The Interaction Of Cu(â…¡), Fe(â…¢), Zn(â…¡) With Serum Albumin And Competitive Binding Study Between Fe(â…¢)and Zn(â…¡) With Serum Albumin Under The Effect Of UV Irradiation

Firstly the effect of UV-C irradiation to human serum albumin and bovine serum albumin has been studied. After irradiation fluorescence quenching occurred swiftly, UV abosorption increased slightly, resonance scattering peaks red shifted significantly. And the IR spectra almost keep unchanged even after 3 day's irradiation, which means the characteristic chemical bonds of serum albumin still exist. Because of the discrepancies in the structure of HSA and BSA , BSA changed more drastic than HSA. Secondly the interaction between metal ions and UV irradiated serum albumins has been studied.It has been found that the binding ability between Cu(â…¡) and Fe(â…¢)ions and albumin get weaker and weaker after albumin being exposed to UV light.This may be the consequence of conformational changes of serum albumin and the photooxidation of Trp residues. Judging from the UV-spectrum the coordination center doesn't change. However the interaction of the Zn(â…¡)-irradiated albumin is quite different from that of the unirradiated system. In the end, the interaction of UV irradiated metal ion-albumin system was studied. When HSA and BSA are irradiated in the presence of metal ions, the Stern-Volmer plots lost linearity and the inflexions increased ,which means the heterogeneous binding sites increased. The coordination center also underwent great changes. The above phenomena may attribute to a kind of double inducement mechanism, UV light induces structural change of HSA and BSA, as a result, the original binding of metal ions to albumin is destroyed to some extent. Consequently, metal ions interact with albumin in a new way to adapt the new structure, the new binding also induces conformational change. UV light and metal ions induce the conformational change simultaneously, thus the change was enhanced. Part Two With UV spectroscopy ,fluorescence spectroscopy and viscosity method,the competitive binding capabilities of Fe(â…¢) and Zn(â…¡) to HSA or BSA at physiological pH have been studied. It was found that the binding capabilities of Fe(â…¢) to serum albumin is much stronger than that of Zn(â…¡), no matter the albumin were irradiated or not . At physiological pH, the UV absorption peaks of the Fe(â…¢) -Zn(â…¡)-serum albumin system were caused by the LMCT transition.With the increase of the concentration of the Fe(â…¢) -Zn(â…¡)-serum albumin system at molar ratio 1:1:1, its coordination center changes from octahedron to square-pyramid.When the concentration of the serum albumin was fixed and the ratio of metal ions to serum albumin increased,there exists similar configuration of the coordination center. After serum albumins were irradiated the change of coordination center become easier.