Andreasson B, Nordenskiöld L, Braunlin W H, Schultz J, Stilbs P
Division of Physical Chemistry, University of Stockholm, Sweden.
Biochemistry. 1993 Jan 26;32(3):961-7. doi: 10.1021/bi00054a029.
The 1H NMR pulsed field gradient self-diffusion method has been used to measure the diffusion coefficient of the polyamine analogue methylspermidine (completely N-methylated spermidine) in DNA solution, as a function of the concentration ratio of methylspermidine to DNA phosphate. Three different DNA's have been investigated: d(GC)4 (8 base pairs), core length calf thymus DNA (approximately 120 base pairs), and sonicated high molecular weight calf thymus DNA (average 7500 base pairs). For a constant ratio of methylspermidine to DNA phosphate, the diffusion coefficient decreases with increasing DNA length. Moreover, at low concentration ratios the diffusion coefficient of methylspermidine approaches a limiting value that is close to that of the DNA molecule. The experimental data are well reproduced by a two-state diffusion model. In this model the diffusion coefficient of the polyamine is a population-weighted average of polyamine associated with DNA (with a diffusion coefficient given by that of the DNA molecule) and polyamine free in solution.
1H NMR脉冲场梯度自扩散方法已被用于测量多胺类似物甲基亚精胺（完全N-甲基化的亚精胺）在DNA溶液中的扩散系数，该系数是甲基亚精胺与DNA磷酸浓度比的函数。已研究了三种不同的DNA：d(GC)4（8个碱基对）、核心长度的小牛胸腺DNA（约120个碱基对）和超声处理的高分子量小牛胸腺DNA（平均7500个碱基对）。对于甲基亚精胺与DNA磷酸的恒定比例，扩散系数随DNA长度增加而降低。此外，在低浓度比下，甲基亚精胺的扩散系数接近一个极限值，该极限值接近DNA分子的扩散系数。实验数据通过双态扩散模型得到了很好的再现。在该模型中，多胺的扩散系数是与DNA结合的多胺（其扩散系数由DNA分子的扩散系数给出）和溶液中游离多胺的群体加权平均值。
