Browsing by Author "Noothalapati, Hemanth"

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Evidence of C-F-P and aromatic pi-F-P weak interactions in imidazolium ionic liquids and its consequences
(2018-04-05)
Panja, Sumit Kumar
;
Srivastava, Nitin
;
Srivastava, Jyoti
;
Prasad, Namburi Eswara
;
Noothalapati, Hemanth
A simple change from alkyl group to alkene in side chain of imidazolium cation with same anion resulted in a drastic impact on physical properties (e.g., melting point) from bmimPF(6) IL to cmimPF(6) IL The underlying reasons have been elucidated by structural and interaction studies with the help of DSC, SCXRD, vibrational and multi-nuclear NMR spectroscopic techniques. Experiments reveal existence of new weak interactions involving the carbon and pi cloud of the imidazolium aromatic ring with fluoride of PF6 anion (i.e., C-2-F-P and pi-F-P) in cmimPF(6) but are absent in structurally similar prototype IL bmimPF(6). Though weak, these interactions helped to form ladder type supramolecular arrangement, resulting in quite high melting point for cmimPF(6) IL compared to bmimPF(6) IL These findings emphasize that an IL system can behave uniquely because of the existence of uncommon weak interactions. (C) 2017 Elsevier B.V. All rights reserved.
Exploring Metabolic Pathways in Vivo by a Combined Approach of Mixed Stable Isotope-Labeled Raman Microspectroscopy and Multivariate Curve Resolution Analysis
(2014-08-05)
Noothalapati, Hemanth
;
Shigeto, Shinsuke
;
應用化學系
;
應用化學系分子科學碩博班
;
Department of Applied Chemistry
Understanding cellular metabolism is a major challenge in current systems biology and has triggered extensive metabolomics research, which in most cases involves destructive analysis. However, the information obtainable only in a nondestructive manner will be required for accurately mapping the global structure of the organism's metabolic network at a given instant. Here we report that metabolic pathways can be explored in vivo by mixed stable isotope-labeled Raman microspectroscopy in conjunction with multivariate curve resolution analysis. As a model system, we studied ergosterol biosynthesis in single living fission yeast cells grown in mixtures of normal and C-13-labeled glucose as the sole carbon source. The multivariate spectral data analysis of space-resolved Raman spectra revealed the intrinsic spectra and relative abundances of all isotopomers of ergosterol whose carbon atoms in the 5,7-diene moiety of the sterol skeleton are either partly or fully substituted with C-13. Our approach is applicable to other metabolites and will earn a place in the toolbox of metabolomic analysis.
Exploring Metabolic Pathways in Vivo by a Combined Approach of Mixed Stable Isotope-Labeled Raman Microspectroscopy and Multivariate Curve Resolution Analysis
(2014-08-05)
Noothalapati, Hemanth
;
Shigeto, Shinsuke
;
應用化學系
;
應用化學系分子科學碩博班
;
Department of Applied Chemistry
Understanding cellular metabolism is a major challenge in current systems biology and has triggered extensive metabolomics research, which in most cases involves destructive analysis. However, the information obtainable only in a nondestructive manner will be required for accurately mapping the global structure of the organism\'s metabolic network at a given instant. Here we report that metabolic pathways can be explored in vivo by mixed stable isotope-labeled Raman microspectroscopy in conjunction with multivariate curve resolution analysis. As a model system, we studied ergosterol biosynthesis in single living fission yeast cells grown in mixtures of normal and C-13-labeled glucose as the sole carbon source. The multivariate spectral data analysis of space-resolved Raman spectra revealed the intrinsic spectra and relative abundances of all isotopomers of ergosterol whose carbon atoms in the 5,7-diene moiety of the sterol skeleton are either partly or fully substituted with C-13. Our approach is applicable to other metabolites and will earn a place in the toolbox of metabolomic analysis.
Imaging phospholipid conformational disorder and packing in giant multilamellar liposome by confocal Raman microspectroscopy
(2017-12-05)
Noothalapati, Hemanth
;
Iwasaki, Keita
;
Yoshimoto, Chikako
;
Yoshikiyo, Keisuke
;
Nishikawa, Tomoe
Liposomes are closed phospholipid bilayer systems that have profound applications in fundamental cell biology, pharmaceutics and medicine. Depending on the composition (pure or mixture of phospholipids, presence of cholesterol) and preparation protocol; intra- and inter-chain molecular interactions vary leading to changes in the quality (order and packing) of liposomes. So far it is not possible to image conformational disorders and packing densities within a liposome in a straightforward manner. In this study, we utilized confocal Raman microspectroscopy to visualize structural disorders and packingefficiency within a giant multilamellar liposome model by focusing mainly on three regions in the vibrational spectrum (C-C stretching, C-H deformation and C-H stretching). We estimated properties such as trans/gauche isomers and lateral packing probability. Interestingly, our Raman imaging studies revealed gel phase rich domains and heterogeneous lateral packing within the giant multilamellar liposome. (C) 2017 Elsevier B.V. All rights reserved.
Importance of weak interactions and conformational equilibrium in N-butyl-N-methylpiperidinium bis(trifluromethanesulfonyl) imide room temperature ionic liquids: Vibrational and theoretical studies
(2014-11-01)
Shukla, Madhulata
;
Noothalapati, Hemanth
;
Shigeto, Shinsuke
;
Saha, Satyen
;
應用化學系
Piperidinium cation-based room temperature ionic liquids (RTILs) constitute an important class of ILs because of their unique electrochemical properties as well as non-aromatic nature of the cation. However, detailed structural studies are yet to be done. In this paper, we discuss the molecular structure and vibrational spectra of N-butyl-N-methylpiperidinium bis(trifluromethanesulfonyl) imide, (PIP14NTf2; where, PIP14 is N-butyl-N-methylpiperidinium and NTf2 is bis(trifluromethanesulfonyl) imide), obtained with a combined approach of infrared (IR) and Raman spectroscopies in the liquid state and density functional theory (DFT) and Hartree-Fock (H-F) based theoretical calculations. DFT calculations, which are found to produce the most stable geometry compared to other two methods (MP2 and H-F), reproduce the experimental IR and Raman spectra reasonably well. Our findings reveal structural properties that profoundly influence intermolecular interactions and melting point. There exists a large variation in the melting point of the ILs studied. While the bromide salt of the piperidinium derivative (PIP14Br) is solid with very high melting point (241 degrees C), the corresponding NTf2 salt is low viscous liquid at room temperature (mp: -25 degrees C). bmimBr (bmim = 1-butyl-1-methylimidazolium) exhibits a substantially lower melting point of 79 degrees C than PIP14Br, suggesting that more number of strong classical hydrogen bonding interactions in the latter is primarily responsible for the much higher melting point. In addition, involvement of the alkyl group in PIP14 in H-bonding interaction provides additional rigidity in n-butyl chain which is otherwise absent in bmimBr. Interaction energy for PIP14Br is found to be higher than PIP14NTf2, showing a positive correlation between interaction energy and melting point. A blue shift in C-H stretching wavenumber as evident from IR and Raman spectra of PIP14Br IL is a clear indication of the stronger hydrogen bonding as compared to PIP14NTf2 IL. Furthermore, we experimentally observe the existence of cisoid-transoid conformational equilibrium of NTf2- anion in the Raman spectrum of PIP14NTf2 for the first time and determined that transoid NTf2- anion to be more stable than the corresponding cisoid conformer by 1.04 kcal/mol using DFT. Examination of various conformational possibilities of the cation shows that the butyl group preferentially exists in gauche conformation. (C) 2014 Elsevier B.V. All rights reserved.
Label-free Chemical Imaging of Fungal Spore Walls by Raman Microscopy and Multivariate Curve Resolution Analysis
(2016-06-09)
Noothalapati, Hemanth
;
Sasaki, Takahiro
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Kaino, Tomohiro
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Kawamukai, Makoto
;
Ando, Masahiro
Fungal cell walls are medically important since they represent a drug target site for antifungal medication. So far there is no method to directly visualize structurally similar cell wall components such as alpha-glucan, beta-glucan and mannan with high specificity, especially in a label-free manner. In this study, we have developed a Raman spectroscopy based molecular imaging method and combined multivariate curve resolution analysis to enable detection and visualization of multiple polysaccharide components simultaneously at the single cell level. Our results show that vegetative cell and ascus walls are made up of both alpha- and beta-glucans while spore wall is exclusively made of alpha-glucan. Co-localization studies reveal the absence of mannans in ascus wall but are distributed primarily in spores. Such detailed picture is believed to further enhance our understanding of the dynamic spore wall architecture, eventually leading to advancements in drug discovery and development in the near future.
Significance of weak interactions in imidazolium picrate ionic liquids: spectroscopic and theoretical studies for molecular level understanding
(2015-01-01)
Panja, Sumit Kumar
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Dwivedi, Nidhi
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Noothalapati, Hemanth
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Shigeto, Shinsuke
;
Sikder, A. K.
The effects of interionic hydrogen bonding and pi-pi stacking interactions on the physical properties of a new series of picrate anion based ionic liquids (ILs) have been investigated experimentally and theoretically. The existence of aromatic (C-2-H center dot center dot center dot O) and aliphatic (C-7-H center dot center dot center dot O-N-22 and C-6-H center dot center dot center dot O-N-20) hydrogen bonding and pi-pi stacking interactions in these ILs has been observed using various spectroscopic techniques. The aromatic and aliphatic C-H center dot center dot center dot O hydrogen bonding interactions are found to have a crucial role in binding the imidazolium cation and picrate anion together. However, the pi-pi stacking interactions between two successive layers are found to play a decisive role in tight packing in ILs leading to differences in physical properties. The drastic difference in the melting points of the methyl and propyl derivatives (mmimPic and pmimPic respectively) have been found to be primarily due to the difference in the strength and varieties of pi-pi stacking interactions. While in mmimPic, several different types of pi-pi stacking interactions between the aromatic rings (such as picrate-picrate, picrate-imidazole and imidazolium-imidazolium cation rings) are observed, only one type of pi-pi stacking interaction (picrate-picrate rings) is found to exist in the pmimPic IL. NMR spectroscopic studies reveal that the interaction of these ILs with solvent molecules is different and depends on the dielectric constant of the solvent. While an ion solvation model explains the solvation in high dielectric solvents, an ion-pair solvation model is found to be more appropriate for low dielectric constant solvents. The enhanced stability of these investigated picrate ILs compared with that of inorganic picrate salts under high doses of gamma radiation clearly indicates the importance of weak interionic interactions in ILs, and also opens up the possibility of the application of picrate ILs as prospective diluents in nuclear separation for advanced fuel cycling process.
Studying anti-oxidative properties of inclusion complexes of alpha-lipoic acid with gamma-cyclodextrin in single living fission yeast by confocal Raman microspectroscopy
(2018-05-15)
Noothalapati, Hemanth
;
Ikarashi, Ryo
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Iwasaki, Keita
;
Nishida, Tatsuro
;
Kaino, Tomohiro
alpha-lipoic acid (ALA) is an essential cofactor for many enzyme complexes in aerobic metabolism, especially in mitochondria of eukaryotic cells where respiration takes place. It also has excellent anti-oxidative properties. The acid has two stereo-isomers, R- and S-lipoic acid (R-LA and S-LA), but only the R-LA has biological significance and is exclusively produced in our body. A mutant strain of fission yeast, Delta dpsl, cannot synthesize coenzyme Q10, which is essential during yeast respiration, leading to oxidative stress. Therefore, it shows growth delay in the minimal medium. We studied anti-oxidant properties of ALA in its free form and their inclusion complexes with gamma-cyclodextrin using this mutant yeast model. Both free forms R- and S-LA as well as 1:1 inclusion complexes with gamma-cyclodexhin recovered growth of Delta dps1 depending on the concentration and form. However, it has no effect on the growth of wild type fission yeast strain at all. Raman microspectroscopy was employed to understand the anti-oxidant property at the molecular level. A sensitive Raman band at 1602 cm(-1) was monitored with and without addition of ALAs. It was found that 0.5 mM and 1.0 mM concentrations of ALAs had similar effect in both free and inclusion forms. At 2.5 mM ALAs, free forms inhibited the growth while inclusion complexes helped in recovered. 5.0 mM ALA showed inhibitory effect irrespective of form. Our results suggest that the Raman band at 1602 cm(-1) is a good measure of oxidative stress in fission yeast. (C) 2018 Elsevier B.V. All rights reserved.
Towards the development of a non-bioptic diagnostic technique for eosinophilic esophagitis using Raman spectroscopy
(2016-07)
Noothalapati, Hemanth
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Uemura, Suguru
;
Ohshima, Naoki
;
Kinoshita, Yoshikazu
;
Ando, Masahiro
Eosinophilic esophagitis (EoE) is believed to be a rare pathological condition that is characterized by dense infiltration of eosinophils in esophageal epithelial layer. Occurrence of this disease worldwide has started increasing rapidly in the last decade. Routine endoscopic observations can help in diagnosis only if clear longitudinal furrows or multiple concentric rings are observed but does not give any definitive conclusion in the early stages. Hence esophageal tissue samples are collected from multiple sites by biopsy and the number of eosinophils is counted after staining. Such a procedure is time consuming and has an inherent risk of bleeding, eventually damaging esophagus. Hence we developed a resonance Raman spectroscopy based approach to detect eosinophils in esophagus using mouse models. Our results show the presence of eosinophils in mice esophageal tissues suffering from inflammation by administering interleukin-33 while there are none in control mice. We believe this method can be used in clinical application for diagnosing EoE in the near future. (C) 2016 Elsevier B.V. All rights reserved.