ChemInform Abstract: Calculated and Experimental NMR Chemical Shifts of p‐Menthane‐3,9‐diols. A Combination of Molecular Dynamics and Quantum Mechanics to Determine the Structure and the Solvent Effects.

Casanovas, Jordi; Namba, Adriana M.; León, Salvador; Aquino, Gilberto L. B.; Silva, Gil Valdo Jose da; Alemán, Carlos

doi:10.1002/chin.200137183

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“…For studies specifically using NMR, quantum chemical simulations for the prediction of spectra have been a valuable tool for the community. In the last two decades, density functional theory (DFT), an exceptionally well-established approach for high-throughput chemical calculations with the advantage of high performance for less computational cost, has been widely applied to predict NMR chemical shifts [89][90][91] of molecules and conformers [92][93][94] in different custom solvent conditions [95][96][97]. Furthermore, structural elucidation is one of the most practical uses of NMR, and it is common to utilize NMR chemical shift calculations along with experimental shifts to identify compound mixtures [98][99][100] and to aid reassignment of structures or stereostructure assignment [101][102][103].…”

Section: Introductionmentioning

confidence: 99%

An initial investigation of accuracy required for the identification of small molecules in complex samples using quantum chemical calculated NMR chemical shifts

et al. 2022

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The majority of primary and secondary metabolites in nature have yet to be identified, representing a major challenge for metabolomics studies that currently require reference libraries from analyses of authentic compounds. Using currently available analytical methods, complete chemical characterization of metabolomes is infeasible for both technical and economic reasons. For example, unambiguous identification of metabolites is limited by the availability of authentic chemical standards, which, for the majority of molecules, do not exist. Computationally predicted or calculated data are a viable solution to expand the currently limited metabolite reference libraries, if such methods are shown to be sufficiently accurate. For example, determining nuclear magnetic resonance (NMR) spectroscopy spectra in silico has shown promise in the identification and delineation of metabolite structures. Many researchers have been taking advantage of density functional theory (DFT), a computationally inexpensive yet reputable method for the prediction of carbon and proton NMR spectra of metabolites. However, such methods are expected to have some error in predicted 13C and 1H NMR spectra with respect to experimentally measured values. This leads us to the question–what accuracy is required in predicted 13C and 1H NMR chemical shifts for confident metabolite identification? Using the set of 11,716 small molecules found in the Human Metabolome Database (HMDB), we simulated both experimental and theoretical NMR chemical shift databases. We investigated the level of accuracy required for identification of metabolites in simulated pure and impure samples by matching predicted chemical shifts to experimental data. We found 90% or more of molecules in simulated pure samples can be successfully identified when errors of 1H and 13C chemical shifts in water are below 0.6 and 7.1 ppm, respectively, and below 0.5 and 4.6 ppm in chloroform solvation, respectively. In simulated complex mixtures, as the complexity of the mixture increased, greater accuracy of the calculated chemical shifts was required, as expected. However, if the number of molecules in the mixture is known, e.g., when NMR is combined with MS and sample complexity is low, the likelihood of confident molecular identification increased by 90%.

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