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A sensitive fluorescent probe for the polar solvation dynamics at protein-surfactant interfaces
Singh, P.,Choudhury, S.,Singha, S.,Jun, Y.,Chakraborty, S.,Sengupta, J.,Das, R.,Ahn, K. H.,Pal, S. Royal Society of Chemistry 2017 Physical chemistry chemical physics Vol.19 No.19
<P>Relaxation dynamics at the surface of biologically important macromolecules is important taking into account their functionality in molecular recognition. Over the years it has been shown that the solvation dynamics of a fluorescent probe at biomolecular surfaces and interfaces account for the relaxation dynamics of polar residues and associated water molecules. However, the sensitivity of the dynamics depends largely on the localization and exposure of the probe. For noncovalent fluorescent probes, localization at the region of interest in addition to surface exposure is an added challenge compared to the covalently attached probes at the biological interfaces. Here we have used a synthesized donor-acceptor type dipolar fluorophore, 6-acetyl-(2-((4-hydroxycyclohexyl)(methyl) amino) naphthalene) (ACYMAN), for the investigation of the solvation dynamics of a model protein-surfactant interface. A significant structural rearrangement of a model histone protein (H1) upon interaction with anionic surfactant sodium dodecyl sulphate (SDS) as revealed from the circular dichroism (CD) studies is nicely corroborated in the solvation dynamics of the probe at the interface. The polarization gated fluorescence anisotropy of the probe compared to that at the SDS micellar surface clearly reveals the localization of the probe at the protein-surfactant interface. We have also compared the sensitivity of ACYMAN with other solvation probes including coumarin 500 (C500) and 4-(dicyanomethylene)-2-methyl-6-(p-dimethylamino-styryl)-4H-pyran (DCM). In comparison to ACYMAN, both C500 and DCM fail to probe the interfacial solvation dynamics of a model protein-surfactant interface. While C500 is found to be delocalized from the protein-surfactant interface, DCM becomes destabilized upon the formation of the interface (protein-surfactant complex). The timescales obtained from this novel probe have also been compared with other femtosecond resolved studies and molecular dynamics simulations.</P>
Arp 202: a TDG formed in a parent's extended dark matter halo?
Scott, T C,Lagos, P,Ramya, S,Sengupta, C,Paudel, S,Sahu, D K,Misra, K,Woo, J -H,Sohn, B W Oxford University Press 2018 MONTHLY NOTICES- ROYAL ASTRONOMICAL SOCIETY Vol.475 No.1
<P>We report on H alpha+ [N II] imaging of the Arp 202 interacting pair and its tidal dwarf galaxy (TDG) candidate as well as a GMOS long slit spectrum from the TDG candidate, observed with the Gemini North telescope. Our H alpha + [N II] imaging reveals the TDG to have an elongated structure, similar to 1.9 kpc in length with the two principal star-forming knots at either end. Our observations also show the TDG candidate has a recessional V-H alpha similar to 3032km s(-1), within 100 km s(-1) of the parent pair's mean velocity and an oxygen abundance of 12+log(O/H) = 8.10 +/- 0.41. The TDG's oxygen abundance is in good agreement with that of a star-forming region in NGC 2719A, one of the parent galaxies, which has an estimated oxygen abundance of 12+log(O/H) = 8.05 +/- 0.41. The TDG's V-H alpha and oxygen abundance confirm previous results validating the candidate as a TDG. The absence of detectable emission from the TDG in Spitzer 3.6 and 4.5 vim images together with the lack of absorption lines and weak continuum in the spectrum is consistent with absence the of an old population (greater than or similar to 0.5 Gyr). The location of the TDG within the interaction debris and the absence of indicators of an old stellar population in the TDG is consistent with a scenario in which the TDG is formed from H I stripped from the parent galaxies and within the extended dark matter halo of one of the parents as proposed by Bournaud et al. and Duc et al.</P>
PREPARATION AND MICROSTRUCTURAL CHARACTERIZATION OF NANOCRYSTALLINE Mn-DOPED ZnO
B. ROY,O. MONDAL,A. DEB,S. P. SENGUPTA,P. CHATERJEE,M. PAL 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2011 NANO Vol.6 No.4
Mn-doped ZnO, a dilute magnetic semiconductor (DMS), has been prepared in nanocrystalline form by using a soft chemical route. The concurrent diffusional growth of both nanocrystalline Mn-doped ZnO and secondary spinel phase ZnMn_2O_4 in annealed samples have been studied by using a modified Rietveld method and transmission electron microscope (TEM). Rietveld analysis reveals that both the compounds start growing when Mn concentration is lower and the volume fraction of crystalline spinel phase ZnMn_2O_4 decreases sharply when Mn concentration increases. TEM study indicates that average particle sizes of both the phases are in nanometer dimensions and are highly crystalline in nature. Magnetization increases initially and then almost saturates with the increase of Mn concentration. The enhanced magnetization could be a combined effect of Mn ions and surface ferromagnetism of nanoparticles.
Shukla Vikram,Gera Bhuvaneshwar,Ganju Sunil,Varma Salil,Maheshwari N.K.,Guchhait P.K.,Sengupta S. 한국원자력학회 2022 Nuclear Engineering and Technology Vol.54 No.11
Hydrogen mitigation using Passive Autocatalytic Recombiners (PARs) has been widely accepted methodology inside reactor containment of accident struck Nuclear Power Plants. They reduce hydrogen concentration inside reactor containment by recombining it with oxygen from containment air on catalyst surfaces at ambient temperatures. Exothermic heat of reaction drives the product steam upwards, establishing natural convection around PAR, thus invoking homogenisation inside containment. CFD models resolving individual catalyst plate channels of PAR provide good insight about temperature and hydrogen recombination. But very thin catalyst plates compared to large dimensions of the enclosures involved result in intensive calculations. Hence, empirical correlations specific to PARs being modelled are often used in integral containment studies. In this work, an experimentally validated CFD model of PAR has been employed for developing an empirical correlation for Indian PAR. For this purpose, detailed parametric study involving different gas mixture variables at PAR inlet has been performed. For each case, respective values of gas mixture variables at recombiner outlet have been tabulated. The obtained data matrix has then been processed using regression analysis to obtain a set of correlations between inlet and outlet variables. The empirical correlation thus developed, can be easily plugged into commercially available CFD software.