APPLICATION OF THE METHOD OF PHAGE-T4 DNA LIGASE-CATALYZED RING-CLOSURE TO THE STUDY OF DNA-STRUCTURE .2. NACL-DEPENDENCE OF DNA FLEXIBILITY AND HELICAL REPEAT
APPLICATION OF THE METHOD OF PHAGE-T4 DNA LIGASE-CATALYZED RING-CLOSURE TO THE STUDY OF DNA-STRUCTURE .2. NACL-DEPENDENCE OF DNA FLEXIBILITY AND HELICAL REPEAT
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DOI：
10.1016/0022-2836(90)90131-5
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发表时间：
1990-03-20
影响因子：
5.6
通讯作者：
HAGERMAN, PJ
中科院分区：
文献类型：
--
作者：
TAYLOR, WH;HAGERMAN, PJ
在这项工作中，我们证明，它是poosible确定摩尔环化因子jM从单一的连接反应，其中环状和线性二聚体DNA物种同时形成从线性单体。这种方法代表了对先前方法的显著改进，在先前方法中，从两个单独过程的速率常数的比率评估jM;即（1）线性DNA的环化和（2）两个线性分子缔合以形成线性二聚体。 测定366个碱基对分子的jM得到5 × 10 - 6。10-8 M，与5 × 6的值非常一致。10-8 M由海岸等人对相同分子测定。使用目前的方法用于确定的JM，我们已经研究了对NaCl浓度（0至162 mM-NaCl，1 mM-MgCl 2）的DNA的横向和扭转的灵活性的依赖性。主要的观察结果是，这两个量在上述NaCl浓度范围内基本上是恒定的，持续长度P约为450（±）。15)ANG，以及扭转弹性常数C <$2 <$0（±）。0.cnt.2）×10 - 19尔格厘米。这些观察结果与先前的理论预测一致，即P在10至20 mM以上变得基本上不依赖于NaCl浓度。我们已经检查了DNA的螺旋重复在上述范围内对NaCl浓度的依赖性，并且发现每圈10·44个碱基对的值在该范围内基本上是恒定的。这最后一个结果表明，早期的研究高估了盐浓度对DNA螺旋扭曲的依赖性。
In this work we demonstrate that it is poosible to determine the molar cyclization factor jM from single ligation reactions in which both circular and linear dimer DNA species are formed concurrently from linear monomers. This approach represents a significant improvement over previous methods, in which jM is evaluated from the ratio of the rate constants for two separate processes; namely (1) the cyclization of linear DNA and (2) the association of two linear molecules to form linear dimers. Determination of jM for a 366 base-pair molecule yields 5.cntdot.8 .times. 10-8 M, in close agreement with the value of 5.cntdot.6 .times. 10-8 M determined by Shore et al. for the same molecule. Using the current approach for the determination of jM, we have investigated the dependence on NaCl concentration (0 to 162 mM-NaCl, 1 mM-MgCl2) of both the lateral and torsional flexibilities of DNA. The principal observation is that both quantities are essentially constant over the above range of NaCl concentrations, with the persistence length P.apprxeq.450 (.+-.15) .ANG., and the torsional elastic constant C.apprxeq.2.cntdot.0 (.+-.0.cntdot.2) .times. 10-19 erg cm. These observations are in accord with the previous theoretical prediction that P becomes essentially independent of NaCl concentration above 10 to 20 mM. We have examined the dependence of the helical repeat of DNA on NaCl concentration over the above range, and have found the value of 10.cntdot.44 base-pairs per turn to be essentially constant over that range. This last result suggests that earlier studies have overestimated the dependence of DNA helical twist on salt concentration.