{"id":"c89d9dbf-05b5-5850-b8b2-6a3b69f27426","stable_key":"911fb3c7-8cc3-5667-b677-5682fab67648:histidine-urocanate-uv","predicate":"isomerizes_to","statement":"UV exposure converted trans-urocanic-acid standard to cis isomer; UVB produced faster conversion than UVA under the tested conditions.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"context_dependent","is_public":true,"mechanism_event_id":"02525945-8c20-5630-9f71-df7f4d317361","mechanism_event_label":"Light changes the shape of a histidine-derived skin molecule.","subject":{"id":"86f82ca3-8f80-5c1f-b724-27b78660c2a9","slug":"trans-urocanate","display_name":"trans-Urocanate","entity_type_key":"small_molecule"},"object":{"id":"6e77d061-146f-5223-8464-effa3f6216de","slug":"cis-urocanate","display_name":"cis-Urocanate","entity_type_key":"small_molecule"},"evidence_count":1,"mechanism_event":{"id":"02525945-8c20-5630-9f71-df7f4d317361","stable_key":"911fb3c7-8cc3-5667-b677-5682fab67648:histidine-urocanate-uv-event","event_type":"observed_relationship","label":"Light changes the shape of a histidine-derived skin molecule.","description":"UV exposure converted trans-urocanic-acid standard to cis isomer; UVB produced faster conversion than UVA under the tested conditions.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"86f82ca3-8f80-5c1f-b724-27b78660c2a9","slug":"trans-urocanate","display_name":"trans-Urocanate","entity_type_key":"small_molecule"},"role":"subject","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"6e77d061-146f-5223-8464-effa3f6216de","slug":"cis-urocanate","display_name":"cis-Urocanate","entity_type_key":"small_molecule"},"role":"target","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""},{"entity":{"id":"44374451-3436-5136-a8ae-5dcc6d8c353b","slug":"histidine","display_name":"L-Histidine","entity_type_key":"small_molecule"},"role":"context_participant","stoichiometry":null,"state_label":"","sequence_order":2,"notes":""}]},"contexts":[{"dimension":"evidence_access","value_text":"Primary abstract","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"In-vitro standards plus analytical measurement of histidine and urocanate isomers in skin washes from eight volunteers.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Photochemistry in standards does not establish a clinical sunscreen effect from oral histidine.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient_topic","value_text":"L-Histidine collection; species, compartment, exposure, co-substrates and manipulation remain explicit.","comparator":null,"unit":null,"notes":"","entity":{"slug":"histidine","display_name":"L-Histidine","entity_type_key":"small_molecule"}},{"dimension":"plain_language","value_text":"Light changes the shape of a histidine-derived skin molecule.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"Determination of histidine and urocanic acid isomers in the human skin by high-performance capillary electrophoresis. · 2000 · https://pubmed.ncbi.nlm.nih.gov/11129077/ · DOI 10.1016/s0378-4347(00)00376-5","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"d933f6dd-fa53-54e8-9e01-37a40a08a886","evidence_kind":"source_excerpt","locator":"Lines 434-440","start_line":434,"end_line":440,"excerpt":"## histidine-urocanate-uv\nLight changes the shape of a histidine-derived skin molecule.\nUV exposure converted trans-urocanic-acid standard to cis isomer; UVB produced faster conversion than UVA under the tested conditions.\nModel: In-vitro standards plus analytical measurement of histidine and urocanate isomers in skin washes from eight volunteers.\nLimitations: Photochemistry in standards does not establish a clinical sunscreen effect from oral histidine.\nEvidence access: Primary abstract\nDetermination of histidine and urocanic acid isomers in the human skin by high-performance capillary electrophoresis. · 2000 · https://pubmed.ncbi.nlm.nih.gov/11129077/ · DOI 10.1016/s0378-4347(00)00376-5","model_system":"In-vitro standards plus analytical measurement of histidine and urocanate isomers in skin washes from eight volunteers.","directness":"reported_statement","verification_status":"source_derived_draft","notes":"Original curation paraphrase; evidence access and experimental limitations specified.","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"ce59e6c9-1213-523b-9d0b-400b7a81cd1c","stable_key":"import-911fb3c7-8cc3-5667-b677-5682fab67648","title":"L-Histidine: supply, catabolism, histamine, receptors and cross-nutrient mechanisms (2026-09-19)","document_type":"imported_text","citation_label":"AI-assisted research curation; primary references, access levels and experimental limitations individually identified. 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