title: Photophysical studies on the supramolecular photochirogenesis for the photocyclodimerization of 2-anthracenecarboxylate within human serum albumin.
abstract: The mechanism for the chirogenesis in the photocyclodimerization of 2-anthracenecarboxylate (AC) bound to human serum albumin (HSA) was investigated using time-resolved fluorescence measurements in the presence of HSA inhibitors and/or an AC singlet excited state quencher. The photophysical studies were correlated with product studies to explain the high enantiomeric excess (ee) observed for the chiral photoproducts. AC binds to HSA in five different binding sites with decreasing affinities. AC bound to the sites with the highest affinity (sites 1 and 2) is unreactive, and the AC can be displaced from these sites by the use of known inhibitors. Time-resolved fluorescence studies isolated a singlet excited state AC bound to a site which exhibited moderate protection from interactions with species in the aqueous phase. This site was assigned to binding site 3, where the chiral photoproducts are formed with a high ee based on the correlation of the photophysical studies with product studies in the presence of a quencher. These results show that the use of inhibitors for multiple binding site proteins is useful to uncover the properties of binding sites for which guest binding has only moderate affinity and where the photophysical characterization of these binding sites is not possible in the absence of inhibitors.
authors.affiliation: Department of Chemistry, University of Victoria, P.O. Box 3065, Victoria, British Columbia V8W 3V6, Canada.
authors.forename: Tamara C S
authors.initials: TC
authors.lastname: Pace
authors.forename: Masaki
authors.initials: M
authors.lastname: Nishijima
authors.forename: Takehiko
authors.initials: T
authors.lastname: Wada
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Inoue
authors.forename: Cornelia
authors.initials: C
authors.lastname: Bohne
mesh_terms: D000873:Anthracenes / Q000737:chemistry* / Q000378:metabolism*; D001665:Binding Sites; D001667:Binding, Competitive; D002264:Carboxylic Acids / Q000737:chemistry* / Q000378:metabolism*; D006801:Humans; D007463:Iodobenzoates / Q000378:metabolism / Q000494:pharmacology; D008697:Methane / Q000031:analogs & derivatives / Q000378:metabolism / Q000494:pharmacology; D009595:Nitroparaffins / Q000378:metabolism / Q000494:pharmacology; D010782:Photolysis; D012709:Serum Albumin / Q000037:antagonists & inhibitors / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D013237:Stereoisomerism; D013379:Substrate Specificity; D013997:Time Factors
chemical_list: C476641:2-anthracenecarboxylate; D000873:Anthracenes; D002264:Carboxylic Acids; D007463:Iodobenzoates; D009595:Nitroparaffins; D012709:Serum Albumin; D008697:Methane; C008640:nitromethane