Probing the influences of urea on the interaction of sinomenine with human serum albumin by steady-state fluorescence.

Daojin Li, Dongfeng Hong, Han Guo, Jianjun Chen, Baoming Ji

College of Chemistry and Chemical Engineering, Luoyang Normal University, Luoyang 471022, China.

Journal of photochemistry and photobiology. B, Biology 2012 Dec 5

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The binding of sinomenine to human serum albumin (HSA) in aqueous solution in the absence and presence of urea has been studied by fluorescence and the three-dimensional (3D) fluorescence at pH 7.40. Subdomain IIA binding site of human serum albumin (HSA) was characterized by examining the change in HSA fluorescence. The quenching rate constants and binding constants were calculated in the absence and presence of the denaturant. The results point to a static quenching mechanism operating in the complexes. However, the binding ability of sinomenine to denatured HSA is weaker than that of sinomenine to native HSA. Denaturation of HSA in the presence of urea is almost complete at [urea]≥ 8.0M. Upon unfolding, two fluorescence peaks were observed. One peak was assigned to the fluorescence of Trp-214 residue in a polar environment, and the other peak was assigned to the fluorescence of tyrosine residues. Compared to the free HSA, the HSA-sinomenine complex is more stable in the presence of urea. Copyright © 2012 Elsevier B.V. All rights reserved.

Citation

Daojin Li, Dongfeng Hong, Han Guo, Jianjun Chen, Baoming Ji. Probing the influences of urea on the interaction of sinomenine with human serum albumin by steady-state fluorescence. Journal of photochemistry and photobiology. B, Biology. 2012 Dec 5;117:126-31