Definition of Angular Dependence of 1H-15N Coupling Constants in Amino Sugars

氨基糖中 1H-15N 偶联常数的角度依赖性的定义

• 批准号: 7594245
• 负责人: rachel schneerson
• 金额: $ 8.11万
• 依托单位: EUNICE KENNEDY SHRIVER NATIONAL INSTITUTE OF CHILD HEALTH & HUMAN DEVELOPMENT
• 依托单位国家: 美国
• 资助国家: 美国
• 起止时间: 至
• 项目状态: 未结题
• 来源: https://reporter.nih.gov/project-details/7594245
• 关键词: Acetylgalactosamine; Acetylglucosamine; Adopted; Amino Sugars; Aminoglycoside Antibiotics; Bacterial Polysaccharides; COSY; Cell Nucleus; Chemicals; Condition; Coupled; Coupling; Data; Dependence; Deuterium; Deuterium Oxide; Equation; Evolution; Galactosamine; Gills; Glucosamine; Glucose; Hydrochloride Salt; Hydroxyl Radical; Linear Regressions; Measurement; Measures; Mechanics; Methods; Modeling; Molecular Conformation; N-acetylmannosamine; Neisseria meningitidis; Nitrogen; Nuclear; Numbers; Object Attachment; Organic solvent product; Phase; Physiologic pulse; Physiological; Polysaccharides; Procedures; Protons; Publishing; Pulse taking; Relaxation; Resolution; Shigella dysenteriae; Shigella sonnei; Solutions; Solvents; Structure; System; Techniques; Testing; Time; Trifluoroacetic Acid; Water; Work; amino group; aqueous; base; interest; mannosamine; molecular dynamics; multiplet; programs; pyranose; quantum; research study; success; sugar; vaccine development

Definition Of The Stereochemical Dependence Of 1H-15N Coupling Constants In Amino Sugar Derivatives: Amino sugars are common components of bacterial polysaccharides, either as their N-acetylated forms (for example, Neisseria meningitidis group A, Shigella dysenteriae type 1) or as sugars having a free amino group (Shigella sonnei). As part of a program of vaccine development based on such polysaccharides, we are interested in extending the use of nitrogen NMR parameters for the structural, stereochemical, and conformational analysis of these materials. In our previous work, the 15N-1H coupling constants of a suite of organic-soluble amino sugar derivatives were measured by the inverse-detected, heteronuclear single quantum, multiple bond correlation (HSQMBC) technique. These derivatives were selected for the initial study because their expected long relaxation times appeared to offer the greatest chance of success for application of the multi-pulse HSQMBC technique, and because the derivatives available contained 15N and 1H nuclei in several different stereochemical orientations. The magnitudes of the vicinal 1H-15N coupling constants were correlated with the geometry of the coupled nuclei in the conformations of the amino sugar models, as determined by molecular dynamics/mechanics computations. Non-linear regression of the vicinal 1H-15N coupling constants to the HCCN dihedral angles determined by molecular dynamics led to definition of a new Karplus equation: 3JHCCN = 3.1 cos2 phi = 0.6 cos phi + 0.4, which describes the dependence of the vicinal, 3JHCCN coupling constant on the HCCN dihedral angle phi in amino sugars derivatives. During the past year, these measurements have been extended to the common amino sugars in aqueous solution, conditions that correspond more closely to physiological conditions than the organic solvents used in our initial work. These common amino sugars are precisely those which occur commonly in bacterial polysaccharides, including N-acetylglucosamine, N-acetylmannosamine, N-acetylgalactosamine, and 3-acetamido-3-deoxy-D-glucose, and the free amino sugars glucosamine, mannosamine, and galactosamine, studied as their stable hydrochloride salts. The recently published CPMG-HSQMBC NMR technique (Kover et al., 2006) was adopted for these measurements. This technique involves repetitive refocusing of nuclear magnetization by the Carr-Purcell-Meiboom-Gill procedure to suppress evolution of proton magnetization, thus affording anti-phase, HSQMBC NMR spectra of higher quality than the older method. A number of polar and semi-polar solvent systems have been tested, including deuterium oxide, 10% deuterium oxide:90% water, methylsulfoxide-d6, and 107:1 w/v methylsulfoxide-d6:trifluoroacetic acid. At the commencement of this study, it was not known whether dipolar relaxation of the 15N nucleus by an attached proton would be required for application of the HSQMBC method, and, therefore, whether deuterium oxide could be used as a solvent at all. In deuterium oxide, all of the OH and NH protons are expected to undergo deuterium exchange, thus removing the strong dipolar relaxation mechanism provided by these protons. However, the results of the study have revealed that dipolar relaxation by 1H directly bonded to 15N is not required for success of the experiment, and therefore, that the use of deuterium oxide is entirely feasible. In our previous work, we found that the determination of vicinal 1H15N coupling constants from the HSQMBC NMR spectra is most facile if the inverse-detected 1H multiplets have minimum multiplicity, a situation that pertains when the sugar hydroxyl protons are in rapid chemical exchange, or have been exchanged with deuterium. In the present work, we observed that the use of deuterium oxide as solvent fulfils both of these conditions. The use of semi-polar methylsulfoxide-d6 was also investigated. We found that the use of a solvent containing 1 part of trifluoroacetic acid in 107 parts of methylsulfoxide-d6 catalyzed rapid hydroxyl proton exchange, thus removing the hydroxyl proton coupling constants from the multiplets, and facilitating interpretation of the spectra. Interpretation of the HSQMBC NMR spectra requires complete 1H and 13C assignments for the amino sugars. Therefore, part of the project involves analyzing the 1D 1H and 13C NMR spectra of mixtures of the anomers of the amino sugars, with 2D COSY and 2D HSQC spectra used to obtain definitive 1H and 13C assignments, respectively, for the pyranose anomers. Analysis of the NMR data is underway, and the results are expected to provide a clearer understanding of the effects of the orientation of electronegative substituents on the 1H-15N coupling constants, as well as additional information on their dihedral angle dependence.

氨基糖衍生物1H-15N偶联常数立体化学依赖性的定义： 氨基糖是细菌多糖的常见成分，既可以是N-乙酰化形式(例如，脑膜炎奈瑟菌A组、1型志贺氏菌)，也可以是含有游离氨基的糖(宋内志贺菌)。作为基于这种多糖的疫苗开发计划的一部分，我们有兴趣扩大氮核磁共振参数的使用，用于这些材料的结构、立体化学和构象分析。 在我们以前的工作中，用反探测异核单量子多键相关(HSQMBC)技术测定了一系列有机可溶性氨基糖衍生物的15N-1H偶联常数。之所以选择这些衍生物进行初步研究，是因为它们预期的较长驰豫时间似乎为多脉冲HSQMBC技术的应用提供了最大的成功机会，而且因为现有的衍生物含有几个不同立体化学取向的15N和1H核。 通过分子动力学/力学计算，1H-15N附近偶联常数的大小与氨基糖模型构象中偶合核的几何形状有关。由分子动力学确定的邻位1H-15N偶联常数与HCCN二面角的非线性回归得到了一个新的Karplus方程：3JHCCN=3.1 cos 2Phi=0.6 cos Phi+0.4，该方程描述了邻位3JHCCN偶合常数与氨基糖衍生物中HCCN二面角Phi的关系。 在过去的一年里，这些测量已经扩展到水溶液中的常见氨基糖，与我们最初工作中使用的有机溶剂相比，这些条件更符合生理条件。这些常见的氨基糖正是细菌多糖中常见的那些，包括N-乙酰氨基葡萄糖、N-乙酰甘露糖胺、N-乙酰半乳糖胺和3-乙酰氨基-3-脱氧-D-葡萄糖，以及作为其稳定盐酸盐的游离氨基糖氨基葡萄糖、甘露糖和半乳糖。最近发表的CPMG-HSQMBC核磁共振技术(Kover等人，2006年)被用于这些测量。这项技术包括通过Carr-Purcell-Meiom-Gill过程重复重聚焦核磁化，以抑制质子磁化的演化，从而提供比旧方法更高质量的反相HSQMBC核磁共振谱。 对一些极性和半极性的溶剂体系进行了测试，包括氧化氢、10%氧化氢：90%水、甲基亚砜-d6和107：1w/v甲基亚砜-d6：三氟乙酸。在本研究开始时，尚不清楚HSQMBC方法的应用是否需要附加质子对15N原子核的偶极驰豫，因此也不知道氧化氢是否可以用作溶剂。在氢氧化物中，所有的氢质子和氢质子都可以进行重氢交换，从而消除了这些质子所提供的强偶极弛豫机制。然而，研究结果表明，1H直接键合到15N的偶极驰豫不是实验成功所必需的，因此，使用氧化氢是完全可行的。 在我们以前的工作中，我们发现，如果反向检测的1H多重数具有最小的重数，则从HSQMBC核磁共振谱确定邻近的1H15N耦合常数是最容易的，这种情况属于糖羟基质子快速化学交换或已与氘交换的情况。在目前的工作中，我们观察到使用氧化氢作为溶剂满足这两个条件。还研究了半极性甲基亚砜-d6的用途。我们发现，在107份甲基亚砜-d6中使用含有1份三氟乙酸的溶剂可以催化快速的羟质子交换，从而从多重态中去除羟质子耦合常数，从而便于对光谱的解释。 解释HSQMBC核磁共振谱需要对氨基糖进行完整的1H和13C指定。因此，该项目的一部分涉及分析氨基糖异构体混合物的1D、1H和13C核磁共振谱，并分别使用2D COSY和2D HSQC谱来确定吡喃糖异构体的1H和13C归属。 核磁共振数据的分析正在进行中，结果有望提供更清楚的了解电负性取代基的取向对1H-15N偶合常数的影响，以及关于它们的二面角相关性的更多信息。