白茯苓凝集素的荧光光谱研究

白茯苓凝集素（ＳＬＬ）分子中含有４个色氨酸（Ｔｒｐ）残基，ＮＢＳ修饰测得这４个Ｔｒｐ残基位于分子表面。ＳＬＬ在天然状态下荧光发射峰位于３３５ｎｍ处，离子强度和温度对其荧光光谱均无明显的影响。ＮＢＳ修饰后的ＳＬＬ失去凝血活性，相应荧光光谱的强度减弱，荧光发射峰发生蓝移，提示ＳＬＬ的构象发生改变。用ＫＩ·ＣｓＣｌ和丙烯酰胺淬灭剂研究ＳＬＬ分子中Ｔｒｐ残基的微环境，发现丙烯酰胺和ＣｓＣｌ能淬灭分子中１００％和５０％的Ｔｒｐ残基的荧光，而ＫＩ完全不能淬灭ＳＬＬ分子中Ｔｒｐ残基的荧光，因此Ｔｒｐ残基周围存在阴离子区，或者Ｔｒｐ残基处于分子表面的疏水环境中。

A STUDY OF LECTIN FROM SMILAX LAUCEAEFOLA ROXB VAR.OPACA A.DC BY FLUORESCENCE SPECTROSCOPY

Tryptophan (Trp) residues of lectin from Smilax lauceafolia Roxb Var. opaca A. DC(SLL) were determined with p-dimethyiamino (DBA). The result showed thatthere were 4 Trp residues in SLL. They were an on the surface of SLL, as demonstrated bychemical modification with N-Bromosuccinimide (NBS). The fluorescence spectra of SLL excited at 280nm and 295nm showed a maximum at 335nm. Change of temperature didn't obviously affect the fluorescence emission spectra. The fluorescence intensity of SLL modified byNBS decreased with an excitation wavelength of 295mp and the emission peak had ablue-shift of 7nm. SLL modified by NBS lost the agglutination activity. These resuits impliedthat conformation of SLL modaified by NBS was changed. The Trp residue fluorescence ofSLL was not quenched by KI, but 50% and 100%was quenched by CsCl and acrylamiderespectively. We deduced that the Trp residues of SLL were located in the hydrophobic pocketof the glycoprotein surface.