Aronssohn G, Travers F
Nucleic Acids Res. 1976 May;3(5):1373-85. doi: 10.1093/nar/3.5.1373.
pK values of ionisation of cytidine residues, in poly C and poly I. poly C, have been determined by potentiometric titration as a function of either ionic strength (Na+) or Mg2+ concentration. The results are interpreted as a consequence of the existence of a local pH, prevailing in the vicinity of the polynucleotides, smaller than that of the bulk solution. This local pH is dependent upon the electrostatic potential psi due to the negatively charged phosphate groups of the polynucleotide. Moreover psi can be modulated through variation of either ionic strength or Mg2+ concentration. At a given pH Mg2+ addition leads to the release of protons which, in the case of complex systems of limited stability, might be detected by the use of the pH-stat method. Possible functional implications for genetic translation systems are examined.
通过电位滴定法测定了聚C和聚I·聚C中胞苷残基的电离pK值，该值是离子强度（Na⁺）或Mg²⁺浓度的函数。结果被解释为多核苷酸附近存在局部pH值，该局部pH值小于本体溶液的pH值。这种局部pH值取决于由于多核苷酸带负电荷的磷酸基团而产生的静电势ψ。此外，ψ可以通过改变离子强度或Mg²⁺浓度来调节。在给定pH值下，添加Mg²⁺会导致质子释放，在稳定性有限的复杂系统中，这可以通过pH计法检测到。文中还研究了对基因翻译系统可能的功能影响。
