SIVA UMAPATHY | Indian Institute of Science (original) (raw)
Papers by SIVA UMAPATHY
Journal of Photochemistry and Photobiology A-chemistry, Jun 1, 1997
3, 6-Dibromo-N-ethylcarbazole (DBNEC) and its polymeric analogue poly-3, 6-dibromovinylcarbazole ... more 3, 6-Dibromo-N-ethylcarbazole (DBNEC) and its polymeric analogue poly-3, 6-dibromovinylcarbazole (PDBVCz) were studied by transient absorption spectroscopy. The transient absorption spectrum of the 3, 6-dibromo-N-ethylcarbazole radical cation and ...
Analytical and Bioanalytical Chemistry, Jun 17, 2020
Current Science, 1993
Application of ultrafast lasers to chemistry and biology has been an active area of research in t... more Application of ultrafast lasers to chemistry and biology has been an active area of research in the international scene for over a decade for physical and biophysical chemists. Perhaps, ultrafast laser spectroscopy is one of the most versatile tools available today to experimentally study structure and dynamics in the time domain of nanoseconds (10(-9) sec) to femtoseconds (10(-15) sec). In this article we attempt to highlight some of the recent developments in ultrafast laser spectroscopy with particular reference to vibrational spectroscopy, viz. infrared and Raman spectroscopy, in the above time domain.
Analytical chemistry, Jan 28, 2018
Radiation is the standard therapy used for treating Glioblastoma (GBM), a grade IV brain cancer. ... more Radiation is the standard therapy used for treating Glioblastoma (GBM), a grade IV brain cancer. Glioma Stem-like Cells (GSCs), an integral part of GBM, enforces resistance to radiation therapy of GBM. Studying the differential biomolecular composition of GSCs with varying levels of radiation sensitivity can aid in identifying the molecules and their associated pathways which impose resistance to cells thereby unraveling new targets which would serve as potential adjuvant therapy. Raman spectroscopy being a noninvasive, label free technique can determine the biomolecular constituent of cells under live conditions. In this study, we have deduced Raman spectral signatures to predict the radiosensitivity of any GSC accurately using the inherent and radiation induced biomolecular composition. Our study identified the differential regulation of several biomolecules which can be potential targets for adjuvant therapy. We radiosensitized the resistant GSCs using small molecule inhibitors s...
The Journal of Chemical Physics
In this study, near- and off-resonance Raman spectra of cadmium sulfide (CdS) quantum rods (NRs) ... more In this study, near- and off-resonance Raman spectra of cadmium sulfide (CdS) quantum rods (NRs) and 4-mercaptobenzoic acid (4-MBA) adsorbed CdS NRs are reported. The envelopes of characteristic optical phonon modes in the near-resonance Raman spectrum of CdS NRs are deconvoluted by following the phonon confinement model. As compared with off-resonant Raman spectra, optical phonon modes scattering cross section is amplified significantly in near-resonance Raman spectra through the Fröhlich interaction. The Huang–Rhys factor defining the strength of the Fröhlich interaction is estimated (∼0.468). Moreover, the adsorption of different concentrations of 4-mercaptobenzoic acid (4-MBA) onto CdS NRs produces surface strain in CdS NRs originating due to surface reconstruction and consequently blue and red shifts in off-resonance (514.5 nm) Raman spectra depending on the concentration of 4-MBA. These consequences are attributed to compressive and tensile strains, respectively. Relative to b...
Springer Proceedings in Physics, 1992
Time-resolved resonance Raman spectroscopy (TR3S) has widely been used to establish the vibration... more Time-resolved resonance Raman spectroscopy (TR3S) has widely been used to establish the vibrational structure and the nature of the metal-ligand charge transfer (MLCT) triplet excited state of d6 transition metal complexes [1–6]. In particular, bipyridyl complexes of ruthenium(II) have been studied extensively by TR3S [1, 3–6]. Recently however, certain aspects of the procedures used to interpret the TR3S data have been questioned [3–5]. In this paper, we reconsider those aspects with particular reference to ruthenium(II) tris (bipyridine) (RBY).
Analytical and Bioanalytical Chemistry, 2020
Analytical and Bioanalytical Chemistry, 2019
The Journal of Chemical Physics, 2018
Integrated Ferroelectrics, 2017
ABSTRACT Graphene quantum dots (GQDs) and CeO2-GQDs were synthesized by using a facile hydrotherm... more ABSTRACT Graphene quantum dots (GQDs) and CeO2-GQDs were synthesized by using a facile hydrothermal method at 140°C. All the synthesized materials were characterized by TEM, UV-Vis Spectroscopy, FT-IR, Raman Spectroscopy and PL. Ceria decorated GQDs show different emission peaks with different excitation of wavelengths. The discrete change in dominant luminescence features of the GQDs and their composites indicate that the variation in PL occurs because of alteration in its shape, size and bandgap. Based on the experimental results of PL peak wavelength, the emission is attributed to quasi-molecular PL from the fragments composed of a few aromatic rings with oxygen containing functional groups.
Journal of Chemical Sciences, 2012
Chemical Physics Letters, 1998
Encyclopedia of Analytical Chemistry
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2021
Proteins are large, complex molecules responsible for various biological processes. However, prot... more Proteins are large, complex molecules responsible for various biological processes. However, protein misfolding may lead to various life-threatening diseases. Therefore, it is vital to understand the shape and structure of proteins. Despite numerous techniques, a mechanistic understanding of the protein folding process is still unclear. Therefore, new techniques are continually being explored. In the present article, we have discussed the importance of Raman spectroscopy, Raman Optical Activity (ROA) and various other advancements in Raman spectroscopy to understand protein structure and conformational changes based on the review of our earlier work and recent literature. A Raman spectrum of a protein provides unique signatures for various secondary structures like helices, beta-sheets, turns, random structures, etc., and various amino acid residues such as tyrosine, tryptophan, and phenylalanine. We have shown how Raman spectra can differentiate between bovine serum albumin (BSA) and lysozyme protein based on their difference in sequence and structure (primary, secondary and tertiary). Although it is challenging to elucidate the structure of a protein using a Raman spectrum alone, Raman spectra can be used to differentiate small changes in conformations of proteins such as BSA during melting. Various new advancements in technique and data analyses in Raman spectroscopic studies of proteins have been discussed. The last part of the review focuses on the importance of the ROA spectrum to understand additional features about proteins. The ROA spectrum is rich in information about the protein backbone due to its rigidity compared to its side chains. Furthermore, the ROA spectra of lysozyme and BSA have been presented to show how ROA provides extra information about the solvent properties of proteins.
Biotechnology Letters, 2020
The Journal of Physical Chemistry C, 2018
RSC Advances, 2018
This paper reviews various facets of Raman spectroscopy. This encompasses biomolecule fingerprint... more This paper reviews various facets of Raman spectroscopy. This encompasses biomolecule fingerprinting and conformational analysis, discrimination of healthy vs. diseased states, depth-specific information of materials and 3D Raman imaging.
Angewandte Chemie, 2018
Mesoporous carbon nitrides (MCN) with C3 N4 stoichiometry could find applications in fields rangi... more Mesoporous carbon nitrides (MCN) with C3 N4 stoichiometry could find applications in fields ranging from catalysis, sensing, and adsorption-separation to biotechnology. The extension of the synthesis of MCN with different nitrogen contents and chemical structures promises access to a wider range of applications. Herein we prepare mesoporous C3 N5 with a combined triazole and triazine framework via a simple self-assembly of 5-amino-1H-tetrazole (5-ATTZ). We are able to hybridize these nanostructures with graphene by using graphene-mesoporous-silica hybrids as a template to tune the electronic properties. DFT calculations and spectroscopic analyses clearly demonstrate that the C3 N5 consists of 1 triazole and 2 triazine moieties. The triazole-based mesoporous C3 N5 and its graphene hybrids are found to be highly active for oxygen reduction reaction (ORR) with a higher diffusion-limiting current density and a decreased overpotential than those of bulk g-C3 N4 .
Journal of Photochemistry and Photobiology A-chemistry, Jun 1, 1997
3, 6-Dibromo-N-ethylcarbazole (DBNEC) and its polymeric analogue poly-3, 6-dibromovinylcarbazole ... more 3, 6-Dibromo-N-ethylcarbazole (DBNEC) and its polymeric analogue poly-3, 6-dibromovinylcarbazole (PDBVCz) were studied by transient absorption spectroscopy. The transient absorption spectrum of the 3, 6-dibromo-N-ethylcarbazole radical cation and ...
Analytical and Bioanalytical Chemistry, Jun 17, 2020
Current Science, 1993
Application of ultrafast lasers to chemistry and biology has been an active area of research in t... more Application of ultrafast lasers to chemistry and biology has been an active area of research in the international scene for over a decade for physical and biophysical chemists. Perhaps, ultrafast laser spectroscopy is one of the most versatile tools available today to experimentally study structure and dynamics in the time domain of nanoseconds (10(-9) sec) to femtoseconds (10(-15) sec). In this article we attempt to highlight some of the recent developments in ultrafast laser spectroscopy with particular reference to vibrational spectroscopy, viz. infrared and Raman spectroscopy, in the above time domain.
Analytical chemistry, Jan 28, 2018
Radiation is the standard therapy used for treating Glioblastoma (GBM), a grade IV brain cancer. ... more Radiation is the standard therapy used for treating Glioblastoma (GBM), a grade IV brain cancer. Glioma Stem-like Cells (GSCs), an integral part of GBM, enforces resistance to radiation therapy of GBM. Studying the differential biomolecular composition of GSCs with varying levels of radiation sensitivity can aid in identifying the molecules and their associated pathways which impose resistance to cells thereby unraveling new targets which would serve as potential adjuvant therapy. Raman spectroscopy being a noninvasive, label free technique can determine the biomolecular constituent of cells under live conditions. In this study, we have deduced Raman spectral signatures to predict the radiosensitivity of any GSC accurately using the inherent and radiation induced biomolecular composition. Our study identified the differential regulation of several biomolecules which can be potential targets for adjuvant therapy. We radiosensitized the resistant GSCs using small molecule inhibitors s...
The Journal of Chemical Physics
In this study, near- and off-resonance Raman spectra of cadmium sulfide (CdS) quantum rods (NRs) ... more In this study, near- and off-resonance Raman spectra of cadmium sulfide (CdS) quantum rods (NRs) and 4-mercaptobenzoic acid (4-MBA) adsorbed CdS NRs are reported. The envelopes of characteristic optical phonon modes in the near-resonance Raman spectrum of CdS NRs are deconvoluted by following the phonon confinement model. As compared with off-resonant Raman spectra, optical phonon modes scattering cross section is amplified significantly in near-resonance Raman spectra through the Fröhlich interaction. The Huang–Rhys factor defining the strength of the Fröhlich interaction is estimated (∼0.468). Moreover, the adsorption of different concentrations of 4-mercaptobenzoic acid (4-MBA) onto CdS NRs produces surface strain in CdS NRs originating due to surface reconstruction and consequently blue and red shifts in off-resonance (514.5 nm) Raman spectra depending on the concentration of 4-MBA. These consequences are attributed to compressive and tensile strains, respectively. Relative to b...
Springer Proceedings in Physics, 1992
Time-resolved resonance Raman spectroscopy (TR3S) has widely been used to establish the vibration... more Time-resolved resonance Raman spectroscopy (TR3S) has widely been used to establish the vibrational structure and the nature of the metal-ligand charge transfer (MLCT) triplet excited state of d6 transition metal complexes [1–6]. In particular, bipyridyl complexes of ruthenium(II) have been studied extensively by TR3S [1, 3–6]. Recently however, certain aspects of the procedures used to interpret the TR3S data have been questioned [3–5]. In this paper, we reconsider those aspects with particular reference to ruthenium(II) tris (bipyridine) (RBY).
Analytical and Bioanalytical Chemistry, 2020
Analytical and Bioanalytical Chemistry, 2019
The Journal of Chemical Physics, 2018
Integrated Ferroelectrics, 2017
ABSTRACT Graphene quantum dots (GQDs) and CeO2-GQDs were synthesized by using a facile hydrotherm... more ABSTRACT Graphene quantum dots (GQDs) and CeO2-GQDs were synthesized by using a facile hydrothermal method at 140°C. All the synthesized materials were characterized by TEM, UV-Vis Spectroscopy, FT-IR, Raman Spectroscopy and PL. Ceria decorated GQDs show different emission peaks with different excitation of wavelengths. The discrete change in dominant luminescence features of the GQDs and their composites indicate that the variation in PL occurs because of alteration in its shape, size and bandgap. Based on the experimental results of PL peak wavelength, the emission is attributed to quasi-molecular PL from the fragments composed of a few aromatic rings with oxygen containing functional groups.
Journal of Chemical Sciences, 2012
Chemical Physics Letters, 1998
Encyclopedia of Analytical Chemistry
Spectrochimica Acta Part A: Molecular and Biomolecular Spectroscopy, 2021
Proteins are large, complex molecules responsible for various biological processes. However, prot... more Proteins are large, complex molecules responsible for various biological processes. However, protein misfolding may lead to various life-threatening diseases. Therefore, it is vital to understand the shape and structure of proteins. Despite numerous techniques, a mechanistic understanding of the protein folding process is still unclear. Therefore, new techniques are continually being explored. In the present article, we have discussed the importance of Raman spectroscopy, Raman Optical Activity (ROA) and various other advancements in Raman spectroscopy to understand protein structure and conformational changes based on the review of our earlier work and recent literature. A Raman spectrum of a protein provides unique signatures for various secondary structures like helices, beta-sheets, turns, random structures, etc., and various amino acid residues such as tyrosine, tryptophan, and phenylalanine. We have shown how Raman spectra can differentiate between bovine serum albumin (BSA) and lysozyme protein based on their difference in sequence and structure (primary, secondary and tertiary). Although it is challenging to elucidate the structure of a protein using a Raman spectrum alone, Raman spectra can be used to differentiate small changes in conformations of proteins such as BSA during melting. Various new advancements in technique and data analyses in Raman spectroscopic studies of proteins have been discussed. The last part of the review focuses on the importance of the ROA spectrum to understand additional features about proteins. The ROA spectrum is rich in information about the protein backbone due to its rigidity compared to its side chains. Furthermore, the ROA spectra of lysozyme and BSA have been presented to show how ROA provides extra information about the solvent properties of proteins.
Biotechnology Letters, 2020
The Journal of Physical Chemistry C, 2018
RSC Advances, 2018
This paper reviews various facets of Raman spectroscopy. This encompasses biomolecule fingerprint... more This paper reviews various facets of Raman spectroscopy. This encompasses biomolecule fingerprinting and conformational analysis, discrimination of healthy vs. diseased states, depth-specific information of materials and 3D Raman imaging.
Angewandte Chemie, 2018
Mesoporous carbon nitrides (MCN) with C3 N4 stoichiometry could find applications in fields rangi... more Mesoporous carbon nitrides (MCN) with C3 N4 stoichiometry could find applications in fields ranging from catalysis, sensing, and adsorption-separation to biotechnology. The extension of the synthesis of MCN with different nitrogen contents and chemical structures promises access to a wider range of applications. Herein we prepare mesoporous C3 N5 with a combined triazole and triazine framework via a simple self-assembly of 5-amino-1H-tetrazole (5-ATTZ). We are able to hybridize these nanostructures with graphene by using graphene-mesoporous-silica hybrids as a template to tune the electronic properties. DFT calculations and spectroscopic analyses clearly demonstrate that the C3 N5 consists of 1 triazole and 2 triazine moieties. The triazole-based mesoporous C3 N5 and its graphene hybrids are found to be highly active for oxygen reduction reaction (ORR) with a higher diffusion-limiting current density and a decreased overpotential than those of bulk g-C3 N4 .