title: The interaction between Ag+ and bovine serum albumin: a spectroscopic investigation.
abstract: By using spectroscopic methods, we probed the interaction of Ag(+) with bovine serum albumin (BSA) in an aqueous environment. Fluorescence of BSA quenched by Ag(+) is a dynamic quenching process. Two binding modes-a strong one at low concentration of Ag(+) and a weak one at high concentration were found. The association constant (K(A)) and the number of binding sites (n) were 4.88×10(3)M(-1) and 1.17 for strong binding, and 17.6M(-1) and 0.547 for weak binding at 293K. The results of thermodynamic parameters ΔH(θ), ΔG(θ) and ΔS(θ) for instinct binding modes at different temperatures indicated that the hydrogen bonding and van der Waals interaction play a major role for low Ag(+)/BSA ratio while electrostatic association for high Ag(+)/BSA ratio. Data of UV-Vis and Circular dichroism (CD) suggested that with the increasing amount of Ag(+), the secondary structure undergoes a decrease in α-helix and an increase in β content and the backbone of BSA experiences a micro-environmental alteration. Furthermore, the distance r between donor (Trp-212) and acceptor (Ag(+)) was evaluated to be 10nm according to nonradiative energy transfer theory.
authors.affiliation: Shandong Provincial Key Laboratory of Water Pollution Control and Resource Reuse, School of Environmental Science and Engineering, Shandong University, China–America CRC for Environment & Health, Shandong Province, 27# Shanda South Road, Jinan 250100, PR China.
authors.forename: Xingchen
authors.initials: X
authors.lastname: Zhao
authors.forename: Rutao
authors.initials: R
authors.lastname: Liu
authors.forename: Yue
authors.initials: Y
authors.lastname: Teng
authors.forename: Xiaofang
authors.initials: X
authors.lastname: Liu
mesh_terms: D002942:Circular Dichroism; D004347:Drug Interactions; D004735:Energy Transfer; D004785:Environmental Pollutants / Q000737:chemistry; D046529:Microscopy, Electron, Transmission; D015394:Molecular Structure; D017434:Protein Structure, Tertiary; D012710:Serum Albumin, Bovine / Q000737:chemistry*; D012834:Silver / Q000097:blood / Q000737:chemistry*; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet; D013329:Structure-Activity Relationship; D013816:Thermodynamics
chemical_list: D004785:Environmental Pollutants; D012710:Serum Albumin, Bovine; D012834:Silver