Ankur Jain - Academia.edu (original) (raw)

Papers by Ankur Jain

Nature, Jan 26, 2011

Proteins perform most cellular functions in macromolecular complexes. The same protein often part... more Proteins perform most cellular functions in macromolecular complexes. The same protein often participates in different complexes to exhibit diverse functionality. Current ensemble approaches of identifying cellular protein interactions cannot reveal physiological permutations of these interactions. Here we describe a single-molecule pull-down (SiMPull) assay that combines the principles of a conventional pull-down assay with single-molecule fluorescence microscopy and enables direct visualization of individual cellular protein complexes. SiMPull can reveal how many proteins and of which kinds are present in the in vivo complex, as we show using protein kinase A. We then demonstrate a wide applicability to various signalling proteins found in the cytosol, membrane and cellular organelles, and to endogenous protein complexes from animal tissue extracts. The pulled-down proteins are functional and are used, without further processing, for single-molecule biochemical studies. SiMPull should provide a rapid, sensitive and robust platform for analysing protein assemblies in biological pathways.

Investigative ophthalmology & visual science, 2012

Glaucoma is a leading cause of visual impairment and blindness, with elevated intraocular pressur... more Glaucoma is a leading cause of visual impairment and blindness, with elevated intraocular pressure (IOP) as a major causative risk factor. Glucocorticoid (GC) therapy causes morphologic and biochemical changes in the trabecular meshwork (TM), an ocular tissue involved in regulating IOP, which can lead to the development of glaucoma in susceptible individuals (steroid responders). Steroid responders comprise 40% of the general population and are at higher risk of developing glaucoma. In addition, a majority of glaucoma patients are steroid responders. Differential distribution of various isoforms of GC receptor (GR) may be responsible for this heterogeneity in the steroid response. The alternatively spliced GRβ isoform acts as dominant negative regulator of classical GRα transcriptional activity. mRNA splicing is mediated by spliceosomes, which include serine-arginine rich proteins (SRps). The purpose of this study was to determine whether specific SRps regulate levels of these isoforms and thereby GC response in TM cells. Quantitative RT-PCR, Western blot analysis, and immunocytochemistry were used to determine the differential expression of different SRps (SRp20, 30c, and 40) in human normal and glaucomatous TM cell strains. Bioinformatics was used to find putative binding sites for SRp20 and SRp40 on exon 9 of the GR gene. A peptide modulator of splicing (bombesin) and SRp expression vectors were used to modulate SRp levels and determine their effects on GRα/GRβ ratios as well as dexamethasone (DEX) responsiveness via GRE- luciferase reporter activity, fibronectin, and myocilin induction in TM cells. SRp20, SRp30c, and SRp40 regulate GR splicing and the GC response in TM cells. Modulation of SRp levels altered the GRβ/α ratio that correlated with DEX responsiveness. Bombesin decreased SRp20; increased SRp30c, SRp40 levels, and GRβ/α ratio, and suppressed DEX response in TM cells. Relative levels of SRp20, SRp30c, and SRp40 in TM cells control differential expression of the two alternatively spliced isoforms of the GR and thereby regulate GC responsiveness. Different levels and/or activities of these SRps may account for differential GC sensitivity among the normal and glaucoma populations.

Nature protocols, 2012

This protocol describes a single molecule pull-down (SiMPull) assay for analyzing physiological p... more This protocol describes a single molecule pull-down (SiMPull) assay for analyzing physiological protein complexes. The assay combines the conventional pull-down assay with single molecule total internal reflection fluorescence microscopy, and allows probing single macromolecular complexes directly from cell or tissue extracts. In this method, antibodies against the protein of interest are immobilized on a passivated microscope slide. When cell extracts are applied, the surface-tethered antibody captures the protein together with its physiological interaction partners. After washing away the unbound components, single molecule fluorescence microscopy is used to probe the pulled down proteins. Captured proteins are visualized through genetically encoded fluorescent protein tags or through antibody labeling. This ultra-sensitive assay requires at least 10-fold less reagents, is significantly faster and provides quantitative data compared to western blot analysis. Furthermore, SiMPull can distinguish between multiple association states of the same protein. SiMPull is generally applicable to proteins from a variety of cellular contexts and to endogenous proteins. Starting with the cell extracts and passivated slides, the assay requires 1.5 -2.5 hours for data acquisition and analysis.

Investigative ophthalmology & visual science, 2013

Elevated intraocular pressure (IOP) is a major risk factor in glaucoma. Various changes in the tr... more Elevated intraocular pressure (IOP) is a major risk factor in glaucoma. Various changes in the trabecular meshwork (TM) are responsible for elevated IOP. Glucocorticoids (GCs) increase IOP and mediate biochemical changes in the TM, similar to those associated with primary open-angle glaucoma (POAG). There are differences in steroid responsiveness among the population. Approximately 40% of individuals significantly elevate IOP (i.e., responders) upon GC administration, while others do not (i.e., nonresponders). The responders are at higher risk of developing POAG compared to the nonresponders. In addition, almost all POAG patients are steroid responders. GC responsiveness is regulated by the relative levels of the active GC receptor alpha (GRα) and the alternatively spliced dominant negative regulator isoform GRβ. Glaucomatous TM cell strains have a lower GRβ-GRα ratio compared to normal TM cells, making them more sensitive to GCs. Our purpose was to investigate the role of a special class of natural products called thailanstatins (TSTs) in GR alternative splicing and GC response in cultured human TM cells. Quantitative RT-PCR and Western immunoblotting were used to study the effect of TSTs on GRβ-GRα ratios in human TM cell strains. Effects of TSTs on dexamethasone (DEX) responsiveness were assessed by GRE-luciferase reporter activity assay and fibronectin (FN) induction in TM cells. TSTs increased the GRβ-GRα ratio in TM cells. Increased GRβ-GRα ratios were associated with decreased DEX-mediated FN induction and GRE-luciferase activity. TSTs modulate the GR splicing process to enhance GRβ levels and thereby decrease the GC response in cultured human TM cells. These TSTs, or similar compounds, may potentially be new glaucoma therapeutic agents.

Journal of ocular pharmacology and therapeutics : the official journal of the Association for Ocular Pharmacology and Therapeutics

Glucocorticoid (GC)-induced ocular hypertension (OHT) is a serious side effect of GC therapy in s... more Glucocorticoid (GC)-induced ocular hypertension (OHT) is a serious side effect of GC therapy in susceptible individuals. This OHT is due to increased aqueous humor (AH) outflow resistance in the trabecular meshwork (TM) caused by GC-mediated changes in TM structure and function. GCs may also play a role in the development of primary open-angle glaucoma (POAG). Elevated cortisol levels in the AH or enhanced GC sensitivity may be one of the reasons for elevated intraocular pressure in POAG patients. The GC OHT responder population is at greater risk of developing POAG compared with non-responders. We recently have gained insight into the molecular mechanisms responsible for this differential GC responsiveness, which is attributed to differences in GC receptor isoform expression in the TM. This article summarizes current knowledge on alternative GC receptor splicing to generate GC receptor alpha (GRα) and GRβ and their roles in the regulation of GC responsiveness in normal and glaucoma TM.

Page 1. 147 5.2 Materials science There have been a large number of experiments in materials scie... more Page 1. 147 5.2 Materials science There have been a large number of experiments in materials science with energetic ion beams on the problems mainly related to ion beam induced modifications and a few on characterization of materials. ...

Page 1. Delivered by Ingenta to: ? IP : 93.91.26.12 Fri, 17 Jun 2011 18:47:42 RESEARCH AR TICLE C... more Page 1. Delivered by Ingenta to: ? IP : 93.91.26.12 Fri, 17 Jun 2011 18:47:42 RESEARCH AR TICLE Copyright © 2007 American Scientific Publishers All rights reserved Printed in the United States of America Journal of Scanning Probe Microscopy Vol. 2, 36–40, 2007 ...

The hydrogenation behaviour of RNi 5 /Co (R = Ce, La) bi-layer thin films has been investigated. ... more The hydrogenation behaviour of RNi 5 /Co (R = Ce, La) bi-layer thin films has been investigated. To prevent the poisoning of surface of thin films due to the gases like O 2 , CO 2 , etc. the films were well coated by a thin over layer of cobalt because of its resistance to oxidation. Thin film samples were characterized by means of XRD. In order to investigate the effect of hydrogen on the surface structure of the film, the optical micrograph and transmission spectra of as deposited and hydrogenated thin film samples have been carried out. It can be concluded from the transmittance spectra that the hydrogenation of the film causing an increment in the transmission. Thin metallic films switch reversibly from their initial reflecting state to visually transparent states when exposed to gaseous hydrogen. It has also been confirmed from the change in optical micrographs of the films. It has been found that the resistance of film increases with the absorption of hydrogen. The resistance of the same decreases with desorption of hydrogen. The effect of temperature and hydrogen exposing time on the resistance of the film has also been studied. ᭧

The use of thin films for hydrogen storage has become very important as the main process of absor... more The use of thin films for hydrogen storage has become very important as the main process of absorption and desorption of hydrogen takes place on the surface of the material. The incorporation of hydrogen into thin film form is relatively new field of research and provides an opportunity to examine a number of unusual properties, which are not visible in the bulk hydrides. Considerable amount of work has been done in our laboratory to investigate hydrogen absorption mechanism in FeTi, LaNi , and MmNi 4.5 Al 0.5 thin film metal hydrides.

Mg-x wt% ZrCrCo (x = 25, 50) composites are prepared by high energy milling. These composites are... more Mg-x wt% ZrCrCo (x = 25, 50) composites are prepared by high energy milling. These composites are studied in terms of their structural, morphological, and hydrogenation properties. XRD results suggest no reaction between Mg and ZrCrCo not only after milling but also after hydriding treatment. Both counterparts are found to be converted in their hydride state on hydrogen exposure. The maximum storage capacity is found to be 5.4 and 3.8 wt% at 300°C for x = 25 and 50 respectively in Mg-x wt% ZrCrCo composite. The presence of alloy phase greatly enhances the sorption kinetics even at lower temperature. The composite with 50% ZrCrCo content could desorb 90% of its total hydrogen capacity within 60 min at 250°C, while it takes less than 10 min to desorb its total capacity at 300°C.

ABSTRACT Recently KSiH3 has been proposed as an attractive contender towards hydrogen storage med... more ABSTRACT Recently KSiH3 has been proposed as an attractive contender towards hydrogen storage media, owing to its high storage capacity i.e. 4.3 wt% within a good P-T window. The high activation energy for desorption allows KSiH3 to desorb hydrogen slowly only at 200°C in more than 5 hours. Moreover, the efforts to improve the kinetics by means of milling with carbon powder disproportionate KSiH3 into KH, Si & K-Si intermetallic phases. A number of known nano-metals viz. Ni, Co, and Nb are attempted in order to improve the sorption properties of KSiH3. Nano-Ni is found to be most effective catalyst with the lowest value of activation energy 106kJmol-1 in comparison to 142kJmol-1 for as annealed KSi sample.

A number of known catalysts, which have been proven to be very effective for several hydrogen spe... more A number of known catalysts, which have been proven to be very effective for several hydrogen species, were studied in order to determine their effects on the hydrogen ab/desorption properties of KSiH3. Among all the catalysts used in this work, mesoporous Nb2O5 is found to be quite effective, with a reduction in activation energy from 142 kJ mol(-1) for pristine KSi to 63 kJ mol(-1) for mesoporous-Nb2O5-added KSi, thus allowing desorption to start at 100-120 °C. Any disproportionation is not observed in the controlled hydrogenation process. The mechanism for this improvement is also proposed in detail. The kinetic modifications on the ab/desorption properties of KSiH3 provide an alternative to the well-known family of heavy BCC alloys which are capable of working in the same temperature range but with a lower gravimetric hydrogen content, almost half of the KSi system.

The high stability of Lithium hydride is a bottleneck to use it as hydrogen storage media. The pr... more The high stability of Lithium hydride is a bottleneck to use it as hydrogen storage media. The present paper is an effort to destabilize it using Sn as a dopant. Li 4.4 Sn is chosen due to its highest lithium content among all the possible stoichiometries. It is found that the real composition is Li 17 Sn 4 rather than Li 4.4 Sn. Hydrogenation measurements suggest the existence of two step reaction. Li 17 Sn 4 first react with hydrogen to form a mixture of LiH and Li 13 Sn 5 , which further transformed into a mixed phase of LiSn and LiH as final product under studied hydrogenation condition. The enthalpy values for the above mentioned reactions are found to be À93 ± 11 kJ/mol H 2 and À37 ± 2 kJ/mol H 2 for 1st and 2nd step respectively. These values are much lower than the values observed for pure LiH. Finally these hydrogenation properties were used to calculate the electrochemical potential values required for lithiation/delithiation. The value for potential for 1st step and 2nd step reaction is found to be 0.456 V and 0.746 V for Li-Sn system, which is in good agreement with the values calculated through direct electrochemical methods.

Lithium hydride has high hydrogen capacity (12.7 mass %), but could not be considered as practica... more Lithium hydride has high hydrogen capacity (12.7 mass %), but could not be considered as practical hydrogen storage media because of being very stable (required 900°C for 0.1 MPa desorption pressure). Recently, C and Si have been found suitable to reduce the stability of LiH. This motivates us to investigate the properties of other alloys of Li, formed with the other elements. In the present work, Li 3.75 Ge (Li 15 Ge 4 ) alloy was synthesized by mechanical milling, which transformed into Li 4.2 Ge (Li 21.1875 Ge 5 ) and Li 3.5 Ge (Li 7 Ge 2 ) phases during the vacuum heating at 400°C. Hydrogenation of thus formed alloys at 400°C under 3 MPa hydrogen pressure during PCI experiment transforms this mixed phase into Li 2 GeH 0.5 (Li 4 Ge 2 H) and LiH phase. A remarkable decrease in the desorption temperature (∼300−450°C) is observed by preparing the above alloy with Ge as observed from TG-DTA-MS experiment. The enthalpy of the reaction has also been calculated using the van't Hoff plot. The present work concluded with the establishment of a direct relationship between hydrogen storage parameters and electrochemical parameters using the Nernst equation and van't Hoff equation. A good agreement is found between the values of required potential for lithiation/delithiation as obtained by two methods.

The dynamics and bonding of the complex hydrides LiBH 4 and LiAlH 4 have been investigated by vib... more The dynamics and bonding of the complex hydrides LiBH 4 and LiAlH 4 have been investigated by vibrational spectroscopy. The combination of infrared, Raman, and inelastic neutron-scattering (INS) spectroscopies on hydrided and deuterided samples reveals a complete picture of the dynamics of the BH − 4 respectively AlH − 4 anions as well as the lattice. The results are explained along a rigid anion model. The straightforward interpretation of isotope effects allows its use in tracer diffusion experiments revealing the diffusion coefficients of hydrogen containing species in LiBH 4 and LiAlH 4 .

ABSTRACT This study aims at an investigation of the impurity gases emitted during the decompositi... more ABSTRACT This study aims at an investigation of the impurity gases emitted during the decomposition of borohydrides. For this we have set up a quantitative gas analysis based on a combination of FTIR spectroscopy and gravimetry. We show that the emission of various intermediates, in particular diborane, depends sensitively on the reaction conditions, including gas mean free path lengths, hydrogen backpressure, and sample pretreatment. Adduct-free Mg(BH(4))(2) and LiBH(4) emit diborane only at the impurity level, while for LiZn(2)(BH(4))(5) diborane is the main decomposition product. The decomposition reaction of LiZn(2)(BH(4))(5) proceeds via a collision-induced dissociation of Zn(BH(4))(2) in Ar at ambient pressures. Various additives were tested aiming at catalyzing the decomposition of the desorbed diborane.

We aimed to develop microsensors for eventual glucose monitoring in diabetes, based on fluorescen... more We aimed to develop microsensors for eventual glucose monitoring in diabetes, based on fluorescence lifetime changes in glucose/galactose-binding protein (GBP) labelled with the environmentally sensitive fluorophore dye, badan. A mutant of GBP was labelled with badan near the binding site, the protein adsorbed to microparticles of CaCO(3) as templates and encapsulated in alternating nano-layers of poly-L-lysine and heparin. We used fluorescence lifetime imaging (FLIM) with two-photon excitation and time-correlated single-photon counting to visualize the lifetime changes in the capsules. Addition of glucose increased the mean lifetime of GBP-badan by a maximum of approximately 2 ns. Analysis of fluorescence decay curves was consistent with two GBP states, a short-lifetime component (approximately 0.8 ns), likely representing the open form of the protein with no bound glucose, and a long-lifetime component (approximately 3.1 ns) representing the closed form with bound glucose and where the lobes of GBP have closed round the dye creating a more hydrophobic environment. FLIM demonstrated that increasing glucose increased the fractional proportion of the long-lifetime component. We conclude that fluorescence lifetime-based glucose sensing using GBP encapsulated with nano-engineered layer-by-layer films is a glucose monitoring technology suitable for development in diabetes management.

Nature, Jan 26, 2011

Proteins perform most cellular functions in macromolecular complexes. The same protein often part... more Proteins perform most cellular functions in macromolecular complexes. The same protein often participates in different complexes to exhibit diverse functionality. Current ensemble approaches of identifying cellular protein interactions cannot reveal physiological permutations of these interactions. Here we describe a single-molecule pull-down (SiMPull) assay that combines the principles of a conventional pull-down assay with single-molecule fluorescence microscopy and enables direct visualization of individual cellular protein complexes. SiMPull can reveal how many proteins and of which kinds are present in the in vivo complex, as we show using protein kinase A. We then demonstrate a wide applicability to various signalling proteins found in the cytosol, membrane and cellular organelles, and to endogenous protein complexes from animal tissue extracts. The pulled-down proteins are functional and are used, without further processing, for single-molecule biochemical studies. SiMPull should provide a rapid, sensitive and robust platform for analysing protein assemblies in biological pathways.

Investigative ophthalmology & visual science, 2012

Glaucoma is a leading cause of visual impairment and blindness, with elevated intraocular pressur... more Glaucoma is a leading cause of visual impairment and blindness, with elevated intraocular pressure (IOP) as a major causative risk factor. Glucocorticoid (GC) therapy causes morphologic and biochemical changes in the trabecular meshwork (TM), an ocular tissue involved in regulating IOP, which can lead to the development of glaucoma in susceptible individuals (steroid responders). Steroid responders comprise 40% of the general population and are at higher risk of developing glaucoma. In addition, a majority of glaucoma patients are steroid responders. Differential distribution of various isoforms of GC receptor (GR) may be responsible for this heterogeneity in the steroid response. The alternatively spliced GRβ isoform acts as dominant negative regulator of classical GRα transcriptional activity. mRNA splicing is mediated by spliceosomes, which include serine-arginine rich proteins (SRps). The purpose of this study was to determine whether specific SRps regulate levels of these isoforms and thereby GC response in TM cells. Quantitative RT-PCR, Western blot analysis, and immunocytochemistry were used to determine the differential expression of different SRps (SRp20, 30c, and 40) in human normal and glaucomatous TM cell strains. Bioinformatics was used to find putative binding sites for SRp20 and SRp40 on exon 9 of the GR gene. A peptide modulator of splicing (bombesin) and SRp expression vectors were used to modulate SRp levels and determine their effects on GRα/GRβ ratios as well as dexamethasone (DEX) responsiveness via GRE- luciferase reporter activity, fibronectin, and myocilin induction in TM cells. SRp20, SRp30c, and SRp40 regulate GR splicing and the GC response in TM cells. Modulation of SRp levels altered the GRβ/α ratio that correlated with DEX responsiveness. Bombesin decreased SRp20; increased SRp30c, SRp40 levels, and GRβ/α ratio, and suppressed DEX response in TM cells. Relative levels of SRp20, SRp30c, and SRp40 in TM cells control differential expression of the two alternatively spliced isoforms of the GR and thereby regulate GC responsiveness. Different levels and/or activities of these SRps may account for differential GC sensitivity among the normal and glaucoma populations.

Nature protocols, 2012

This protocol describes a single molecule pull-down (SiMPull) assay for analyzing physiological p... more This protocol describes a single molecule pull-down (SiMPull) assay for analyzing physiological protein complexes. The assay combines the conventional pull-down assay with single molecule total internal reflection fluorescence microscopy, and allows probing single macromolecular complexes directly from cell or tissue extracts. In this method, antibodies against the protein of interest are immobilized on a passivated microscope slide. When cell extracts are applied, the surface-tethered antibody captures the protein together with its physiological interaction partners. After washing away the unbound components, single molecule fluorescence microscopy is used to probe the pulled down proteins. Captured proteins are visualized through genetically encoded fluorescent protein tags or through antibody labeling. This ultra-sensitive assay requires at least 10-fold less reagents, is significantly faster and provides quantitative data compared to western blot analysis. Furthermore, SiMPull can distinguish between multiple association states of the same protein. SiMPull is generally applicable to proteins from a variety of cellular contexts and to endogenous proteins. Starting with the cell extracts and passivated slides, the assay requires 1.5 -2.5 hours for data acquisition and analysis.

Investigative ophthalmology & visual science, 2013

Elevated intraocular pressure (IOP) is a major risk factor in glaucoma. Various changes in the tr... more Elevated intraocular pressure (IOP) is a major risk factor in glaucoma. Various changes in the trabecular meshwork (TM) are responsible for elevated IOP. Glucocorticoids (GCs) increase IOP and mediate biochemical changes in the TM, similar to those associated with primary open-angle glaucoma (POAG). There are differences in steroid responsiveness among the population. Approximately 40% of individuals significantly elevate IOP (i.e., responders) upon GC administration, while others do not (i.e., nonresponders). The responders are at higher risk of developing POAG compared to the nonresponders. In addition, almost all POAG patients are steroid responders. GC responsiveness is regulated by the relative levels of the active GC receptor alpha (GRα) and the alternatively spliced dominant negative regulator isoform GRβ. Glaucomatous TM cell strains have a lower GRβ-GRα ratio compared to normal TM cells, making them more sensitive to GCs. Our purpose was to investigate the role of a special class of natural products called thailanstatins (TSTs) in GR alternative splicing and GC response in cultured human TM cells. Quantitative RT-PCR and Western immunoblotting were used to study the effect of TSTs on GRβ-GRα ratios in human TM cell strains. Effects of TSTs on dexamethasone (DEX) responsiveness were assessed by GRE-luciferase reporter activity assay and fibronectin (FN) induction in TM cells. TSTs increased the GRβ-GRα ratio in TM cells. Increased GRβ-GRα ratios were associated with decreased DEX-mediated FN induction and GRE-luciferase activity. TSTs modulate the GR splicing process to enhance GRβ levels and thereby decrease the GC response in cultured human TM cells. These TSTs, or similar compounds, may potentially be new glaucoma therapeutic agents.

Journal of ocular pharmacology and therapeutics : the official journal of the Association for Ocular Pharmacology and Therapeutics

Glucocorticoid (GC)-induced ocular hypertension (OHT) is a serious side effect of GC therapy in s... more Glucocorticoid (GC)-induced ocular hypertension (OHT) is a serious side effect of GC therapy in susceptible individuals. This OHT is due to increased aqueous humor (AH) outflow resistance in the trabecular meshwork (TM) caused by GC-mediated changes in TM structure and function. GCs may also play a role in the development of primary open-angle glaucoma (POAG). Elevated cortisol levels in the AH or enhanced GC sensitivity may be one of the reasons for elevated intraocular pressure in POAG patients. The GC OHT responder population is at greater risk of developing POAG compared with non-responders. We recently have gained insight into the molecular mechanisms responsible for this differential GC responsiveness, which is attributed to differences in GC receptor isoform expression in the TM. This article summarizes current knowledge on alternative GC receptor splicing to generate GC receptor alpha (GRα) and GRβ and their roles in the regulation of GC responsiveness in normal and glaucoma TM.

Page 1. 147 5.2 Materials science There have been a large number of experiments in materials scie... more Page 1. 147 5.2 Materials science There have been a large number of experiments in materials science with energetic ion beams on the problems mainly related to ion beam induced modifications and a few on characterization of materials. ...

Page 1. Delivered by Ingenta to: ? IP : 93.91.26.12 Fri, 17 Jun 2011 18:47:42 RESEARCH AR TICLE C... more Page 1. Delivered by Ingenta to: ? IP : 93.91.26.12 Fri, 17 Jun 2011 18:47:42 RESEARCH AR TICLE Copyright © 2007 American Scientific Publishers All rights reserved Printed in the United States of America Journal of Scanning Probe Microscopy Vol. 2, 36–40, 2007 ...

The hydrogenation behaviour of RNi 5 /Co (R = Ce, La) bi-layer thin films has been investigated. ... more The hydrogenation behaviour of RNi 5 /Co (R = Ce, La) bi-layer thin films has been investigated. To prevent the poisoning of surface of thin films due to the gases like O 2 , CO 2 , etc. the films were well coated by a thin over layer of cobalt because of its resistance to oxidation. Thin film samples were characterized by means of XRD. In order to investigate the effect of hydrogen on the surface structure of the film, the optical micrograph and transmission spectra of as deposited and hydrogenated thin film samples have been carried out. It can be concluded from the transmittance spectra that the hydrogenation of the film causing an increment in the transmission. Thin metallic films switch reversibly from their initial reflecting state to visually transparent states when exposed to gaseous hydrogen. It has also been confirmed from the change in optical micrographs of the films. It has been found that the resistance of film increases with the absorption of hydrogen. The resistance of the same decreases with desorption of hydrogen. The effect of temperature and hydrogen exposing time on the resistance of the film has also been studied. ᭧

The use of thin films for hydrogen storage has become very important as the main process of absor... more The use of thin films for hydrogen storage has become very important as the main process of absorption and desorption of hydrogen takes place on the surface of the material. The incorporation of hydrogen into thin film form is relatively new field of research and provides an opportunity to examine a number of unusual properties, which are not visible in the bulk hydrides. Considerable amount of work has been done in our laboratory to investigate hydrogen absorption mechanism in FeTi, LaNi , and MmNi 4.5 Al 0.5 thin film metal hydrides.

Mg-x wt% ZrCrCo (x = 25, 50) composites are prepared by high energy milling. These composites are... more Mg-x wt% ZrCrCo (x = 25, 50) composites are prepared by high energy milling. These composites are studied in terms of their structural, morphological, and hydrogenation properties. XRD results suggest no reaction between Mg and ZrCrCo not only after milling but also after hydriding treatment. Both counterparts are found to be converted in their hydride state on hydrogen exposure. The maximum storage capacity is found to be 5.4 and 3.8 wt% at 300°C for x = 25 and 50 respectively in Mg-x wt% ZrCrCo composite. The presence of alloy phase greatly enhances the sorption kinetics even at lower temperature. The composite with 50% ZrCrCo content could desorb 90% of its total hydrogen capacity within 60 min at 250°C, while it takes less than 10 min to desorb its total capacity at 300°C.

ABSTRACT Recently KSiH3 has been proposed as an attractive contender towards hydrogen storage med... more ABSTRACT Recently KSiH3 has been proposed as an attractive contender towards hydrogen storage media, owing to its high storage capacity i.e. 4.3 wt% within a good P-T window. The high activation energy for desorption allows KSiH3 to desorb hydrogen slowly only at 200°C in more than 5 hours. Moreover, the efforts to improve the kinetics by means of milling with carbon powder disproportionate KSiH3 into KH, Si & K-Si intermetallic phases. A number of known nano-metals viz. Ni, Co, and Nb are attempted in order to improve the sorption properties of KSiH3. Nano-Ni is found to be most effective catalyst with the lowest value of activation energy 106kJmol-1 in comparison to 142kJmol-1 for as annealed KSi sample.

A number of known catalysts, which have been proven to be very effective for several hydrogen spe... more A number of known catalysts, which have been proven to be very effective for several hydrogen species, were studied in order to determine their effects on the hydrogen ab/desorption properties of KSiH3. Among all the catalysts used in this work, mesoporous Nb2O5 is found to be quite effective, with a reduction in activation energy from 142 kJ mol(-1) for pristine KSi to 63 kJ mol(-1) for mesoporous-Nb2O5-added KSi, thus allowing desorption to start at 100-120 °C. Any disproportionation is not observed in the controlled hydrogenation process. The mechanism for this improvement is also proposed in detail. The kinetic modifications on the ab/desorption properties of KSiH3 provide an alternative to the well-known family of heavy BCC alloys which are capable of working in the same temperature range but with a lower gravimetric hydrogen content, almost half of the KSi system.

The high stability of Lithium hydride is a bottleneck to use it as hydrogen storage media. The pr... more The high stability of Lithium hydride is a bottleneck to use it as hydrogen storage media. The present paper is an effort to destabilize it using Sn as a dopant. Li 4.4 Sn is chosen due to its highest lithium content among all the possible stoichiometries. It is found that the real composition is Li 17 Sn 4 rather than Li 4.4 Sn. Hydrogenation measurements suggest the existence of two step reaction. Li 17 Sn 4 first react with hydrogen to form a mixture of LiH and Li 13 Sn 5 , which further transformed into a mixed phase of LiSn and LiH as final product under studied hydrogenation condition. The enthalpy values for the above mentioned reactions are found to be À93 ± 11 kJ/mol H 2 and À37 ± 2 kJ/mol H 2 for 1st and 2nd step respectively. These values are much lower than the values observed for pure LiH. Finally these hydrogenation properties were used to calculate the electrochemical potential values required for lithiation/delithiation. The value for potential for 1st step and 2nd step reaction is found to be 0.456 V and 0.746 V for Li-Sn system, which is in good agreement with the values calculated through direct electrochemical methods.

Lithium hydride has high hydrogen capacity (12.7 mass %), but could not be considered as practica... more Lithium hydride has high hydrogen capacity (12.7 mass %), but could not be considered as practical hydrogen storage media because of being very stable (required 900°C for 0.1 MPa desorption pressure). Recently, C and Si have been found suitable to reduce the stability of LiH. This motivates us to investigate the properties of other alloys of Li, formed with the other elements. In the present work, Li 3.75 Ge (Li 15 Ge 4 ) alloy was synthesized by mechanical milling, which transformed into Li 4.2 Ge (Li 21.1875 Ge 5 ) and Li 3.5 Ge (Li 7 Ge 2 ) phases during the vacuum heating at 400°C. Hydrogenation of thus formed alloys at 400°C under 3 MPa hydrogen pressure during PCI experiment transforms this mixed phase into Li 2 GeH 0.5 (Li 4 Ge 2 H) and LiH phase. A remarkable decrease in the desorption temperature (∼300−450°C) is observed by preparing the above alloy with Ge as observed from TG-DTA-MS experiment. The enthalpy of the reaction has also been calculated using the van't Hoff plot. The present work concluded with the establishment of a direct relationship between hydrogen storage parameters and electrochemical parameters using the Nernst equation and van't Hoff equation. A good agreement is found between the values of required potential for lithiation/delithiation as obtained by two methods.

The dynamics and bonding of the complex hydrides LiBH 4 and LiAlH 4 have been investigated by vib... more The dynamics and bonding of the complex hydrides LiBH 4 and LiAlH 4 have been investigated by vibrational spectroscopy. The combination of infrared, Raman, and inelastic neutron-scattering (INS) spectroscopies on hydrided and deuterided samples reveals a complete picture of the dynamics of the BH − 4 respectively AlH − 4 anions as well as the lattice. The results are explained along a rigid anion model. The straightforward interpretation of isotope effects allows its use in tracer diffusion experiments revealing the diffusion coefficients of hydrogen containing species in LiBH 4 and LiAlH 4 .

ABSTRACT This study aims at an investigation of the impurity gases emitted during the decompositi... more ABSTRACT This study aims at an investigation of the impurity gases emitted during the decomposition of borohydrides. For this we have set up a quantitative gas analysis based on a combination of FTIR spectroscopy and gravimetry. We show that the emission of various intermediates, in particular diborane, depends sensitively on the reaction conditions, including gas mean free path lengths, hydrogen backpressure, and sample pretreatment. Adduct-free Mg(BH(4))(2) and LiBH(4) emit diborane only at the impurity level, while for LiZn(2)(BH(4))(5) diborane is the main decomposition product. The decomposition reaction of LiZn(2)(BH(4))(5) proceeds via a collision-induced dissociation of Zn(BH(4))(2) in Ar at ambient pressures. Various additives were tested aiming at catalyzing the decomposition of the desorbed diborane.

We aimed to develop microsensors for eventual glucose monitoring in diabetes, based on fluorescen... more We aimed to develop microsensors for eventual glucose monitoring in diabetes, based on fluorescence lifetime changes in glucose/galactose-binding protein (GBP) labelled with the environmentally sensitive fluorophore dye, badan. A mutant of GBP was labelled with badan near the binding site, the protein adsorbed to microparticles of CaCO(3) as templates and encapsulated in alternating nano-layers of poly-L-lysine and heparin. We used fluorescence lifetime imaging (FLIM) with two-photon excitation and time-correlated single-photon counting to visualize the lifetime changes in the capsules. Addition of glucose increased the mean lifetime of GBP-badan by a maximum of approximately 2 ns. Analysis of fluorescence decay curves was consistent with two GBP states, a short-lifetime component (approximately 0.8 ns), likely representing the open form of the protein with no bound glucose, and a long-lifetime component (approximately 3.1 ns) representing the closed form with bound glucose and where the lobes of GBP have closed round the dye creating a more hydrophobic environment. FLIM demonstrated that increasing glucose increased the fractional proportion of the long-lifetime component. We conclude that fluorescence lifetime-based glucose sensing using GBP encapsulated with nano-engineered layer-by-layer films is a glucose monitoring technology suitable for development in diabetes management.