{"id":"abd1f8eb-a4bb-5654-887c-e521df7f88ed","stable_key":"1deb434a-3547-51a0-a038-87b1ce79ec38:vd-act-skin-thermal-isomerization","predicate":"thermally_isomerizes_to","statement":"Skin-generated previtamin D3 underwent temperature-dependent isomerization to cholecalciferol, taking at least three days to complete under the reported conditions.","claim_class":"mechanistic","status":"source_derived_draft","evidence_grade":"ungraded","direction":"positive","is_public":true,"mechanism_event_id":"beebc6c0-5bd7-569c-be61-2a9ceaa72d58","mechanism_event_label":"The first skin photoproduct rearranges into vitamin D3.","subject":{"id":"a1afa10a-5cad-5821-b11c-35a98b3fc4c5","slug":"previtamin-d3","display_name":"Previtamin D3","entity_type_key":"small_molecule"},"object":{"id":"b162e431-b442-5400-9335-ec91f7875a4e","slug":"cholecalciferol","display_name":"Cholecalciferol","entity_type_key":"small_molecule"},"evidence_count":1,"mechanism_event":{"id":"beebc6c0-5bd7-569c-be61-2a9ceaa72d58","stable_key":"1deb434a-3547-51a0-a038-87b1ce79ec38:vd-act-skin-thermal-isomerization-event","event_type":"biochemical_relationship","label":"The first skin photoproduct rearranges into vitamin D3.","description":"Skin-generated previtamin D3 underwent temperature-dependent isomerization to cholecalciferol, taking at least three days to complete under the reported conditions.","status":"provisional","compartment":null,"participants":[{"entity":{"id":"a1afa10a-5cad-5821-b11c-35a98b3fc4c5","slug":"previtamin-d3","display_name":"Previtamin D3","entity_type_key":"small_molecule"},"role":"substrate","stoichiometry":null,"state_label":"","sequence_order":0,"notes":""},{"entity":{"id":"b162e431-b442-5400-9335-ec91f7875a4e","slug":"cholecalciferol","display_name":"Cholecalciferol","entity_type_key":"small_molecule"},"role":"product","stoichiometry":null,"state_label":"","sequence_order":1,"notes":""}]},"contexts":[{"dimension":"cross_nutrient","value_text":"false","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"evidence_location","value_text":"Primary abstract; skin photochemistry and transport experiments.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"experimental_model","value_text":"Human skin photochemistry","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"exposure","value_text":"Solar UV exposure followed by thermal conversion; at least 3 days for completion.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"limitations","value_text":"Completion time is experiment-specific and is not an absorption half-life.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"nutrient","value_text":"Vitamin D2 and D3","comparator":null,"unit":null,"notes":"","entity":{"slug":"vitamin-d","display_name":"Vitamin D2 and D3","entity_type_key":"chemical_species"}},{"dimension":"nutrient_topic","value_text":"Vitamin D2 and D3 research collection; topical membership is not evidence of a direct dietary effect.","comparator":null,"unit":null,"notes":"","entity":{"slug":"vitamin-d","display_name":"Vitamin D2 and D3","entity_type_key":"chemical_species"}},{"dimension":"organism","value_text":"Homo sapiens","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"plain_language","value_text":"The first skin photoproduct rearranges into vitamin D3.","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"primary_references","value_text":"[holick1980] Photosynthesis of previtamin D3 in human skin and the physiologic consequences. (1980). https://pubmed.ncbi.nlm.nih.gov/6251551/ DOI: 10.1126/science.6251551","comparator":null,"unit":null,"notes":"","entity":null},{"dimension":"tissue_or_cell_type","value_text":"skin","comparator":null,"unit":null,"notes":"","entity":null}],"evidence":[{"id":"eb17f7d4-ca18-5c51-8f71-4a5de7c990d8","evidence_kind":"source_excerpt","locator":"Lines 106-119","start_line":106,"end_line":119,"excerpt":"### vd-act-skin-thermal-isomerization\nSkin-generated previtamin D3 underwent temperature-dependent isomerization to cholecalciferol, taking at least three days to complete under the reported conditions.\nCondition category: normal\nnutrient_topic: Vitamin D2 and D3 research collection; topical membership is not evidence of a direct dietary effect.\nplain_language: The first skin photoproduct rearranges into vitamin D3.\norganism: Homo sapiens\ntissue_or_cell_type: skin\nexperimental_model: Human skin photochemistry\nlimitations: Completion time is experiment-specific and is not an absorption half-life.\nexposure: Solar UV exposure followed by thermal conversion; at least 3 days for completion.\ncross_nutrient: false\nevidence_location: Primary abstract; skin photochemistry and transport experiments.\nnutrient: Vitamin D2 and D3\n[holick1980] Photosynthesis of previtamin D3 in human skin and the physiologic consequences. (1980). https://pubmed.ncbi.nlm.nih.gov/6251551/ DOI: 10.1126/science.6251551","model_system":"Human skin photochemistry","directness":"author_interpretation","verification_status":"source_derived_draft","notes":"Exact curation-document quotation, not publisher quotation. Study references: [holick1980] Photosynthesis of previtamin D3 in human skin and the physiologic consequences. (1980). https://pubmed.ncbi.nlm.nih.gov/6251551/ DOI: 10.1126/science.6251551","relationship":"supports","weight":1.0,"link_notes":"","source":{"id":"c95c763c-5b31-5b3f-a2f8-2dfe5ef0d3ca","stable_key":"import-1deb434a-3547-51a0-a038-87b1ce79ec38","title":"Vitamin D2 and D3: mechanisms, deficiency and nutrient interactions (2026-09-17)","document_type":"imported_text","citation_label":"AI-assisted literature curation; primary study URLs and scope retained in the document and extraction. 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