用DFT-B3LYP方法对低聚物(PF30T)_n[n(芴):n(硫芴)=2:1,物质的量之比,n=1～4],(PF50T)_n[n(芴):n(硫芴) =1:1,物质的量之比,n=1～4]体系全优化,得到两系列低聚物的电离能(IP_(a,v))、电子亲和势(EA_(a,v))、空穴抽取能(HEP)、电子抽取能(EEP),在此基础上用ZINDO和TD-DFT方法计算吸收光谱,分析了两个系列的HOMO-LUMO能隙随着n递增的变化趋势及硫芴含量对低聚物电子结构和光谱性质的影响,推断了高聚物的电子和光谱性质,用ab initio CIS方法优化了低聚物的S_1激发态结构并分析了其与发射光谱的关系,研究显示:2,8位引入的硫芴基团,破坏了链的共轭,而且随着硫芴含量的增加,HOMO-LUMO能隙变大,光谱蓝移:激发态结构趋于共面化。
Tryptophan(Trp) residues in inulinase were modified by chemical reagent N-bromossuccinimide(NBS).The results of Spande′s method indicate that there were seventeen Trp residues in inulinase and five of them were located on the surface of the enzyme.Three of these Trp residues were none-essential residues which showed the fastest rate by Zhou′s plot.Two relative faster reacting residues were both essential for the activity of the enzyme.The other twelve were the slowest or none-reactive residues for the reaction.The study on fluorescence quenching of inulinase shows that KI could not quench all of the fluorescence from Trp residues in inulinase which indicate that there are two kinds of Trp residues in inulinase acrylamide(Acr),a polarized quencher without electronic charge could quench almost all of the fluorescence from Trp residues in inuoinase while there are still seventy percernt of the activity of the enzyme left.The collisional quenching constants(K_D) of inulinase at different concentrations of Acr were calculated in terms of Stern-Volmer equation.
