The Study Of Binding Equilibrium And Subsequent Effect Between Co(Ⅱ),Fe(Ⅱ),Phosphotungstic Acid And HSA Or BSA

Part IA notable hysteretic effect has been observed in the interaction of Co( II) with human serum albumin (HSA) or bovine serum albumin (BSA) by using UV-Visible spectrometry at physiological pH(7.43), which shows that the binding between Co( II) and HSA or BSA may induce a slow transition of HSA or BSA (A-B transition). And the rate constants and activation parameters of this transition have been measured and discussed. It is inferred that such a conformation transition may occur due to the binding of the first Co( II) ion with the peptide segment of N-terminal residues 1-3, which results in a "hinged movement" of the relatively hydrophobic "valley" in the IA subdomain. This process leads to a slow conformational transition in the albumins, makes the other binding sites of Co( II) exposed, and shows a positive cooperativity effect. The LMCT(ligand to metal charge transition) bands of Co( II )-HSA and Co( II)BSA systems also show a kind of hypochromic effect featuring the dipole-dipole interaction mechanism. This phenomenon israrely report.Part IIA notable hysteretic effect has been observed in the interaction of Fe( II) with human serum albumin (HSA) or bovine serum albumin (BSA) by usln2 UV-Visible spectrometry at the isoelectric point pH(5.3), which shows that the binding between Fe( II) and HSA or BSA may induce a slow conformational transition of HSA or BSA from the conformation of weaker affinity for Fe( II) to the one of stronger affinity (T-R transition). And the rate constants and activation parameters of this transition have been measuredo Project supporte4by the National Science Foundation of China (NO. 299621001),and the Foundation for Talents of the Ten~ Hunred. Thousand in Guangxi.3and discussed. It is inferred that such a conformation transition may occur due to the binding of the first Fe( II) ion with sreum albumin. This process leads to a slow conformational transition in the albumins, makes the other binding sites of Fe( II) exposed, and shows a positive cooperativity effect. The binding equilibrium between Fe( II) and human serum albumin (HSA) or bovine serum albumin (BSA) has been studied by equilibrium dialysis for the first time. The Scatchard analysis indicated that there exist one strong binding site of Fe( II) in both HSA and BSA, and the successive stability constants of Fe( II )-HSA and Fe( II )-BSA systems are obtained by non-linear least-squares methods fitting Bjerrum formula.Part IllThe binding equilibrium between phosphotungstic acid (H7[P(W20,)6] o XH2O;PTA) and human serum albumin (HSA) or bovine serum albumin (BSA) has been studied by UV-Vis, fluorescence spectroscopies and equilibrium dialysis. It has been observed for the first tune that UV absorption enhanced and the fluorescence quenched as the PTA binding to HSA or BSA at physiological pH (7.43 ± 0.02). The Scatchard analysis indicats that there exist one strong binding site of PTA in both HSA and BSA, and the successive stable constants of these two systems are obtained by non-linear least-squares methods fitting Bjerrum formula.