Browsing by Author "Krishna Kishor Dey"

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A Description of the Local Structure and Dynamics of Ketoconazole Molecule by Solid-State NMR Measurements and DFT Calculations: Proposition for NMR Crystallography
(John Wiley and Sons Inc, 2021) Krishna Kishor Dey; Milind M. Deshmukh; Manasi Ghosh
An azole class antifungal agent, ketoconazole, is widely used in the treatment of mucosal fungal infections that arise due to AIDS immunosuppression, organ transplantation, and cancer chemotherapy. The structure and dynamics of various molecular moieties of ketoconazole are thoroughly studied by measuring chemical shift anisotropy tensor and site-specific spin-lattice relaxation time. The local correlation time at crystallographically different carbon nuclei sites is also calculated. The chemical shift anisotropy (CSA) parameters at the crystallographically distinct sites of ketoconazole are determined by the 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 method outlined by Torchia (T1CP). The values of the principal components of CSA parameters extracted by the 2DPASS CP-MAS ssNMR experiment are supported by density functional theory (DFT) calculations. The CSA parameters are high for those carbon nuclei, whose spin-lattice relaxation rate is slow, and it is low for those carbon nuclei whose spin-lattice relaxation rate is fast. It suggests that the spin-lattice relaxation mechanism is mainly governed by chemical-shift anisotropy interaction for these carbon nuclei. A huge variation of the spin-lattice relaxation time and the local correlation time are observed for numerous carbon nuclei that reside on the side-chain of the molecule. The spin-lattice relaxation time varies from 500 s to 8 s, and the order of the local correlation time varies from (Formula presented.) s to (Formula presented.) s. These types of studies in which the chemical shift anisotropy (CSA) parameters and spin-lattice relaxation time provide information about the electronic configuration and the spin dynamics at the various crystallographic locations of the drug molecule will enrich the field “NMR crystallography.” It will also help to develop the strategies for the administration of antifungal drugs by providing information about the structure and dynamics of various parts of the drug molecule. © 2021 Wiley-VCH GmbH
Analysis of metabolite profiles of haemolymph in developmental stages of the silkmoth with high-resolution nuclear magnetic resonance
(Springer Science and Business Media Deutschland GmbH, 2023) Lekhan Lodhi; Manasi Ghosh; Krishna Kishor Dey; Janak Dulari Ahi
Metabolite profiles of the haemolymph of the silkmoth, Bombyx mori (L.) (Lepidoptera: Bombycidae) provide crucial information on metabolic changes during larval to adult development. The metabolite profile of endogenous low molecular weight organic metabolites and amino acids in the haemolymph of the 4th instar on the first and fourth day, the 5th instar on the fourth and seventh day, the prepupa (spinning 5th instar), the pupa on the fourth day, the pupa on the eighth day and the adult moth (newly hatched) was studied. More than 20 metabolites could be assigned and quantified. It was found that concentrations of alanine, succinate, betaine and histidine were relatively high during the larval feeding period, but these concentrations decreased at the beginning of wandering. Concentration differences were also observed for trehalose, organic amines (putrescine), organic acids (quinate, lactate, acetate), intermediates of the tricarboxylic acid cycle (citrate, 2-ketoglutarate and succinate), betaine and metabolites of purine, choline and pyrimidines as the insect passed through different developmental stages. The metabolic profile of the silkmoth during the different stages would provide important information about the developmental biology of the insect. The study will illuminate the path of biochemical and metabolomic research in the silkmoth. © 2023, The Author(s), under exclusive licence to Plant Science and Biodiversity Centre, Slovak Academy of Sciences (SAS), Institute of Zoology, Slovak Academy of Sciences (SAS), Institute of Molecular Biology, Slovak Academy of Sciences (SAS).
Analyzing atomic scale structural details and nuclear spin dynamics of four macrolide antibiotics: erythromycin, clarithromycin, azithromycin, and roxithromycin
(Royal Society of Chemistry, 2024) Bijay Laxmi Pradhan; Lekhan Lodhi; Krishna Kishor Dey; Manasi Ghosh
The current investigation centers on elucidating the intricate molecular architecture and dynamic behavior of four macrolide antibiotics, specifically erythromycin, clarithromycin, azithromycin, and roxithromycin, through the application of sophisticated solid-state nuclear magnetic resonance (SSNMR) methodologies. We have measured the principal components of chemical shift anisotropy (CSA) parameters, and the site-specific spin-lattice relaxation time at carbon nuclei sites. To extract the principal components of CSA parameters, we have employed 13C 2DPASS CP-MAS SSNMR experiments at two different values of magic angle spinning (MAS) frequencies, namely 2 kHz and 600 Hz. Additionally, the spatial correlation between 13C and 1H nuclei has been investigated using 1H-13C frequency switched Lee-Goldburg heteronuclear correlation (FSLGHETCOR) experiment at a MAS frequency of 24 kHz. Our findings demonstrate that the incorporation of diverse functional groups, such as the ketone group and oxime group with the lactone ring, exerts notable influences on the structure and dynamics of the macrolide antibiotic. In particular, we have observed a significant decrease in the spin-lattice relaxation time of carbon nuclei residing on the lactone ring, desosamine, and cladinose in roxithromycin, compared to erythromycin. Overall, our findings provide detailed insight into the relationship between the structure and dynamics of macrolide antibiotics, which is eventually correlated with their biological activity. This knowledge can be utilized to develop new and more effective drugs by providing a rational basis for drug discovery and design. © 2024 The Royal Society of Chemistry.
Atomic-Scale Resolution Insights into Structural and Dynamic Differences between Ofloxacin and Levofloxacin
(American Chemical Society, 2023) Bijay Laxmi Pradhan; Jai Prakash Yadav; Lekhan Lodhi; Prince Sen; Krishna Kishor Dey; Manasi Ghosh
This study employs advanced solid-state NMR techniques to investigate the atomic-level structure and dynamics of two enantiomers: ofloxacin and levofloxacin. The investigation focuses on critical attributes, such as the principal components of the chemical shift anisotropy (CSA) tensor, the spatial proximity of 1H and 13C nuclei, and site-specific 13C spin-lattice relaxation time, to reveal the local electronic environment surrounding specific nuclei. Levofloxacin, the levo-isomer of ofloxacin, exhibits higher antibiotic efficacy than its counterpart, and the dissimilarities in the CSA parameters indicate significant differences in the local electronic configuration and nuclear spin dynamics between the two enantiomers. Additionally, the study employs the 1H-13C frequency-switched Lee-Goldburg heteronuclear correlation (FSLGHETCOR) experiment to identify the presence of heteronuclear correlations between specific nuclei (C15 and H7 nuclei and C13 and H12 nuclei) in ofloxacin but not in levofloxacin. These observations offer insights into the link between bioavailability and nuclear spin dynamics, underscoring the significance of NMR crystallography approaches in advanced drug design. © 2023 The Authors. Published by American Chemical Society.
Designing Salen-Based Porous Organic Polymers for Enhanced Electrolytic Water Splitting into Oxygen
(John Wiley and Sons Inc, 2024) Hiranmoy Pal; Arun Karmakar; Arnab Sadhukhan; Kalipada Koner; Shayan Karak; Rahul Kumar Sharma; Manasi Ghosh; Krishna Kishor Dey; Biswarup Pathak; Subrata Kundu; Rahul Banerjee
The development of electricity-driven oxygen evolution reaction (OER) is a potent solution for energy storage applications. In recent years, there is a surge in interest in designing transition metal-based catalysts with stable linkages, presenting an efficient alternative to noble metal-based electrocatalysts. Transition metal complexes linked by salen ligands garner considerable attention due to their capacity to chelate and stabilize metal ions. This work presents a novel approach by strategically incorporating the metal–salen core into a porous organic polymer (POP) backbone, thereby fabricating a highly effective electrocatalyst for oxygen evolution. The judicious selection of metal–salen active sites, coupled with the intramolecular free volume (IMFV) of the triptycene core and the high specific surface area of the salen–POPs, result in superior OER activity. By precisely tuning the structure through variation of the transition metal in the salen unit, deep insights are gained into their electrocatalytic behavior. Notably, the most efficient catalyst, Ni-DHDA-TAT, exhibits an impressively low overpotential (η10) of ≈ 270 mV at a current density of 10 mA cm−2 for OER (in 1 m KOH). Further, Ni-DHDA-TAT retains its activity even after 50 h of chronoamperometry and 1000 cyclic voltammetry cycles with negligible degradation in its initial performance. © 2024 Wiley-VCH GmbH.
Determination of chemical shift anisotropy tensor and molecular correlation time of proton pump inhibitor omeprazole by solid state NMR measurements
(Royal Society of Chemistry, 2020) Krishna Kishor Dey; Manasi Ghosh
The correlation between the structure and dynamics of the proton pump inhibitor omeprazole is portrayed by extracting chemical shift anisotropy (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. Omeprazole has a chiral structure centered at the sulfur atom between the pyridine and benzimidazole rings. The C2 and C8 atoms are connected with the sulfoxide bond, whose electronic environment influences the activity against P. falciparum in vitro. Both isotropic and anisotropic chemical shifts of C2 are substantially higher than those of the C8 nuclei. The presence of "nucleophilic suction pumps"creates a deshielding effect on the C2 nuclei. On the contrary, the shielding effect on the C8 nuclei is created by the pyridine ring with strong magnetic susceptibility. The CSA parameters of the carbon nuclei that reside on the pyridine and benzimidazole rings are higher than the carbon nuclei that reside on the methyl and methoxy groups. The presence of hydrogen bonding and the existence of π-electrons on the pyridine and benzimidazole rings are the reasons for the higher values of the CSA parameters. The dimeric structure is formed by two centrosymmetric omeprazole molecules by the action of intermolecular hydrogen bonding. The dimeric structure is stabilized by van der Waals contacts between the pyridine ring of one molecule and the benzimidazole ring of another. The benzimidazole ring also forms stacking interactions with another centrosymmetric molecule. All these interactions are responsible for the robust structure of the molecule and this is considered as the reason for the higher values of the spin-lattice relaxation time and the molecular correlation time of the central molecular framework compared to the peripheral molecular fragments. This atomic scale resolution of the structure and dynamics of such a valuable drug will illuminate the way for discovering advanced medicines. This journal is © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
Determination of the correlation between the structure and dynamics of deflazacort by solid state NMR measurements
(Royal Society of Chemistry, 2020) Krishna Kishor Dey; Manasi Ghosh
The correlation between the structure and dynamics of glucocorticoid deflazacort is determined by extracting principal elements of the chemical shift anisotropy (CSA) tensor at twenty-five crystallographically different carbon nuclei sites by a two-dimensional phase adjusted spinning sideband (2DPASS) cross-polarization (CP) magic angle spinning (MAS) solid-state nuclear magnetic resonance (SSNMR) experiment and 13C spin-lattice relaxation time by a Torchia CP experiment. The molecular correlation time at crystallographically different carbon sites is evaluated by bearing in mind that the hetero-nuclear dipole-dipole coupling and chemical shift anisotropy interactions play a dominant role in the spin-lattice relaxation mechanism for the 13C carbon nucleus. The structure and dynamics of deflazacort are correlated with the pharmacological activity of the drug. These types of investigations will facilitate to ascertain the correlation between the structure and dynamics of glucocorticoids, which is necessary to develop advanced medicine. © The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.
Doping impacts of La2O3 on physical, structural, optical and radiation shielding properties of (30-x)BaCO3-30TiO2-40SiO2-xLa2O3 (0 ≤ x ≤ 6) glasses for optoelectronic applications
(Institute of Physics, 2023) Rajat Kumar Mishra; Savita Kumari; Shweta; Prince Sen; Sarvesh Kumar Avinashi; Zaireen Fatima; Harel Thomas; Manasi Ghosh; Krishna Kishor Dey; Chandkiram Gautam
Herein, synthesis of novel barium silicate glasses doped with La2O3 in the system (30-x)BaCO3-30TiO2-40SiO2-xLa2O3, BTSL (0 ≤ x ≤ 6) via fast melt-quenching technique was carried out. Further, to confirm the amorphous behaviour of prepared glass samples, x-ray diffraction (XRD) and field emission scanning electron microscopy (FESEM) were carried out. The density of all prepared glasses was determined using Archimedes’ principle and found to be in an increasing manner. To investigate the doping influence of La2O3 on the glasses, few more physical properties like molar volume (Vm), polaron radius (rp), and field strength (Fs) were also studied and found to be increased due to incorporation of La2O3 into BTSL glassy system. Moreover, to explore the structural, functional, and bonding mechanism of the glasses, FTIR, Raman and 29Si-MAS-ssNMR spectroscopies were performed. Further, to investigate the numerous optical parameters, UV-visible spectroscopy was executed, and energy band gaps were found in the decreasing manner as increasing the La2O3 concentrations. Additionally, to study the optoelectronic properties, refractive indices (η) and optical dielectric constant (ϵ) were determined and revealed the increasing behaviour and found suitable material for optoelectronic devices. Furthermore, the radiation shielding parameters, mass attenuation coefficient (MAC), linear attenuation coefficient (LAC), etc were determined using Phy-X/PSD software and these parameters are increased owing to the doping of La2O3. Among all fabricated glasses, (30-x)BaCO3-30TiO2−40SiO2−6La2O3, BTS6L glass exhibited outstanding optical and radiation attenuation properties; can be tailored for the fabrication of optoelectronic and radiation protection devices. © 2023 IOP Publishing Ltd.
Enhancing glass-forming ability and mechanical properties of barium-calcium-aluminate glasses through ZnO inclusion
(Elsevier B.V., 2024) Saswata Chakraborty; Sudheer Ganisetti; Sathravada Balaji; Sultan Khan; Sushanta K. Mohapatra; Pritha Patra; Prince Sen; Manasi Ghosh; Krishna Kishor Dey; N.M. Anoop Krishnan; Kaushik Biswas; Amarnath R Allu; Kalyandurg Annapurna
Calcium aluminate (CA) glasses have garnered attention in the field of infrared photonics due to their low phonon energy. Nonetheless, the poor glass-forming ability (GFA) and strong crystallization tendency have hindered their utilization in various technological applications. Therefore, we demonstrate here that the substitution of ZnO for CaO enhances the GFA of 29Al2O3–(66X)CaO–5BaO–(X)ZnO (X = 0,7,10,15,20,25) glasses and improves their mechanical properties. The structural characterization using Raman, 27Al MAS-NMR spectroscopy and MD simulations reveal that, Zn2+ ions adopt tetrahedral coordination and contribute as network formers along with Al3+ ions. Notably, MD simulations indicate a preference of ZnO4 units for the CaO6 sites to convert non-bridging oxygens to bridging oxygens. The decrease in glass transition temperature and the increase in elastic modulus is noticed which correlated with the structural changes in the studied glasses. These findings provide valuable insights into the design and development of stable multicomponent CA glasses for photonic applications. © 2024
Exploring the structure and dynamics of soft and hard cuticle of Bombyx mori using solid-state NMR techniques
(Nature Research, 2024) Lekhan Lodhi; Janak Dulari Ahi; Neelima Gupta; Bijay Laxmi Pradhan; Prince Sen; Manasi Ghosh; Krishna Kishor Dey
This study conducts a comprehensive analysis and comparison of Bombyx mori cuticles across different developmental stages, ranging from larval to adult, utilizing advanced solid-state NMR techniques. The primary objective is to elucidate the underlying reasons for the contrasting hardness of adult cuticles and softness of larval cuticles. Notably, PXRD analysis reveals a prominent broad peak at 19.34°, indicating the predominantly amorphous nature of both larval and adult cuticles. Analysis of 13C CP-MAS SSNMR spectra highlights an elevated proportion of phenoxy carbon in adult cuticles (6.77%) compared to larval cuticles (1.24%). Furthermore, a distinctive resonance line at 144 ppm is exclusively observed in adult cuticles, due to catechols, suggesting potential biochemical pathway variations during development. Significant variations in the primary components of 13C chemical shift anisotropy (CSA) tensors for aliphatic carbons of amino acids, catechols, and lipids between adult and larval cuticles indicate alterations in electronic environments. Additionally, the shorter spin–lattice relaxation time of carbon nuclei in larval cuticles compared to adult cuticles implies slower motional dynamics with enhanced degree of sclerotization in adults. By investigating the internal structure and dynamics of cuticles, this research not only contributes to biomimetic material development but also enhances our understanding of structural changes across different developmental stages of B. mori. © The Author(s) 2024.
Fabrication of bioactive transparent glass ceramics 55SiO2–25Na2O-(15-x)CaO–5P2O5- xZrO2 (0≤x≤6): Physical, structural and in vitro cell viability insights for biomedical applications
(Elsevier Ltd, 2024) Shweta; Rajat Kumar Mishra; Bijay Laxmi Pradhan; Shama Parveen; Priyatama Behera; Sarvesh Kumar Avinashi; Savita Kumari; Zaireen Fatima; Prince Sen; Saurabh Kumar; Monalisa Mishra; Monisha Banerjee; Krishna Kishor Dey; Manasi Ghosh; Chandkiram Gautam
Zirconia (ZrO2) reinforced transparent glass ceramics (TGCs) are excellent materials for enhanced cell viability and biocompatibility for biomedical applications. Herein, ZrO2 doped SiO2–Na2O–CaO–P2O5 base compositions derived from traditional melt-quench technique. The impacts of ZrO2 on the physical, structural, optical, morphological, and biological evaluation were studied. XRD discloses the major phase formation of buchwaldite (CaNaPO4) and disodium calcium silicate (Na2CaSiO4). Density of the TGC samples was calculated and found to be in the range of 2.535–2.910 g/cm3. The optical parameters, and particle size were estimated and analyzed. Herein, ZrO2 plays a significant role as a network modifier and various bond assignments in the glassy network that confirmed by FTIR spectroscopy. Surface morphology and its elemental investigations were also studied using SEM and XPS techniques. Solid state NMR spectrum on 23Na, 29Si, and 31P nucleus were studied for various interactions. Moreover, the cell viability of the fabricated samples on the cancer cells were analyzed and resulted to possess the half maximum inhibitory concentrations (IC50) of the samples were calculated and valued to be 92 to 40 μg/ml respectively. The sample 55SiO2–25Na2O–9CaO–5P2O5–6ZrO2 (BG4) demonstrated a remarkable biological activity for bone regeneration and implants. Further, the cell cytotoxicity was evaluated by performing trypan blue assay, DAPI and DCFH-DA staining on the TGC samples. The data assembled in this research approves the hypothesis that the TGCs represent a feasible material for the biomedical applications for bone and tooth implants. © 2024 Elsevier Ltd and Techna Group S.r.l.
Influence of carbon nanotubes reinforcement on the structural feature and bioactivity of SiO2–Al2O3–MgO–K2CO3–CaO–MgF2 bioglass
(Springer Science and Business Media Deutschland GmbH, 2021) Shweta; Chandkiram Gautam; Krishna Kishor Dey; Manasi Ghosh; Ravi Prakash; Kriti Sharma; Divya Singh
Various glass compositions were synthesized using a melt-quenching technique doped with different concentrations of carbon nanotubes (CNTs) from 0.1 to 0.7% in the glassy system SiO2–Al2O3–MgO–K2CO3–CaO–MgF2. Density was determined by employing a liquid displacement method. Several physical parameters such as molar volume (Vm), oxygen molar volume (Vo) were calculated and found to be decreases from 36.49 ± 0.729 to 24.28 ± 0.485 × 10–6 m3/mol, and 21.86 ± 0.437 to 14.60 ± 0.292 × 10–6 m3/mol, respectively. However, density and oxygen packing density (OPD) increases from 1.99 ± 0.099 to 2.98 ± 0.149 × 103 kg/m3 and 45.74 ± 0.914 to 68.49 ± 1.369 × 10–3 kg-atom/l with increasing content of CNT. In the present study, reinforcement effects of CNTs were explained using several spectroscopic techniques like Fourier transform infrared, ultraviolet–visible (UV–Vis), Raman, and nuclear magnetic resonance (NMR) spectroscopy, respectively. Based on Tauc plots of the UV–Vis spectra, the energy band gap was determined and their values decreased from 6.95 to 6.23 × 10–19 J which is owing to the formation of non-bridging oxygen (NBO) in the glassy matrix. Contact angle measurements were also performed to check the wettability of the glasses and their values increased with CNT % from 18.14° to 77.8°. 29Si-MAS-NMR spectroscopic study revealed the random distribution of two different cations, Ca 2 + and Mg 2 + within the glasses which lead to structural and topological frustration. To check the cell viability, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide and alkaline phosphatase assay were also performed. Owing to outstanding stability in various fluids like saline water, distilled water, and hydrochloric acid, the fabricated glasses exhibited functional activities with an adequate proliferation of rat calverail osteoblast cells. Consequently, based on the various characterization techniques such as mechanical, tribological, and biological activities, the fabricated bioactive glasses can be used for biomedical and multifunctional applications. © 2021, The Author(s), under exclusive licence to Springer-Verlag GmbH, DE part of Springer Nature.
Influence on Crystallinity of Nanoporous Covalent Organic Frameworks for Efficient Sequestration of Organic Iodides and Iodine
(American Chemical Society, 2025) Atikur Hassan; Subhadip Mondal; Sk Abdul Wahed; Swapnanil Goswami; Akhtar Alam; Manasi Ghosh; Krishna Kishor Dey; Neeladri Das
In spent nuclear fuel (SNF) reprocessing plants, various off-gas systems (OGS) are known to contain significant amounts of radioactive 129I2, CH3129I, and CH3CH2129I. The capture and immobilization of volatile contaminants, such as iodine, methyl iodide, and ethyl iodide, is a critical challenge. Herein, we report four crystalline nanoscalar COFs with large surface areas and Lewis basic centers that enable effective capture of I2, CH3I, and CH3CH2I under various conditions. COF-OH0 exhibited one of the highest reported adsorption capacities for organic iodides, reaching 1.6 g g-1 for CH3I and 1.1 g g-1 for CH3CH2I at 75 °C. COF-OH0 exhibited impressive static and dynamic iodine capture capacities of 4.46 and 2.8 g g-1, respectively, at 75 °C. Treatment with radioactive organic iodides (ROIs) induces a postsynthetic modification that converts imine N sites to cationic centers through quaternization. The resulting cationic framework is effective for selective adsorption of toxic anionic contaminants from water. In dynamic adsorption studies, COF-OH0 demonstrated exceptional capture capacities of 1.83 and 1.95 g g-1 for triiodide anion and molecular iodine from water, respectively. Our findings suggest that an increase in the number of −OH groups within these tautomeric COFs reduces the capacity to capture iodine and organic iodide. Mechanistic insights were provided by in silico studies and analytical techniques, enhancing the understanding of I2 and iodine species uptake mechanisms while contributing to the development of the adsorbents. © 2025 American Chemical Society.
Interrelationship between solubility and nuclear spin–lattice relaxation time in cellulose derivatives with solid-state NMR
(Springer Science and Business Media B.V., 2024) Krishna Kishor Dey; Manasi Ghosh
Cellulose is insoluble in water and most of the ionic liquids, but due to the substitution of hydroxyethyl, hydroxypropyl, and methoxy groups with the glucose residue, the cellulose derivatives Hydroxyethyl Cellulose (HEC) and Hydroxypropyl Methyl Cellulose (HPMC) become soluble in cold as well as hot water. The aim of the present investigations is to probe the origin of the enhanced solubility in cellulose derivatives HEC, and HPMC at atomic scale resolution by applying 13C cross-polarization magic angle spinning (CP-MAS) SSNMR experiment, 13C two-dimensional phase-adjusted spinning sideband (2DPASS) CP-MAS SSNMR experiment, and site specific 13C spin–lattice relaxation time measurements. The local-correlation time is also calculated for HEC and HPMC by using values of spin–lattice relaxation time and principal components of CSA parameters. The 13C spin–lattice relaxation time and 13C local correlation time are drastically decreased in HEC, and HPMC compared to cellulose, suggesting a notable increase in the motional dynamics of cellulose derivatives. Hence, the motional dynamics is enhanced in cellulose derivatives due to esterification, and is one of the reasons of enhanced solubility. The microscopic parameter, the nuclear spin–lattice relaxation rate of polysaccharide is interrelated with the solubility, a macroscopic property. Graphical abstract: (Figure presented.) © The Author(s), under exclusive licence to Springer Nature B.V. 2024.
Investigating structural and dynamic changes in cellulose due to nanocrystallization
(Springer Science and Business Media B.V., 2025) Bijay Laxmi Pradhan; Prince Sen; Krishna Kishor Dey; Manasi Ghosh
Cellulose nanocrystals (CNCs) is synthesized from alpha-cellulose by acid hydrolysis method, and formation of nanocrystallization is comprised by using various microscopic and spectroscopic techniques like PXRD, XPS, Raman, FTIR, PL, UV-Vis, DSC, TGA, DLS, SEM, TEM. Nanocrystalline cellulose shows a notably higher photoluminescence (PL) intensity than cellulose, which enhances its ability to absorb and emit visible light. This increase in PL intensity is attributed to a smaller particle size of CNCs, greater surface area, and quantum confinement effects. The higher intensity of the XPS spectrum further supports the larger surface area of CNCs. PXRD and Raman spectroscopy results show that CNCs has a higher crystallinity index than cellulose. Through deconvolution of the 13C CP-MAS SSNMR spectrum, we confirmed a significant reduction in the relative abundance of the amorphous region of cellulose (43.61%) to just 4.97% in CNCs. The 13C CP-MAS SSNMR spectrum of CNCs, at the C4, C6, C2C3C5 nuclei sites, can be fitted by two distinct lines for both amorphous and crystalline region, indicating the formation of a co-crystal from two nanocrystallites. Despite this, the principal components of the CSA (chemical shift anisotropy) tensor remain unchanged, suggesting similar electronic environments for these two nanocrystallites. The spin-lattice relaxation time and local correlation time of cellulose and CNCs are determined for chemically distinct carbon nuclei residing on D-glucopyranose units. It is noteworthy that the 13C spin-lattice relaxation time and 13C local correlation time are longer for each chemically distinct nucleus in CNCs compared to cellulose. It can be predicted by observing the NMR relaxometry data that the longer relaxation time in CNCs is due to the enhancement of crystallinity index. Hence, a correlation between the crystallinity index and nuclear spin dynamics can be established by NMR relaxometry measurements. These findings offer significant insights into the intricate structure and dynamic behavior of cellulose and nanocrystalline cellulose (CNCs), crucial for advancing biomimetic material design, which has huge applications across the pharmaceutical, textile, and cosmetics industries. © The Author(s), under exclusive licence to Springer Nature B.V. 2025.
Investigation of the Influence of Various Functional Groups on the Dynamics of Glucocorticoids
(American Chemical Society, 2022) Jai Prakash Yadav; Lekhan Lodhi; Tamseel Fatma; Krishna Kishor Dey; Manasi Ghosh
The basic configuration of glucocorticoid consists of four-fused rings associated with one cyclohexadienone ring, two cyclohexane rings, and one cyclopentane ring. The ways the structure and dynamics of five glucocorticoids (prednisone, prednisolone, prednisolone acetate, methylprednisolone, and methylprednisolone acetate) are altered because of the substitution of various functional groups with these four-fused rings are studied thoroughly by applying sophisticated solid-state nuclear magnetic resonance (NMR) methodologies. The biological activities of these glucocorticoids are also changed because of the attachment of various functional groups with these four-fused rings. The substitution of the hydroxyl group (with the C11 atom of the cyclohexane ring) in place of the keto group enhances the potential of the glucocorticoid to cross the cellular membrane. As a result, the bioavailability of prednisolone (the hydroxyl group is attached with the C11 atom of the cyclohexane ring) is increased compared to prednisone (the keto group is attached with the C11 atom of cyclohexane rings). Another notable point is that the spin-lattice relaxation rate at crystallographically distinct carbon nuclei sites of prednisolone is increased compared to that of the prednisone, which implies that the motional degrees of freedom of glucocorticoid is increased because of the substitution of the hydroxyl group in place of the keto group of the cyclohexane ring. The attachment of the methyl group with the C6 atom of cyclohexane rings further reduces the spin-lattice relaxation time at crystallographically distinct carbon nuclei sites of glucocorticoid and its bioactivity is also increased. By comparing the spin-lattice relaxation time and the local correlation time at crystallographically different carbon nuclei sites of three steroids prednisone, prednisolone, and methylprednisolone, it is observed that both the spin-lattice relaxation time and the local correlation time gradually decrease at each crystallographically distinct carbon nuclei sites when we move from prednisone to prednisolone to methyl-prednisolone. On the other hand, if we compare the same for prednisolone, prednisolone acetate, and methylprednisolone acetate, then we also observe that both the spin-lattice relaxation time and the local-correlation time gradually decrease from prednisolone to prednisolone acetate to methylprednisolone acetate for all chemically different carbon nuclei. It is also noticeable that both the spin-lattice relaxation time and the local-correlation time gradually decrease from prednisone to prednisolone to prednisolone acetate to methylprednisolone to methylprednisolone acetate for most of the carbon nuclei sites. From in silico analysis, it is also revealed that the bioavailability and efficacy of the glucocorticoid increase from prednisone to prednisolone to prednisolone acetate to methylprednisolone to methylprednisolone acetate. Hence, it can be concluded that the biological activity and the motional degrees of freedom of the glucocorticoids are highly correlated. These types of studies provide a clear picture of the structure-activity relationship of the drug molecules, which will enlighten the path of developing highly potent glucocorticoids with minimum side effects. Another important aspect of these types of studies is to provide information about the electronics configuration and nuclear spin dynamics at crystallographically different carbon nuclei sites of five glucocorticoids, which will enrich the field of "NMR crystallography". © 2022 American Chemical Society. All rights reserved.
Investigation of the Structure and Dynamics of Antiviral Drug Adefovir Dipivoxil by Site-Specific Spin-Lattice Relaxation Time Measurements and Chemical Shift Anisotropy Tensor Measurements
(American Chemical Society, 2020) Krishna Kishor Dey; Manasi Ghosh
Adefovir is regarded as a potential antiviral agent. However, it cannot be considered as a valuable drug candidate due to its high polarity that limits its permeability across the human intestinal mucosa. When the ribose phosphate group of adefovir is replaced by the isopolar phosphonomethyl ether functionality, it neutralizes the negative charge of the drug. This makes the drug lipid-soluble and potent to diffuse across the cell membrane. The prodrug adefovir dipivoxil is regarded as a potent antiviral drug against hepatitis B virus (HBV), human immunodeficiency virus (HIV), Rauscher murine leukemia virus (R-MuLV), murine cytomegalovirus (MCMV), herpes simplex virus (HSV), simian immunodeficiency virus (SIV), and feline immunodeficiency virus (FIV). The correlation between the structure and the dynamics of adefovir dipivoxil is determined by measuring the principal components of chemical shift anisotropy (CSA) tensor, site-specific spin-lattice relaxation time, and molecular correlation time at crystallographically different carbon nuclei sites. The CSA parameters, spin-lattice relaxation time, and molecular correlation time of phosphorous nucleus of the organophosphate group of adefovir dipivoxil molecule are also determined. The spin-lattice relaxation time of carbon nuclei varies from 1 to 107 s. The range of molecular correlation time also varies from 10-4 to 10-8 s. These remarkable diversities of motional dynamics of the molecules imply that there exist various motional degrees of freedom within this valuable drug and these motional degrees of freedom are independent of each other, which may be the reason for the biological activities exhibited by the drug. The correlation between structure and dynamics of such an important antiviral drug adefovir dipivoxil can be visualized by these types of extensive spectroscopic measurements, which will enlighten the path of inventing advanced medicine in the pharmaceutical industry, and it will also illuminate the understanding of the structure-activity relationships of antiviral drug. ©
NMR Crystallographic Approach to Study the Variation of the Dynamics of Quinine and Its Quasienantiomer Quinidine
(American Chemical Society, 2022) Lekhan Lodhi; Jai Prakash Yadav; Toshio Yamazaki; Nghia Tuan Duong; Srinivasa L. Poojary; Krishna Kishor Dey; Yusuke Nishiyama; Manasi Ghosh
The structure and dynamics of quinine and its quasienantiomer quinidine were studied at the atomic resolution by measuring the chemical shift anisotropy (CSA) tensor and site-specific spin-lattice relaxation time. For quinine, there are three crystallographically independent molecules "a", "b", and "c"in an asymmetric unit since its 13C CP-MAS SSNMR spectrum features three distinct resonance peaks for certain carbon nuclei. The 13C assignments are fulfilled by DFT calculations. The experimental 13C isotropic chemical shifts well match the calculated values. These variations of isotropic chemical shift for three independent molecules are also observed by two-dimensional 13C-1H heteronuclear correlation spectroscopy (HETCOR) of quinine. The spin-lattice relaxation time, and the principal components of CSA parameters are also varied substantially for certain carbon nuclei of "a", "b", and "c"molecules. For quinidine, its 13C CP-MAS SSNMR spectrum is remarkably different from that of quinine despite, their almost identical solution NMR spectra. Furthermore, the remarkable change in the structure and dynamics of quasienantiomers are also observed including the steric effect of the substituent vinyl group, the variation of helical motifs, and the variation of the strength of the intermolecular hydrogen bonds. The variation of the structure and dynamics of quasienantiomers are thoroughly studied by solid-state NMR measurements. These types of studies will enrich the field of NMR crystallography. © 2022 American Chemical Society.
Physical, Structural, and Optical Properties of ZrO2 Reinforced (100-x–y)[SrTiO3]-x[2B2O3.SiO2]-y[ZrO2] Glasses
(Springer Science and Business Media B.V., 2023) Rajat Kumar Mishra; Shweta; Prince Sen; Krishna Kishor Dey; Manasi Ghosh; Chandkiram Gautam
Several attempts were made to fabricate zirconia (ZrO2) reinforced strontium titanate (SrTiO3) borosilicate glasses in the system (100-x–y)[SrTiO3]-x[2B2O3.SiO2]-y[ZrO2] (38 ≤ x ≤ 39, 0 ≤ y ≤ 4 by mole %) via a rapid melt-quenching method. To check the amorphous behaviour of the prepared glasses, XRD measurements were performed. Further, density of the bulk transparent glasses was evaluated by liquid-displacement method (Archimedes’ principle) and found to be in the range of 2.6068–3.0720 gcm−3. To study the effect of ZrO2 doping on the fabricated glasses, various physical parameters such as oxygen molar volume (Omv), molar volume (Vm), oxygen packing density (OPD), ion-concentrations (N), etc. were determined. Further, to investigate the molecular structure, and bonding information, FTIR spectroscopy was performed. Additionally, to determine the various optical properties, the UV–visible spectroscopy was also performed, and with the help of Davis-Mott plots, increasing optical band gap energies were obtained in the range of 4.29—4.78 eV. Besides these parameters, an optical dielectric constant (ε), and average refractive index (η) were determined which lies within the increasing range of 120.0374–207.3341 and 1.9269–2.0690 respectively. Moreover, to elaborate the structure of the fabricated glasses, 29Si and 11B MAS SSNMR spectra were recorded which shows the formation of silicate networks which became highly polymerized with increasing concentrations of ZrO2. © 2023, The Author(s), under exclusive licence to Springer Nature B.V.
Precise Measurement of Qn Species Distributions in Modified Silicate Glass Using Phase-Adjusted Spinning Sideband NMR Experiment
(Springer Science and Business Media B.V., 2023) Prince Sen; Bijay Laxmi Pradhan; Lekhan Lodhi; Manasi Ghosh; Krishna Kishor Dey
Quantification of the distribution of Q(n) species, representing the number of bridging oxygens (n) around a silicate tetrahedra in potassium disilicate glass, is achieved using the two-dimensional Phase-Adjusted Spinning Sideband (2D PASS) sequence. Furthermore, we compare the relative concentrations of each Q(n) species obtained through the PASS method with a previous study utilizing the Magic Angle Flipping (MAF) technique on the same glass composition. While MAF has been employed in prior research to enhance the precision of Q(n) species measurements in glasses, it necessitates a specialized probe capable of reorienting the rotor axis. In contrast, alternatives like MAT or 2D PASS are more appealing as they can be implemented using a conventional MAS probe. In this study, we demonstrate that the PASS experiment provides comparable accuracy to MAF while significantly reducing the required time. Graphical Abstract: [Figure not available: see fulltext.] © 2023, The Author(s), under exclusive licence to Springer Nature B.V.