{"id":"c5e05d35-0194-5327-bfeb-513d9f04fb7d","stable_key":"18100170-a014-51c3-adeb-9dab4162b8cc:zinc-affinity","predicate":"context_dependent_observation","statement":"Purified FTS bound zinc with apparent Kd (5 +/- 2) x 10^-7 M at pH 7.5; binding was undetectable below pH 6 in this assay.","claim_class":"mechanistic","status":"source_recorded","evidence_grade":"ungraded","direction":"context_dependent","is_public":true,"mechanism_event_id":"0924c98b-c4e6-5405-af42-4418f275a6e5","mechanism_event_label":"Purified FTS bound zinc with apparent Kd (5 +/- 2) x 10^-7 M at pH 7.5; binding was undetectable below pH 6 in this assay.","subject":{"id":"9bac7a31-4b5b-59f2-8dad-39269ddbb8b1","slug":"fts-peptide","display_name":"Zinc-free FTS nonapeptide component","entity_type_key":"peptide"},"object":{"id":"c42b9296-be70-516b-b473-9111a42618fb","slug":"thymulin-zinc-binding","display_name":"Purified FTS zinc-binding affinity and metal-dependent conformation","entity_type_key":"cellular_process"},"evidence_count":1,"mechanism_event":{"id":"0924c98b-c4e6-5405-af42-4418f275a6e5","stable_key":"18100170-a014-51c3-adeb-9dab4162b8cc:zinc-affinity-event","event_type":"biochemical_relationship","label":"Purified FTS bound zinc with apparent Kd (5 +/- 2) x 10^-7 M at pH 7.5; binding was undetectable below pH 6 in this assay.","description":"A separate binding study reported an apparent zinc dissociation constant of **(5 ± 2) × 10⁻⁷ M at pH 7.5** and no detectable binding below pH 6 under its assay conditions. Other tested metals competed for binding. These are purified-system measurements, not a threshold for dietary intake, plasma zinc or thymulin failure inside a patient. They make pH and competing ligands relevant experimental variables. [Zinc-binding study, 1984](https://pubmed.ncbi.nlm.nih.gov/6538097/)","status":"provisional","compartment":null,"participants":[{"entity":{"id":"9bac7a31-4b5b-59f2-8dad-39269ddbb8b1","slug":"fts-peptide","display_name":"Zinc-free FTS nonapeptide component","entity_type_key":"peptide"},"role":"tested factor","stoichiometry":null,"state_label":"pH below 6","sequence_order":0,"notes":""},{"entity":{"id":"c42b9296-be70-516b-b473-9111a42618fb","slug":"thymulin-zinc-binding","display_name":"Purified FTS zinc-binding affinity and metal-dependent conformation","entity_type_key":"cellular_process"},"role":"measured outcome","stoichiometry":null,"state_label":"mixed","sequence_order":1,"notes":""},{"entity":{"id":"49c806c2-7041-5020-8b3b-fa04ffa122ac","slug":"zinc-ion","display_name":"Zinc(II) ion","entity_type_key":"ion"},"role":"binding metal","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""}]},"contexts":[{"dimension":"evidence_access","value_text":"Primary bibliographic record and abstract checked; full methods/figures not comprehensively reviewed.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_contrast","value_text":"{\"intervention\": \"pH below 6\", \"comparator\": \"pH 7.5\", \"endpoint\": \"Purified FTS bound zinc with apparent Kd (5 +/- 2) x 10^-7 M at pH 7.5; binding was undetectable below pH 6 in this assay.\", \"effect_direction\": \"mixed\", \"combination\": \"single\", \"conditions\": []}","comparator":null,"unit":null,"notes":"Explicit extracted experimental comparison; source-derived draft.","entity":null},{"dimension":"experimental_model","value_text":"Purified-system binding assay; pH 7.5 versus below pH 6.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"interpretation_status","value_text":"Source-derived extraction of a fact-checked reference; access is explicit, not independent raw-data verification.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Interpret only within the recorded preparation, exposure and comparator. The complete source passage retains qualifications; unspecified doses/timing have not been extracted here. No clinical efficacy, nutrient deficiency or unique molecular mediation is inferred.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"Purified FTS bound zinc with apparent Kd (5 +/- 2) x 10^-7 M at pH 7.5; binding was undetectable below pH 6 in this assay.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"Studies on the zinc binding site to the serum thymic factor. | 1984 | DOI 10.1016/0304-4165(84)90116-8 | PMID 6538097 | https://pubmed.ncbi.nlm.nih.gov/6538097/","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"source_locator","value_text":"Reviewed reference lines 25-25; exact primary location described in quoted passage where extracted.","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"bd0cd598-233f-50f7-9f73-89ef6c47c249","evidence_kind":"source_excerpt","locator":"Lines 25-25","start_line":25,"end_line":25,"excerpt":"A separate binding study reported an apparent zinc dissociation constant of **(5 ± 2) × 10⁻⁷ M at pH 7.5** and no detectable binding below pH 6 under its assay conditions. Other tested metals competed for binding. These are purified-system measurements, not a threshold for dietary intake, plasma zinc or thymulin failure inside a patient. They make pH and competing ligands relevant experimental variables. [Zinc-binding study, 1984](https://pubmed.ncbi.nlm.nih.gov/6538097/)","model_system":"Purified-system binding assay; pH 7.5 versus below pH 6.","directness":"reported_statement","verification_status":"source_recorded","notes":"Exact excerpt of the retained AI-assisted reviewed reference; primary sources are cited in primary_references and access scope is retained. Not a verbatim quotation from a primary paper.","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"e1871d49-9c6b-547b-a1bb-6e2b9270ca89","stable_key":"import-18100170-a014-51c3-adeb-9dab4162b8cc","title":"Thymulin: detailed mechanisms of action (reviewed 3 October 2026)","document_type":"imported_text","citation_label":"Original AI-assisted review of primary studies and, where relevant, official regulatory records. Access level is retained per claim. Corrections, null results and unresolved questions remain explicit. Not publisher full text or independent replication.","file_path":"","sha256":"6e8ed0d7a5e23fc822f2ab418e0c4fb2411c01fcaa330039e8d7d93218cacc88","revision_id":"8c0e3449-9bbd-57c0-bb5e-de83f044f2ac","review_status":"source_recorded","notes":""}}],"relations":[],"conflicts":[],"corrections":[],"research":null}