Department Of Chemistry

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Insulin resistance induces a segmental difference in thoracic and abdominal aorta: Differential expression of AT1 and AT2 receptors
(2012) Karpe, P.A.; Gupta, J.; Marthong, R.F.; Ramarao, P.; Tikoo, K.
Objectives: The study was pursued to understand and compare the vascular reactivity to angiotensin II (Ang II) and its receptor expression in thoracic and abdominal aorta under insulin resistance. Methods: Vascular reactivity to Ang II was recorded isometrically, AT1/AT2 receptor gene and protein expression was checked by RT-PCR and western blotting, respectively, and abundance of phospho (serine-10 Ph) H3 on promoter regions of Agtr1/Agtr2 genes was done by chromatin immunoprecipitation assay in aortic rings isolated from high fat diet (HFD)-fed rats. Results: Our functional studies showed an increased (Emax in mg/mm 2: Con: 319 ? 29 and HFD: 1095 ? 72, P < 0.001) and unaltered (E max in mg/mm 2: Con: 299 ? 29 and HFD: 350 ? 20, mean ? SEM, n = 6) Ang II-induced contractile responses in thoracic and abdominal aorta of HFD rats, respectively, as compared to control rats. Interestingly, AT2R-mediated relaxation was increased in abdominal aorta (% relaxation: Con: 25 ? 5.3 and HFD: 76.4 ? 8.9, P < 0.001) of HFD rats but not in thoracic aorta (% relaxation: Con: 25 ? 5.2 and HFD: 32 ? 5.2, mean ? SEM, n = 6). At the molecular level, increased mRNA (?14-folds) and protein expression (?2.5-folds) of AT2R in abdominal aorta of HFD rats was found as compared to control rats. However, AT1R mRNA and protein expression did not show any change. Chromatin immunoprecipitation with phospho H3 showed increased abundance of ser-10 phosphorylation on Agtr1 and Agtr2 gene promoter regions in thoracic and abdominal segments, respectively. But it got decreased on Agtr2 and Agtr1 genes promoter regions in thoracic and abdominal segments, respectively. Conclusion: We provide first evidence that insulin resistance induces segmental difference in thoracic and abdominal aorta and this may provide reason of heterogeneity for incidence of aneurysms. ? 2011 Wolters Kluwer Health | Lippincott Williams & Wilkins.
Nonlinear Optical Switching and Enhanced Nonlinear Optical Response of Au–CdSe Heteronanostructures
(ACS Publications, 2014) Sreeramulu, V.; Haldar, Krishan Kant; Patra, Amitava; Rao, D. Narayana
The metal–semiconductor heterostructures have recently emerged as a new class of functional materials for their potential applications due to plasmon-exciton interactions. Here, we demonstrate the nonlinear optical switching and enhanced nonlinear optical response of Au–CdSe heterostructures. The nonlinear optical properties of CdSe quantum dots and Au–CdSe heteronanostructures are investigated by using a Z-scan technique at 532 nm picosecond laser pulses, and 800 nm femtosecond laser pulses. Interestingly, we observe switching behavior from saturable absorption (SA) to reverse saturable absorption (RSA) with increasing laser intensity. The effective two-photon absorption cross section (σeff) of Au–CdSe heteronanostructures is greatly enhanced which is attributed to charge transfer between CdSe and Au nanoparticles. The nonlinear refraction changes its sign from positive to negative nonlinearity at higher intensities for Au–CdSe heterostructures. Third order nonlinear optical susceptibility is being measured by using the DFWM technique at 532 nm. Similar switching behavior is observed in Au–CdSe heteronanostructures at nonresonant excitations (800 nm), where a CdSe quantum dot shows reverse saturable absorption behavior attributed to the two-photon absorption. The optical switching behavior of these heterostructures could play a potential role in photonics and optoelectronic applications.
Essential Oils: New Perspectives in Human Health and Wellness.
(Hindawi, 2014) Firenzuoli, Fabio; Jaitak, Vikas; Horvath, Gyorgyi; Bassole, Imael Henri Nestor; Setzer,William N.; Gori, Luigi
Essential oils are natural products, derived from aromatic plants, traditionally used all over the world for disinfection, as anti-inflammatory, relaxing, and stimulating substances, and with potential and modern exploitation in clinical medicine. The earliest recorded mention of the techniques and methods used to produce essential oils is believed to be that of Ibn al-Baitar (1188�1248). The chemical composition of these essential oils varies widely depending upon the geographical location, botanical origin, genetics, bacterial endophytes, and extraction techniques. Essential oils are commonly used in food and cosmetic industries. They can be used as natural alternatives to synthetic preparations to prevent and treat infectious diseases. They are used traditionally to treat other diseases like respiratory tract, digestive system, gynecological, andrological, endocrine, cardiovascular, nervous system, and skin infections. Many of them have shown anticancer activities, too.
Invitro anti-mutagenic potential of potentilla fulgens: A western himalayan plant
(Informatics Publishing Limited, 2014) Monga, P.; Kaur, R.; Jaitak, Vikas
Invitro anti-mutagenic potential of different extracts/fractions of Potentilla fulgens has been made by an Ames histidine reversion assay using TA98 and TA100 tester strains of Salmonella typhimurium against the direct-acting mutagens, 4-Nitro-O-phenylenediamine (NPD) and Sodium azide. P. fulgens has been used in traditional system of medicine as anti-hyperglycemic, hypoglycemic, anti-hyperlipidemic, anti-oxidant, anti-inflammatory and anti-ulcerogenic agent. Results indicated that n-butanol and water fractions showed strong inhibition activity against the mutagens (NPD, Sodium azide) in both co-incubation as well as pre-incubation treatments in TA98 and TA100 tester strains. ? 2017, Informatics Publishing Limited. All rights reserved.
Diselenophosphate-Induced Conversion of an Achiral [Cu20H11 {S2P (OiPr) 2} 9] into a Chiral [Cu20H11 {Se2P (OiPr) 2} 9] Polyhydrido Nanocluster.
(Wiley, 2015) Rajendra S. Dhayal.; Jian-Hong Liao.; Xiaoping Wang.; Yu-Chiao Liu.; Ming-His Chiang.; Samia Kahlal.; Jean-Yves Saillard.; C. W. Liu
A polyhydrido copper nanocluster, [Cu20H11{Se2P(OiPr)2}9] (2H), which exhibits an intrinsically chiral inorganic core of C3 symmetry, was synthesized from achiral [Cu20H11{S2P(OiPr)2}9] (1H) of C3h symmetry by a ligand?exchange method. The structure has a distorted cuboctahedral Cu13 core, two triangular faces of which are capped along the C3 axis, one by a Cu6 cupola and the other by a single Cu atom. The Cu20 framework is further stabilized by 9 diselenophosphate and 11 hydride ligands. The number of hydride, phosphorus, and selenium resonances and their splitting patterns in multinuclear NMR spectra of 2H indicate that the chiral Cu20H11 core retains its C3 symmetry in solution. The 11 hydride ligands were located by neutron diffraction experiments and shown to be capping ?3?H and interstitial ?5?H ligands (in square?pyramidal and trigonal?bipyramidal cavities), as supported by DFT calculations on [Cu20H11(Se2PH2)9] (2H?) as a simplified model.
Imine/amide-imidazole conjugates derived from 5-amino-4-cyano-N1-substituted benzyl imidazole: Microwave-assisted synthesis and anticancer activity via selective topoisomerase-II-? inhibition
(Elsevier Ltd, 2015) Negi, Arvind; Alex, Jimi Marin; Amrutkar, Suyog M.; Baviskar, Ashish T.; Joshi, Gaurav; Singh, Sandeep; Banerjee, Uttam Chand; Kumar, Raj
Microwave-accelerated synthesis and anticancer activity of novel imine/amide-imidazole conjugates derived from 5-amino-4-cyano-N1-substituted benzyl imidazole against a panel of seven cancer cell lines are reported for the first time. Compounds ARK-4, 10 and 12 in the series show promising in vitro anti proliferative activity with low micromolar IC 50 values against A-459 (lung), Hep-G2 (liver) and H-460 (liver) cancer cell lines. Compounds caused the increase in ROS levels as well as mitochondrial membrane depolarization, which might induce apoptosis. Further, mechanistic interventions on biological and molecular modeling data supported that compounds inhibited topoisomerase-II selectively.- 2015 Elsevier Ltd. All rights reserved.
Heck−Suzuki Tandem Reaction for the Synthesis of 3‑Benzazepines
(ACS Publications, 2015) Peshkov, Anatoly A.; Peshkov, Vsevolod A.; Pereshivko, Olga P.; Hecke, Kristof Van; Kumar, Rakesh; Eycken, Erik V. Van der
A novel procedure for the Heck−Suzuki tandem reaction suitable for the construction of nitrogen-containing medium rings was developed to provide access toward the 3-benzazepine framework.
In situ reductive regeneration of zerovalent iron nanoparticles immobilized on cellulose for atom efficient Cr(vi) adsorption
(Royal Society of Chemistry, 2015) Sharma, Archana Kumari; Kumar, Rabindra; Mittal, Sunil; Hussain, Shamima; Arora, Meenu; Sharma, R.C.; Babu, J. Nagendra
Zerovalent iron nanoparticles (nZVI) (11.8 - 0.2% w/w) immobilized on microcrystalline cellulose (C-nZVI) were synthesized and studied for Cr(vi) sorption. The material showed good atom economy for Cr(vi) adsorption (562.8 mg g-1 of nZVI). Oxidation of cellulose to cellulose dialdehyde leads to in situ regeneration of nZVI which is responsible for the atom efficient Cr(vi) sorption by C-nZVI.
Analysis of the pH-dependent thermodynamic stability, local motions, and microsecond folding kinetics of carbonmonoxycytochrome c
(Academic Press Inc., 2016) Kumar, Rajesh
This paper analyzes the effect of pH on thermodynamic stability, low-frequency local motions and microsecond folding kinetics of carbonmonoxycytochrome c (Cyt-CO) all across the alkaline pH-unfolding transition of protein. Thermodynamic analysis of urea-induced unfolding transitions of Cyt-CO measured between pH 6 and pH 11.9 reveals that Cyt-CO is maximally stable at pH?9.5. Dilution of unfolded Cyt-CO into refolding medium forms a native-like compact state (NCO-state), where Fe2+?CO interaction persists. Kinetic and thermodynamic parameters measured for slow thermally-driven CO dissociation (NCO?N+CO) and association (N+CO?NCO) reactions between pH 6.5 and pH 13 reveal that the thermal-motions of M80-containing ?-loop are decreased in subdenaturing limit of alkaline pH. Laser photolysis of Fe2+-CO bond in NCO-state triggers the microsecond folding (NCO?N). The microsecond kinetics measured all across the alkaline pH-unfolding transition of Cyt-CO produce rate rollover in the refolding limb of chevron plot, which suggests a glass transition of NCO en route to N. Between pH 7 and pH 11.9, the natural logarithm of the microsecond folding rate varies by?<?1.5 units while the natural logarithm of apparent equilibrium constant varies by 11.8 units. This finding indicates that the pH-dependent ionic-interactions greatly affect the global stability of protein but have very small effect on folding kinetics. ? 2016 Elsevier Inc.
Shell thickness matters! Energy transfer and rectification study of Au/ZnO core/shell nanoparticles
(Academic Press Inc., 2016) Haldar, Krishna Kanta; Sen, Tapasi
In the present study we report the influence of shell thickness on fluorescence resonance energy transfer between Au/ZnO core-shell nanoparticles and Rhodamine 6G dye by steady-state and time-resolved spectroscopy and rectification behaviours. Au/ZnO core-shell nanoparticles with different shell thickness were synthesized in aqueous solution by chemically depositing zinc oxide on gold nanoparticles surface. A pronounced effect on the photoluminescence (PL) intensity and shortening of the decay time of the dye in presence of Au/ZnO core-shell nanoparticles is observed. The calculated energy transfer efficiencies from dye to Au/ZnO are 62.5%, 79.2%, 53.6% and 46.7% for 1.5 nm, 3 nm, 5 nm and 8 nm thickness of shell, respectively. Using FRET process, the calculated distances (r) are 117.8, 113.2 ? 129.9 ? and 136.7 ? for 1.5 nm, 3 nm, 5 nm and 8 nm thick Au/ZnO core-shell nanoparticles, respectively. The distances (d) between the donor and acceptor are 71.0, 57.8, 76.2 and 81.6 ? for 1.5 nm, 3 nm, 5 nm and 8 nm thick core-shell Au/ZnO nanoparticles, respectively, using the efficiency of surface energy transfer (SET). The current-voltage (I-V) curve of hybrid Au/ZnO clearly exhibits a rectifying nature and represents the n-type Schottky diode characteristics with a typical turn-on voltage of between 0.6 and 1.3 V. It was found that the rectifying ratio increases from 20 to 90 with decreasing the thickness of the shell from 5 nm to 3 nm and with shell thickness of 8 nm, electrical transport through the core-shell is similar to what is observed with pure ZnO samples nanoparticles. The results indicated that the Au/ZnO core-shell nanoparticles with an average shell thickness of 3 nm exhibited the maximum energy transfer efficiencies (79.2%) and rectification (rectifying ratio 90). ? 2016
[Ag20{S2P(OR)2}12]: A Superatom Complex with a Chiral Metallic Core and High Potential for Isomerism
(Wiley-VCH Verlag, 2016) Dhayal, R.S.; Lin, Y.-R.; Liao, J.-H.; Chen, Y.-J.; Liu, Y.-C.; Chiang, M.-H.; Kahlal, S.; Saillard, J.-Y.; Liu, C.W.
The synthesis and structural determination of a silver nanocluster [Ag20{S2P(OiPr)2}12] (2), which contains an intrinsic chiral metallic core, is produced by reduction of one silver ion from the eight-electron superatom complex [Ag21{S2P(OiPr)2}12](PF6) (1) by borohydrides. Single-crystal X-ray analysis displays an Ag20core of pseudo C3symmetry comprising a silver-centered Ag13icosahedron capped by seven silver atoms. Its n-propyl derivative, [Ag20{S2P(OnPr)2}12] (3), can also be prepared by the treatment of silver(I) salts and dithiophosphates in a stoichiometric ratio in the presence of excess amount of [BH4]?. Crystal structure analyses reveal that the capping silver-atom positions relative to their icosahedral core are distinctly different in 2 and 3 and generate isomeric, chiral Ag20cores. Both Ag20clusters display an emission maximum in the near IR region. DFT calculations are consistent with a description within the superatom model of an 8-electron [Ag13]5+core protected by a [Ag7{S2P(OR)2}12]5?external shell. Two additional structural variations are predicted by DFT, showing the potential for isomerism in such [Ag20{S2P(OR)2}12] species. ? 2016 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim
Polyhydrido Copper Clusters: Synthetic Advances, Structural Diversity, and Nanocluster-to-Nanoparticle Conversion
(American Chemical Society, 2016) Dhyal, Rajendra S; Zyl, Werner E. van; Liu, C. W.; Dhayal, R.S.; Van Zyl, W.E.; Liu, C.W.
Conspectus: Metal hydride clusters have historically been studied to unravel their aesthetically pleasing molecular structures and interesting properties, especially toward hydrogen related applications. Central to this work is the hydride ligand, H?, the smallest closed-shell spherical anion known. Two new developments in polyhydrido nanocluster chemistry include the determination of heretofore unknown hydride coordination modes and novel structural constructs, and conversion from the molecular entities to rhombus-shaped copper nanoparticles (CuNPs). These advances, together with hydrogen evolution and catalysis, have provided both experimentalists and theorists with a rich scientific directive to further explore. The isolation of hexameric [{(Ph3P)CuH}6] (Stryker reagent) could be regarded as the springboard for the recent emergence of polyhydrido copper cluster chemistry due to its utilization in a variety of organic chemical transformations. The stability of clusters of various nuclearity was improved through phosphine, pyridine, and carbene type ligands. Our focus lies with the isolation of novel copper (poly)hydride clusters using mostly the phosphor-1,1-dithiolato type ligands. We found such chalcogen-stabilized clusters to be exceptionally air and moisture stable over a wide range of nuclearities (Cu7 to Cu32). In this Account, we (i) report on state-of-the-art copper hydride cluster chemistry, especially with regards to the diverse and novel structural types generally, and newly discovered hydride coordination modes in particular, (ii) demonstrate the indispensable power of neutron diffraction for the unambiguous assignment and location of hydride ligand(s) within a cluster, and (iii) prove unique transformations that can occur not only between well characterized high nuclearity clusters, but also how such clusters can transform to uniquely shaped nanoparticles of several nanometers in diameter through copper hydride reduction.The increase in the number of low- to high-nuclearity hydride clusters allows for different means by which they can be classified. We chose a classification based on the coordination mode of hydride ligand within the cluster. This includes copper clusters associated with bridging (?2-H) and capping (?3-H) hydride modes, followed by an interstitial (?4-H) hydride mode that was introduced for the first time into octa- and hepta-nuclear copper clusters stabilized by dichalcogen-type ligands. This breakthrough provided a means to explore higher nuclearity polyhydrido nanoclusters, which contain both capping (?3-H) and interstitial (?(4-6)-H) hydrides. The presence of bidentate ligands having mixed S/P dative sites led to air- and moisture-stable copper hydride nanoclusters. The formation of rhombus-shaped nanoparticles (CuNPs) from copper polyhydrides in the presence of excess borohydrides suggests the presence of metal hydrides as intermediates during the formation of nanoparticles. ? 2015 American Chemical Society.
Nonlinear optical switching and optical limiting in colloidal CdSe quantum dots investigated by nanosecond Z-scan measurement
(Elsevier Ltd, 2016) Valligatla, S.; Haldar, K.K.; Patra, A.; Desai, N.R.
The semiconductor nanocrystals are found to be promising class of third order nonlinear optical materials because of quantum confinement effects. Here, we highlight the nonlinear optical switching and optical limiting of cadmium selenide (CdSe) quantum dots (QDs) using nanosecond Z-scan measurement. The intensity dependent nonlinear absorption and nonlinear refraction of CdSe QDs were investigated by applying the Z-scan technique with 532 nm, nanosecond laser pulses. At lower intensities, the nonlinear process is dominated by saturable absorption (SA) and it is changed to reverse saturable absorption (RSA) at higher intensities. The SA behaviour is attributed to the ground state bleaching and the RSA is ascribed to free carrier absorption (FCA) of CdSe QDs. The nonlinear optical switching behaviour and reverse saturable absorption makes CdSe QDs are good candidate for all-optical device and optical limiting applications. ? 2016 Elsevier Ltd.
Nonlinear Optical Switching and Enhanced Nonlinear Optical Response of Au−CdSe Heteronanostructures
(ACS Publications, 2016) Sreeramulu, V.; Haldar, Krishna Kanta; Patra, Amitava; Rao, D. Narayana
The metal−semiconductor heterostructures have recently emerged as a new class of functional materials for their potential applications due to plasmonexciton interactions. Here, we demonstrate the nonlinear optical switching and enhanced nonlinear optical response of Au−CdSe heterostructures. The nonlinear optical properties of CdSe quantum dots and Au−CdSe heteronanostructures are investigated by using a Z-scan technique at 532 nm picosecond laser pulses, and 800 nm femtosecond laser pulses. Interestingly, we observe switching behavior from saturable absorption (SA) to reverse saturable absorption (RSA) with increasing laser intensity. The effective two-photon absorption cross section (σeff) of Au−CdSe heteronanostructures is greatly enhanced which is attributed to charge transfer between CdSe and Au nanoparticles. The nonlinear refraction changes its sign from positive to negative nonlinearity at higher intensities for Au−CdSe heterostructures. Third order nonlinear optical susceptibility is being measured by using the DFWM technique at 532 nm. Similar switching behavior is observed in Au−CdSe heteronanostructures at nonresonant excitations (800 nm), where a CdSe quantum dot shows reverse saturable absorption behavior attributed to the two-photon absorption. The optical switching behavior of these heterostructures could play a potential role in photonics and optoelectronic applications.
Sorptive removal of arsenite [As(III)] and arsenate [As(V)] by fuller's earth immobilized nanoscale zero-valent iron nanoparticles (F-nZVI): Effect of Fe 0 loading on adsorption activity
(Elsevier Ltd, 2016) Yadav R.; Sharma A.K.; Babu J.N.
Fuller's earth immobilized nanoscale zerovalent iron (F-nZVI 1-8) were synthesized by borohydride reduction method. The iron loading of fuller's earth immobilized nZVI was varied from 5 to 50% (w/w) in these F-nZVI 1-8. The F-nZVI 1-8 were characterized by FE-SEM-EDX, FTIR, BET, XRD and TGA. The FE-SEM analysis showed an increase in agglomeration of nZVI on the immobilized material with increase in the loading of Fe 0 . F-nZVI 1-8 were studied for adsorptive removal of As(III) and As(V) from aqueous solution, with an emphasis on the effect of Fe 0 loading of adsorbent on arsenic remediation. Iron loading has a significant role in adsorption of As(III) and As(V) on F-nZVI, with increase in adsorption with optimum iron loading of 20% (w/w) on fuller's earth (F-nZVI-4). However, increase in loading above 20%, resulted in no significant increase in As(III) and As(V) adsorption. The adsorption results fitted well with Langmuir and Freundlich isotherm models and the maximum adsorption capacity of F-nZVI-4 for As(III) and As(V) were observed to be 50.08 and 91.42 mg/g, respectively. The adsorption isotherm and kinetic studies indicate a rapid removal of As(III) and As(V) from the aqueous solution in the presence of F-nZVI 1-8, with an substantially high rate of removal for arsenic with F-nZVI-4.
Genetic engineering of poplar: Current achievements and future goals
(Springer Singapore, 2017) Yadav R.; Yadav N.; Goutam U.; Kumar S.; Chaudhury A.
Global biomass demand for industrial applications is ever increasing especially in biofuels and pulp industries. Poplar is likely to have great biological advantages over the other forest trees which include small genome size, large number of species, rapid juvenile growth, ease of clonal propagation, easy recovery of genetic transformants, and available genome draft. Wide and sustainable farming of rapidly growing trees such as poplars may supplement to attain the requirement of renewable resources. This chapter covers the progress in both basic and applied studies in poplar genetic tailoring. Certain advices are given for future direction of the research in poplar genetic tailoring so as to achieve the needs of environmental cleansing system and the timber industries. Emerging new thoughts for designing wood improvement approaches are discussed.
Mechanisms of tubulin binding ligands to target cancer cells: Updates on their therapeutic potential and clinical trials
(Bentham Science Publishers B.V., 2017) Kumar, Bhupinder; Kumar, Rakesh; Skvortsova, Ira; Kumar, Vinod
Background: A number of chemically diverse substances bind to the tubulin and inhibit cell proliferation by disrupting microtubule dynamics. There are four binding sites for the ligands binding to the tubulin; taxane/epothilone and laulimalide/peloruside binding ligands stabilize microtubule while vinca and colchicine binding site agents promote microtubule depolymerization. Most of the tubulin binding ligands disturb the tubulin-microtubule dynamic equilibrium but these may exhibit anticancer activities through different mechanisms. Taxanes and epothilones are widely used cytotoxic agents and are found effective against different types of human malignancies. However, taxanes are susceptible to pgp mediated multi-drug resistance, dose limiting hematopoietic toxicity and cumulative neurotoxicity. Vinca alkaloids are already in clinical practice, but ligands binding to the colchicine site are still in the different stages of clinical trials. Objective: In the current review article, plausible mechanistic details about the interactions of ligands at the binding pocket and subsequent changes in the tubulin structure are described. The review article also illustrated different formulations of the tubulin binding agents in combination with other chemotherapeutic agents and their therapeutic potential against various human malignancies. Conclusion: Tubulin targeting agents emerged as one of the most successful anticancer drugs and a number of structurally different chemical compounds are in advance stages of clinical development. ? 2017 Bentham Science Publishers.
Structural and electronic investigation of metal-semiconductor hybrid tetrapod hetero-structures
(Springer Verlag, 2017) Haldar, K.K.; Muley, V.Y.; Datar, S.; Patra, A.
This article highlights the new electronic properties of tetrapod hetero-structures with metal Au core and semiconductor CdSe arms, which is one of the new classes of hybrid metal-semiconductor nanostructures. From the analysis of XRD, HRTEM, HAADF-STEM images, and EDAX line-scan studies, the growth mechanism of all these hetero-structures is proposed. These findings are important from the basic fundamental aspects of understanding the shape control of hetero-structures. Scanning tunneling spectroscopic study confirms the coulomb staircase-like features near Au which is characteristic of Au nanoparticles and the gap increases as we move the tip towards CdSe. Analysis suggests that the resonance tunneling occurs between valance band edge (conduction band edge) of CdSe and coulomb stairs of Au dot. These tetrapod hetero-structures could pave the way for designing new optical-based materials for developing new challenging photonic devices. ? 2017, Springer International Publishing Switzerland.
Core-Size-Dependent Catalytic Properties of Bimetallic Au/Ag Core− Shell Nanoparticles
(ACS Publications, 2017) Haldar, Krishna Kanta; Kundu, Simanta; Patra, Amitava
Bimetallic core−shell nanoparticles have recently emerged as a new class of functional materials because of their potential applications in catalysis, surface enhanced Raman scattering (SERS) substrate and photonics etc. Here, we have synthesized Au/Ag bimetallic core−shell nanoparticles with varying the core diameter. The red-shifting of the both plasmonic peaks of Ag and Au confirms the core−shell structure of the nanoparticles. Transmission electron microscopy (TEM) analysis, line scan EDS measurement and UV−vis study confirm the formation of core−shell nanoparticles. We have examined the catalytic activity of these core−shell nanostructures in the reaction between 4- nitrophenol (4-NP) and NaBH4 to form 4-aminophenol (4-AP) and the efficiency of the catalytic reaction is found to be increased with increasing the core size of Au/Ag core−shell nanocrystals. The catalytic efficiency varies from 41.8 to 96.5% with varying core size from 10 to 100 nm of Au/Ag core−shell nanoparticles, and the Au100/Ag bimetallic core−shell nanoparticle is found to be 12-fold more active than that of the pure Au nanoparticles with 100 nm diameter. Thus, the catalytic properties of the metal nanoparticles are significantly enhanced because of the Au/Ag core−shell structure, and the rate is dependent on the size of the core of the nanoparticles.
Role of Macromolecular Crowding on Stability and Iron Release Kinetics of Serum Transferrin
(American Chemical Society, 2017) Kumar, Sandeep; Sharma, Deepak; Kumar, Rajesh
The macromolecular crowding influences the structural stability and functional properties of transferrin (Tf). The equilibrium as well as kinetic studies of Tf at different concentrations of crowding agents (dextran 40, dextran 70, and ficoll 70) and at a fixed concentration of dextran 40 under different concentrations of NaCl at pH 7.4 and 5.6 (?1) revealed that (i) the crowder environment increases the diferric-Tf (Fe2Tf) stability against iron loss and overall denaturation of the protein, (ii) both in the absence and presence of crowder, the presence of salt promotes the loss of iron and overall denaturation of Fe2Tf which is due to ionic screening of electrostatic interactions, (iii) the crowder environment retards iron release from monoferric N-lobe of Tf (FeNTf) by increasing enthalpic barrier, (iv) the retardation of iron release by crowding is enthalpically dominated than the entropic one, (v) both in the absence and presence of crowder, the presence of salt accelerates the iron release from FeNTf due to ionic screening of electrostatic interactions and anion binding to KISAB sites, and (vi) the crowders environment is unable to diminish (a) the salt-induced destabilization of Fe2Tf against the loss of iron and overall denaturation and (b) the anion effect and ionic screening of diffusive counterions responsible to promote iron release from FeNTf. ? 2017 American Chemical Society.