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Debnath D.K.,University of Aarhus | Debnath D.K.,Malda College | Basaiawmoit R.V.,University of Aarhus | Nielsen K.L.,University of Aalborg | Otzen D.E.,University of Aarhus
Protein Engineering, Design and Selection | Year: 2011

Membranes not only provide cellular compartmentalization but influence protein behavior and folding by virtue of the multitude of different lipid types. We have studied the impact of lipid composition on the folding of the membrane-associated protein Mistic from B. subtilis. We use dimerisation via the single Cys3 residue as monitor for the degree of correct folding, since mis- or unfolding will expose the otherwise buried Cys3. We find great variability in how lipids affect protein production and dimerization, ranging from high production and low dimerization via increased production and higher dimerization to low production and low dimerization. Phosphocholine (PC) vesicles, in particular di-oleoyl-PC, lead to the highest production levels. Shorter chain lengths lead to reduced production but higher levels of dimerization. Different lipids may promote correct folding of Mistic to different extents, mediated by proper hydrophobic matching (attained for long-chain but not short-chain PC vesicles) and the existence of a fluid phase (the gel phase reduces production as well as dimerization, probably by immobilizing Mistic on the surface). The very fact that different lipids have an effect indicates that Mistic behaves like a bona fide membrane protein with a clear preference for membranes of a certain thickness and flexibility. © The Author 2010. Published by Oxford University Press. All rights reserved.

Sarkar U.K.,Malda College | Debnath D.K.,Malda College | Hossain W.,Malda College
Journal of Molecular Structure | Year: 2014

A pH controlled SERS study of 1H-2(phenylazo) imidazole (PaiH) is reported. A combination of different conformations is evident; majority preferring a particular conformation at a given pH. PaiH is in cis-form at concentrations 10-6-10-5 M at pH = 7 which undergoes azo to hydrozone conformation in alkaline pH whereas the azo-Ns participate in the electronic interaction at acidic pH. Significant reduction of HOMO-LUMO gap indicates the possibility of PaiH of being an organic semiconductor. © 2014 Elsevier B.V. All rights reserved.

Hossain W.,Malda College | Ghosh M.,IACS | Sinha C.,Jadavpur University | Debnath D.K.,Malda College | Sarkar U.K.,Malda College
Chemical Physics Letters | Year: 2013

Raman spectra and SERS of 1H-2(Phenylazo) imidazole (PaiH) adsorbed on silver nano particles are reported. Monomolecular layer is formed at a concentration of 5 × 10 6 M. A trans-to-cis isomerisation of PaiH is suggested by the cis-signature peak at 570 cm 1. In absorption spectra a single π-π* band at 358 nm is observed at higher concentrations whereas the π-π* and the π-π* bands appear at 370 nm and 456 nm, respectively, at a concentration of 5 × 10 6 M. This is in support of the hypothesis of trans-to-cis-isomerisation with lowering of concentration. DFT calculations are shown. © 2013 Elsevier B.V. All rights reserved.

Bari M.W.,Indian Center for Space Physics | Chatterjee A.K.,Indian Center for Space Physics | Chatterjee A.K.,Malda College
Indian Journal of Physics | Year: 2013

The class transitions of light curves from soft class (high count) to hard class (low count) or vice versa of the Black Hole Candidate (BHC) X-ray transient source 4U 1630-47 were observed during the 2008 outburst. The detailed spectral and timing analysis of the X-ray data of the source obtained from Rossi X-ray Timing Explorer (RXTE) were carried out. It was found that the variation of the flux and inner disk temperature with Modified Julian Day (MJD) followed almost same nature. When flux of the object increased, inner disk temperature also increased. Mean photon count rates in the light curves were seen to change before, after and during the outburst. We observed that during class transitions the slopes of the power density spectra (PDS) changed but it remained same when there was no transition. It was also observed that PDS of soft class became steeper than that of the hard class. The variation in the accretion rates, which was thought to be the sole cause of the class-to-class variation, must be nearly freely falling like other compact objects such as GRS 1915 + 105, Cygnus X-I and Cygnus X-3. © 2012 Indian Association for the Cultivation of Science.

Chatterjee A.K.,Indian Center for Space Physics | Chatterjee A.K.,Malda College | Nandy N.,Indian Center for Space Physics | Bari M.W.,Indian Center for Space Physics | Choudhury A.K.,Indian Center for Space Physics
AIP Conference Proceedings | Year: 2010

The anomalous behavior of D-layer preparation time of the ionosphere are observed only before, during and after the earthquakes, which took place in the neighbouring region by monitoring the Very Low Frequency (VLF) signal using Gyrator II loop antenna. The anomalies were also observed in the sunrise terminator times during seismically active days. These anomalous behavior may be due to the Lithosphere - Ionosphere coupling. These anomalies may be a precursor of earthquake. © 2010 American Institute of Physics.

Nandy N.,Indian Center for Space Physics | Chatterjee A.K.,Indian Center for Space Physics | Chatterjee A.K.,Malda College | Bari M.W.,Indian Center for Space Physics | Choudhury A.K.,Indian Center for Space Physics
AIP Conference Proceedings | Year: 2010

Sudden Ionospheric disturbances due to solar flares were detected by monitoring the very low frequency (VLF) data. The observed flares were compared with the Geostationary Operational Environmental Satellite (GOES) X-ray data. It is observed that there is no time lag between the peaks of our VLF observation and GOES X-ray data in morning session but there is a time lag in the afternoon. It may be due to ionization and recombination effect. © 2010 American Institute of Physics.

Vipin P.,National Institute of Oceanography of India | Vipin P.,CSIR - Central Electrochemical Research Institute | Sarkar K.,National Institute of Oceanography of India | Sarkar K.,CSIR - Central Electrochemical Research Institute | And 15 more authors.
Journal of Marine Systems | Year: 2015

We used satellite-derived sea-surface-temperature (SST) data along with in-situ data collected along a meridional transect between 18.85 and 20.25°N along 69.2°E to describe the evolution of an SST filament and front during 25 November to 1 December in the northeastern Arabian Sea (NEAS). Both features were ~100km long, lasted about a week, and were associated with weak temperature gradients (~0.07°Ckm-1). The in-situ data were collected first using a suite of surface sensors during a north-south mapping of this transect and showed the existence of a chlorophyll maximum within the filament. This surface data acquisition was followed by a high-resolution south-north CTD (conductivity-temperature-depth) sampling along the transect. In the two days that elapsed between the two in-situ measurements, the filament had shrunk in size and moved northward. In general, the current direction was northwestward and advected these mesoscale features. The CTD data also showed an SST front towards the northern end of the transect. In both these features, the chlorophyll concentration was higher than in the surrounding waters. The temperature and salinity data from the CTD suggest upward mixing or pumping of water from the base of the mixed layer, where a chlorophyll maximum was present, into the mixed layer that was about 60m thick. A striking diurnal cycle was evident in the chlorophyll concentration, with higher values tending to occur closer to the surface during the night. The in-situ data from both surface sensors and CTD, and so also satellite-derived chlorophyll data, showed higher chlorophyll concentration, particularly at sub-surface levels, between the filament and the front, but there was no corresponding signature in the temperature and salinity data. Analysis of the SST fronts in the satellite data shows that fronts weaker than those associated with the filament and the front had crossed the transect in this region a day or two preceding the sampling of the front. © 2015 Elsevier B.V.

Surface enhanced Raman spectroscopic (SERS) study of biologically important inosine molecules adsorbed in Ag-sol is reported for the first time. Possible adsorption mechanism is discussed. The enhancement is significantly influenced by the concentration of inosine in Ag-sols. The in plane base ring breathing mode appears at 715 cm-1 in solid phase and is shifted to 724 cm -1 in aqueous solution. Appearance of this band at 736 cm -1 in the adsorbed state suggests C(2′) endo-anti conformation at concentrations up to 5 × 10-7 M at which monomolecular layer is formed on the silver surface. However, C(3′) endo-syn conformation is suggested at a concentration of 5 × 10-11 M. Inosine molecule, possibly, interact with the silver nano-particles through C5′ atom at higher concentration. The π system of electrons of the hypoxanthine ring may be involved in the adsorption process at lower concentration. Monomolecular layer is formed at concentrations of 5 × 10-7 M and 5 × 10-11 M indicating perpendicular and parallel adsorption respectively. Density functional calculations are performed for the explanation of the experimental results. © 2013 Elsevier Ltd. All rights reserved.

Prasad A.,Malda College | Das M.K.,North Bengal University
Liquid Crystals | Year: 2014

The temperature variation of the splay and bend elastic constants of a binary system exhibiting nematic-induced smectic Ad and re-entrant nematic phases measured by electric field-induced Freedericksz transition method has been reported. As bend deformation is not permitted in the smectic A phase, bend elastic constant (K33) could only be determined in the nematic and re-entrant nematic phases. In both the nematic phases, the splay elastic constant has the same order of magnitude and does not show any pretransitional effect. However, in the induced smectic Ad phase, the value of K11 is about one to two orders higher than that in the nematic phases. The bend elastic constant shows a strong pretransitional effect near the nematic-smectic and smectic-re-entrant nematic phase transitions. The influence of the presence of the induced smectic phase is observed even in those mixtures which have no induced smectic phases. As the smectic phase is approached, the ratio K33/K11 increases rapidly and diverges to infinity. © 2014 Taylor & Francis.

Banerjee T.,Saha Institute of Nuclear Physics | Chandra A.K.,Saha Institute of Nuclear Physics | Chandra A.K.,Malda College | Basu A.,Saha Institute of Nuclear Physics
Physical Review E - Statistical, Nonlinear, and Soft Matter Physics | Year: 2015

We construct a one-dimensional totally asymmetric simple exclusion process (TASEP) on a ring with two segments having unequal hopping rates, coupled to particle nonconserving Langmuir kinetics (LK) characterized by equal attachment and detachment rates. In the steady state, in the limit of competing LK and TASEP, the model is always found in states of phase coexistence. We uncover a nonequilibrium phase transition between a three-phase and a two-phase coexistence in the faster segment, controlled by the underlying inhomogeneity configurations and LK. The model is always found to be half-filled on average in the steady state, regardless of the hopping rates and the attachment-detachment rate. © 2015 American Physical Society.

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