Cain R J, Glick G D
University of Michigan, Department of Chemistry, Ann Arbor 48109-1055, USA.
Nucleic Acids Res. 1997 Feb 15;25(4):836-42. doi: 10.1093/nar/25.4.836.
The base pair lifetimes and apparent dissociation constants of a 21 base DNA hairpin and an analog possessing a disulfide cross-link bridging the 3'- and 5'-terminal bases were determined by measuring imino proton exchange rates as a function of exchange catalyst concentration and temperature. A comparison of the lifetimes and apparent dissociation constants for corresponding base pairs of the two hairpins indicates that the cross-link neither increases the number of base pairs involved in fraying nor alters the lifetime, dissociation constant, or the opened structure from which exchange occurs for the base pairs that are not frayed. The cross-link does, however, stabilize the frayed penultimate base pair of the stem duplex. Significantly, it appears that the disulfide cross-link is more effective at preventing fraying of the penultimate base pair than is the 5 base hairpin loop. Because this disulfide cross-link can be incorporated site specifically, and does not adversely affect static or dynamic properties of DNA, it should prove very useful in studies of nucleic acid structure and function.
通过测量亚氨基质子交换速率作为交换催化剂浓度和温度的函数，确定了一个21个碱基的DNA发夹以及一个具有二硫键交联连接3'和5'末端碱基的类似物的碱基对寿命和表观解离常数。对两个发夹相应碱基对的寿命和表观解离常数进行比较表明，该交联既不会增加参与解链的碱基对数量，也不会改变未解链碱基对的寿命、解离常数或发生交换的开放结构。然而，该交联确实稳定了茎双链体中倒数第二个解链的碱基对。值得注意的是，二硫键交联在防止倒数第二个碱基对解链方面似乎比5个碱基的发夹环更有效。由于这种二硫键交联可以位点特异性地掺入，并且不会对DNA的静态或动态性质产生不利影响，因此它在核酸结构和功能研究中应该非常有用。
