中文摘要：

利用荧光光谱和紫外光谱研究了脲（Urea）对牛血清白蛋白（BSA）结构的影响以及氧氟沙星（Oflx）与脲诱导的BSA结合的情况。结果显示：Urea诱导BSA变性历经两步、三态且伴随中间态形成的过程中,随着Urea浓度的增大,BSA荧光强度降低并先蓝移（344～336nm）,后又红移至350nm.Urea浓度在4.6～5.2mol/L范围时,Oflx对BSA中间态有强的猝灭作用（KQ=10.46×104L/mol,Urea4.8mol/L）和较大的结合常数（KA=3.8807×105L/mol,Urea4.8mol/L）,但是结合位点数小（n=0.76,Urea5.0mol/L）,能量传递效率低（E=0.3002,Urea4.8mol/L）。同步荧光光谱显示：Urea诱导BSA去折叠时,色氨酸残基（Trp-212）微环境并未发生改变,而酪氨酸残基（Tyr）的最大荧光发射峰蓝移,Oflx的加入诱导Trp-212的微环境更具疏水性，Oflx加速了Urea对BSA的失活作用。

英文摘要：

Structural alteration of urea-induced bovine serum albumin （BSA） and interaction of oflxacin （Oflx） with urea-induced BSA were investigated by UV-Vis and fluorescence spectroscopy. The results indicated that BSA followed a two-step, three-state transition with an intermediate in the process of unfolding. With increasing the concentration of urea, it can be found that the fluorescence of BSA decreased early with a blue shift of about 8 nm （from 344 to 336 nm） and subsequently a red shift to 350 nm. When urea concentrations varied from 4.6 to 5.2 mol/L, oflx quenched the fluorescence of an intermediate of BSA with the optimal condition as fluorescence quenching constants （KQ= 10.46×10^4 L/mol, urea 4.8 mol/L） and binding constants （KA=3.8807×10^5 L/mol, urea 4.8 mol/L）, whereas with small binding sites （n=0.76, urea 5.0 mol/L） and low energy transfer efficiency （E=0.3002, urea 4.8 mol/L）. Synchronous fluorescence spectrometry showed that during the unfolding of BSA induced by urea, tryptophan residue （Trp-212） residue rnicroenvironment had no changes, at the same time the maximal fluorescence peak of tyrosine residues （Tyr） shifted towards short-wavelength. The introduction of oflx indued Tip microenvironment to be more hydrophobic, which also accelerated the denaturation of BSA by urea.