Sorokin V A, Blagoi Y P, Valeev V A, Lisnyak Y V
J Inorg Biochem. 1983 Oct;19(2):143-52. doi: 10.1016/0162-0134(83)85020-x.
Ultraviolet differential spectra of poly A we studied in the presence of Ca2+ ions with 10(-3)M Na+ in the solution. At concentrations lower than 10(-3)M Ca2+, the ions bind to phosphate groups of the single helical polymer, thus increasing its degree of helicity. At higher concentrations, the ions start binding to the bases of poly A, producing aggregates whose effective radius, as found with an electric microscope, is not more than 10(2) A. These particles stack to form aggregates of an order-of-magnitude higher size. The mutual orientation of bases in the poly A aggregates is of a high degree of order. The calculation of concentration dependences of Ca2+-poly A binding constants shows that this process is cooperative.
我们研究了在溶液中存在10⁻³M Na⁺ 时聚腺苷酸（poly A）的紫外差分光谱。当Ca²⁺ 浓度低于10⁻³M时，离子与单螺旋聚合物的磷酸基团结合，从而增加其螺旋度。在较高浓度下，离子开始与聚腺苷酸的碱基结合，产生聚集体，用电镜观察发现其有效半径不超过10² Å。这些颗粒堆积形成尺寸大一个数量级的聚集体。聚腺苷酸聚集体中碱基的相互取向具有高度有序性。Ca²⁺ -聚腺苷酸结合常数的浓度依赖性计算表明，该过程是协同的。
