H-1-NMR STUDY OF THE BASE-PAIRING REACTIONS OF D(GGAATTCC) - SALT EFFECTS ON THE EQUILIBRIA AND KINETICS OF STRAND ASSOCIATION
H-1-NMR STUDY OF THE BASE-PAIRING REACTIONS OF D(GGAATTCC) - SALT EFFECTS ON THE EQUILIBRIA AND KINETICS OF STRAND ASSOCIATION
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DOI：
10.1021/bi00217a026
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发表时间：
1991-01-22
期刊：
影响因子：
2.9
通讯作者：
BLOOMFIELD, VA
中科院分区：
文献类型：
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作者：
BRAUNLIN, WH;BLOOMFIELD, VA
先前，我们检查了d（GGAATTCC）的亚氨基质子弛豫，以表征盐和多胺对该寡核苷酸的碱基对开放动力学的影响[Braunlin，W. H、&布卢姆菲尔德，V. A.（1988）Biochemistry 27，1184 - 1191]。 在这里，我们报告盐依赖测量的NMR行为的不可交换的碱质子共振的d（GGAATTCC）。 从化学位移测量，我们发现一个意想不到的大盐依赖性K（a），螺旋缔合的平衡常数。 在八聚体双链体解离时，总共释放1.8 +/-0.3钠离子。 大多数的盐依赖性的平衡常数可以追溯到一个大的盐依赖性的缔合速率。 因此，1.4 +/-0.2钠离子在螺旋缔合的限速步骤期间缔合。 在协议与我们以前的亚氨基质子的结果，我们还发现了一个显着的盐依赖性的双链体解离速率。 螺旋缔合的活化能非常小，并且可能是负的;缔合平衡的大部分温度依赖性可以追溯到双链体解离的大活化能（约50千卡/摩尔）。
Previously, we examined the imino proton relaxation of d(GGAATTCC) in order to characterize salt and polyamine effects on the base-pair opening kinetics of this oligonucleotide [Braunlin, W. H., & Bloomfield, V. A. (1988) Biochemistry 27, 1184-1191]. Here, we report salt-dependent measurements of the NMR behavior of the nonexchangeable base proton resonances of d(GGAATTCC). From chemical shift measurements, we find an unexpectedly large salt dependence of K(a), the equilibrium constant for helix association. A total of 1.8 +/- 0.3 sodium ions are thermodynamically released upon dissociation of the octamer duplex. Most of the salt dependence of the equilibrium constant can be traced to a large salt dependence of the association rate. Thus, 1.4 +/- 0.2 sodium ions associate during the rate-limiting step of helix association. In agreement with our previous imino proton results, we also find a significant salt dependence of the duplex dissociation rate. Activation energies for helix association are very small, and possibly negative; most of the temperature dependence of the association equilibrium can be traced to a large activation energy (approximately 50 kcal/mol) for duplex dissociation.