NBD-Cl与头发表面半胱氨酸残基的相互作用研究

在碱性条件下用巯基乙酸使头发表面角蛋白质胱氨酸转为半胱氨酸残基,再以荧光试剂NBD-Cl着色处理头发。采用荧光光谱法和衰减式全反射傅立叶红外光谱法研究头发表面半胱氨酸残基与NBD-Cl的相互作用。结果表明该相互作用受处理溶液介质pH的影响,随溶液pH2～5改变λem-max发生红移。介质pH3处理的发样NBD-Cl取代位点可能为半胱氨酸上巯基。介质pH3处理的发样表面衰减式全反射红外光谱结果出现硝基对称伸缩振动峰,进一步支持NBD-Cl与头发表面半胱氨酸发生特异性结合的结论。NBD-Cl浓度改变对NBD-Cl与头发表面基团(巯基或胺基)反应的选择性无影响。实验结果表明Cu2+、Pb2+、Fe3+减弱NBD-Cl与头发表面半胱氨酸残基的相互作用,Ni2+的存在基本无影响。

The Reaction of NBD-Cl and Cysteine Residue on Hair Cuticle

In this work, thioglycolie acid was used as a reducing agent in the disconnection of -SS- groups under alkaline condi- tion which make eystine transfer to cysteine residue on hair cuticle. The reaction of NBD-CI and cysteine residue of human hair was investigated with attenuated total reflection fourier transform infrared spectroscopy （ATR FT-IR） and fluorescence spec- trometry. The results indicate that the λem-max from treated hair surface displayed red shift with increasing pH between 2-5 and the reaction of the cysteine with NBD-Cl is pH-dependent. The thiol group of cysteine of treated hair could be substituted by NBD-C1. This supposal was further conformed with NO2 symmetric stretching vibration which was found in the ATR FT-IR spectra of hair samples treated with NBD-Cl at pH3 medium. The selectivity of reaction on submitted group （thiol or amine） was not influenced by NBD-CI concentration. The existence of some cationic ions, such as Cu2＋ , Pb2＋ , Fe3＋ would weaken the reaction, while Ni2 ＋ has no obvious effect.