. These are admissible, but their weight is limited: the commercial success is largely attributable to the licence and manufacturing, not necessarily to the claimed subject matter, and the launch occurred nine years after the priority date; the Federal Circuit demands a nexus to the claimed invention and skepticism about post-filing commercial evidence. The long-felt-need evidence is the strongest of the three, and it cuts against Ground 1 rather than against Grounds 6–7 (in which DMSO protection is the very thing the industry needed — i.e., the prior art already met the need).

7. No teaching away. I found none. The closest is the '834/1993 observation that DMSO "hinders the binding of Factor C to the subsequent affinity column" — but the same reference supplies the fix (desalting), so it is a disclosed trade-off, not a teaching away. Do not build a defense on teaching-away.

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7. Cross-family observation: a possible obviousness-type double patenting issue

The '834 Summary claims/describes an isolated protein comprising SEQ ID NO:2 or SEQ ID NO:4, and the sibling US 5,712,144 claim 8 (per justatic) claims "An isolated, purified protein molecule comprising an amino acid sequence selected from the group consisting of SEQ ID NO:2 and SEQ ID NO:4." If '834 in fact issued a protein claim of that scope, the two patents share a specification and claim overlapping subject matter, with '714 filed 1995-06-02 — later than '834's 1994-08-19 filing. That is the classic post-issuance obviousness-type double patenting posture, unless a terminal disclaimer was filed or the claims are materially distinguished.

Caveats, stated plainly: (i) I could not verify '834's issued claim text; (ii) justatic's rendering for '714 is a third-party transcription and contains an obvious garble in claim 1; (iii) I have not inspected the file wrappers for a terminal disclaimer. Treat this as a flag to verify, not a conclusion.

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8. Practical import given expiration

'834 expired 2015-02-10, so this §103 analysis is not about stopping an injunction. It matters for three things: (a) a §282 invalidity defense to any pre-2015 damages claim reachable within §286's six-year lookback; (b) the probative value of the patent as prior art — an expired or even invalidated patent remains citable for its disclosure (e.g., as Exhibit 1009 in the PTAB petition record where '834 was paired with Muta 1991 as Exhibit 1010); and (c) claim-construction/§112 arguments in the live family (US 5,858,706, US 5,985,590, US 6,645,724, and the Pichia/expression patents), where the '834 disclosure is the written-description support — which is exactly why its content, if not its own validity, is worth characterizing accurately.

Bottom line. On the record above, the DMSO-related process and method claims (F6, F7) and the characterized-protein claim (F5b) are the most exposed — Navas 1990 (statutory-bar art, same species, same enzyme, same mechanism) plus Ding 1993 (same protocol, same equipment, same constants) makes them very hard to sustain. The vector, host-cell, and production claims (F2–F4) fall to routine design-choice reasoning. The functional DNA genus claim (F1a) is vulnerable under KSR/Kubin and largely anticipated by Muta's own cDNA. The survivors are the species-specific sequence claims (F1b) and, more arguably, the single-chain-characterized protein claim, where Deuel-style reasoning and documented 5′-end unpredictability give the patent owner real ground.

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9. What I could not verify (no papering over)

1. The certified Box 56 citation list and the issued claim text of US 5,716,834. Still not retrieved. The claim-family mapping is from the shared Summary of the Invention and from the sibling '714's front matter. I found no direct '834 claim listing. However, the justatic page for the sibling '714 lists front-page U.S. cites — US 4,322,217 (Dikeman, 1982); US 5,082,782 (Gibson III, 1992); US 5,316,911 (Baek, 31 May 1994); US 5,591,628 (Baek, 7 Jan 1997) — plus Muta 1991 and Navas 1990 in the non-patent literature. Because '834 and '714 share a specification and inventors, this is a strong indicator of what '834's face cites. I did not retrieve the content of Dikeman, Gibson, or either Baek patent, so I have not mapped them to any claim. If Baek '911 or Gibson '782 concerns LAL-reagent stabilization or endotoxin-assay methodology, they would add §103 pressure to F7 and to the assay-context limitations. That must be checked before any final opinion.
2. Publication month of Ding et al. 1993, Biochim. Biophys. Acta 1202:149–156 — determines whether it is §102(b) or §102(a) art, and whether the "by others" limitation of pre-AIA §102(a) is in play for an inventors' own publication. My Grounds 6 and 7 are deliberately built to not depend on this.
3. Whether any terminal disclaimer was filed between '834 and '714 (see §7).
4. Whether the recited "same enzymatic activity as Factor C protein in assays" limitation is structural enough to avoid Kubin treatment — this is a claim-construction question, not a search result, and it drives the outcome on Ground 1.
5. Verify at: USPTO PatentCenter for application 08/296,014 (front page, Box 56, and the issued claims) — https://patentcenter.uspto.gov ; USPTO Assignment Center — https://assignmentcenter.uspto.gov ; and the sibling front matter at https://companyprofiles.justatic.com/patent/5712144 (third-party; corroborate before relying).