Gago F, Richards W G
Physical Chemistry Laboratory, Oxford, England.
FEBS Lett. 1989 Jan 2;242(2):270-4. doi: 10.1016/0014-5793(89)80483-1.
A single strand of oligonucleotide can bind to double helical DNA under certain conditions. This must involve some unwinding of the original double helix in a process leading to the formation of a three-stranded region. The free energy for such an entropically unlikely reaction may come from a change in the degree of supercoiling of the original DNA. The conformation of the triple strand is investigated here using computer graphics and molecular mechanics calculations. It is suggested that on binding the oligonucleotide (strand 3) to two paired strands (1 and 2) in a supercoiled DNA molecule, strand 2 might adopt a left-handed conformation whilst strand 1 and strand 3 pair in the normal Watson-Crick B-configuration.
在特定条件下，单链寡核苷酸能与双螺旋DNA结合。这必然涉及到原始双螺旋在形成三链区域的过程中发生一定程度的解旋。这种熵变不太可能发生的反应的自由能可能来自于原始DNA超螺旋程度的变化。本文利用计算机图形学和分子力学计算研究了三链的构象。研究表明，在超螺旋DNA分子中，寡核苷酸（链3）与两条配对链（链1和链2）结合时，链2可能会采取左手构象，而链1和链3则以正常的沃森-克里克B型构象配对。
