Mahendra Nath Roy

Host–guest inclusion complexes of α and β-cyclodextrins with α-amino acids

Studies of molecular inclusions of a congener series of guest amino acid molecules into the host cavity of α and β-cyclodextrins in aqueous solution have been focused on modern research gaining far reaching effect. With both the α and β-cyclodextrins, it is found that 1 : 1 hosts–guest inclusion complexes are formed with all the guest molecules at both low and high pH. The variation of the thermodynamic parameters with guest size and state are used to draw inferences about contributions to the overall binding from the driving forces, viz., hydrophobic effect, van der Waals forces, H-bonds, electrostatic forces, structural effect and configurational theory. The formation and comparative study of inclusion complexes have been analyzed by available data supplemented with surface tension, pH, density, viscosity, and refractive index.

NMR, surface tension and conductivity studies to determine the inclusion mechanism: thermodynamics of host–guest inclusion complexes of natural amino acids in aqueous cyclodextrins

The assembly of two natural amino acids (viz., L-arginine and L-histidine) as guests with α and β-cyclodextrins as hosts to form inclusion complexes in aqueous medium has been demonstrated which are highly suitable for diverse applications in modern bio-medical sciences. The 1H NMR study establishes the formation of inclusion complexes, while surface tension and conductivity studies confirm that the inclusion complexes have been formed with 1 : 1 stoichiometry. The nature of the complexes has been established using thermodynamic parameters, based on density, viscosity, and refractive index measurements. The contributions of different groups of the guest molecules towards the limiting apparent molar volume and the viscosity-B coefficient are determined and solvation numbers are calculated. All the parameters support the formation of the inclusion complexes, which are explained based upon hydrophobic effects, H-bonds, electrostatic forces and structural effects.

Studies of viscous antagonism, excess molar volume and isentropic compressibility in aqueous mixed solvent systems at different temperatures

Densities and viscosities for the ternary liquid mixtures of water + ethylene glycol +tetrahydrofuran, water + ethylene glycol + 1,4-dioxane, water + ethylene glycol + N,N-dimethylformamide and water + ethylene glycol + dimethyl sulphoxide have been measured as a function of the composition at 298.15, 308.15 and 318.15 K. From the experimental measurements, viscosity deviations (Δη), antagonic index (I A) and excess molar volumes (V E) have been evaluated. The speeds of sound have been also measured and excess isentropic compressibilities ( ) are calculated at 298.15 K. The results are discussed and interpreted in terms of molecular package and specific interaction predominated by hydrogen bonding.

Molecular interactions of α-amino acids insight into aqueous β-cyclodextrin systems

Qualitative and quantitative analysis of molecular interaction prevailing in glycine, l-alanine, l-valine and aqueous solution of β-cyclodextrin (β-CD) have been probed by thermophysical properties. Density (ρ), viscosity (η), and ultrasonic speed (u) measurements have been reported at different temperatures. The extent of interaction (solute–solvent interaction) is expressed in terms of the limiting apparent molar volume (

Probing inclusion complexes of cyclodextrins with amino acids by physicochemical approach

\phi_{\text{V}}^{0}

Conductivity studies of sodium iodide in pure tetrahydrofuran and aqueous binary mixtures of tetrahydrofuran and 1,4-dioxane at 298.15 K

ϕV0), viscosity B-coefficient and limiting apparent molar adiabatic compressibility (

Apparent molar volume, viscosity B -coefficient, and adiabatic compressibility of tetrabutylammonium bromide in aqueous ascorbic acid solutions at T = 298.15, 308.15, and 318.15 K

\phi_{\text{K}}^{0}