【摘要】 背景:以往研究多采用紫外/可见光谱、电导和电泳等方法研究金属离子与氨基酸之间的作用,但以UV-Vis光谱、荧光光谱方法研究L-组氨酸同银离子在水溶液中反应的机制少见报道。目的:采用UV-Vis光谱、荧光光谱方法研究L-组氨酸同银离子的作用机制。方法:用UV-Vis、荧光光谱法研究了组氨酸同银离子间的相互作用,考察介质的pH、Ag+离子、组氨酸、甲醛、十二烷基硫酸钠、三羟甲基氨基甲烷浓度以及光照强度和光照时间等条件对组氨酸同Ag+离子作用的影响,探究反应机制。结果与结论:pH电位滴定法测定L-组氨酸离解常数为9.21,用半n_法求得组氨酸-Ag的逐级稳定常数为㏒K1=5.56,㏒K2=4.05,20℃时组氨酸-Ag体系的电动电位为2.10×10-4V。根据pH电位滴定法和Iob法确定该配合物的组成为组氨酸∶Ag=2∶1。同组氨酸相比,组氨酸-Ag体系在295.3nm有一肩峰,它对应于咪唑环产生的π-π*跃迁。而242.0nm左右出现的吸收峰属于组氨酸中C=O的n-π*跃迁。组氨酸-Ag体系产生的荧光发射光谱归属为5D0→7F2电子偶极跃迁。同相同条件下的参比液相比,不仅发射波长蓝移,而且导致荧光猝灭。结果表明,组氨酸中的咪唑环参与了同银离子的成键作用。组氨酸同银离子发生反应后,首先生成六配位配合物,然后银离子再被甲醛还原为超细银粒而被组氨酸所包裹。更多还原

【Abstract】 BACKGROUND:Traditionally,UV/visible spectra,conductivity,electrophoresis and other methods are commonly applied for studying the interaction of metal ions and amino acids,but UV-Vis spectroscopy and fluorescence spectroscopy for L-histidine reacted with silver ion in aqueous solution is rarely reported.OBJECTIVE:To investigate the interaction between silver ion and histidine using UV/VIS and fluorescence spectra.METHODS:The influence of pH,multicomponent concentration such as histidine,silver ion,formaldehyde,sodium dodecyl sulfate and trihydroxymethyl aminomethane,as well as illumination strength and time,on the interaction between silver ion and histidine were investigated,and the mechanism of reaction was also explored.RESULTS AND CONCLUSION:Applied pH potentiometer titration method,the dissociation constants of histidine was defined 9.21.The stepwise stability constants of histidine-silver was㏒K1=5.56 and㏒K2=4.05,respectively by using half n _ method.At 20℃,the electric potential of histidine-silver system was 2.10×10-4V.According to pH potentiometer titration and Iob method,the compound was consisted of histidine:Ag=2:1.Compared with histidine,histidine-silver systems reached a shoulder peak at 295.3 nm,which was assigned to conjugate double bond of imidazole ring that easily generatedπ-π*transition.And an absorption peak close to 242 nm can be assigned to n-π*transition of the C=O group of the histidine-silver.The fluorescence emission spectra of histidine-silver systems belonged to5D0→7F2 electric dipole transition.Compared with reference solutions under the same conditions,it not only emitted wavelengths blue shift,but also induced fluorescence quenching.Results showed that,imidazole ring was involved in the bonding action with silver ion.The reaction process is to firstly generate six-coordination complex,secondly reduce the silver ion into ultrafine silver particles which are bound by histidine.更多还原