title: Photoactivable analogs for labeling 25-hydroxyvitamin D3 serum binding protein and for 1,25-dihydroxyvitamin D3 intestinal receptor protein.
abstract: 3-Azidobenzoates and 3-azidonitrobenzoates of 25-hydroxyvitamin D3 as well as 3-deoxy-3-azido-25-hydroxyvitamin D3 and 3-deoxy-3-azido-1,25-dihydroxyvitamin D3 were prepared as photoaffinity labels for vitamin D serum binding protein and 1,25-dihydroxyvitamin D3 intestinal receptor protein.  The compounds prepared were easily activated by short- or long-wavelength uv light, as monitored by uv and ir spectrometry.  The efficacy of the compounds to compete with 25-hydroxyvitamin D3 or 1,25-dihydroxyvitamin D3 for the binding site of serum binding protein and receptor, respectively, was studied to evaluate the vitamin D label with the highest affinity for the protein.  The presence of an azidobenzoate or azidonitrobenzoate substituent at the C-3 position of 25-OH-D3 significantly decreased (10(4)- to 10(6)-fold) the binding activity.  However, the labels containing the azido substituent attached directly to the vitamin D skeleton at the C-3 position showed a high affinity, only 20- to 150-fold lower than that of the parent compounds with their respective proteins.  Therefore, 3-deoxy-3-azidovitamins present potential ligands for photolabeling of vitamin D proteins and for studying the structures of the protein active sites.
authors.affiliation: Department of Biochemistry, University of Wisconsin, Madison 53706, USA.
authors.forename: A
authors.initials: A
authors.lastname: Kutner
authors.forename: R P
authors.initials: RP
authors.lastname: Link
authors.forename: H K
authors.initials: HK
authors.lastname: Schnoes
authors.forename: H F
authors.initials: HF
authors.lastname: DeLuca
mesh_terms: D001386:Azides / Q000138:chemical synthesis*; D001665:Binding Sites; D001667:Binding, Competitive; D002112:Calcifediol / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism / Q000528:radiation effects; D002117:Calcitriol / Q000031:analogs & derivatives* / Q000737:chemistry / Q000378:metabolism / Q000528:radiation effects; D009578:Nitrobenzenes / Q000138:chemical synthesis*; D019920:Photoaffinity Labels / Q000138:chemical synthesis* / Q000378:metabolism / Q000528:radiation effects; D010782:Photolysis; D018167:Receptors, Calcitriol / Q000737:chemistry / Q000378:metabolism; D014466:Ultraviolet Rays; D014809:Vitamin D-Binding Protein / Q000737:chemistry / Q000378:metabolism
chemical_list: D001386:Azides; D009578:Nitrobenzenes; D019920:Photoaffinity Labels; D018167:Receptors, Calcitriol; D014809:Vitamin D-Binding Protein; D002117:Calcitriol; D002112:Calcifediol