Interaction of Carrier Protein with Potential Metallic Drug Candidate N-Glycoside ‘GATPT’: Validation by Multi-Spectroscopic and Molecular Docking Approaches

Lysozyme is often used as a model protein to study interaction with drug molecules and to understand biological processes which help in illuminating the therapeutic effectiveness of the drug. In the present work, in vitro interaction studies of 1-{(2-hydroxyethyl)amino}-2-amino-1,2-dideoxy-d-glucose triphenyl tin (IV) (GATPT) complex with lysozyme were carried out by employing various biophysical methods such as absorption, fluorescence, and circular dichroism (CD) spectroscopies. The experimental results revealed efficient binding affinity of GATPT with lysozyme with intrinsic binding (K_b) and binding constant (K) values in the order of 10⁵ M⁻¹. The number of binding sites and thermodynamic parameters ΔG, ΔH, and ΔS at four different temperatures were also calculated and the interaction of GATPT with lysozyme was found to be enthalpy and entropy driven. The CD spectra revealed alterations in the population of α–helical content within the secondary structure of lysozyme in presence of GATPT complex. The morphological analysis of the complex with lysozyme and lysozyme-DNA condensates was carried out by employing confocal and SEM studies. Furthermore, the molecular docking studies confirmed the interaction of GATPT within the larger hydrophobic pocket of the lysozyme via several non-covalent interactions.     

Variational calculation of metal surface energies

A one-parameter model potential variational calculation of jellium—metal surface energies in the local density approximation is performed, the results very closely approximating those of the self-consistent calculations of Lang and Kohn. The use of this model potential for the determination of superior upper bounds for the surface energy and the study of various density gradient expansions is indicated.     

Massless particles and cosmology

Post recombination density perturbations have been studied in a two-component matter-radiation universe. The study has been carried out for variable matter and radiation densities. The possibility of the existence of different kinds of neutrinos in addition to the electronic, muonic and taonic has been considered and conclusions have been drawn as to the upper limit of the radiation density for different values of Ω _m .     

Synthesis,characterization, electrochemistry and kinetics of CTDNA binding of a bis ciprofloxacin borate copper(II) complex

A new boroderivative of ciprofloxacin and its Cu^II complex has been synthesized and characterized by elemental analysis, i.r., e.p.r., u.v.–vis., n.m.r. spectroscopy. Molar conductance measurements show that the complex is ionic. E.p.r. values and electronic spectral data suggest that it possesses square planar geometry. The reaction kinetics of the ligand K[C₃₄H₃₆N₆O₆F₂B] and its Cu^II complex with calf thymus DNA (CTDNA) has been monitored spectrophotometrically in aqueous media. The K _obs value has been calculated under pseudo-first order conditions and it has been observed that the Cu^II complex is a more efficient DNA inhibitor than the free borate of ciprofloxacin. The redox behavior of the Cu^II complex in the presence and in the absence of CTDNA in aqueous solution has been investigated by cyclic voltammetry. The cyclic voltammogram of the Cu^II complex exhibits one quasireversible redox wave for a one-electron transfer corresponding to Cu^II/Cu^I redox couple with E _1/2 values –0.613 and –0.649 V respectively. On interaction with CTDNA, the Cu^II complex exhibits a shift in E _1/2 values corresponding to 0.013 and 0.035 V respectively.     

New homodi-and heterotrinuclear metal complexes of Schiff base compartmental ligand: interaction studies of copper complexes with calf thymus DNA

The new homodinuclear complexes 1–4 of the type [LM^II ₂Cl₂], heterotrinuclear complexes 5 and 6 of the type [LM^II ₂Sn^IVCl₆] where M = Cu^II, Mn^II, Co^II, Ni^II and Cu^II and Ni^II, respectively have been synthesized and characterized by elemental analysis and various spectroscopic techniques. The homodinuclear complexes possess two different environments (N₂ and N₂O₂donor sets) for holding the metal ions. The metal ion in N₂ set exhibits square planar geometry with two chloride ions in the inner sphere but rhombic structure is found in tetradentate N₂O₂ Schiff base cavity while in heterotrinuclear complexes Sn^IV atom is in the octahedral environment. The interaction of complexes 1 and 5 with calf thymus DNA was carried out by absorption spectroscopy and cyclic voltammetry. The intrinsic binding constants (K _b ) of complex 1 and 5 were determined as 3.2 × 10³ M⁻¹ and 9.6 × 10³ M⁻¹, respectively suggesting that complex 5 binds more strongly to CT-DNA than complex 1. Fluorescence studies along with viscosity measurements have also been checked to authenticate the binding of metal complexes with DNA.     

New metal compounds and their reactivity towards bovine milk casein

The l,2-bis(sulphapyridyl)oxamide ligand [L] and its complexes with Fe^III, Co^II, Cu^II and Zn^II chloride were synthesized and characterized by elemental analyses, i.r., n.m.r., e.p.r. and u.v.–vis. spectroscopy and molar conductance measurements. Spectroscopic studies show that all the complexes are octahedral and covalent. The electrochemical behaviour of the Co^II complex was monitored by cyclic voltammetry in a buffer/DMF solution (95:5). The E ⁰ values –0.622 and –0.502 V reveal a reversible one electron redox wave attributed to a Co^II/Co^I redox couple at a scan rate of 0.1 V s^–1. The interaction of the Co^II complex with bovine milk casein (BMC) was studied at the same scan rate, which reveals a strong binding as the E ⁰ values shift to more negative potential (E ⁰ = –0.908 and –0.703 V). The cyclic voltammograms of the Co^II complex bound by BMC were recorded at different pH's. The plot of E ⁰ versus pH showed that E ⁰ values are maximal at pH 7.4 indicating good interaction between the BMC and the Co^II complex which is further confirmed by kinetic data. The kinetic studies of the Co^II complex bound to BMC was monitored in phosphate buffer solution at different pH's by spectrophotometry. The absorbance changes were monitored at 278 nm ( _max for BMC) with respect to time and pseudo-first-order rate constants, K _obs, were obtained from the slope and intercept of the straight line using the least squares regression method. The plot of absorbance versus time at different pH's was linear up to 80% completion of the reaction. The pH-rate profile data reveals that the reactions are pH dependent.     

N2S2 macrocyclic ligands. Synthesis and characterization of novel transition metal complexes of the type [LM(Si2Me6NH)2]2+ and [L′M(Si2Me6NH)2]2+

Summary Novel N₂S₂ macrocyclic ligands, L and L [SS-diethyl(1,3-diaminopropane) dithiocarbamate], [SS-cyclohexyl spiro-(1,3-diaminopropane) dithiocarbamate] and their complexes with Mn^II, Fe^II, Co^II, Ni^II and Cu^II have been characterized by elemental analyses, conductivity measurements, i.r., u.v.-vis. and n.m.r. spectra. The divalent transition metal complexes appear to be square planar and achieve octahedral geometry when treated with bis(trimethylsilyl)-amine to yield new heterobimetallic complexes.