Definition of Angular Dependence of 1H-15N Coupling Cons

1H-15N 联轴器角度依赖性的定义

• 批准号: 7334229
• 负责人: rachel schneerson
• 金额: --
• 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/7334229
• 关键词: Definition; Angular; Dependence; 1H; 15N

High-resolution nuclear magnetic resonance spectroscopy is a powerful method for analysis of the conformations, molecular structures, purity, and stereochemistry of carbohydrates, including monosaccharide, oligosaccharide, and polysaccharide types that are of prime interest in bacterial vaccine development. Part of our function is to provide analytical NMR support as needed for current vaccine projects in the lab that involve the characterization of saccharide structure and purity. Another part includes more fundamental investigations of the application of measurements of NMR chemical shifts, nuclear spin-spin coupling constants, and nuclear Overhauser effects to the structural analysis of carbohydrates. We also characterize the molecular geometry of saccharides of interest in these studies by molecular dynamics computations followed by energy minimization by molecular mechanics. DEFINITION OF THE ANGULAR DEPENDENCE OF 1H-15N COUPLING CONSTANTS IN AMINO SUGAR DERIVATIVES: Amino sugars are common components of bacterial polysaccharides. 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 recent studies of amino sugar derivatives, the NH to ND induced isotope effects on the chemical shifts of 13C nuclei surrounding the nitrogen atom have been characterized. The high sensitivity of an NMR cryoprobe allowed the rapid acquisition of well-resolved 1D and 2D NMR spectra, before significant anomerization of the N-acetyl-amino-deoxy sugars had occurred, thus facilitating their spectral assignment. In our current work, the 15N-1H coupling constants of various derivatives of amino sugars have been measured by the inverse-detected, heteronuclear single quantum, multiple bond correlation (HSQMBC) technique, and the values so obtained compared with those measured by the more traditional procedure of synthesizing highly enriched 15N-labeled amino sugar derivatives and analyzing their 1H NMR spectra. The HSQMBC method is highly selective, in this instance filtering out all non-15N NMR interactions, thereby yielding simplified NMR spectra. Acquisition of the HSQMBC spectra from reasonably small quantities of materials (for example, 30 mg/0.5 mL) having 15N at natural abundance was facilitated by the enhanced sensitivity of a 1H/13C/15N inverse NMR cryoprobe. A number of bicyclic amino sugar models of fixed or known geometry have been studied, including a series of methyl 2- and 3-amino-4,6-O-benzylidene-deoxy-alpha-D-hexopyranosides in chair or skew boat conformations, and methyl 2,6-anhydro-3-deoxy-3-phthalimido-alpha-D-mannopyranoside in a locked, almost classical boat conformation. The major conformational features of these molecules have been determined from 1H-1H NMR coupling constants measured by complete assignment of the 1H NMR spectra of the amino derivatives. The magnitudes of the vicinal 1H-15N coupling constants have been correlated with the geometry of the coupled nuclei in the conformations of the amino sugar models, as determined by molecular dynamics/mechanics computations. Various methods for analysis of the HSQMBC spectra have been investigated. The most convenient method was found to be "NMR multiplet total width subtraction", based on the fact that the total width of first order NMR multiplets is equal to the sum of their coupling constants. 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. Applications of the equation are expected in NMR analysis of the stereochemistry of amino sugar components of nitrogen-containing saccharides and aminoglycoside antibiotics.

高分辨率核磁共振光谱是一种分析碳水化合物构象、分子结构、纯度和立体化学的有力方法，包括细菌疫苗开发中最感兴趣的单糖、寡糖和多糖类型。我们的部分职能是根据需要为实验室中涉及糖结构和纯度表征的当前疫苗项目提供分析NMR支持。另一部分包括NMR化学位移，核自旋-自旋耦合常数和核Overhauser效应的测量应用于碳水化合物的结构分析的更基本的调查。我们还通过分子动力学计算，然后通过分子力学的能量最小化来表征这些研究中感兴趣的分子几何结构。 氨基糖衍生物中1H-15 N偶合常数的角度依赖性的定义：氨基糖是细菌多糖的常见组分。作为基于这种多糖的疫苗开发计划的一部分，我们有兴趣扩展氮NMR参数用于这些材料的结构，立体化学和构象分析。在我们最近的氨基糖衍生物的研究中，NH到ND诱导的同位素效应对氮原子周围的13 C核的化学位移已被表征。NMR冷冻探针的高灵敏度允许快速采集良好分辨的1D和2D NMR光谱，在N-乙酰基-氨基-脱氧糖发生显著的端基异构化之前，从而促进其光谱归属。 本工作采用反向检测、异源单量子多键相关（HSQMBC）技术测定了各种氨基糖衍生物的~（15）N-~（15）H偶合常数，并与传统的合成高富集~（15）N-标记氨基糖衍生物并分析其~ 1H NMR谱的方法进行了比较。HSQMBC方法是高度选择性的，在这种情况下过滤掉所有非15 N NMR相互作用，从而产生简化的NMR光谱。通过1H/13 C/15 N反向NMR冷冻探针的增强的灵敏度，促进了从合理少量的具有天然丰度的15 N的材料（例如，30 mg/0.5 mL）获得HSQMBC光谱。 已经研究了许多固定或已知几何形状的双环氨基糖模型，包括一系列呈椅子或斜船构象的甲基2-和3-氨基-4，6-O-亚苄基-脱氧-α-D-吡喃己糖苷，以及呈锁定的、几乎经典的船构象的甲基2，6-脱水-3-脱氧-3-邻苯二甲酰亚氨基-α-D-吡喃甘露糖苷。这些分子的主要构象特征已被确定从1H-1H NMR耦合常数测量的1H NMR光谱的氨基衍生物的完全归属。邻位1H-15 N耦合常数的大小已与耦合核的几何形状的构象的氨基糖模型，确定由分子动力学/力学计算。对HSQMBC光谱的各种分析方法进行了研究。最简便的方法是“NMR多重峰总宽相减法”，因为一级NMR多重峰的总宽等于它们的耦合常数之和。 用分子动力学方法测定了HCCN二面角与邻位1H-15 N偶合常数的非线性回归，得到了一个新的Karplus方程：3 JHCCN = 3.1 cos 2 phi = 0.6 cos phi + 0.4，该方程描述了氨基糖衍生物中邻位3 JHCCN偶合常数与HCCN二面角phi的关系。该方程可望在含氮抗生素和氨基糖苷类抗生素的氨基糖组分立体化学的NMR分析中得到应用。