CH-O HYDROGEN BONDS

描述：本项目的中心目标是了解 CH之间形成的正常弱相互作用的基本方面 质子供体和含有电负性O或N的受体基团 原子。 这些所谓的CH X（或更常见的CH）。O）H键在大的 生物系统中的数字，如蛋白质和核酸，但非常 人们对它们的强度等基本特征知之甚少， 他们的存在对三维空间的限制 它们所在的生物分子的结构。 由于晶体结构 我不能说任何给定的相互作用的强度，这个项目 这是从头计算。 制定适当的模型 系统，加上现在可行的高精度， 使这种计算能够阐明这些信息， 这是任何其他方式都无法实现的互动。 这 项目将代表一个仔细和系统的治疗CH。X 相互作用，从非常弱的力量，不同的是， 烃-烃，甚至超过常规氢键， 实力 CH基团参与氢键的潜力将是 研究了一系列系统：a）不同的sp（n）杂交， C原子，B）具有与CH不同接近度的电负性基团 供体，c）包括不同的受体基团，d）具有 特定的生化相关性;例如，α-CH 2肽。 这项工作将寻找各种性质，可能与一个 另 找到一个有吸引力的CH。O相互作用，以及 相关的平衡，优选的几何计算将确定 结合能对拉伸和弯曲变形的敏感性; 也就是说，将评估势能表面。 计算将 解决CH中是否存在协同性。X键，如果是这样，是什么键 程度

DESCRIPTION: The central goal of this project is an understanding of the fundamental aspects of the normally weak interactions formed between a CH proton donor and an acceptor group containing the electronegative O or N atom. These so-called CH..X (or more commonly CH..O) H-bonds occur in large numbers in biological systems such as proteins and nucleic acids, yet very little is known about even such fundamental features as their strength, and the constraints that their presence places upon the three-dimensional structure of the biomolecule in which they occur. Since crystal structures can say little about the strength of any given interaction, this project turns to ab initio calculations. The formulation of appropriate model systems, coupled with the high levels of accuracy which are now feasible, enables calculations of this sort to elucidate information about these interactions which are simply not attainable by any other means. This project will represent a careful and systematic treatment of CH..X interactions, varying from very weak forces, that differ little from hydrocarbon-hydrocarbon, to those that surpass even conventional H-bonds in strength. The potential of the CH group to participate in a H-bond will be investigated for a range of systems: a) differing in sp(n) hybridization of the C atom, b) with varying proximity of an electronegative group to the CH donor, c) including different acceptor groups, d) groups that have particular biochemical relevance; e.g., the alpha-CH2 group of peptides. The work will search for various properties that may be correlated with one another. Having identified an attractive CH..O interaction, and an associated equilibrium, preferred geometry calculations will determine the sensitivity of the binding energy to stretching and bending deformations; i.e., a potential energy surface will be evaluated. Calculations will address whether cooperativity occurs in CH..X bonds, and if so, to what extent.