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首页> 外文期刊>Nanotechnology >Anisotropic diffusion of point defects in a two-dimensional crystal of streptavidin observed by high-speed atomic force microscopy
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Anisotropic diffusion of point defects in a two-dimensional crystal of streptavidin observed by high-speed atomic force microscopy

机译：高速原子力显微镜观察到链霉亲和素二维晶体中点缺陷的各向异性扩散

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摘要

The diffusion of individual point defects in a two-dimensional streptavidin crystal formed on biotin-containing supported lipid bilayers was observed by high-speed atomic force microscopy. The two-dimensional diffusion of monovacancy defects exhibited anisotropy correlated with the two crystallographic axes in the orthorhombic C222 crystal; in the 2D plane, one axis ( the a-axis) is comprised of contiguous biotin-bound subunit pairs whereas the other axis ( the b-axis) is comprised of contiguous biotin-unbound subunit pairs. The diffusivity along the b-axis is approximately 2.4 times larger than that along the a-axis. This anisotropy is ascribed to the difference in the association free energy between the biotin-bound subunit-subunit interaction and the biotin-unbound subunit-subunit interaction. The preferred intermolecular contact occurs between the biotin-unbound subunits. The difference in the intermolecular binding energy between the two types of subunit pair is estimated to be approximately 0.52 kcal mol(-1). Another observed dynamic behavior of point defects was fusion of two point defects into a larger defect, which occurred much more frequently than the fission of a point defect into smaller defects. The diffusivity of point defects increased with increasing defect size. The fusion and the higher diffusivity of larger defects are suggested to be involved in the mechanism for the formation of defect-free crystals.
机译：通过高速原子力显微镜观察到在含生物素的负载脂质双层上形成的二维链霉抗生物素蛋白晶体中单个点缺陷的扩散。单晶缺陷的二维扩散在正交C222晶体中表现出与两个晶轴相关的各向异性。在2D平面中，一个轴（a轴）由连续的生物素结合的亚基对组成，而另一轴（b轴）由连续的生物素未结合的亚基对组成。沿b轴的扩散率大约是沿a轴的扩散率的2.4倍。该各向异性归因于生物素结合的亚基-亚基相互作用与生物素未结合的亚基-亚基相互作用之间的缔合自由能的差异。优选的分子间接触发生在未结合生物素的亚基之间。两种亚基对之间的分子间结合能的差异估计约为0.52 kcal mol（-1）。观察到的点缺陷的动态行为是将两个点缺陷融合为一个较大的缺陷，这种现象的发生频率比将点缺陷分裂为较小的缺陷的频率要高得多。点缺陷的扩散度随缺陷尺寸的增加而增加。较大的缺陷的融合和较高的扩散率被认为与无缺陷晶体的形成机理有关。

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