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首页> 外文期刊>Biophysical Chemistry: An International Journal Devoted to the Physical Chemistry of Biological Phenomena >Temperature-dependence of the bending elastic constant of DNA and extension of the two-state model. Tests and new insights
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Temperature-dependence of the bending elastic constant of DNA and extension of the two-state model. Tests and new insights

机译：DNA弯曲弹性常数的温度依赖性及两种模型的延伸。 测试和新的见解

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Review and analyses of the experimental data indicate that in nearly all cases bending elastic constants of the effective springs between bp of DNA actually undergo a net increase with increasing T from 278 to 315 K. The exceptions to this rule are bending elastic constants obtained from equilibrium topoisomer distributions of a 2686 bp pUC19 DNA by assuming a fixed T-independent value of the torsion elastic constant. When the same data are analyzed using measured T-dependent values of the torsion elastic constant, which decline with increasing T, a modest increase in bending elastic constant with increasing T is obtained. After revising the torsion elastic constants of the previously formulated two-state cooperative transition model to account for additional data, that model is fitted to the bending elastic constants reckoned from the aforementioned topoisomer distributions to determine the best-fit values for each state. The rather good fit implies a strong negative linear correlation between the inverse bending and inverse torsion elastic constants as T is varied. Predictions of the resulting two-state model, wherein each state has fixed bending and torsion elastic constants, agree surprisingly well with single-molecule relative extension and torque data. The same model also yields good agreement with numerous other experimental data. With increasing T the equilibrium is shifted from the (longer, torsionally stiffer, flexurally softer) b-state toward the (shorter, torsionally softer, flexurally stiffer) a-state. This transition is suggested to be the origin of the so-called broad pre-melting transition exhibited by many, but not all, DNAs.
机译：实验数据的审查和分析表明，在几乎所有案例中，DNA BP之间的有效弹簧的弯曲弹性常数实际上与278到315 K的增加时净增加。该规则的例外是弯曲从平衡获得的弹性常数。通过假设扭转弹性常数的固定T型独立值来分布2686bp PUC19 DNA的拓扑分布。当使用测量的T型从扭力恒定的测量值进行分析相同的数据时，通过增加T的扭转弹性常数下降，获得弯曲弹性常数随着越来越多的T.在修改先前配制的两态协同转换模型的扭力弹性常数以解释额外的数据之后，该模型适用于从上述Topoisomer分布中估计的弯曲弹性常数，以确定每个状态的最佳值。相当良好的拟合意味着变化的逆弯曲和逆扭转弹性常数之间的强负线性相关性。所得到的两个状态模型的预测，其中每个状态具有固定的弯曲和扭力弹性常数，与单分子相对延伸和扭矩数据令人惊讶地吻合良好。相同的型号也与许多其他实验数据产生良好的一致性。随着增加的T，平衡从（更长，扭转的更致柔软的弯曲更柔软）B状态朝向（较短，扭转的更柔软，柔性纤巧）a-状态。建议这种转变是由许多人展出的所谓的广泛预熔化过渡的起源，但并非所有的DNA。

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