Mika Jacek T, van den Bogaart Geert, Veenhoff Liesbeth, Krasnikov Victor, Poolman Bert
Department of Biochemistry, Groningen Biomolecular Science and Biotechnology Institute, Netherlands.
Mol Microbiol. 2010 Jul 1;77(1):200-7. doi: 10.1111/j.1365-2958.2010.07201.x. Epub 2010 May 12.
We determined the diffusion coefficients (D) of (macro)molecules of different sizes (from approximately 0.5 to 600 kDa) in the cytoplasm of live Escherichia coli cells under normal osmotic conditions and osmotic upshift. D values decreased with increasing molecular weight of the molecules. Upon osmotic upshift, the decrease in D of NBD-glucose was much smaller than that of macromolecules. Barriers for diffusion were found in osmotically challenged cells only for GFP and larger proteins. These barriers are likely formed by the nucleoid and crowding of the cytoplasm. The cytoplasm of E. coli appears as a meshwork allowing the free passage of small molecules while restricting the diffusion of bigger ones.
我们测定了不同大小（约0.5至600 kDa）的（大）分子在正常渗透压条件和渗透压升高情况下活的大肠杆菌细胞胞质中的扩散系数（D）。D值随分子分子量的增加而降低。渗透压升高时，NBD - 葡萄糖的D值下降幅度远小于大分子。仅在受到渗透压挑战的细胞中发现绿色荧光蛋白（GFP）和更大蛋白质存在扩散障碍。这些障碍可能由类核和细胞质拥挤形成。大肠杆菌的细胞质呈现为一个网络结构，允许小分子自由通过，同时限制大分子的扩散。
