ANATOLIA: NMR software for spectral analysis of total lineshape (original) (raw)
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The Journal of organic chemistry, 2002
A systematic procedure to decipher first-order 1 H NMR multiplets is described. This method is a very practical tool for extracting coupling constant values. It requires only that one (a) learn to identify each of the 2 n (n ) number of spin 1 / 2 nuclei to which the proton is coupled) "units of intensity" of a multiplet and (b) then apply a clearly delineated sequence of iterative steps that allows the J's to be assigned in order (from smallest to largest). The approach is even easier to use than one described previously (J. Org. Chem. 1994, 59, 4096-4103).
A two-stage approach to automatic determination of1H NMR coupling constants
Magnetic Resonance in Chemistry, 2005
H NMR scalar coupling constants are a rich source of information on molecular structure, but their extraction from spectra can be less than straightforward. Previous approaches to J extraction include methods proposed by Hoye, Golotvin, and the 'modified J-doubling' method. Here we describe the ACCA method, currently implemented in the NMR package MestReC, which allows a high degree of automation in the extraction of coupling patterns even in the case of complex multiplets with sublinewidth splitting. The new approach is illustrated by application to strychnine, for which it has detected previously unreported couplings.
Concepts in Magnetic Resonance Part A, 2013
This article discusses the existing methods to correlate NMR parameters describing the high resolution NMR spectra of liquids and solid systems with their structural parameters. Those methods are divided into direct and indirect ones. This article includes two types of direct methods: those based on the Nuclear Overhauser Effect (NOE) contributions to the NMR relaxation and those based on direct measurements of the dipolar couplings using several experimental approaches. Indirect methods are based on the intrinsic dependence of J couplings and shieldings on the atomic coordinates of the atoms in a molecule and its surroundings, requiring complex quantum mechanical calculations to relate NMR spectral properties to molecular and crystal structure. This article discusses how changes in chemical bonding, conformation, and stereo configurations that cause measurable changes in NMR parameters closely related to molecular and crystal structure. The final section provides information about the software and hardware required to perform calculations needed to solve structural problems using high resolution NMR. This article intends to provide molecular structural researchers new to the field of NMR, with an overall panorama of the potential of using high resolution NMR for structure elucidation, when other more traditional techniques are not feasible. To this end and to emphasize the didactic value of this work, after each section a brief conclusion has been added to recap the critical concepts.
Theoretical NMR correlations based Structure Discussion
Journal of cheminformatics, 2011
ABSTRACT: The constitutional assignment of natural products by NMR spectroscopy is usually based on 2D NMR experiments like COSY, HSQC, and HMBC. The actual difficulty of the structure elucidation problem depends more on the type of the investigated molecule than on its size. The moment HMBC data is involved in the process or a large number of heteroatoms is present, a possibility of multiple solutions fitting the same data set exists. A structure elucidation software can be used to find such alternative constitutional assignments and help in the discussion in order to find the correct solution. But this is rarely done. This article describes the use of theoretical NMR correlation data in the structure elucidation process with WEBCOCON, not for the initial constitutional assignments, but to define how well a suggested molecule could have been described by NMR correlation data. The results of this analysis can be used to decide on further steps needed to assure the correctness of the...
Chemistry (Weinheim an der Bergstrasse, Germany), 2015
Among the NMR spectroscopic parameters, long-range heteronuclear coupling constants convey invaluable information on torsion angles relevant to glycosidic linkages of carbohydrates. A broadband homonuclear decoupled PSYCHE CPMG-HSQMBC method for the precise and direct measurement of multiple-bond heteronuclear couplings is presented. The PSYCHE scheme built into the pulse sequence efficiently eliminates unwanted proton-proton splittings from the heteronuclear multiplets so that the desired heteronuclear couplings can be determined simply by measuring frequency differences between peak maxima of pure antiphase doublets. Moreover, PSYCHE CPMG-HSQMBC can provide significant improvement in sensitivity as compared to an earlier Zangger-Sterk-based method. Applications of the proposed pulse sequence are demonstrated for the extraction of (n) J((1) H,(77) Se) and (n) J((1) H,(13) C) values, respectively, in carbohydrates; further extensions can be envisioned in any J-based structural and c...
CcpNmr AnalysisAssign: a flexible platform for integrated NMR analysis
Journal of biomolecular NMR, 2016
NMR spectroscopy is an indispensably powerful technique for the analysis of biomolecules under ambient conditions, both for structural- and functional studies. However, in practice the complexity of the technique has often frustrated its application by non-specialists. In this paper, we present CcpNmr version-3, the latest software release from the Collaborative Computational Project for NMR, for all aspects of NMR data analysis, including liquid- and solid-state NMR data. This software has been designed to be simple, functional and flexible, and aims to ensure that routine tasks can be performed in a straightforward manner. We have designed the software according to modern software engineering principles and leveraged the capabilities of modern graphics libraries to simplify a variety of data analysis tasks. We describe the process of backbone assignment as an example of the flexibility and simplicity of implementing workflows, as well as the toolkit used to create the necessary gr...
R -factor, Free R , and Complete Cross-Validation for Dipolar Coupling Refinement of NMR Structures
Journal of the American Chemical Society, 1999
NMR structure determination of macromolecules involves a minimization problem in which atomic models, subject to restraints relating to idealized covalent geometry and nonbonded contacts, are fitted to experimental observables. The latter comprise restraints between atoms separated by e6 Å, such as NOEderived interproton distances, torsion angles, coupling constants, and chemical shifts, as well as restraints that provide direct information on long-range order such as dipolar couplings. An expression for the dipolar coupling R-factor is derived which provides a quantitative and readily interpretable measure of the agreement between observed and calculated dipolar couplings. The dipolar R-factor expresses the ratio of the observed rms difference between observed and calculated values with that expected for a totally random distribution of vectors. The latter can be calculated exactly from the magnitude of the alignment tensor. The dipolar R-factor scales between 0 and 1, where a value of 0 indicates perfect agreement between observed and calculated dipolar couplings, and a completely random structure yields a value of 1. The dipolar coupling R-factor is readily amenable to complete cross-validation, with multiple pairs of working and test data sets, thereby permitting one to assess the quality of the fit to the experimental dipolar couplings and to avoid overfitting the experimental data. The application of the dipolar R-factor with complete cross-validation is demonstrated using experimental data for the protein cyanovirin-N.
The NMR-WEBLAB: An internet approach to NMR lineshape analysis
Applied Magnetic Resonance, 2001
The nuclear magnetic resonance (NMR) WEBLAB is described, providing an interactive tool for analyzing NMR spectra of solids and anisotropic liquids to elucidate their molecular dynamics. It is a collection of programs freely available over the Internet at http://www.mpip-mainz.mpg.de/weblab4O/ that permit the interpretation of one-dimensional NMR spectra in the case of motions occurring on a cone and of two-dimensional exchange NMR data for discrete jumps. The programs are described in detail and analytical formulae for the averaged interaction tensor components that govern the spectra in the fast motional limit are derived in an appendix. To facilitate the validation of the results obtained from the WEBLAB, we present examples for two-and three-site jumps and demonstrate how WEBLAB can be utilized for analyzing more complex motions around more than one axis as met, e.g., in poly(diethysiloxane), where experimental data are available.