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31.
Md. Selim Arpita Sengupta Sadhu Kalyan K. Mukherjea 《Monatshefte für Chemie / Chemical Monthly》2010,40(1):933-938
Abstract
Binding of chlorophyllin (Chln), a food-grade additive molecule with hemoglobin (Hb), has been studied by photophysical and photochemical methods with a view to unravel the biochemical transport pathway of it. The binding affinity constant and binding sites between Chln and Hb are determined and found to be 3.3 × 105 M−1 and 15 (on tryptophan basis), respectively. Fluorimetric quenching experiments entail that Chln is bound in the vicinity of the tryptophan residue of Hb. Circular dichroism studies suggest that Chln induces a change in the α-helical content of Hb. Chlorophyllin is bound in the vicinity of the tryptophan residue of hemoglobin, which has been confirmed from spectrofluorimetric studies, when a quenching in the tryptophan fluorescence occurs because of the chlorophyllin-induced exposure of the tryptophan residue to hydrophillic zone. The cyclic voltammetric studies indicate that the redox reaction of FeII of Hb is inhibited shielding of it by the Chln molecule. 相似文献32.
Tanmay Chattopadhyay Manami Ghosh Arpita Banerjee Kazi Sabnam Banu Debasis Das Munirathinam Nethaji 《Transition Metal Chemistry》2007,32(4):531-535
Linkage isomers trans-bis(N-propyl-1,2-diaminoethane)dinitronickel(II) (brown, 1), trans-bis(N-isopropyl-1,2-diaminoethane)dinitritonickel(II) (blue-violet, 2a) and trans-bis(N-isopropyl-1,2-diaminoethane)dinitronickel(II) (brown, 2b) have been synthesized from solution and X-ray single crystal structure analysis of complex (1) has been performed. Simultaneous TG-DTA analyses reveal that complex (1) exhibits two successive phase transitions before to undergo decomposition (initial temperature of decomposition, Ti = 215
°C). The first one is reversible (82–98 °C; ΔH = 1.75 kJ mol−1 for heating and 93–77 °C; ΔH = −1.65 kJ mol−1 for cooling) and the second one is irreversible endothermic (135–150 °C kJ mol−1; ΔH = 1.80 kJ mol−1) phase transition. No visual color changes are observed in any of the two transitions. The causes related to the first phase
transition remain unexplored. However, on the basis of IR spectral studies the second phase transition is supposed to be due
to conformational changes of the diamine chelate rings. On the other hand, complexes (2a) and (2b) undergo decomposition without showing any phase transition [Ti = 185 and 195 °C for (2a) and (2b), respectively]. 相似文献
33.
N-Benzoylphenylhydroxylamine is employed as a precipitant for the determination of molybdenum (VI). The precipitate can be weighed either directly or as molybdenum trioxide after ignition. Molybdenum can be determined in the presence of appreciable amounts of iron(III), cobalt(II), copper(II), chromium(VI) and vanadium (V). 相似文献
34.
Arpita Dey Ran Chen Feng Li Subhamita Maitra Jean-Francois Hernandez Guo-Chun Zhou Bruno Vincent 《Molecules (Basel, Switzerland)》2021,26(24)
Alzheimer’s disease (AD) is a devastating neurodegenerative disorder, one of the main characteristics of which is the abnormal accumulation of amyloid peptide (Aβ) in the brain. Whereas β-secretase supports Aβ formation along the amyloidogenic processing of the β-amyloid precursor protein (βAPP), α-secretase counterbalances this pathway by both preventing Aβ production and triggering the release of the neuroprotective sAPPα metabolite. Therefore, stimulating α-secretase and/or inhibiting β-secretase can be considered a promising anti-AD therapeutic track. In this context, we tested andrographolide, a labdane diterpene derived from the plant Andrographis paniculata, as well as 24 synthesized derivatives, for their ability to induce sAPPα production in cultured SH-SY5Y human neuroblastoma cells. Following several rounds of screening, we identified three hits that were subjected to full characterization. Interestingly, andrographolide (8,17-olefinic) and its close derivative 14α-(5′,7′-dichloro-8′-quinolyloxy)-3,19-acetonylidene (compound 9) behave as moderate α-secretase activators, while 14α-(2′-methyl-5′,7′-dichloro-8′-quinolyloxy)-8,9-olefinic compounds 31 (3,19-acetonylidene) and 37 (3,19-diol), whose two structures are quite similar although distant from that of andrographolide and 9, stand as β-secretase inhibitors. Importantly, these results were confirmed in human HEK293 cells and these compounds do not trigger toxicity in either cell line. Altogether, these findings may represent an encouraging starting point for the future development of andrographolide-based compounds aimed at both activating α-secretase and inhibiting β-secretase that could prove useful in our quest for the therapeutic treatment of AD. 相似文献
35.
A.K. Srivastava Avni Pandey Arpita Nath Shraddha Chaurasia 《Journal of Saudi Chemical Society》2009,13(3):263-267
A series of alkenyldiarylmethanes (ADAMs) were subjected to QSAR analysis by using linear free energy relationship model of Hansch. QSAR has been developed using steric, electronic and topological parameters along with appropriate dummy variable. Statistical techniques were applied to identify the structural and physicochemical requirements for ADAMs. The results are critically discussed on the basis of regression data and cross-validation techniques. 相似文献
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40.
Arpita Ghosh Somenath Chakrabarty 《The European Physical Journal A - Hadrons and Nuclei》2011,47(4):56
We have studied various physical properties of magnetically deformed atoms and the associated matter, replacing the atoms
by the deformed Wigner-Seitz (WS) cells at the crustal region of strongly magnetized neutron stars (magnetars). A relativistic
version of the Thomas-Fermi (TF) model in the presence of a strong magnetic field in cylindrical coordinates is used to study
the properties of such matter. 相似文献