Interactions Between U(Ⅵ) And Bovine Serum Albumin/Heptapeptide

Uranium is a toxic and radioactive heavy metal. It is believed that the major deleterioushealth effects of uranium poisoning arise from biochemical interactions in vivo, instead ofradiological effects. Uranium entering the food chain finally through migration and diffusionprocess in environmental media, poses a great potential risk to human exposure. With the rapiddevelopment of nuclear power, nuclear proliferation and nuclear security are paied moreattention. Interest in bio-toxicology of uranium has been growing enormously in recent years.Serum albumins such as bovine serum albumin (BSA) have been used to study the interactionswith metals, since they are the most abundant protein constituent in the blood plasma, and playmultiple physiological roles, including buffering and nutrition in vivo. Besides, they play animportant role in binding and transporting of essential, therapeutic, and toxic metals. However,the investigations about the interactions between serum albumins and U(VI) are rare.However, these studies of U(VI) binding to proteins mostly focus on macroscopic aspectssuch as conditions thermodynamic equilibrium constant, whereas metal-binding-inducedstructural change of the proteins is less well understood, although it is of highly significance forunderstanding the corresponding biological functional changes of associated proteins. On theother hand, spectroscopic method such as Fourier transformation infrared spectroscopy (FT-IR)has been recognized as a powerful tool for determining the chemical structure changes ofproteins. The amide I band (1700-1600cm-1) in FT-IR is primarily used to determinate secondarystructures of proteins. FT-IR spectroscopy implemented with attenuated total reflection (ATR)has been widely used to monitor the secondary structural changes of biological sample.In the present work, fluorescence spectroscopy in combination with FT-IR/ATR was used to investigate the interactions between U(VI) and BSA in aqueous solutions at physiological pH.The binding mechanism between uranyl cation and BSA with respect to the fluorescencequenching constants, binding constants, and the binding site number was investigated at differenttemperatures. Moreover, the changes of conformational changes of BSA induced by binding ofU(VI) were examined by FT-IR spectroscopy，using the second derivative and curve fittingtechniques. The α-helix of BSA-U(VI) complexes decreased significantly compared to the nativeBSA. Correspondingly, the β-sheets, turns, and random coil structures all increased. It meant thata part of α-helix was transformed progressively into other structures. The secondary structuralchanges of BSA were affected due to the U(VI) binding. Specific conformation is very importantto the specific biological function of poteins. The changes of second structural changes of BSAcould inhibit or damage its biological activity，which will provide some theoretical basis for thestudies on the toxicity mechanism of U(VI) in the biological.We repotred the studies of interaction interactions between U(VI) and BSA at molecular level.And the results have, to a certain degree, indicated the mechanism for interactions between U(VI)and proteins in aqueous solutions. The structure architecture changes of the protein may disruptor daaged its native biological activity. Our study would shed light on further understanding thepossible toxicity mechanism of U(VI) to protein.In addition, we explored tentatively the effect of pH value to the interaction between U(VI)and heptapeptide HPPSPPH via the fluorescence spectroscopy and UV-vis spectrophotometerspectrometry.