Complementary fluorescence and phosphorescence study of the interaction of brompheniramine with human serum albumin.

Silvia Tardioli, Ivonne Lammers, Jan-Hein Hooijschuur, Freek Ariese, Gert van der Zwan, Cees Gooijer

Department of Biomolecular Analysis and Spectroscopy, LaserLaB, VU University Amsterdam, De Boelelaan 1083, 1081 HV Amsterdam, The Netherlands.

The journal of physical chemistry. B 2012 Jun 21

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Binding of the antihistamine drug brompheniramine (BPA) to human serum albumin (HSA) is studied by measuring quenching of the fluorescence and room temperature phosphorescence (RTP) of tryptophan. The modified Stern-Volmer equation was used to derive association constants and accessible fractions from the steady-state fluorescence data. Decay associated spectra (DAS) revealed three tryptophan fluorescence lifetimes, indicating the presence of three HSA conformations. BPA causes mainly static quenching of the long-living, solvent-exposed conformer. RTP spectra and lifetimes, recorded under deoxygenated conditions in the presence of 0.2 M KI, provided additional kinetic information about the HSA-BPA interactions. Fluorescence DAS that were also recorded in the presence of 0.2 M KI revealed that the solvent-exposed conformer is the major contributor to the RTP signal. The phosphorescence quenching is mostly dynamic at pH 7 and mostly static at pH 9, presumably related to the protonation state of the alkylamino chain of BPA. This provides direct insight into the binding mode of the antihistamine drug, as well as kinetic information at both the nanosecond and the millisecond time scales.

Citation

Silvia Tardioli, Ivonne Lammers, Jan-Hein Hooijschuur, Freek Ariese, Gert van der Zwan, Cees Gooijer. Complementary fluorescence and phosphorescence study of the interaction of brompheniramine with human serum albumin. The journal of physical chemistry. B. 2012 Jun 21;116(24):7033-9