Minasian K A, Vorob'ev A F, Malenkov G G
Mol Biol (Mosk). 1987 Sep-Oct;21(5):1329-38.
The enthalpies of the guanidinium chloride (Gu.HCl) with sodium DNA salt in the solutions in B- and A-conformations in the mixtures of ethanol-water at 298.15 K and the enthalpies of solution of guanidinium chloride in the mixtures of ethanol-water at 298.15 K in a whole range of the compositions of mixed solvents were measured calorimetrically. It was established that in a field of B-A-transition of DNA the values of interaction enthalpies of Gu.HCl with DNA practically do not depend on the composition of the solvent. The concentrations of Na-ions in water-ethanol solutions of DNA containing Gu.HCl were determined by the potentiometric method. It was revealed that the interaction of the equimolar quantities of Gu.HCl and DNA leads to the complete replacement of Na-cations, which are naturally linked with DNA, into solution. From the results obtained the enthalpy of B-A-conformation transition DNA at 298.15 K was determined (-2.50 +/- 0.10 kJ/mole).
在298.15K下，通过量热法测量了氯化胍（Gu.HCl）与处于B型和A型构象的DNA钠盐在乙醇 - 水混合溶液中的焓，以及在298.15K下整个混合溶剂组成范围内氯化胍在乙醇 - 水混合溶液中的溶解焓。结果表明，在DNA的B - A转变区域，Gu.HCl与DNA的相互作用焓值实际上不依赖于溶剂的组成。通过电位滴定法测定了含有Gu.HCl的DNA水 - 乙醇溶液中Na离子的浓度。结果显示，等摩尔量的Gu.HCl与DNA的相互作用导致与DNA自然结合的Na阳离子完全被置换到溶液中。根据所得结果，确定了298.15K下DNA的B - A构象转变焓（-2.50±0.10kJ/摩尔）。
