Publications by authors named "Preeti Prajapati"

4 Publications

  • Page 1 of 1

Vibrational and conformational analysis of structural phase transition in Estradiol 17β valerate with temperature.

Spectrochim Acta A Mol Biomol Spectrosc 2021 Dec 24;263:120219. Epub 2021 Jul 24.

Instituto de Fìsica de São Carlos, Universidade de São Paulo,C.P 369, 13560-970,São Carlos, S P, Brazil.

Estradiol 17β valerate (E2V) is a hormonal medicine widely used in hormone replacement therapy. E2V undergoes a reversible isosymmetric structural phase transition at low temperature (̴ 250 K) which results from the reorientation of the valerate chain. The reversible isosymmetric structural phase transition follows Ehrenfest's classification when described as first-order and Buerger's classification when classified as order-disorder. The conformational difference also induces changes in molecular torsional angles and on the hydrogen bond pattern. In combination with density functional theory (DFT) calculations, vibrational spectroscopy has been used to correlate the valerate chain modes with the modifications of the dihedral angles on phase transition. We are expecting improvement in our understanding of the phase transition mechanism driven by the temperature. The Conformational analysis reveals the feasible structures corresponding to changes in the dihedral angles associated with the valerate chain. The infrared spectra of calculated conformers are in good agreement with the experimental spectra of E2V structure recorded at room temperature revealing that the changes in valerate chain modes at 1115 cm, 1200 cmand 1415 cm fingerprint the molecular conformation. An investigation made to determine the ligand-protein interaction of E2V through docking against estrogen receptor (ER) reveals the inhibitive and agonist nature of E2V.
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http://dx.doi.org/10.1016/j.saa.2021.120219DOI Listing
December 2021

Molecular structure and quantum descriptors of cefradine by using vibrational spectroscopy (IR and Raman), NBO, AIM, chemical reactivity and molecular docking.

Spectrochim Acta A Mol Biomol Spectrosc 2021 Feb 24;246:118976. Epub 2020 Sep 24.

Department of Physics, University of Lucknow, Lucknow 226 007, India. Electronic address:

This study aims to investigate the structural and vibrational features of cefradine (the first-generation cephalosporin antibiotic) based on spectroscopic experiments and theoretical quantum chemical approach. The fundamental structural aspects of cefradine have been examined based on optimized geometry, spectroscopic behavior, intermolecular interaction, chemical reactivity, intramolecular hydrogen bonding, and molecular docking analysis. The most stable minimum energy conformer of the title molecule was identified by performing a one-dimensional potential energy surface scan along the rotational bonds at B3LYP/6-311++G (d,p) level of theory. The vibrational features of the molecule and information about the coupled modes were predicted. The chemical reactivity and stability of all the possible conformers of cefradine were estimated based on the HOMO-LUMO energy gap and NBO approach. The overall picture of accumulation of charges on individual atoms of the molecule was predicted by molecular electrostatic potential (MEP) surface map which in turn identifies the nucleophilic and electrophilic region or sites. The quantitative analysis of electrophilicity and nucleophilicity indices was done by Hirshfeld charge analysis and it was found that N8 atom is the most prominent site for nucleophilic attack while C14 atom is feasible for electrophilic attack. QTAIM study has also been performed to investigate the nature and strength of hydrogen bonding interactions. Besides, molecular docking studies were performed to examine the active binding residues of the target.
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http://dx.doi.org/10.1016/j.saa.2020.118976DOI Listing
February 2021

Combined spectroscopic and quantum chemical approach to study the effect of hydrogen bonding interactions in ezetimibe.

Spectrochim Acta A Mol Biomol Spectrosc 2019 Jan 13;206:246-253. Epub 2018 Aug 13.

Department of Physics, University of Lucknow, Lucknow 226007, India.

Molecular structure, chemical and physical reactivity, spectroscopic behavior, intermolecular interactions play an important role in understanding the biological nature of pharmaceutical drugs. The objective of the study is to combine the spectroscopic and computational methodology for the investigation of structural behavior of ezetimibe (EZT). Computational study was done on monomeric, dimeric and trimeric models of EZT using B3LYP/6-311G(d,p). Hydrogen bond interactions were taken into consideration to validate the theoretical results with the experimental one. Results obtained for trimeric model were better than monomer and dimer. HOMO-LUMO energy band gap shows that the chemical reactivity calculated using dimeric and trimeric model is higher than that of monomeric model. Higher value of electrophilicity index (ω = 2.5654 eV) also confirms that trimer behaves as a strong electrophile in comparison with monomer and dimer. To examine the hyperconjugation interactions and the stability of the molecule, natural bond analysis (NBO) was done on dimer and trimer of EZT. Nature and the strength of hydrogen bonds were examined by quantum theory of atoms in molecules (QTAIM). Binding energy calculated from counterpoise method was -7.40 kcal/mol for dimer and -21.47 kcal/mol for trimer.
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http://dx.doi.org/10.1016/j.saa.2018.08.023DOI Listing
January 2019

Spectroscopic and molecular structure (monomeric and dimeric model) investigation of Febuxostat: A combined experimental and theoretical study.

Spectrochim Acta A Mol Biomol Spectrosc 2018 Oct 22;203:1-12. Epub 2018 May 22.

Department of Pharmaceutics, National Institute of Pharmaceutical Education and Research (NIPER), Sector-67, S.A.S. Nagar, Punjab 160062, India.

Febuxostat (FXT) is a urate-lowering drug and xanthine oxidase inhibitor which is used for the treatment of hyperuricemia and gout caused by increased levels of uric acid in the blood (hyperuricemia). The present study aims to provide deeper knowledge of the structural, vibrational spectroscopic and physiochemical properties of FXT based on monomeric and dimeric model with the aid of combination of experimental and computational methods. The conformational analysis of form Q has been done to predict the possible structure of unknown form A. Vibrational spectra of form A and Q has been compared to get an idea of hydrogen bonding interactions of form A. A computational study of FXT has been executed at different level (B3LYP, M06-2X, WB97XD) of theory and 6-31 G (d, p) basis set for dimeric model to elucidate the nature of intermolecular hydrogen bond. The red shift observed in the stretching modes of OH, CO groups and blue shift in stretching mode of CN group in experimental as well as in theoretical spectra explains the involvement of these groups in intermolecular hydrogen bonding. NBO analysis shows that change in electron density (ED) in the lone pair orbital to σ* antibonding orbital (LP1 (N39) → σ* (O3-H38)) with maximum value of E(2) energy confirms the presence of hydrogen bond (N39⋯H38-O3) leading to dimer formation. Study of topological parameters was executed for dimer using Bader's atoms in molecules (AIM) theory predicting the partially covalent nature of hydrogen bonds present in the molecule. The study of molecular electrostatic potential surface (MEPS) map ascertains that the CO, CN group are prone to electrophilic attack and OH group is active towards nucleophilic attack. The lower energy band gap and higher value of softness of dimeric model of FXT indicates its more reactivity, polarisability than monomeric model. The local reactivity descriptors predict the order of reactive sites towards electrophilic, nucleophilic and radical attack. An investigation made to determine the ligand protein interaction of FXT through docking with different molecular targets reveals the inhibitive as well as antibacterial nature of FXT.
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http://dx.doi.org/10.1016/j.saa.2018.05.074DOI Listing
October 2018
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