【摘要】 本文报道了天花粉蛋白质紫外光谱的研究;计算了有关的热力学函数;对分子的稳定性和碱变性过程进行了分析和讨论;指出分子可能存在一个由α螺旋组成的较稳定的“核心”更多还原

【Abstract】 In order to explore the relationship between the structure and function of the protein trichosanthin, the molecular conformation in solution has been studied by ultraviolet spectroscopy .The enviroment of tyrsine residues in the molecule has been investigated by solvent perturbation difference spctroscopy. Several pertubants with different molecular dimensions were used in the pH rang of 8.6 to 2.5. The results show that approximately 40% of the thirteen phenolic groups are "exposed" and the rest are "buried" in the interior of the molecule. The effect of the various per-turbants with different molecular dimansions on ultraviolet spectra are almost the same.Spectrophotometric titrations have been carried out at 20℃,24.5℃,33.8℃ and 38℃. At 20℃ and 24.5℃, the titration curve of natural trichosanthin has been shown to be of two steps. The first step takes place between pH 9 and pH 11.5 it is reversible and time independent. The second step above pH 11.5,it is irreversible and time dependent. At 33.8℃ or 38℃,the titration curve seems to have a third step, which suggests that trichosanthin molecule has a rather stable core.The apparent pK’ for the first step under four different temperatures and the thermodynamic parameters of the process at 24.5℃ have also been calculeted. The results and it’s relation to the 3-dimentional structure of trichosanthin have been examined and discussed.更多还原