Determination of chemical shift anisotropy tensor and molecular correlation time of proton pump inhibitor omeprazole by solid state NMR measurements

2020 ◽  
Vol 44 (44) ◽  
pp. 19393-19403
Author(s):  
Krishna Kishor Dey ◽  
Manasi Ghosh
Keyword(s):  
Correlation Time ◽  
Chemical Shift Anisotropy ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Spin Lattice ◽  
Structure And Dynamics ◽  
Molecular Correlation ◽  
Anisotropy Tensor

The correlation between the structure and dynamics of omeprazole is portrayed by extracting CSA parameters through the 13C 2DPASS CP-MAS SSNMR experiment, site specific spin–lattice relaxation time by Torchia CP experiment, and calculation of the molecular correlation time.

scholarly journals Study the Structure and Dynamics of Antifungal Agent Ketoconazole by CSA and Site-Specific Spin-Lattice Relaxation Time Measurements

2021 ◽  
Author(s):  
Krishna Kishor Dey ◽  
Manasi Ghosh
Keyword(s):  
Relaxation Time ◽  
Correlation Time ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Site Specific ◽  
Spin Lattice Relaxation Time ◽  
Spin Lattice ◽  
Structure And Dynamics ◽  
Molecular Correlation

Abstract An azole antifungal agent, ketoconazole, is widely used in the treatment of mucosal fungal infections related to AIDS immunosuppression, organ transplantation, and cancer chemotherapy. The structure and dynamics of ketoconazole are thoroughly studied by chemical shift anisotropy tensor and site-specific spin-lattice relaxation time measurements. The molecular correlation time at crystallographically different carbon sites is calculated by considering that the spin-lattice relaxation mechanism for the 13C nucleus is mainly governed by chemical shift anisotropy interaction and hetero-nuclear dipole-dipole coupling. The CSA parameters at the crystallographically distinct sites of ketoconazole are determined by two-dimensional phase adjusted spinning sideband (2D PASS) cross-polarization magic angle spinning (CP-MAS) solid-state NMR experiment. The site-specific spin-lattice relaxation time is measured by the Torchia CP experiment. The spin-lattice relaxation rate is slow for all the carbon nuclei sites except C2, C3, C4, C5, and C26 carbon nuclei reside on the piperazine ring and the methyl group. It suggests the close-pack arrangement of the molecule due to π-π stacking interaction. The molecular correlation time of all the carbon atoms reside on the benzene ring, 1,3-dioxolane ring, imidazole ring, and the 2,4-dichlorobenzene ring is of the order of 10-4 s, while it is of the order of 10-7 s for carbon atoms reside on the piperazine ring. The CSA parameters of the carbon nuclei on the piperazine ring (C2, C3, C4, C5), and the methyl group (C26) are very low compared to other carbon nuclei. The CSA parameters are very high for carbon nuclei reside on the benzene ring, imidazole ring, and the 2,4-dichlorobenzene ring due to the presence of π-electrons. A huge variation of the spin-lattice relaxation time and the molecular correlation time are observed for numerous carbon nuclei situated on the side-chain of ketoconazole. The spin-lattice relaxation time varies from 500 s to 8 s, and the molecular correlation time varies in the range of 10-4s to 10-7s. These types of investigations portrayed the correlation between the structure and dynamics of the antifungal drug ketoconazole, which will help to develop the advanced antifungal drugs. Additionally, the CSA information of the drug molecules will be immensely useful for NMR crystallography.

Carbon-13 Spin–Lattice Relaxation Times for Selected Steroids

1975 ◽  
Vol 53 (3) ◽  
pp. 338-342 ◽  
Author(s):  
John W. ApSimon ◽  
Helmut Beierbeck ◽  
John K. Saunders
Keyword(s):  
Conformational Changes ◽  
Correlation Time ◽  
Relaxation Times ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Methyl Group ◽  
Spin Lattice ◽  
Molecular Correlation ◽  
Anisotropic Motion

The spin–lattice relaxation time (T1) data for a number of androstane and cholestane derivatives is presented. The NT1 value of carbon-3 in several of the compounds is found to be shorter than the average NT1 value for the other ring carbons which is interpreted in terms of anisotropic motion with the long steroid axis being the preferred axis of rotation. As this effect is only observed for carbon-3, an effective molecular correlation time can be calculated from the average NT1 value for all other CH and CH2 carbons. The correlation time (τi) for internal rotation of a methyl group is shown to depend on the number of 1,3 diaxial methyl group – hydrogen interactions. Thus τi(C-19) is shorter than τi(C-18) for androstane, τi(C-19) is shorter for trans-cholestanol than for either cis-cholestanol or cholesterol. The effects of substituents and conformational changes on τi as well as the effect of solvent on T1 are discussed.

scholarly journals An atomic resolution description of folic acid using solid state NMR measurements

RSC Advances ◽  
2020 ◽  
Vol 10 (42) ◽  
pp. 24973-24984 ◽  
Author(s):  
Manasi Ghosh ◽  
Shovanlal Gayen ◽  
Krishna Kishor Dey
Keyword(s):  
Folic Acid ◽  
Solid State Nmr ◽  
Chemical Shift Anisotropy ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Site Specific ◽  
Spin Lattice ◽  
Anisotropy Tensor ◽  
Cp Mas Nmr

The chemical shift anisotropy tensor and site specific spin-lattice relaxation time of folic acid were determined by a 13C 2DPASS CP-MAS NMR experiment and Torchia CP experiment respectively.

Determination of the correlation between the structure and dynamics of deflazacort by solid state NMR measurements

2020 ◽  
Vol 44 (42) ◽  
pp. 18419-18430 ◽  
Author(s):  
Krishna Kishor Dey ◽  
Manasi Ghosh
Keyword(s):  
Relaxation Time ◽  
Solid State ◽  
Solid State Nmr ◽  
Lattice Relaxation ◽  
Lattice Relaxation Time ◽  
Spin Lattice Relaxation ◽  
Spin Lattice Relaxation Time ◽  
Spin Lattice ◽  
Structure And Dynamics

The correlation between the structure and dynamics of glucocorticoid deflazacort is determined by a 2DPASS CP-MAS SSNMR experiment and 13C spin–lattice relaxation time by a Torchia CP experiment.

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