杜仲抗真菌蛋白晶体生长的原子力显微成像研究——快速生长与晶面生长速率

Fast Growth Rates of Eucommia Antifungal Protein(EAFP) Crystals Observed by Atomic Force Microscope

杜仲抗真菌蛋白(Eucommiaantifungalprotein,EAFP)的单晶体具有在几小时内就可长大的快速生长特性.用原子力显微成像(atomicforcemicroscope,AFM)技术,原位实时观测了EAFP单斜晶体生长过程中的｛10 0｝表面形貌动态变化,并分别在不同的过饱和度下测量了其生长速率.结果表明,EAFP晶体生长的速率与蛋白质溶液的过饱和度相关,在过饱和度高时(σ =1 78)晶面生长极快;在中等过饱和度(σ =1 5)下,其晶面台阶的生长速率沿b,c方向分别为 12nm/s和 2 4 2nm/s,比溶菌酶生长速率(6～ 7nm/s)快很多;在蛋白质浓度很低的情况下,其生长速率仍与其他蛋白质相当.EAFP晶体快速生长可能与该分子尺寸较小,内部结构紧凑,分子骨架呈刚性和分子表面性质等其固有特性密切相关.沉淀剂浓度对EAFP晶体生长也有影响.过饱和度很低时,提高沉淀剂浓度会干扰晶体生长.

Eucommia antifungal protein (EAFP) crystals can be easily grown into big crystals in several hours. By in situ atomic force microscopy (AFM) the dynamic topographic changes were observed on the surfaces of several EAFP crystals and growth rates were measured at different supersaturations of the protein solution. The results of AFM experiments indicated that growth rates of EAFP crystals were strongly and directly related to the supersaturations, in addition to the inherent structural rigidity and the interior stability of the molecule. At higher supersaturation (sigma = 1.78) the EAFP crystals grew very fast; at moderate supersaturation (sigma = 1.5) the growth rates were 12 nm/s and 24.2 nm/s along the crystallographic axes b, c of the {100} surface respectively, which were faster than that of lysozyme (6 similar to 7 nm/ s). Even at lower supersaturation the EAFP crystals grew almost as fast as other protein crystals did. The effects of the concentration of precipitator on crystal growth observed on the crystal growth of AFM at lower supersaturation were also presented.