Kozyavkin S A, Lyubchenko Y L
Nucleic Acids Res. 1984 May 25;12(10):4339-49. doi: 10.1093/nar/12.10.4339.
To investigate the effects of heating rate on the DNA melting profile and to test the predictions of the theory of slow relaxation processes in DNA melting (1) concerning these effects, we obtained differential melting curves for the Bsp I C1 fragment of T7 DNA (1461 bp) and the Sma I-Eco RI fragment of Col E1 DNA (1291 bp) at heating rates of 0.05 and 0.5 deg/min. At low ionic strength (0.02 M Na+) the heating rate has been shown to affect the position of the third peak in melting curve for C1 fragment. According to the melting maps (2), this peak corresponds to the unwinding of the section between the end of the molecule and the region already melted. At high ionic strength (0.2 M Na+), when the melting of this DNA is reversible (3), the position of the peaks does not depend on the heating rate. In the case of the Col E1 DNA fragment the heating rate affects, as might be expected from the melting maps (4), only the last peak, as the melting of the last section is always nonequilibrium. The results of the study are in good qualitative agreement and in satisfactory quantitative agreement with the theoretical predictions (1).
为了研究升温速率对DNA解链曲线的影响，并检验DNA解链过程中慢弛豫过程理论（1）关于这些影响的预测，我们获得了T7 DNA的Bsp I C1片段（1461 bp）和Col E1 DNA的Sma I - Eco RI片段（1291 bp）在升温速率为0.05和0.5℃/分钟时的差示解链曲线。在低离子强度（0.02 M Na+）下，升温速率已被证明会影响C1片段解链曲线中第三个峰的位置。根据解链图谱（2），这个峰对应于分子末端与已解链区域之间部分的解旋。在高离子强度（0.2 M Na+）下，当这种DNA的解链是可逆的（3）时，峰的位置不依赖于升温速率。对于Col E1 DNA片段，正如从解链图谱（4）中可能预期的那样，升温速率仅影响最后一个峰，因为最后一段的解链总是非平衡的。研究结果与理论预测（1）在定性上吻合良好，在定量上也令人满意。
