@article { ISI:000250755100004, title = {Fluorescence quenching and time-resolved fluorescence studies of alpha-Mannosidase from Aspergillus fischeri (NCIM 508)}, journal = {Journal of Fluorescence}, volume = {17}, number = {6}, year = {2007}, month = {NOV}, pages = {599-605}, publisher = {SPRINGER/PLENUM PUBLISHERS}, type = {Article}, address = {233 SPRING ST, NEW YORK, NY 10013 USA}, abstract = {

Apart from the vital role in glycoprotein biosynthesis and degradation, alpha-mannosidase is currently an important therapeutic target for the development of anticancer agents. Fluorescence quenching and time-resolved fluorescence of alpha-mannosidase, a multitryptophan protein from Aspergillus fischeri were carried out to investigate the tryptophan environment. The tryptophans were found to be differentially exposed to the solvent and were not fully accessible to the neutral quencher indicating heterogeneity in the environment. Quenching of the fluorescence by acrylamide was collisional. Surface tryptophans were found to have predominantly positively charged amino acids around them and differentially accessible to the ionic quenchers. Denaturation led to more exposure of tryptophans to the solvent and consequently in the significant increase in quenching with all the quenchers. The native enzyme showed two different lifetimes, tau (1) (1.51 ns) and tau (2) (5.99 ns). The average lifetime of the native protein (tau) (3.187 ns) was not affected much after denaturation (tau) (3.219 ns), while average lifetime of the quenched protein samples was drastically reduced (1.995 ns for acrylamide and 1.537 ns for iodide). This is an attempt towards the conformational studies of alpha-mannosidase.

}, keywords = {alpha-Mannosidase, Denaturation, fluorescence, lifetime, Solute quenching}, issn = {1053-0509}, doi = {10.1007/s10895-007-0227-8}, author = {Shashidhara, K. S. and Gaikwad, Sushama M.} } @article { ISI:000247807900003, title = {Synthesis and characterization of novel polyurethanes based on 4,4 {\textquoteleft}-[1,4-phenylenedi-diazene-2,1-dlyl] bis(2-carboxyphenol) and 4,4 {\textquoteleft}-[1,4-phenylenedi-diazene-2,1-diyl] bis(2-chlorophenol) hard segments}, journal = {Reactive \& Functional Polymers}, volume = {67}, number = {6}, year = {2007}, month = {JUN}, pages = {503-514}, publisher = {ELSEVIER SCIENCE BV}, type = {Article}, address = {PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS}, abstract = {

Eight novel polyurethanes (PUs) based on 4,4{\textquoteright}-[1,4-phenylenedi-diazene-2,1-diyl]bis(2-carboxyphenot) and 4,4{\textquoteright}-[1,4phenylenedi-diazene-2,1-diyl]bis(2-chloro- phenol) as hard segments with four diisocyanates viz., 4,4-diphenyl-methane diisocyanate, toluene 2,4-diisocyanate, isophorone diisocyanate and hexamethylene diisocyanate were prepared. Structural and thermal characterization of the segmented PUs were determined by FT-IR, UV spectrophotometry, fluoroscence spectroscopy, H-1 NMR, C-13 NMR spectroscopy and DTA/TGA analysis. All the PUs contain domains of semi-crystalline and amorphous structures, as indicated by X-ray diffraction. PUs were soluble in polar aprotic solvents like N-methyl-2-pyrrolidone (NMP), dimethyl formamide (DMF) and dimethylsulfoxide (DIVISO). (c) 2007 Elsevier Ltd. All rights reserved.

}, keywords = {azo polymers, fluorescence, hard segments, Morphology, phase separation, polyurethanes, spectroscopy, Thermal properties}, issn = {1381-5148}, doi = {10.1016/j.reactfunctpolym.2007.02.003}, author = {Raghu, A. V. and Gadaginamath, G. S. and Mathew, Nevin T. and Halligudi, Shivaraj B. and Aminabhavi, Tejraj M.} } @article { ISI:000256743300032, title = {Insight into the micellization of dodecyldimethylethylammonium bromide (DDAB) in the presence of bovine serum albumin (BSA)}, journal = {Journal of Colloid and Interface Science}, volume = {323}, number = {2}, year = {2008}, month = {JUL}, pages = {426-434}, publisher = {ACADEMIC PRESS INC ELSEVIER SCIENCE}, type = {Article}, address = {525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA}, abstract = {

in this work, we report the effect of concentration of bovine serum albumin (BSA) on the micellization of a cationic surfactant, doclecyldimethylethylammonium bromide (DDAB). Several samples covering a wide range of concentrations of protein and surfactant have been investigated. The interactions between the moieties are investigated by measuring fluorescence quenching of BSA molecules. The aggregation number of DDAB micelles is found to be small in the presence of BSA. The formation of DDAB-BSA complex is confirmed by FTIR. Absorbance spectroscopy indicates that at higher concentration, the conformational stability of BSA in DDAB is higher. The viscosity data for protein-surfactant systems confirm conformational changes in protein chains induced by the surfactant. The cmc values for DDAB increase with increasing concentration of BSA. At higher temperatures the micellization-complexation becomes enthalpy-dominated. (c) 2008 Elsevier Inc. All rights reserved.

}, keywords = {Aggregation number, BSA, conductivity, conformational stability, DDAB, FFIR, fluorescence, UV-visible, viscosity}, issn = {0021-9797}, doi = {10.1016/j.jcis.2008.04.026}, author = {Mehta, S. K. and Bhawna and Bhasin, K. K. and Kumar, Anil} } @article { ISI:000253896400027, title = {Steady state and time-resolved fluorescence studies of a hemagglutinin from Moringa oleifera}, journal = {Journal of Fluorescence}, volume = {18}, number = {2}, year = {2008}, month = {MAR}, pages = {479-485}, publisher = {SPRINGER/PLENUM PUBLISHERS}, address = {233 SPRING ST, NEW YORK, NY 10013 USA}, abstract = {

The saccharide binding and conformational characterization of a hemagglutinin, a low molecular weight protein from the seeds of Moringa oleifera was studied using steady state and time resolved fluorescence. The lectin binds sugars LacNAc (K-a = 1380 M-1) and fructose (K-a = 975 M-1), as determined by the fluorescence spectroscopy. It has a single tryptophan per monomer which is exposed on the surface and is in a strong electropositive environment as revealed by quenching with iodide. Quenching of the fluorescence by acrylamide involved both static (K-s = 0.216 M-1) and collisional (K-sv= 8.19 M-1) components. The native protein showed two different lifetimes, tau(1) (1.6 ns) and tau(2) (4.36 ns) which decrease and get converted into a single one, (2.21 ns) after quenching with 0.15 M acrylamide. The bimolecular quenching constant, k(q) was 7.55 x 10(11) M-1 s(-1). ANS binding studies showed that the native protein has exposed hydrophobic patches which get further exposed at extreme acidic or alkaline pH. However, they get buried in the interior of the protein in presence of 1 M GdnHCl or urea.

}, keywords = {ANS binding, fluorescence, Hemagglutinin, lifetime, Moringa oleifera, saccharide binding, Solute quenching}, issn = {1053-0509}, doi = {10.1007/s10895-007-0289-7}, author = {Katre, Uma V. and Suresh, C. G. and Khan, Mohammad Islam and Gaikwad, Sushama M.} } @article { ISI:000264484400007, title = {Comparative studies of two araceous lectins by steady state and time-resolved fluorescence and CD spectroscopy}, journal = {Journal of Fluorescence}, volume = {19}, number = {2}, year = {2009}, month = {MAR}, pages = {239-248}, publisher = {SPRINGER/PLENUM PUBLISHERS}, address = {233 SPRING ST, NEW YORK, NY 10013 USA}, abstract = {

Transitions in the tryptophan microenvironment and secondary structure of two monocot lectins from Sauromatum guttatum and Arisaema tortuosum under different denaturing conditions were studied by steady state and time resolved fluorescence and CD spectroscopy. The lectins exist as tetramers with a single tryptophan residue estimated per monomer, present in a polar environment. Quenching with ionic quenchers showed predominantly electropositive environment for tryptophan residues. Acrylamide had maximum quenching effect. A decrease in KI quenching due to lectin denaturation indicated redistribution of charges as a result of possible conformational change. The two values for lifetimes of tryptophanyl population (1.2-1.4 and 6.3-6.4 ns) reduced substantially on quenching or denaturation. Similarly, both the lectins showed a drastic loss of secondary structure in 5 M Gdn-HCl or 6 M Urea or at pH 2.0 and below. For the first time araceous lectins, like legume lectins are shown to bind adenine. The presence of a compact structure at alkaline pH 10.0-12.0 was observed in CD spectra.

}, keywords = {Araceae lectins, Denaturation, fluorescence, Lifetime spectroscopy, Secondary structure}, issn = {1053-0509}, doi = {10.1007/s10895-008-0409-z}, author = {Dharker, Poorva N. and Gaikwad, Sushama M. and Suresh, C. G. and Dhuna, Vikram and Khan, Mohammad Islam and Singh, Jatinder and Kamboj, Sukhdev Singh} } @article { ISI:000265699700015, title = {Control of molecular aggregation in symmetrically substituted pi-conjugated bulky poly(p-phenylenevinylene)s and their copolymers}, journal = {Journal of Polymer Science Part A-Polymer Chemistry}, volume = {47}, number = {10}, year = {2009}, month = {MAY}, pages = {2631-2646}, publisher = {JOHN WILEY \& SONS INC}, address = {111 RIVER ST, HOBOKEN, NJ 07030 USA}, abstract = {

A new series of symmetrically substituted bulky PPV-copolymers based on poly(bis-2,5-(2-ethylhexyloxy)-1,4-phenylenevinylene) (BEH-PPV) bearing tricyclodecane (TCD) pendants were synthesized to study the effect of chain aggregation in the pi-conjugated polymer backbone. The composition of the copolymers was varied up to 100 mol \% and the structures of the copolymer were confirmed by NMR and FTIR. The molecular weights of the copolymers were obtained as M(w) = 11,500-1,78,800 depending on the TCD-incorporation in BEH-PPV. The origin of the pi-aggregation was investigated using mixture of solvents (polar or nonpolar) or temperature as external stimuli. Absorption, photoluminescence, and time-resolved fluorescence decay techniques were employed as tools to trace molecular aggregation in solution and solid state. The TCD-substituted bulky copolymers showed almost twice the enhancement in photoluminescence compared with that of BEH-PPV Solvent-induced aggregation studies of copolymers revealed the existence of strong molecular aggregation in BEH-PPV compared with that of bulky copolymers. Variable temperature studies further evidence for the reversibility of molecular aggregation on beating/cooling cycles and showed isosbetic points with respect to free and aggregated polymer chains. Time-resolved fluorescent studies confirmed the existence of free and aggregated pi-conjugated species with a life time of 0.1 to 1.0 ns. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polym Chem 47: 2631-2646, 2009

}, keywords = {conjugated polymers, fluorescence, poly(p-phenylenevinylene), solution properties, Structure-property relationship}, issn = {0887-624X}, doi = {10.1002/pola.23348}, author = {Resmi, R. and Amrutha, S. R. and Jayakannan, M.} } @article { ISI:000263163200021, title = {Synthesis and self-organization properties of copolyurethanes based on perylenediimide and naphthalenediimide units}, journal = {Journal of Polymer Science Part A-Polymer Chemistry}, volume = {47}, number = {4}, year = {2009}, month = {FEB}, pages = {1224-1235}, publisher = {JOHN WILEY \& SONS INC}, address = {111 RIVER ST, HOBOKEN, NJ 07030 USA}, abstract = {

A series of perylene and naphthalene diimide-containing random copolyurethanes with different ratios of perylene/naphthalene diimide content was synthesized and characterized. Copolymerization improved the solubility of these rigid aromatic diimides, and the copolymers were soluble in common organic solvents like chloroform, tetrahydrofuran, and so forth. The absorption spectra of perylene-based copolymers showed a red-shifted peak at a wavelength of 557 nm corresponding to J-type aggregates. For naphthalene copolymers, the quenching of fluorescence at higher naphthalene incorporation suggested the presence of aggregates because of the extensive pi-pi stacking of the aromatic core. FTIR spectroscopic analysis showed that the hydrogen bonding tendency of the polymer decreased with increase in perylene/naphthalene incorporation. The fluorescence spectra of the perylene polymers were exactly a mirror image of the absorption spectra. The fluorescence spectra of the naphthalene polymers at higher naphthalene incorporation showed a red-shifted excimer like emission peak, which was assigned as static excimers based on their excitation spectra. These polymers could exhibit two types of secondary interaction modes, namely, hydrogen bonding (via urethane linkage) and pi-stacking (via aromatic perylene or naphthalene units) thus highlighting the importance of polymer design in inducing self-organization at both low and high incorporation of the rigid bisimide moieties. (C) 2009 Wiley Periodicals, Inc. J Polym Sci Part A: Polyrn Chem 47: 1224-1235, 2009

}, keywords = {fluorescence, hydrogen bonding, naphthalene diimide polymers, polyurethane copolymer, self-organization, structure-property relations}, issn = {0887-624X}, doi = {10.1002/pola.23233}, author = {Jancy, B. and Asha, S. K.} } @article { ISI:000280597500004, title = {Conformational and functional transitions in class II alpha-mannosidase from aspergillus fischeri}, journal = {Journal of Fluorescence}, volume = {20}, number = {4}, year = {2010}, month = {JUL}, pages = {827-836}, publisher = {SPRINGER/PLENUM PUBLISHERS}, address = {233 SPRING ST, NEW YORK, NY 10013 USA}, abstract = {

The conformational transitions in an oligomeric and high molecular weight class II alpha-mannosidase from Aspergillus fischeri were examined using fluorescence and CD spectroscopy under chemical, thermal and acid denaturing conditions. The enzyme lost the activity first and then the overall folded conformation and secondary structure. The midpoint values of GdnHCl mediated changes measured by inactivation; fluorescence and negative ellipticity were 0.48 M, 1.5 M and 1.9 M, respectively. The protein almost completely unfolded in 4.0 M GdnHCl but not at 90 A degrees C. The inactivation and unfolding were irreversible. At pH 2.0, the protein exhibited molten-globule like intermediate with rearranged secondary and tertiary structures and exposed hydrophobic amino acids on the surface. This species showed increased accessibility of Trp to the quenchers and got denatured with GdnHCl in a different manner. The insoluble aggregates of a thermally denatured protein could be detected only in the presence of 0.25-0.75 M GdnHCl.

}, keywords = {Aggregation, alpha-Mannosidase, ANS binding, Circular dichroism, fluorescence, GdnHCl, Hydrobicity, Thermal denaturation}, issn = {1053-0509}, doi = {10.1007/s10895-010-0625-1}, author = {Shashidhara, K. S. and Gaikwad, Sushama M.} } @article { ISI:000286021300025, title = {Multistate unfolding of alpha-mannosidase from Canavalia ensiformis (Jack Bean): evidence for the thermostable molten globule}, journal = {Biochemical and Biophysical Research Communications}, volume = {403}, number = {3-4}, year = {2010}, month = {DEC}, pages = {391-397}, publisher = {ACADEMIC PRESS INC ELSEVIER SCIENCE}, address = {525 B ST, STE 1900, SAN DIEGO, CA 92101-4495 USA}, abstract = {

The relevance of partially ordered states of proteins (such as the molten-globule state) in cellular processes is beginning to be understood. We examined the conformational transitions in a multimeric and high molecular weight class II alpha-mannosidase from Canavalia ensiformis (Jack Bean) (Jb alpha-man) utilizing intrinsic fluorescence, solute quenching, hydrophobic dye binding, size exclusion chromatography and circular dichroism (CD) spectroscopy for the protein in presence of Guanidine hydrochloride (GdnHCl). The decomposition analysis of the protein spectra obtained during unfolding showed progressive appearance of class S, I, II and III trp. The parameter A and spectral center of mass showed multi state unfolding of the protein and phase diagram analysis revealed formation of an intermediate of Jb alpha-man in the vicinity of 1 M GdnHCl. The intermediate exhibited compact secondary and distorted tertiary structure with exposed hydrophobic amino acids on the surface, indicating the molten-globule nature. The dissociation, partial unfolding and aggregation of Jb alpha-man occurred simultaneously during chemical denaturation. The molten-globule possessed slightly higher hydrodynamic radius, perturbance in the structure up to 60 degrees C and stability of the structure up to 80 degrees C unlike the native Jack Bean alpha-mannosidase. The modes of chemical and thermal denaturation of the native protein were different. The solute quenching parameters confirmed the altered confirmation of the intermediate. Taken together, our results constitute one of the early reports of formation of GdnHCl induced molten globule in a class II alpha-mannosidase. (C) 2010 Elsevier Inc. All rights reserved.

}, keywords = {alpha-Mannosidase, Circular dichroism, fluorescence, Guanidine hydrochloride, Molten globule, Thermostability, Unfolding}, issn = {0006-291X}, doi = {10.1016/j.bbrc.2010.11.041}, author = {Kumar, Avinash and Gaikwad, Sushama M.} } @article { ISI:000274401600036, title = {Steady state and time resolved fluorescence quenching and chemical modification studies of a lectin from endophytic fungus fusarium solani}, journal = {Journal of Fluorescence}, volume = {20}, number = {1}, year = {2010}, month = {JAN}, pages = {305-313}, publisher = {SPRINGER/PLENUM PUBLISHERS}, address = {233 SPRING ST, NEW YORK, NY 10013 USA}, abstract = {

The solute quenching studies of a lectin from endophytic fungus Fusarium solani were carried out using different quenchers such as acrylamide, succinimide, potassium iodide and cesium chloride. The lectin showed emission maximum at 348 nm indicating relative exposure of tryptophan. The quenchable fraction of the fluorophore was 100\% with acrylamide, whereas it was only 50\% with succinimide. The ionic quenchers iodide and cesium showed opposite effects at different pH. In the case of cesium, raising the pH resulted in increased quenching and accessibility of typtophan residue, while the iodide showed just opposite effect. These studies showed that the single tryptophan residue of the lectin (per monomer) is relatively exposed, and might be in the vicinity of positively charged amino acid residues. Various amino acids of the F. solani lectin were modified using different reagents to obtain information about the hemagglutinating site. The chemical modification studies suggested tyrosine residues can be modified using N-acetylimidazole, which results in complete loss of hemagglutination activity of the lectin. Kinetics of chemical modification suggested involvement of only 2 tyrosine residues. Modification of arginine, cysteine, histidine, lysine, aspartate, glutamate and tryptophan did not result in loss of hemagglutinating activity of the lectin.

}, keywords = {Chemical modification, fluorescence, Fusarium, Lectin, Quenching, Time-resolved}, issn = {1053-0509}, doi = {10.1007/s10895-009-0556-x}, author = {Khan, Feroz and Ahmad, Absar and Khan, Mohammad Islam} } @article { ISI:000289376200002, title = {Electrochemical fluorescence switching from a patternable poly(1,3,4-oxadiazole) thin film}, journal = {Macromolecular Rapid Communications}, volume = {32}, number = {8}, year = {2011}, month = {APR}, pages = {637-643}, publisher = {WILEY-BLACKWELL}, address = {COMMERCE PLACE, 350 MAIN ST, MALDEN 02148, MA USA}, abstract = {

A highly soluble poly(1,3,4-oxadiazole) (POD) substituted with long alkyl chains was examined for electrochemical fluorescence switching. The high solubility of the polymers enabled a simple fabrication of an electrochemical cell, which showed reversible fluorescence switching between dark (n-doping) and bright (neutral) states with a maximum on/off ratio of 2.5 and a cyclability longer than 1000 cycles. Photochemical cleavage of the oxadiazole in POD allowed photo-patterning of the POD film upon exposure to UV source. The patterned POD films displayed patterned image reversibly under a step potential of +1.8/-1.8V.

}, keywords = {fluorescence, lithography, Luminescence, photochemistry, switching device}, issn = {1022-1336}, doi = {10.1002/marc.201000791}, author = {Seo, Seogjae and Kim, Yuna and You, Jungmok and Sarwade, Bhimrao D. and Wadgaonkar, Prakash P. and Menon, Shamal K. and More, Arvind S. and Kim, Eunkyoung} } @article { ISI:000314149000005, title = {Facile one-pot reactive solution blending approach for main-chain donor-acceptor polymeric materials}, journal = {Journal of Polymer Science Part A-Polymer Chemistry}, volume = {51}, number = {3}, year = {2013}, month = {FEB}, pages = {509-524}, publisher = {WILEY-BLACKWELL}, address = {111 RIVER ST, HOBOKEN 07030-5774, NJ USA}, abstract = {

A high-temperature solution blending process has been used to synthesize a series of copolymers incorporating varying mole ratios of perylenebisimide (PBI) into the backbone of an engineering thermoplastic polyester [poly(1,4-cyclohexylenedimethylene-1,4-cyclohexanedicarboxylate)] (PCCD). A random donor-acceptor copolymer incorporating oligo(p-phenylene vinylene) (OPV) and PBI was also synthesized. The chemical incorporation of these chromophores into PCCD was confirmed by carrying out the melt condensation using 1,4-cyclohexanedimethanol and 1,4-dimethylcyclohexane dicarboxylate with hydroxyl-functionalized PBI and OPV derivatives. Higher extent of incorporation of PBI (35 mol \%) could be achieved using the blending approach retaining solubility, film-forming ability, and higher molecular weights. The PBI polymers produced using the two different approaches exhibited structural variations. The polymers formed from the solution blending approach had a semicrystalline nature with blocks of PCCD separating the PBI units, whereas those produced using the melt condensation route were amorphous polymers. This structural variation was reflected in their photophysical properties also with the reactive solution-blended polymers exhibiting higher fluorescence quantum yields. These results demonstrate the easy incorporation of suitably functionalized donor and acceptor moieties into a completely aliphatic polyester backbone to produce free-standing films of hitherto nonprocessable polymers. (C) 2012 Wiley Periodicals, Inc. J. Polym. Sci., Part A: Polym. Chem. 2013, 51, 509-524

}, keywords = {blending, conjugated polymers, fluorescence, PCCD, Perylenebisimide, reactive blending, transesterification}, issn = {0887-624X}, doi = {10.1002/pola.26412}, author = {Nisha, S. Kumari and Asha, S. K.} } @article { ISI:000336733100003, title = {Steady state fluorescence studies of wild type recombinant cinnamoyl CoA reductase (Ll-CCRH1) and its active site mutants}, journal = {Journal of Fluorescence}, volume = {24}, number = {3}, year = {2014}, month = {MAY}, pages = {665-673}, publisher = {SPRINGER/PLENUM PUBLISHERS}, address = {233 SPRING ST, NEW YORK, NY 10013 USA}, abstract = {

Fluorescence quenching and time resolved fluorescence studies of wild type recombinant cinnamoyl CoA reductase (Ll-CCRH1), a multitryptophan protein from Leucaena leucocephala and 10 different active site mutants were carried out to investigate tryptophan environment. The enzyme showed highest affinity for feruloyl CoA (K (a) = 3.72 x 10(5) M-1) over other CoA esters and cinnamaldehydes, as determined by fluorescence spectroscopy. Quenching of the fluorescence by acrylamide for wild type and active site mutants was collisional with almost 100 \% of the tryptophan fluorescence accessible under native condition and remained same after denaturation of protein with 6 M GdnHCl. In wild type Ll-CCRH1, the extent of quenching achieved with iodide (f (a) = 1.0) was significantly higher than cesium ions (f (a) = 0.33) suggesting more density of positive charge around surface of trp conformers under native conditions. Denaturation of wild type protein with 6 M GdnHCl led to significant increase in the quenching with cesium (f (a) = 0.54), whereas quenching with iodide ion was decreased (f (a) = 0.78), indicating reorientation of charge density around trp from positive to negative and heterogeneity in trp environment. The Stern-Volmer plots for wild type and mutants Ll-CCRH1 under native and denatured conditions, with cesium ion yielded biphasic quenching profiles. The extent of quenching for cesium and iodide ions under native and denatured conditions observed in active site mutants was significantly different from wild type Ll-CCRH1 under the same conditions. Thus, single substitution type mutations of active site residues showed heterogeneity in tryptophan microenvironment and differential degree of conformation of protein under native or denatured conditions.

}, keywords = {Active site mutants, Cinnamoyl CoA reductase, fluorescence, Ligand binding, Solute quenching}, issn = {1053-0509}, doi = {10.1007/s10895-013-1343-2}, author = {Sonawane, Prashant and Vishwakarma, Rishi Kishore and Singh, Somesh and Gaikwad, Sushama M. and Khan, Bashir Mohammad} } @article { ISI:000358370700007, title = {Identifying solid luminogens through gold-catalysed intramolecular hydroarylation of alkynes}, journal = {European Journal of Organic Chemistry}, number = {22}, year = {2015}, month = {AUG}, pages = {4860-4867}, publisher = {WILEY-V C H VERLAG GMBH}, address = {POSTFACH 101161, 69451 WEINHEIM, GERMANY}, abstract = {

The identification of a new class of luminogens based on pyrrolo-quinoxaline embedded coumarin (PQC) structures is reported. The reaction relies on the gold-catalyzed hydroarylation reaction of appropriately substituted aryl alkynoates that produces molecules that exhibit solvatochromism and aggregation-induced emission enhancement (AIEE) phenomena. The application of PQCs for live cell imaging has also been demonstrated.

}, keywords = {Cell imaging, Dyes/pigments, fluorescence, Gold, Luminescence, Solvatochromism}, issn = {1434-193X}, doi = {10.1002/ejoc.201500503}, author = {Shaikh, Aslam C. and Shalini, S. and Vaidhyanathan, Ramanathan and Mane, Manoj V. and Barui, Ayan Kumar and Patra, Chitta Ranjan and Venkatesh, Yeduru and Bangal, Prakriti Ranjan and Patil, Nitin T.} } @article { ISI:000367546300012, title = {Synthesis, crystal structure and in vitro DNA binding studies of combretastatin A-4 analogue}, journal = {Croatica Chemica Acta}, volume = {88}, number = {3}, year = {2015}, month = {DEC}, pages = {289-296}, publisher = {CROATIAN CHEMICAL SOC}, address = {MARULICEV TRG 19/II, 41001 ZAGREB, CROATIA}, abstract = {

Synthesis of a novel Combretastatin A-4 analogue using Schiff{\textquoteright}s reaction of benzil and 4-aminoantipyrine has been achieved under solvent free conditions. The structure of compound was examined spectroscopically and confirmed from single crystal diffraction studies. The synthesized Combretastatin A-4 analogue was investigated for its DNA binding ability as the plausible mechanism for its antitumor activity. The binding propensity of the synthesized compound with calf-thymus (CT) DNA was monitored with absorption and emission spectrophotometric titrations. The calculations predict a binding constant of 7.24 x 10(4) for the complex of the synthesized compound with CT DNA which is comparable in magnitude to that of DNA binding of bactericidal drug enoxacin and typical intercalation indicator ethidium bromide (EB). Competitive binding studies of the synthesized compound with EB using fluorescence titration reveal that it displaces the DNA-bound EB and binds in intercalative mode which was further supported by circular dichroism (CD) spectroscopy. The probable site and binding energy of the compound with DNA was further theoretically investigated by molecular docking studies. The significant DNA binding ability of the synthesized Combretastatin A4 analogue as revealed from this study could be related to the anticancer activity of the Combretastatin A4.

}, keywords = {benzil, bio-physical, combretastatin A-4, crystal structure, DNA binding, ethidium bromide, fluorescence, phenazones}, issn = {0011-1643}, doi = {10.5562/cca2662}, author = {Rizvi, Masood Ahmad and Dangat, Yuvraj B. and Yaseen, Zahid and Gupta, Vivek and Khan, Khaliquz Zaman} } @article {46796, title = {Anthrone-spirolactam and quinoline hybrid based sensor for selective fluorescent detection of Fe(3+)ions}, volume = {34}, year = {2020}, month = {OCT}, pages = {e5867}, type = {Article}, abstract = {

The synthesis of a novel, and highly selective Fe(3+)ion sensor based on anthrone-spirolactam and its quinoline hybrid ligand is reported. The designed ligand displayed selective detection of Fe(3+)ions with enhanced fluorescence emission. The complexation of Fe(3+)ion led to a red shift of 32 nm from 420 nm to 452 nm, and a several fold increase in intensity with fluorescent green emission. The complexation (detection) of Fe(3+)ions with ligand resulted in chelation enhanced fluorescence and intramolecular charge transfer through the inhibition of C=N isomerization. This hybrid sensor shows high sensitivity and selectivity, spontaneous response, and works on a wide pH range a minimum detection limit of 6.83 x 10(-8)M. Importantly, the sensor works through the fluorescence turn-on mechanism that overcomes the paramagnetic effect of Fe(3+)ions. The binding mechanism between the ligand and the Fe(3+)ions was established from the Job{\textquoteright}s plot method, optical studies, Fourier transfor infrared spectroscopy, NMR titration, fluorescence life-time studies, and density functional theory optimization. The sensor displayed excellent results in the quantification of Fe(3+)ions from real water samples. Furthermore, due to its biocompatibility nature, fluorescent spotting of Fe(3+)ions in live cells revealed its bioimaging applications.

}, keywords = {anthrone-spirolactam-quinoline, Cell imaging, fluorescence, intramolecular charge transfer, iron}, issn = {0268-2605}, doi = {10.1002/aoc.5867, Early Access Date = JUL 2020}, author = {Darole, Ratanamala S. and Christopher Leslee, Denzil Britto and Mukherjee, Anagh and Gonnade, Rajesh G. and Karuppannan, Sekar and Senthilkumar, Beeran} } @article {46982, title = {Tris-heteroleptic ruthenium(II) polypyridyl complexes: Synthesis, structural characterization, photophysical, electrochemistry and biological properties}, journal = {Journal of Inorganic Biochemistry}, volume = {203}, year = {2020}, month = {FEB}, pages = {110903}, type = {Article}, abstract = {

{Three water-soluble tris-heteroleptic ruthenium(II) polypyridyl complexes [Ru(bpy)(phen)(bpg)](2+) (1), [Ru (bpy)(dppz)(bpg)]2+ (2), and [Ru(phen)(dppz)(bpg)]2+ (3) (where bpy = 2,2{\textquoteright}-bipyridine

}, keywords = {Circular dichroism, Cytotoxicity, fluorescence, Polypyridyl, ruthenium}, issn = {0162-0134}, doi = {10.1016/j.jinorgbio.2019.110903}, author = {Bhat, Satish S. and Kumbhar, Avinash S. and Purandare, Neeraja and Khan, Ayesha and Grampp, Gunter and Loennecke, Peter and Hey-Hawkins, Evamarie and Dixit, Ruchi and Vanka, Kumar} } @article {46984, title = {Tuning phosphorescence features of triphenylamines by varying functional groups and intermolecular interactions}, journal = {Dyes and Pigments}, volume = {173}, year = {2020}, month = {FEB}, pages = {107931}, type = {Article}, abstract = {

Organic room temperature phosphorescent materials are known for their synthetic feasibility, tunable phosphorescence wavelength and lifetime, etc. Hence new design strategies have been applied on various fluorophores to improve phosphorescence features. Among those, triphenylamines are phosphorescence active due to the presence of nitrogen atom, propeller molecular structure, and intermolecular interactions in the crystal state. Here we have studied the room temperature phosphorescence of a series of triphenylamines with various functional groups. Detailed studies have shown that the phosphorescence can be fine-tuned by functional group modification. A long phosphorescence lifetime around 100 ms at room temperature in air can be achieved by the interplay of intermolecular interactions, singlet-triplet energy gap and extent of intersystem crossing using functional group variation. Interestingly, an exciplex assisted ultralong phosphorescence lifetime (more than 20 times) is observed for a combination of triphenylamine and naphthalenemonoimide in air.

}, keywords = {Exciplex, fluorescence, Phosphorescence, triphenylamine}, issn = {0143-7208}, doi = {10.1016/j.dyepig.2019.107931}, author = {Goudappagouda and Asokan, Kiran and Nayak, Rashmi and Krishnan, Retheesh and Babu, Sukumaran Santhosh} } @article {48790, title = {Luminescent 3D printed poly(lactic acid) nanocomposites with enhanced mechanical properties}, journal = {Polymer Engineering and Science}, volume = {63}, year = {2023}, month = {JUL}, pages = {2059-2072}, type = {Article}, abstract = {

The three-dimensional (3D) printing of functional composite materials has gained tremendous interest in recent years. Nevertheless, research on 3D printing of luminescent composite materials is very limited, and the mechanical properties of such 3D-printed composites are poor. Herein, we report the preparation and characterization of a poly(lactic acid) (PLA) composite that, when 3D printed, exhibits enhanced toughness and high solid-state fluorescence quantum yield. Incorporation of only 1 wt\% pyrene butyric acid modified cellulose nanofibers (PBA-m-CNF) and l0 wt\% thermoplastic polyurethane (TPU) into PLA led to 223\% increase in toughness and 21\% increase in tensile modulus of PLA. Scanning electron microscopy (SEM) and X-ray microcomputed tomography (mu-CT) analysis of the fractured cross-sections of 3D printed composites revealed a ductile failure mode. The PLA/PBA-m-CNF1/TPU10 3D printed composite also exhibited a high solid-state fluorescence quantum yield of 38.35\%. To the best of our knowledge, this is the first report to show both enhanced mechanical properties and high solid-state fluorescence emission for 3D printable PLA. Such functional PLA composites could have potential applications in the fabrication of complex-shaped sensors, optical light pipes, etc.

}, keywords = {3D printing, Composite, fluorescence, Nanocellulose, poly(lactic acid), toughness}, issn = {0032-3888}, doi = {10.1002/pen.26345}, author = {Kothavade, Premkumar Anil and Yadav, Prashant and Nidhankar, Aakash D. and Torris, Arun and Pol, Harshawardhan and Kafi, Abdullah and Bateman, Stuart and Sukumaran, Santosh Babu and Shanmuganathan, Kadhiravan} }