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 质子供体和含有负电性O或N的受体基团 原子。这些所谓的CH.X(或更常见的CH.O)氢键以大分子形式存在 蛋白质和核酸等生物系统中的数字，但非常 人们甚至对它们的力量等基本特征知之甚少，而且 它们的存在给三维空间带来的限制 它们所在的生物分子结构。由于晶体结构 我几乎不能说明任何给定交互的强度，此项目 转向从头计算。适当模型的制定 系统，再加上现在可行的高精度水平， 使这类计算能够阐明有关这些的信息 任何其他方式都无法实现的互动。这 该项目将代表着对CH.X的仔细和系统的处理 相互作用，与非常弱的力不同，与 碳氢化合物，到那些甚至超过传统氢键的碳氢化合物 力量。CH基团参与氢键的可能性为 研究了一系列系统：a)不同于SP(N)杂交的 C原子，b)，具有不同的电负性基团与CH 供体，c)包括不同的受体组，d)具有 特定的生化相关性；例如，α-CH2基团的多肽。 这项工作将搜索可能与一个属性相关联的各种属性 又一个。在确定了一个有吸引力的CH.O相互作用之后， 相关的平衡、首选几何计算将决定 结合能对拉伸和弯曲变形的敏感性； 也就是说，势能面将被评估。计算将 解决CH.X键中是否存在协同作用，如果是，协同作用是什么 范围。

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.