title: Influences of urea and guanidine hydrochloride on the interaction of 6-thioguanine with bovine serum albumin.
abstract: The interaction of 6-thioguanine (6-TG) and bovine serum albumin (BSA) in the absence and presence of denaturant (urea and Guanidine hydrochloride) was investigated by fluorescence spectroscopic techniques. Changes of fluorescence intensity both in F(304) and in F(348) of BSA reflected increasing participation of tyrosine fluorescence in the total emission with increasing denaturant, which indicated that energy transfer from tyrosyl residues to tryptophanyl residues became less efficient in the denatured tertiary protein structure. The quenching effects of 6-TG were shown not only on the native but also on the unfolded form of BSA. The quenching constants and binding constants were calculated from the fluorescence spectra of the BSA/6-TG complex both in the absence and presence of the denaturant. The data suggested that the quenching constants and binding constants of 6-TG for BSA decreased with increasing concentration of denaturant. The spectroscopic analysis also showed antidenaturant properties of 6-TG under both denaturant conditions.
authors.affiliation: State Key Laboratory of Bioelectronics, School of Biological Science & Medical Engineering, Southeast University, Si Pai Lou 2#, Nanjing 210096, PR China.
authors.forename: Peng
authors.initials: P
authors.lastname: Qu
authors.forename: Hua
authors.initials: H
authors.lastname: Lu
authors.forename: Xiaoyu
authors.initials: X
authors.lastname: Ding
authors.forename: Yi
authors.initials: Y
authors.lastname: Tao
authors.forename: Zuhong
authors.initials: Z
authors.lastname: Lu
mesh_terms: D000818:Animals; D002021:Buffers; D002417:Cattle; D019791:Guanidine / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration / Q000187:drug effects; D007700:Kinetics; D011489:Protein Denaturation / Q000187:drug effects; D012710:Serum Albumin, Bovine / Q000378:metabolism*; D013050:Spectrometry, Fluorescence; D013866:Thioguanine / Q000737:chemistry / Q000378:metabolism*; D014508:Urea / Q000494:pharmacology*
chemical_list: D002021:Buffers; D012710:Serum Albumin, Bovine; D014508:Urea; D013866:Thioguanine; D019791:Guanidine