Chen H H, Behe M J, Rau D C
Nucleic Acids Res. 1984 Mar 12;12(5):2381-9. doi: 10.1093/nar/12.5.2381.
By working at very low Na+ concentrations (1mM and less), the number of bound Mg(2+), cobalt hexamine (3+), and spermine (4+) necessary to induce the B-Z transition of poly (dG-m5dC) has been directly measured. The results show that if as little as 1 cobalt hexamine(3+) or spermine(4+) is bound per 40-50 nucleotides the transition will occur. A greater fraction of bound Mg(2+) is required, 1 bound Mg(2+)/10 nucleotides. The dependence of the transition midpoint concentrations of oligovalent ions on Na+ concentrations suggests that specific ion binding energies, not included in counterion condensation theory, are responsible for the transition.
通过在极低的钠离子浓度（1毫摩尔及以下）下进行实验，已直接测量出诱导聚（dG-m5dC）发生B-Z转变所需结合的镁离子（2+）、六氨合钴（3+）和精胺（4+）的数量。结果表明，每40 - 50个核苷酸只要结合少至1个六氨合钴（3+）或精胺（4+），转变就会发生。而结合镁离子（2+）的比例要求更高，即每10个核苷酸结合1个镁离子（2+）。多价离子转变中点浓度对钠离子浓度的依赖性表明，抗衡离子凝聚理论中未包含的特定离子结合能是导致转变的原因。
