Chang L S, Yang C C
Department of Biochemistry, Kaohsiung Medical College, Taiwan, ROC.
J Protein Chem. 1993 Oct;12(5):579-83. doi: 10.1007/BF01025122.
Fluorescence measurements of the homologous proteins, notexin and PLA2 enzymes from Naja naja atra, Naja nigricollis, and Hemachatus haemachatus venoms, showed that the wave-length of maximum emission and the quantum yield of their intrinsic fluorescence emission spectra were different. To verify the factors which affected their fluorescence characteristics, the dynamics of tryptophan residues in those homologous proteins were studied by quenching with acrylamide, iodide, and cesium. The degrees of exposure of tryptophanyl groups in notexin and PLA2 enzymes assessed by acrylamide quenching were found to be the major factor that determined their fluorescence characteristics. However, the positively charged groups surrounding tryptophan residues of PLA2 enzymes from N. naja atra and N. nigricollis venoms might affect the quantum yield of their fluorophores. Tryptophan residues of notexin were in an environment with less fluctuation, which did not allow free diffusion of ionic quencher. This might render its tryptophan residues to fluoresce at a shorter wavelength. These results suggested that the structural determinants affecting the intrinsic fluorescence emission of homologous proteins can be easily assessed by quenching studies.
对来自眼镜蛇、黑颈眼镜蛇和裂蝰蛇毒液中的同源蛋白——诺维毒素和磷脂酶A2进行荧光测量，结果表明，它们的最大发射波长及其固有荧光发射光谱的量子产率各不相同。为了验证影响其荧光特性的因素，通过用丙烯酰胺、碘化物和铯进行猝灭，研究了这些同源蛋白中色氨酸残基的动力学。通过丙烯酰胺猝灭评估发现，诺维毒素和磷脂酶A2中色氨酸基团的暴露程度是决定其荧光特性的主要因素。然而，来自眼镜蛇和黑颈眼镜蛇毒液的磷脂酶A2中色氨酸残基周围的带正电荷基团可能会影响其荧光团的量子产率。诺维毒素的色氨酸残基所处环境波动较小，这使得离子猝灭剂无法自由扩散。这可能导致其色氨酸残基在较短波长下发出荧光。这些结果表明，通过猝灭研究可以轻松评估影响同源蛋白固有荧光发射的结构决定因素。
