• DNA分子越长,表面裸露出来带负电的磷酸基团越多,整条分子带的负电就更强,更容易吸附到磁珠表面,只需要较低浓度的PEG和NaCl就可以回收; • DNA分子越短,需要更高浓度的PEG和NaCl将其表面的水化层破坏得更彻底,裸露出来足够多带负电的磷酸基团,才能被磁珠吸附回收。(即回收的DNA片段越小,需要加入的PEG和NaCl浓度越高,磁珠体积更大。) 参考文献: [1] Vasilevskaya V V, Khokhlov A R, Matsuzawa Y, et al. Collapse of single DNA molecule in poly (ethylene glycol) solutions[J]. The Journal of chemical physics, 1995, 102(16): 6595-6602.
[2] Bloomfield V A. DNA condensation[J]. Current opinion in structural biology, 1996, 6(3): 334-341.