Microscopic Structure Of Cu(â…¡),Zn(â…¡) Aqueous Solutions And Their Effects On The Conformation Of Bovine Serum Albumin

As essential microelements, copper and zinc have important biological functions for human body. There had many meaningful studies on their toxicological effects. However, during the process of causing diseases to human body by copper and zinc, water act as important role which is the solvent and maintains the conformation stabilization of proteins. In this thesis, the effect of Cu²⁺,Zn²⁺ on water cluster structure and the structure of its hydrated ions were studied, furthermore, the structures of water cluster and hydrated ions were changed by freeze-thaw disposing, and the change rule of BSA conformation correlated with different structures of water cluster and hydrated ions were investigated too. The detailed work of this thesis has been set out as follows:The influences of ZnCl₂,AlCl₃,CuCl₂,CuSO4 and their individual cations and anions on the water structure were studied with viscosity measurement,17O-NMR and Raman spectra. It was proved that all these compounds increased water association and the size of water clusters. The degree of cations increasing effect on water association were Al₃+>Zn²⁺>Cu²⁺, and Cl- broke more water clusters than SO42-.After freeze-thaw disposed on the trinal distilled water and different concentrations of ZnCl₂,AlCl₃ and CuCl₂ solutions, the water cluster size became smaller, the conductivity increased, the 17O-NMR chemical shift and half-height widths of peaks decreased obviously, and these structures could hold at least 8 hours.The first hydrated shell coordination structure of Cu²⁺ and Zn²⁺ hydrated ions changed with the increasing of aqueous solution concentrations. Cu²⁺ had 3～4 oxygen nearest neighbors with the Cu-O distance being 1.92～1.98 ?. With increasing salt concentration, the coordination station of oxygen atom coordinated with Cu²⁺ were replaced which resulted in the coordination number of Cu²⁺ decreased and the Cu-O distance increased in its first coordination shell; the coordination number of Zn-O were 5～6 with the distance being 2.03～2.05 ?, the proportion of hydrolysis complexes Zn(OH)n(H2O)m(2-n) was increased with the aqueous solution concentrations increasing, which induced the Zn-O coordination number and distance minished.The first coordination shell structure of Cu²⁺ and Zn²⁺ hydrated ions changed obviously after freeze-thaw disposed resulted from the enriching of free water molecular and enhancing of hydrated effects of metal ions. The coordination number of Cu²⁺ and thermal disorder degree increase in first coordination shell, and there was no obvious chang rule of Cu-O distance; the Zn-O coordination number and distance increased in first coordination shell after freeze-thaw treatment.Cu²⁺ and Zn²⁺ combined with BSA strongly. The breaking effect on hydrogen bonds enhanced with the mole ratio of metal ions and BSA increasing, and for the increasing effect of Cu²⁺ and Zn²⁺on water association, the hydrophobic effect between H2O and BSA molecules decreased. These two reasons resulted in the change of stability of BSA and decreasing of the amounts ofα-helices. To BSA solution of 5.0×10-6 mol·L-1, there was a intermediate state of the amounts ofα-helices increased for an enhancement in the hydrophobic interactions of BSA molecule with Cu²⁺ and Zn²⁺ when the mole ratio of Cu²⁺ and BSA were 5～15, Zn²⁺ and BSA were 10～15.It can be conclude that the interaction of CuCl₂ and Zn(NO3)2 solutions on BSA weakened in 8 hours after freeze-thaw disposing on CuCl₂ and Zn(NO3)2 solutions, which resulted in the weakening of UV hyperchromic effect,FTIR amideâ… andâ…¡bands shift and the change of CD spectra intensity, the decreasing of breaking effect on hydrogen bonds inα-helices of BSA, and the lessening of decreasing degree of theα-helices amounts. The effect on BSA conformation was more obviously when CuCl₂ and Zn(NO3)2 reacted with BSA dissolved in the trinal distilled water after freeze-thaw disposed.