Malavasic M, Poklar N, Macek P, Vesnaver G
Department of Chemistry, University of Ljubljana, Slovenia.
Biochim Biophys Acta. 1996 Apr 3;1280(1):65-72. doi: 10.1016/0005-2736(95)00278-2.
The solvent denaturation of equinatoxin II (EqTxII) in aqueous solutions of urea, guanidine hydrochloride (Gu-HCl) and at various pH values was examined by monitoring changes in the protein intrinsic emission fluorescence spectra and in the fluorescence spectra of the added external probe ANS. It has been observed that EqTxII denaturation is reflected in a strong red shift of intrinsic fluorescence emission maxima accompanied by a simultaneous decrease in fluorescence intensity and that guanidine hydrochloride is significantly more powerful denaturant than urea or changing of pH. Comparison of intrinsic fluorescence spectra of EqTxII denatured by one of the three denaturing agents has shown that the fully denatured states of the protein in Gu-HCl and urea are similar and substantially different from those induced by changing of pH. Furthermore, according to the measurements of the ANS-fluorescence in EqTxII solutions as a function of pH the protein exists at pH values below 2.0 in an acid-denatured compact state.
通过监测蛋白质固有发射荧光光谱以及添加的外部探针 8-苯胺基-1-萘磺酸（ANS）的荧光光谱变化，研究了海葵毒素 II（EqTxII）在尿素、盐酸胍（Gu-HCl）水溶液中以及在不同pH值下的溶剂变性情况。据观察，EqTxII变性表现为固有荧光发射最大值的强烈红移，同时荧光强度降低，且盐酸胍作为变性剂比尿素或pH值变化的作用显著更强。对由三种变性剂之一变性的EqTxII的固有荧光光谱进行比较表明，在Gu-HCl和尿素中蛋白质的完全变性状态相似，且与pH值变化所诱导的状态有很大不同。此外，根据EqTxII溶液中ANS荧光随pH值变化的测量结果，该蛋白质在pH值低于2.0时以酸变性紧密状态存在。
