Miller Dorothy J, Lisy James M
University of Illinois at Urbana-Champaign, Urbana, Illinois 61801, USA.
J Phys Chem A. 2007 Dec 13;111(49):12409-16. doi: 10.1021/jp073521i. Epub 2007 Aug 16.
To properly understand the preferred structures and biological properties of proteins, it is important to understand how they are influenced by their immediate environment. Competitive intrapeptide, peptide...water, ion...water, and ion...peptide interactions, such as hydrogen bonding, play a key role in determining the structures, properties, and functionality of proteins. The primary types of hydrogen bonding involving proteins are intramolecular amide...amide (N-H...O=C) and intermolecular amide...water (O-H...O=C and H-O...H-N). n-Methylacetamide (NMA) is a convenient model for investigating these competitive interactions. An analysis of the IR photodissociation (IRPD) spectra of M+(n-methylacetamide)1(H2O)n=0-3 (M=Na and K) in the O-H and N-H spectral regions is presented. Ab initio calculations (MP2/cc-pVDZ) are used as a guide in identifying both the type and location of hydrogen bonds present. In larger clusters, where several structural isomers may be present in the molecular beam, ab initio calculations are also used to suggest assignments for the observed spectral features. The results presented offer insight to the nature of ion...NMA interactions in an aqueous environment and reveal how different ion...ligand pairwise interactions direct the extent of water...water and water...NMA hydrogen bonding observed.
为了正确理解蛋白质的优选结构和生物学特性，了解它们如何受到其直接环境的影响很重要。竞争性的肽内、肽……水、离子……水和离子……肽相互作用，如氢键，在决定蛋白质的结构、性质和功能方面起着关键作用。涉及蛋白质的主要氢键类型是分子内酰胺……酰胺（N-H……O=C）和分子间酰胺……水（O-H……O=C和H-O……H-N）。N-甲基乙酰胺（NMA）是研究这些竞争性相互作用的便捷模型。本文对M+(n-甲基乙酰胺)1(H2O)n=0-3（M=Na和K）在O-H和N-H光谱区域的红外光解离（IRPD）光谱进行了分析。从头算计算（MP2/cc-pVDZ）被用作识别存在的氢键类型和位置的指导。在较大的簇中，分子束中可能存在几种结构异构体，从头算计算也用于为观察到的光谱特征提出归属。所呈现的结果有助于深入了解水环境中离子……NMA相互作用的本质，并揭示不同的离子……配体成对相互作用如何指导观察到的水……水和水……NMA氢键的程度。
