Bonincontro A, Matzeu M, Mazzei F, Minoprio A, Pedone F
Dipartimento di Fisica, Università La Sapienza, Roma, Italy.
Biochim Biophys Acta. 1993 Jan 23;1171(3):288-94. doi: 10.1016/0167-4781(93)90067-n.
The thermodynamic and dielectric properties of a 21 base pair DNA have been evaluated and compared with those of samples with some defects. In particular, fragments in which the absence of a phosphate group (nick) or of two nucleotides (gap) causes chain interruptions were studied. Measurements of ultraviolet absorption as a function of temperature at different oligomer concentrations and at various ionic strengths were performed. Dielectric spectroscopy at radiofrequencies (1 MHz-1 GHz) was applied on aqueous solutions of the duplexes at 5 degrees C, where the solutes are thermally stable. Dielectric dispersions with 30-40 MHz characteristic frequencies were defined. The results of melting experiments indicate a thermal destabilization of the oligomers containing the defects. Electrophoretic data and the dielectric results show that the conformations of the nicked and control samples are very similar, while the oligomer with a gap is more compact with a different charge distribution at the ends.
对一段21个碱基对的DNA的热力学和介电性质进行了评估，并与一些有缺陷的样品的性质进行了比较。特别研究了那些因缺少一个磷酸基团（切口）或两个核苷酸（缺口）而导致链中断的片段。在不同的寡聚物浓度和各种离子强度下，测量了紫外吸收随温度的变化。在5摄氏度时，对双链体的水溶液进行了射频（1 MHz - 1 GHz）介电谱测量，此时溶质热稳定。定义了特征频率为30 - 40 MHz的介电色散。熔解实验结果表明含有缺陷的寡聚物存在热不稳定现象。电泳数据和介电结果表明，有切口的样品和对照样品的构象非常相似，而有缺口的寡聚物更紧凑，末端电荷分布不同。
