title: Analysis of local polarity change around Cys34 in bovine serum albumin during N-->B transition by a polarity-sensitive fluorescence probe.
abstract: The change trend of the local environment of Cys34 domain in bovine serum albumin has been studied as a function of pH value by using thiol-specific and polarity-sensitive fluorescent probe 3-(4-chloro-6-p-maleimidylphenoxyl-1,3,5-triazinylamino)-7-dimethylamino-2-methyl-phenazine. The local polarity of the Cys34 domain is found to rise with the increase of pH values, and the corresponding dielectric constant is raised from 12.8 at pH 6.0 to 23.3 at pH 9.1. The result shows that the environment of the Cys34 domain is rather hydrophobic in normal state at pH 6.0 and becomes a little hydrophilic in the course of N-->B transition, which may be attributed to the slight unfolding of the protein and thus the increasing of exposure of the previously relatively buried Cys34. In addition, the increased dielectric constant (23.3) is much lower than that (80.1) of water, suggesting that the unfolding of bovine serum albumin does not cause the full exposure of the Cys34 to the aqueous media during the transition.
authors.affiliation: Beijing National Laboratory for Molecular Sciences, Institute of Chemistry, Chinese Academy of Sciences, Beijing 100190, China.
authors.forename: Xiaochun
authors.initials: X
authors.lastname: Wang
authors.forename: Lihong
authors.initials: L
authors.lastname: Guo
authors.forename: Huimin
authors.initials: H
authors.lastname: Ma
mesh_terms: D000818:Animals; D002417:Cattle; D002942:Circular Dichroism; D003545:Cysteine / Q000032:analysis* / Q000737:chemistry; D005456:Fluorescent Dyes / Q000737:chemistry*; D006863:Hydrogen-Ion Concentration; D057927:Hydrophobic and Hydrophilic Interactions; D015394:Molecular Structure; D017510:Protein Folding; D017434:Protein Structure, Tertiary; D012710:Serum Albumin, Bovine / Q000032:analysis* / Q000737:chemistry; D013050:Spectrometry, Fluorescence; D013056:Spectrophotometry, Ultraviolet
chemical_list: D005456:Fluorescent Dyes; D012710:Serum Albumin, Bovine; D003545:Cysteine