Stevens C L, Chay T R, Loga S
Biochemistry. 1977 Aug 23;16(17):3727-39. doi: 10.1021/bi00636a001.
By assuming that the opening of hydrogen bonds due to thermal fluctuations is a very fast step and that the reaction of formaldehyde with the imino or amino group is a slow step, we have constructed a model for the unwinding process of poly(A-U) induced by formaldehyde. The denaturation equation derived from the model is essentially the same as that of the zipper model for moderately long chain lengths. The model predicts the following phenomena which are in agreement with our experimental findings. The rate of unwinding is approximately first order for unfractionated polynucleotides and zero order for fractionated samples. This means that formaldehyde ruptures helical residues sequentially starting from the ends and working toward the center. Our model further predicts that the denaturation rate is linearly dependent on -log[Na+] and pH at low ionic strength and is almost independent of [Na+] and pH at high ionic strength. Spectrophotometric measurements on poly(A-U) were done to confirm our theoretical findings.
通过假设由于热涨落导致氢键打开是一个非常快速的步骤，而甲醛与亚氨基或氨基的反应是一个缓慢的步骤，我们构建了一个甲醛诱导的聚（A-U）解旋过程模型。从该模型推导得到的变性方程与中等链长的拉链模型基本相同。该模型预测了以下与我们实验结果相符的现象。对于未分级的多核苷酸，解旋速率近似为一级反应，而对于分级样品则为零级反应。这意味着甲醛从两端开始依次破坏螺旋残基并向中心推进。我们的模型进一步预测，在低离子强度下变性速率与-log[Na⁺]和pH呈线性相关，而在高离子强度下几乎与[Na⁺]和pH无关。对聚（A-U）进行了分光光度测量以证实我们的理论发现。
