Ambikesh Mahapatra

Carbazole functionalized luminescent silver(I), gold(I) and gold(III)–N-heterocyclic carbene complexes: a new synthetic disproportionation approach towards Au(I)–NHC to provide Au(III)–NHC

Synthetic, structural and photophysical properties of carbazole functionalized novel procarbenic species 1-(methyl/picolyl)-3-(N-ethylcarbazolyl)-1H benzimidazoliumhexaflurophosphate (1 and 2) and their N-heterocyclic carbene (NHC) complexes of Ag(I) (3 and 4), Au(I) (5 and 6) and Au(III) (7 and 8) are described. According to the solid-state structures, a linear coordination geometry of Ag(I)–NHC (4) and Au(I)–NHC (6) has been established by X-ray diffraction studies; whereas the Au(III)–NHC complex (7) adopts the square planar geometry. The Au(III)–NHC (7 and 8) complexes have been synthesized from Au(I)–NHC (5 and 6) by capitalizing on a novel disproportionation protocol. Furthermore, the Au–Ccarbene bonds in complexes 7 and 8 are inert towards changes in the oxidation state of the metal atom. All the proligands (1 and 2) and complexes (3–8) are luminescent at room temperature.

Binding interaction of an anionic amino acid surfactant with bovine serum albumin: physicochemical and spectroscopic investigations combined with molecular docking study

The interaction of a synthesised amino acid surfactant, sodium-N-dodecanoylphenylalaninate (AAS) with a transport protein, bovine serum albumin (BSA) has been uncovered employing various physicochemical and spectroscopic techniques like tensiometry, electro kinetic potential measurements, steady-state fluorometry, time-resolved measurements and circular dichroism (CD) at physiological pH and 298 K. The difference in tensiometric responses of AAS in the absence and presence of BSA indicates a significant interaction operative between them. The zeta (ξ) potential measurements have been taken into account in assigning the type of binding interaction between them. The steady-state fluorescence study reveals the sequential unfolding of BSA with stepwise addition of AAS. Stern–Volmer and modified Stern–Volmer plots, Scatchard plots and thermodynamic parameters have been employed to find the type of binding of AAS to BSA. Life-time measurements have been carried out to shed light on the relative amplitude of binding of AAS to the two Trp residues of BSA namely Trp-134 and Trp-213. The changes in protein secondary structure induced by AAS are unveiled by CD measurements. Quantum mechanical calculations involving density functional theory (DFT) and molecular docking analysis have been undertaken to highlight the interactive phenomenon between the two. Thus this work shows a total inspection of an amino acid surfactant–BSA interaction.

Binding affinities of Schiff base Fe(II) complex with BSA and calf-thymus DNA: Spectroscopic investigations and molecular docking analysis.

The binding interaction of a synthesized Schiff base Fe(II) complex with biological macromolecules viz., bovine serum albumin (BSA) and calf thymus(ct)-DNA have been investigated using different spectroscopic techniques coupled with viscosity measurements at physiological pH and 298K. Regular amendments in emission intensities of BSA upon the action of the complex indicate significant interaction between them, and the binding interaction have been characterized by Stern Volmer plots and thermodynamic binding parameters. On the basis of this quenching technique one binding site with binding constant (Kb=(7.6±0.21)×10(5)) between complex and protein have been obtained at 298K. Time-resolved fluorescence studies have also been encountered to understand the mechanism of quenching induced by the complex. Binding affinities of the complex to the fluorophores of BSA namely tryptophan (Trp) and tyrosine (Tyr) have been judged by synchronous fluorescence studies. Secondary structural changes of BSA rooted by the complex has been revealed by CD spectra. On the other hand, hypochromicity of absorption spectra of the complex with the addition of ct-DNA and the gradual reduction in emission intensities of ethidium bromide bound ct-DNA in presence of the complex indicate noticeable interaction between ct-DNA and the complex with the binding constant (4.2±0.11)×10(6)M(-1). Life-time measurements have been studied to determine the relative amplitude of binding of the complex to ct-DNA base pairs. Mode of binding interaction of the complex with ct-DNA has been deciphered by viscosity measurements. CD spectra have also been used to understand the changes in ct-DNA structure upon binding with the metal complex. Density functional theory (DFT) and molecular docking analysis have been employed in highlighting the interactive phenomenon and binding location of the complex with the macromolecules.

Kinetics and Mechanism of the Oxidation of Some Aldoses by Cerium(IV)

Abstract The kinetics of oxidation of some aldoses by cerium(IV) have been studied spectrophotometrically in sulphuric acid medium. The reactions are second order; first order with respect to both cerium(IV) and aldose concentration. The reaction rate decreases with increase in sulphuric acid concentration. The mechanisms for the reactions are discussed.

Coumarinyl thioether Schiff base as a turn-on fluorescent Zn(II) sensor and the complex as chemosensor for the selective recognition of ATP, along with its application in whole cell imaging

The coumarinyl thioether Schiff base, H2L, demonstrates turn-on fluorescence sensing towards Zn2+ ion with a limit of detection (LOD) of 0.068 μM. Different physicochemical techniques (mass, 1H NMR, Jobs) support the formation of a 1 : 1 metal-to-ligand complex, [ZnL]. The fluorogenic complex [ZnL] recognizes ATP in the presence of all other common anions, inorganic phosphates and biologically important phosphates (nucleosides, nucleotides). The proposed sensor has efficiently been used for ATP sensing with a LOD of 6.7 μM, which is the lowest in literature. Exogenous zinc ions in SCC084 (human oral carcinoma) cells have been checked through fluorescence cell imaging process by adding H2L in the medium.

Kinetic investigation on the oxidation of tris(1,10-phenanthroline)iron(II) by oxone: the effect of BSA-SDS interaction.

The kinetic investigations of oxidation of tris(1,10-phenanthroline)iron(II) by oxone have been studied spectrophotometrically in phosphate buffer medium of pH 6.8, temperature 308 K, and ionic strength 0.25 mol L(-1). The reactions were also carried out in presence of globular transport protein, bovine serum albumin (BSA) having isoelectric point 4.9, anionic surfactant sodium dodecyl sulfate (SDS), and their mixtures. The critical aggregation concentration (CAC) and critical micelle concentration (CMC) of SDS in presence of BSA have been determined using conductivity and kinetic measurement techniques. The secondary structure of BSA was examined by Circular Dichroism (CD) measurement at 308 K. The helix nature of BSA decreases with increase of SDS concentration. The effect of pH on rate in presence of BSA is opposite to its absence, and the effect of urea on rate in presence of BSA indicates the denaturation of BSA. The results depict that amphiphile SDS interacts with BSA and different molecular events, for example, specific binding, cooperative binding, protein unfolding, and micelle formation act. Activation parameters of the reaction in different environments have been determined.

Imine-functionalized thioether Zn(II) turn-on fluorescent sensor and its selective sequential logic operations with H2PO4−, DFT computation and live cell imaging

The diformyl thioether Schiff base (H2L) exhibits fluorescent sensing behaviour towards Zn2+ with a limit of detection (LOD) of 0.050 μM, which is far below the WHO guideline (76 μM) in drinking water. The formation of a 1 : 1 metal-to-ligand complex, [ZnL], has been ascertained by X-ray crystallography, Jobs plot and mass spectra. The fluorogenic complex, [ZnL] (either in situ or a solution of the isolated complex) has shown selective ON–OFF emission toward H2PO4−. A two-input, one-output sequential INHIBIT logic circuit has been constructed from H2L, Zn2+ and H2PO4−. The practical applicability of H2L has been examined by the identification of Zn2+ and H2PO4− in the intracellular fluid of African monkey Vero cells.

Mechanism of Interaction of DNA Bases with Pd(II)-azoimidazoles: The Cytosine Case

Cytosine is responsible for maintaining cytosineguanine triple hydrogen bonded bond pairing during coding information transfer of progeny [1,2]. There is a long-standing interest to explore the interaction of carcinogenic agents and anticancer drugs with DNA [3-12]. Inorganic Reaction Mechanisims, Vol. 6, pp. 19-29

Influence of polymer–surfactant interactions on the reactivity of the CoIII–FeII redox couple

In continuation of our recent study on the inner sphere electron transfer reduction of the cobalt(III) complex, [Co(III)(NH(3))(5)N(3)]Cl(2) by Mohrs salt (Fe(II)), we have investigated the effect of neutral polymer (poly(ethylene glycol) with relative molecular mass 200, PEG 200)-surfactant (both cationic and non-ionic) mixture on the kinetics of the same reaction using spectrophotometric and conductometric techniques at 298 K. Both the cationic and non-ionic surfactants have undergone interaction with polymer. Experimental consequences reveal that the catalytic effect imposed by the polymer-surfactant complexes causes significant change of the kinetic activities of the reaction. The gradual enhancement and retardation of the rate have been found with gradual addition of PEG 200 and cationic surfactant respectively. An attempt has been taken to rationalize the experimental findings with proper correlation of the reported literature.

Binding interaction of sodium-N-dodecanoyl sarcosinate with hemoglobin and myoglobin: Physicochemical and spectroscopic studies with molecular docking analysis

The interaction of an amino acid surfactant, sodium-N-dodecanoyl sarcosinate (SDDS), with two heme proteins, hemoglobin (Hb) and myoglobin (Mb), has been studied employing various physicochemical and spectroscopic techniques like tensiometry, UV-Vis spectroscopy, steady-state fluorometry, time-resolved fluorometry, circular dichroism (CD) spectroscopy, calorimetry and stopped flow kinetics at physiological pH of 7.2 and 298K. Tensiometric and fluorometric analysis suggest that the interaction between SDDS and protein starts with the monomer form of the surfactant which produces small induced micelles. The micelles bind to protein backbone causing denaturation of the protein structure, and finally free micelles are formed on further addition of surfactant. Life-time measurements have been performed to shed light on the binding of surfactant around the tryptophan moieties present in the heme proteins. The changes in protein secondary structure induced by AAS collected from CD measurements reveals that the proteins are quite perturbed upon action of SDDS. The enthalpy change values of each stepwise interaction process have been found from isothermal titration calorimetry (ITC). The kinetics of the protein-surfactant interaction process has been studied using stopped flow technique. Quantum mechanical calculations involving density functional theory (DFT) and molecular docking analysis have been performed to highlight the interactive phenomenon between the surfactant and heme proteins. Thus the entire study shows a total inspection of an amino acid surfactant-heme protein interaction.