烟碱与胃蛋白酶相互作用机理初步研究

为了探究口含烟烟碱（NIC）在人体胃部的吸收特性，配制了特定浓度的柠檬酸-柠檬酸钠缓冲溶液使其pH=2.0，并在该条件下配制不同浓度的烟碱溶液样品，随后用该样品作用于胃蛋白酶，利用多种光谱学方法（分子荧光光谱、紫外光谱、红外光谱、圆二色谱）和分子模拟对接技术观察添加不同浓度烟碱前后胃蛋白酶的光谱学变化，初步研究了NIC与胃蛋白酶（Pepsin）相互作用机理。光谱学与分子模拟对接结果表明:1） NIC与Pepsin之间为静态荧光猝灭机制；2） NIC与Pepsin之间通过氢键和范德华力自发的发生相互作用；3） NIC与Pepsin之间存在着一个高亲和力的结合位点；4） NIC和Pepsin之间的相互作用不仅使Pepsin中氨基酸残基的微环境极性增加，同时使得Pepsin多肽链的C=O、C-N和N-H发生了变化，进而导致Pepsin的构象和空间结构发生变化，同时NIC的加入对Pepsin活性呈明显的增强效应。以上研究结果对口含烟产品开发、质量控制和安全评价具有重要理论意义。 

Preliminary investigation on interaction mechanism between nicotine and pepsin

In order to investigate absorption characteristics of human stomach to nicotine (NIC) in tobacco products for oral use, certain concentration of citric acid and sodium citrate buffer solution (pH=2.0) were prepared for simulating gastric conditions and different levels of nicotine solutions were prepared by using buffer solution. After interaction of pepsin with different levels of nicotine, spectrum changes of the pepsin before and after addition of different levels of nicotine were observed by various spectroscopic methods i.e. fluorescence spectrum, ultraviolet spectrum, infrared spectrum, circular dichroism spectrum and molecular docking simulation technology. Action mechanism between nicotine and pepsin was studied. Research of spectroscopy and molecular docking simulation indicated that:1) the quenching mechanism of NIC on pepsin was static fluorescence; 2) NIC and pepsin interacted spontaneously via hydrogen bonding and van der Waals forces; 3) there existed a single high-affinity binding site between NIC and pepsin; 4) interaction between NIC and pepsin increased polarity of microenvironment of amino-acid residues in pepsin, and changed C=O, C-H and N-H of polypeptide chain of pepsin, resulting variation of conformation and spatial structure of pepsin. In the mean time, NIC promoted activity of pepsin when it was added into pepsin at different concentrations. Results of this research can provide references for development, quality control and health risk evaluation of tobacco products for oral use.