Department of Physics, National University of Singapore, Singapore 117542.
J Phys Chem B. 2012 Mar 8;116(9):3031-6. doi: 10.1021/jp2124907. Epub 2012 Feb 24.
The effects of the like-charged proteins bovine serum albumin and hemoglobin on the conformation and compaction of single DNA molecules confined in rectangular nanochannels were investigated with fluorescence microscopy. The channels have lengths of 50 μm and cross-sectional diameters in the range of 80-300 nm. In the wider channels, the DNA molecules are compressed and eventually condense into a compact form with increasing concentration of protein. In the narrow channels, no condensation was observed. The threshold concentration for condensation depends on the channel cross-sectional diameter as well as the ionic strength of the supporting medium. The critical values for full compaction are typically less than one-tenth of a millimolar. In the bulk phase and in the same environmental conditions, no condensation was observed. Anisotropic nanoconfinement hence facilitates compaction of DNA by negatively charged protein. We tentatively interpret this behavior in terms of enhanced depletion interaction between segments of the DNA molecule due to orientation order imposed by the channel walls.
利用荧光显微镜研究了等电点的蛋白质牛血清白蛋白和血红蛋白对在矩形纳米通道中受限的单链 DNA 分子构象和压缩的影响。通道长度为 50μm，横截面直径在 80-300nm 范围内。在较宽的通道中，随着蛋白质浓度的增加，DNA 分子被压缩并最终凝聚成紧凑的形式。在狭窄的通道中，没有观察到凝聚。凝聚的阈值浓度取决于通道的横截面直径以及支撑介质的离子强度。完全压缩的临界值通常小于十分之一毫摩尔。在本体相中和相同的环境条件下，没有观察到凝聚。各向异性的纳米限制因此有利于带负电荷的蛋白质压缩 DNA。我们根据通道壁施加的取向有序性导致 DNA 分子片段之间增强的耗尽相互作用，初步解释了这种行为。
