Comparative phosphorescence and optically detected magnetic resonance studies of fatty acid binding to serum albumin |
| |
Authors: | S Y Mao A H Maki |
| |
Institution: | Department of Chemistry, University of California, Davis 95616. |
| |
Abstract: | The binding of free fatty acid to bovine serum albumin (BSA) and human serum albumin (HSA) was studied by phosphorescence and optical detection of triplet-state magnetic resonance spectroscopy in zero applied magnetic field. We have found that oleic acid perturbs the excited triplet state of Trp-134 but not that of Trp-212 in BSA. The assignment is made by comparing the BSA results with those obtained from oleic acid binding to HSA. The phosphorescence 0,0 band as well as the zero-field splittings of Trp-134 undergoes significant changes upon binding of oleic acid to BSA. Shifts of the 0,0-band wavelength and of the zero-field splittings point to large changes in the Trp-134 local environment which accompany the complex formation. The shifts are progressive until 3-4 mol of oleic acid is added. The spectroscopic changes may be attributed to Stark effects caused by a protein conformational change near Trp-134 in the BSA-oleate complex. Oleic acid binding has a minimal effect on the triplet-state properties of the single Trp-214 of HSA. The binding specificity with regard to chain length and unsaturation is reflected by the differences in the Trp environment when BSA forms complexes with various fatty acids. |
| |
Keywords: | |
|
|