title: Synthesis of 25-hydroxyvitamin D3 3 beta-3'-[N-(4-azido-2-nitrophenyl)amino]propyl ether, a second-generation photoaffinity analogue of 25-hydroxyvitamin D3: photoaffinity labeling of rat serum vitamin D binding protein.
abstract: Vulnerability of 25-hydroxy-[26,27-3H]vitamin D3 3 beta-N-(4-azido-2-nitrophenyl)glycinate, a photoaffinity analogue of 25-hydroxyvitamin D3 (25-OH-D3) (Ray et al., 1986) toward standard conditions of carboxymethylation promoted us to synthesize 25-hydroxyvitamin D3 3 beta-3'-[N-(4-azido-2-nitrophenyl)amino]propyl ether (25-ANE), a hydrolytically stable photoaffinity analogue of 25-OH-D3, and 25-hydroxyvitamin D3 3 beta-3'-[N-(4-azido-2-nitro-[3,5-3H]phenyl)amino] propyl ether (3H-25-ANE), the radiolabeled counterpart of 25-ANE. Competitive binding assays of 25-OH-D3 and 25-ANE with rat serum demonstrated that 25-ANE competes for the 25-OH-D3 binding site in rat serum vitamin D binding protein (rDBP). On the other hand, UV exposure of a sample of purified rat DBP (rDBP), preincubated in the dark with 3H-25-ANE, covalently labeled the protein. However, very little covalent labeling was observed in the absence of UV light or in the presence of a large excess of 25-OH-D3. These results provide strong evidence for the covalent labeling of the 25-OH-D3 binding site in rDBP by 3H-25-ANE.
authors.affiliation: Vitamin D Laboratory, Boston University School of Medicine, Massachusetts 02118.
authors.forename: R
authors.initials: R
authors.lastname: Ray
authors.forename: R
authors.initials: R
authors.lastname: Bouillon
authors.forename: H
authors.initials: H
authors.lastname: Van Baelen
authors.forename: M F
authors.initials: MF
authors.lastname: Holick
mesh_terms: D000345:Affinity Labels; D000818:Animals; D001345:Autoradiography; D001386:Azides / Q000138:chemical synthesis*; D001667:Binding, Competitive; D002112:Calcifediol / Q000031:analogs & derivatives* / Q000138:chemical synthesis / Q000737:chemistry*; D004591:Electrophoresis, Polyacrylamide Gel; D010777:Photochemistry; D051381:Rats; D014466:Ultraviolet Rays; D014809:Vitamin D-Binding Protein / Q000737:chemistry*
chemical_list: D000345:Affinity Labels; D001386:Azides; D014809:Vitamin D-Binding Protein; C068845:25-hydroxyvitamin D3 3'-(N-(4-azido-2-nitrophenyl)amino)propyl ether; D002112:Calcifediol