Chemical changes in bovine serum albumin photoinduced by pterin

ANDRÉS H. THOMAS; BEATRIZ ZURBANO; CAROLINA LORENTE; JAVIER SANTOS; ERNESTO A. ROMAN; M. LAURA DÁNTOLA

JOURNAL OF PHOTOCHEMISTRY AND PHOTOBIOLOGY B-BIOLOGY

ELSEVIER SCIENCE SA

Lugar: Amsterdam; Año: 2014 vol. 141 p. 262 - 268

1011-1344

The exposure to UV-A radiation of bovine serum albumin (BSA) in aerated aqueous solution in the presence of pterin (Ptr), results in chemical and conformational modifications of the protein. Ptr belongs to a family of heterocyclic compounds that are well-known type I (electron-transfer) and type II (singlet oxygen) photosensitizers. The evolution of the photosensitized processes was followed by UV/vis spectrophotometry and fluorescence spectroscopy indicating that tryptophan (Trp) and tyrosine (Tyr) residues were affected. Additionally, conformational changes were evaluated by electrophoresis (SDS-PAGE) and size exclusion chromatography coupled with dynamic light scattering detection, showing that BSA undergoes dimerization, via the formation of Tyr radicals. The degradation of Trp residues takes place faster than the oligomerization of the protein. The photosensitized process is initiated by an electron transfer from BSA to the triplet excited stated of Ptr, being a purely dynamic mechanism.