Li A Z, Qi L J, Shih H H, Marx K A
Department of Chemistry, University of Massachusetts, Lowell 01854, USA.
Biopolymers. 1996 Mar;38(3):367-76. doi: 10.1002/(sici)1097-0282(199603)38:3<367::aid-bip9>3.0.co;2-s.
Pulse gel electrophoresis was used to measure the reduction of mobilities of lambda-DNA-Hind III fragments ranging from 23.130 to 2.027 kilobase pairs in Tris borate buffer solutions mixed with either hexammine cobalt(III), or spermidine3+ trivalent counterions that competed with Tris+ and Na+ for binding onto polyion DNA. The normalized titration curves of mobility were well fit by the two-variable counterion condensation theory. The agreement between measured charge fraction neutralized and counterion condensation prediction was good over a relatively wide range of trivalent cation concentrations at several solution conditions (pH, ionic strength). The effect of ionic strength, trivalent cation concentration, counterion structure, and DNA length on the binding were discussed based on the experimental measurements and the counterion condensation theory.
脉冲凝胶电泳用于测量在与六氨合钴（III）或亚精胺3+三价抗衡离子混合的Tris硼酸缓冲溶液中，λ-DNA-Hind III片段（范围从23.130至2.027千碱基对）迁移率的降低，这些三价抗衡离子与Tris+和Na+竞争结合到聚离子DNA上。迁移率的归一化滴定曲线很好地符合双变量抗衡离子凝聚理论。在几种溶液条件（pH、离子强度）下，在相对较宽的三价阳离子浓度范围内，测得的电荷中和分数与抗衡离子凝聚预测之间的一致性良好。基于实验测量和抗衡离子凝聚理论，讨论了离子强度、三价阳离子浓度、抗衡离子结构和DNA长度对结合的影响。
