title: Binding of doxyl stearic spin labels to human serum albumin: an EPR study.
abstract: The binding of spin-labeled fatty acids (SLFAs) to the human serum albumin (HSA) examined by electron paramagnetic resonance (EPR) spectroscopy was studied to evaluate the potential of the HSA/SLFA/EPR technique as a biomarking tool for cancer. A comparative study was performed on two spin labels with nitroxide groups attached at opposite ends of the fatty acid (FA) chain, 5-doxyl stearic (5-DS) and 16-doxyl stearic (16-DS) acid. The effects of incubation time, different [SLFA]/[HSA] molar ratios, ethanol, and temperature showed that the position of the nitroxide group produces certain differences in binding between the two SLFAs. Spectra for different [SLFA]/[HSA] molar ratios were decomposed into two spectral components, which correspond to the weakly and strongly bound SLFAs. The reduction of SLFA with ascorbate showed the existence of a two component process, fast and slow, confirming the decomposition results. Warfarin has no effect on the binding of the two SLFAs, whereas ibuprofen significantly decreases the binding of 5-DS and has no effect on 16-DS. Together, the results of this study indicate that both SLFAs, 5-DS and 16-DS, should be used for the study of HSA conformational changes in blood induced by various medical conditions.
authors.affiliation: Faculty of Physical Chemistry, University of Belgrade , Studentski trg 12-16, P.O. Box 47, 11158 Belgrade, Serbia.
authors.forename: Aleksandra A
authors.initials: AA
authors.lastname: Pavićević
authors.forename: Ana D
authors.initials: AD
authors.lastname: Popović-Bijelić
authors.forename: Miloš D
authors.initials: MD
authors.lastname: Mojović
authors.forename: Snežana V
authors.initials: SV
authors.lastname: Šušnjar
authors.forename: Goran G
authors.initials: GG
authors.lastname: Bačić
mesh_terms: D001205:Ascorbic Acid / Q000737:chemistry; D003497:Cyclic N-Oxides / Q000737:chemistry / Q000378:metabolism; D004578:Electron Spin Resonance Spectroscopy; D000431:Ethanol / Q000737:chemistry; D006801:Humans; D007052:Ibuprofen / Q000737:chemistry; D011485:Protein Binding; D012709:Serum Albumin / Q000737:chemistry* / Q000378:metabolism; D013113:Spin Labels; D013696:Temperature; D014859:Warfarin / Q000737:chemistry
chemical_list: D003497:Cyclic N-Oxides; D012709:Serum Albumin; D013113:Spin Labels; C005072:5-doxylstearic acid; D000431:Ethanol; C032363:16-nitroxystearic acid; D014859:Warfarin; D001205:Ascorbic Acid; D007052:Ibuprofen