Studies on the interaction between Ag(+) and human serum albumin.
The interaction between Ag(+) and human serum albumin (HSA) has been intensively studied by means of equilibrium dialysis, ligand-to-metal charge transition (LMCT) bands, circular dichroism (CD) and Raman spectroscopy. Scatchard analysis of the results of equilibrium dialysis indicates the presence of two types of binding sites for Ag(+) on HSA, and the orders of magnitude of binding stability constants are found to be 10(5) and 10(4), respectively. During the binding process, a gradual increase in absorbance values of LMCT bands is observed with time-scanning UV absorption spectra, implying the Ag(I) centers are continually formed in HSA. The time-scanning CD spectra provide evidence that the binding of Ag(+) induces HSA to undergo a slow rearrangement of tertiary structure, and to change from the original conformation in the absence of Ag(+) (B-state) to conformation binding with Ag(+) (A-state). The rate constants and activation free energy of A-B transition are calculated. The Raman spectrum of Ag(I)-HSA system shows distinct vibration bands at 224 and 246 cm(-1) in the low-frequency region, which significantly reveal the formation of Ag-S and Ag-N bonds. In addition, the electrostatic interaction between Ag(+) and negatively charged oxygen is also detected with Raman spectroscopy.
Shen
Xing-Can
XC
Department of Chemistry, Nankai University, 94 Weijin Road, Tianjin 300071, China.
Liang
Hong
H
Guo
Jun-Huai
JH
Song
Cheng
C
He
Xi-Wen
XW
Yuan
Yu-Zhou
YZ
D001665:Binding Sites; D002942:Circular Dichroism; D003956:Dialysis / Q000379:methods; D006801:Humans; D007700:Kinetics; D011485:Protein Binding; D012709:Serum Albumin / Q000378:metabolism*; D012834:Silver / Q000737:chemistry / Q000378:metabolism*; D013056:Spectrophotometry, Ultraviolet / Q000379:methods; D013059:Spectrum Analysis, Raman; D013816:Thermodynamics
D012709:Serum Albumin; D012834:Silver