Papers by Smritakshi Phukan
Journal of Photochemistry and Photobiology A: Chemistry, 2015
ABSTRACT
Journal of Photochemistry and Photobiology B: Biology, 2013
The photophysical behavior of the deprotonated form of lumazine (Lum-anion) was studied in biolog... more The photophysical behavior of the deprotonated form of lumazine (Lum-anion) was studied in biologically relevant surfactant systems like sodium dodecyl sulfate (SDS), cetyltrimethylammonium bromide (CTAB) and TritonX-100 (TX-100) and also model water soluble protein, bovine serum albumin (BSA), using steady-state and time-resolved fluorescence spectroscopy in buffer solution of pH 12.0. The association constant values were calculated from modulated fluorescence intensity of Lum-anion in different medium. The interaction of non-ionic surfactant TX-100 was found to be about 10 times greater than SDS and CTAB. However, while the driving force of binding in SDS and/or TX-100 is mainly hydrophobic in nature, electrostatic interaction with the oppositely charged micellar head group is the predominant factor in CTAB. The thermodynamic parameters like enthalpy (ΔH) and entropy (ΔS) change, etc., corresponding to the binding of Lum-anion with BSA were estimated by performing the fluorescence titration experiment at different temperatures. Thermodynamically favorable and strong binding of Lum-anion (K~10(4) M(-1)) into BSA is due to hydrophobic interaction in the ligand binding domain II. However, the binding mechanism is entirely different in presence of protein denaturing agent like urea and electrostatic interaction plays a major role under this condition.
Journal of Photochemistry and Photobiology A: Chemistry, 2012
Journal of Molecular Structure, 2013
Journal of Luminescence, 2013
Chemical Physics, 2013
ABSTRACT The photophysical properties and tautomerization behavior of neutral lumazine were studi... more ABSTRACT The photophysical properties and tautomerization behavior of neutral lumazine were studied by fluorescence spectroscopy and density functional theory calculation. A quantitative estimation of the contributions from different solvatochromic parameters, like solvent polarizibility (π∗), hydrogen bond donation (α) and hydrogen bond accepting (β) ability of the solvent, was made using linear free energy relationships based on the Kamlet–Taft equation. The analysis reveals that the hydrogen bond acceptance ability of the solvent is the most important parameter characterizing the excited state behavior of lumazine. Theoretical calculations result predict an extensive charge redistribution of lumazine upon excitation corresponding to the N3 and N1 proton dissociation sites by solvents in the ground and excited states, respectively. Comparison of S0 and S1 state potential energy curves constructed for several water mediated tautomerization processes by intrinsic reaction coordinate analysis of lumazine-H2O cluster shows that (3,2) and (1,8) hydrogen migrations are the most favorable processes upon excitation.
Journal of Porphyrins and Phthalocyanines, 2010
The synthesized porphyrin derivatives (1-7) and the free base (8) were characterized by UV-vis an... more The synthesized porphyrin derivatives (1-7) and the free base (8) were characterized by UV-vis and ABSTRACT: A modular synthetic approach for preparing a family of porphyrin appended 1,3,4oxadiazoles 9 is described. The porphyrin hydrazides are reacted with aryl aldehydes in presence of Yb(OTf) 3 as catalyst to give porphyrin hydrazones 8 which are then cyclized to porphyrin appended 1,3,4-oxadiazoles 9 using iodobenzene diacetate. Photophysical studies in CHCl 3 solvent shows that the electronic structure of the porphyrin chromophore is not greatly perturbed by the incorporation of the oxadiazole group onto the meso-phenyl ring. Efficient quenching of porphyrin fluorescence was observed in 9g with a pyridinium moiety.
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Papers by Smritakshi Phukan