Parampaul K. Banipal

Hydration behaviour of some mono-, di-, and tri-saccharides in aqueous sodium gluconate solutions at (288.15, 298.15, 308.15 and 318.15) K: Volumetric and rheological approach

Thermodynamic and transport properties are very useful in providing valuable information regarding the hydration characteristics of saccharides and play a pivotal role in the study of taste behaviour of saccharides in mixed aqueous solutions. The effects of sodium gluconate and other sodium salts on the hydration behaviour and the basic taste quality of saccharides have been studied from measured apparent molar volumes (V2,ϕ), partial molar volumes (V2(°)) at infinite-dilution, and viscosity B-coefficients, of eight monosaccharides, six disaccharides and two trisaccharides in (0.25, 0.50, 1.00 and 1.50)molkg(-1) aqueous sodium gluconate solutions over a temperature range of (288.15-318.15)K and at atmospheric pressure. Partial molar volumes of transfer (ΔtV2(°)) and viscosity B-coefficients of transfer (ΔtB) of saccharides and other parameters such as isobaric expansion coefficients, interaction coefficients (using McMillan-Mayer theory), and dB/dT parameters have also been determined and discussed in terms of solute (saccharide)-cosolute (sodium gluconate) interactions.

Effect of magnesium chloride (2:1 electrolyte) on the aqueous solution behavior of some saccharides over the temperature range of 288.15-318.15 K: a volumetric approach.

Infinite-dilution standard partial molar volumes, V(2)(0), for various mono-, di-, and trisaccharides, and their derivatives (methyl glycosides) at molalities ranging from 0.04 to 0.12 mol kg(-1) in aqueous solutions of magnesium chloride of 0.5, 1.0, 2.0, and 3.0 mol kg(-1), have been evaluated over a range of temperatures from 288.15 to 318.15 K by density measurements employing a vibrating-tube densimeter. These data have been utilized to determine the corresponding standard partial molar volumes of transfer, Δ(t)V(2)(0), of saccharides and methyl glycosides from water to aqueous magnesium chloride solutions. The Δ(t)V(2)(0) values have been found to be positive, and their magnitudes increase with an increasing concentration of magnesium chloride in all cases. Partial molar expansion coefficients, (∂V(2)(0)/∂T)(P) and second derivatives thereof, (∂(2)V(2)(0)/∂T(2))(P) have been estimated. The magnitude of V(2)(0) values increases with an increase in temperature, indicating that hydration effects in solutions are strongly sensitive to temperature. Pair and higher order volumetric interaction coefficients (V(AB), V(ABB)) have also been obtained from Δ(t)V(2)(0) values by using the McMillan-Mayer theory. The various parameters have been discussed in terms of the solute (saccharide or methyl glycoside)-co-solute (magnesium chloride) interactions and are thus used to understand the mixing effects due to these interactions. These results have been compared with those earlier reported in the presence of electrolytes. An attempt is made to interpret the volumetric properties data in terms of the stereochemistry of the solutes.

Effect of Sodium Sulphate on the Volumetric, Rheological and Refractometric Properties of some Disaccharides in Aqueous Solutions at Different Temperatures

Density, ρ, viscosity, η, and refractive index, n, of some disaccharides [D(+)-cellobiose, D(+)-lactose monohydrate, D(+)-maltose monohydrate and sucrose] in water and in 0.49850 and 0.99705mol kg-1 aqueous solutions of sodium sulphate [Na2SO4] have been measured at four temperatures [288.15, 298.15, 308.15 and 318.15K]. From these data, the apparent molar volumes, VΦ, and viscosity-B-coefficients using Jones–Dole equation have been determined at different temperatures. The partial molar volumes of transfer, ΔtV20 at infinite dilution and B-coefficients of transfer, ΔtB, have been estimated for transfer of disaccharides from water to aqueous sodium sulphate solutions. Partial molar expansion coefficients, (∂V20/∂T)P and dB/dT coefficients have also been calculated. Gibbs free energy of activation of viscous flow has been calculated by using Feakin´s transition-state theory for the studied systems. D(+)-Cellobiose has shown characteristically different hydration behaviour among the studied disaccharides. The signs and magnitude of ΔtV20, and ΔtB parameters have been discussed in terms of various interactions occurring in these solutions.

Effect of food preservatives on the hydration properties and taste behavior of amino acids: a volumetric and viscometric approach.

Thermodynamic and transport properties of aqueous solutions are very useful in the elucidation of solute-solvent and solute-solute interactions, which help to understand the hydration and taste behavior of solutes. The densities and viscosities of L-glycine, β-alanine and L-leucine have been determined in water and in aqueous solutions of sodium propionate (NaP) and calcium propionate (CaP) at temperatures 298.15 and 308.15K. From these data, apparent molar volumes (V2,ϕ), viscosity B-coefficients and corresponding transfer parameters (ΔtrV2,ϕo and ΔtrB) have been calculated. The dB/dT values suggest that L-glycine and β-alanine act as structure-breaker, while L-leucine acts as structure-maker both in water and in aqueous solutions of NaP and CaP. The decrease in hydration number and change in taste behavior have also been observed with increasing concentration of the cosolute.

Physicochemical aspects of the energetics of binding of sulphanilic acid with bovine serum albumin

The thermodynamic study of the binding of sulphanilic acid with model transport protein bovine serum albumin is a promising approach in the area of synthesizing new sulfa drugs with improved therapeutic effect. Thus, such binding studies play an important role in the rational drug design process. The binding between sulphanilic acid and bovine serum albumin has been studied using calorimetry, light scattering in combination with spectroscopic and microscopic techniques. The calorimetric data reveals the presence of two sequential nature of binding sites where the first binding site has stronger affinity (~10(4)M(-1)) and second binding site has weaker affinity (~10(3)M(-1)). However, the spectroscopic (absorption and fluorescence) results suggest the presence of single low affinity binding site (~10(3)M(-1)) on protein. The contribution of polar and non-polar interactions to the binding process has been explored in the presence of various additives. It is found that sulphanilic acid binds with high affinity at Sudlow site II and with low affinity at Sudlow site I of protein. Light scattering and circular dichroism measurements have been used to study the effect on the molecular topology and conformation of protein, respectively. Thus these studies provide important insights into the binding of sulphanilic acid with bovine serum albumin both quantitatively and qualitatively.

Exploring the thermodynamics and conformational aspects of nicotinic acid binding with bovine serum albumin: a detailed calorimetric, spectroscopic and molecular docking study

The present study reports comprehensive energetic and conformational aspects of the binding of an antihyperlipidemic drug, nicotinic acid (NA), with a model transport protein, bovine serum albumin (BSA) by calorimetry, light scattering, spectroscopic (absorption, fluorescence, 1H-NMR, and circular dichroism) and molecular docking methods. The calorimetric result reveals that NA binds to BSA in a sequential way with a stronger affinity (∼104 M−1) for the first binding site. The study in the presence of various co-solutes (salt, tetrabutylammonium bromide, sucrose, and surfactants) indicates the significant contribution of electrostatic as well as hydrophobic interactions but insignificant contribution of hydrogen bonding to the binding process. In addition, NA was also observed to bind with BSA through π–π interactions as revealed by 1H-NMR and the molecular docking study. The spectroscopic analysis reveals the formation of a complex via a static quenching mechanism. The presence of two sequential binding events has been successfully explained by calorimetry which has also been supported by the fluorescence study. The changes in the size as well as in the secondary structure of BSA were observed upon binding with NA. The stronger binding of NA at Sudlow site I (subdomain IIA) of BSA has been explored by the molecular docking study in combination with specific site probe experiments. Casting light on such drug–protein interactions helps in better understanding the biomolecular recognition and opens up new approaches in rational drug-design processes.

Ultrasonic Studies of Some Mono-, Di-, and Tri-Saccharides in Aqueous Sodium Acetate Solutions at Different Temperatures

Abstract Standard partial molar isentropic compressibilities, K○s,2 at infinite dilution of some mono-, di- and trisaccharides were determined in water and in (0.5, 1.0, 2.0 and 3.0) mol kg–1 aqueous sodium acetate solutions at temperatures, T = (288.15, 298.15, 308.15 and 318.15) K from precise speed of sound measurements. From these data, the standard partial molar isentropic compressibilities of transfer, ΔtK○s,2, pair and triplet interaction coefficients (KAB, KABB) and hydration numbers, Nw have been calculated. These parameters have been discussed in terms of various molecular interactions occurring in solutions. Effect of sodium acetate on the taste quality of various saccharides has been discussed on the basis of apparent massic volume and apparent massic isentropic compressibility parameters. Acoustical properties have also been discussed in relation to previously reported volumetric and rheological studies for these systems.

Effect of sodium acetate and magnesium acetate on the solution behavior of some amino acids in water at 298.15 K : A compressibility approach

Apparent molar adiabatic compressibility, K2,φ,S, of glycine, DL-α-alanine, DL-α-amino-n-butyric acid, L-leucine and L-phenylalanine in water and in (0.5, 1.0, 2.0, 4.0, 5.5 mol kg−1) aqueous sodium acetate and in (0.5, 1.0, 1.5, 2.0 mol kg−1) aqueous magnesium acetate solutions has been determined from sound velocity, u, measurements at 298.15 K. The partial molar adiabatic compressibilities at infinite dilution, K02,S, obtained from K2,φ,S data have been used to calculate the corresponding partial molar adiabatic compressibilities of transfer at infinite dilution, ΔtK02,S, from water to aqueous sodium acetate and magnesium acetate (cosolutes) solutions. The ΔtK02,S values are positive for the studied amino acids in case of both the cosolutes and the values increase with the increase of the concentrations of both the cosolutes. The trends of ΔtK02,S have been rationalized in terms of the hydration of hydrophilic and hydrophobic parts of the amino acids studied. The interaction coefficients and hydration number, nH, have also been calculated and are discussed in terms of the dehydration effect of sodium acetate and magnesium acetate upon the amino acids in solutions. Attempt has been made to correlate these results with the earlier reported volumetric and viscometric studies for the same systems.

Volumetric and UV absorption studies on understanding the solvation behavior of polyhydroxy solutes in l-ascorbic acid(aq) solutions at T=(288.15 to 318.15)K.

Thermodynamic and spectroscopic data characterizing the solvation behavior of polyhydroxy compounds are in demand to get better understanding about the mechanisms of taste chemoreception, protein stabilization, etc. Apparent molar volumes for monosaccharides, disaccharides, derivatives, and polyols in (0.05, 0.15, 0.25 and 0.35) mol kg(-1) aqueous solutions of l-ascorbic acid have been determined from density data measured at (288.15, 298.15, 308.15 and 318.15)K under atmospheric pressure. Standard partial molar volumes at infinite-dilution and corresponding volumes of transfer of solutes from water to L-ascorbic acid(aq) have been calculated. Interaction coefficients and standard partial molar expansibilities have also been evaluated. The basic taste quality of studied solutes has been assessed from apparent massic volumes. UV absorption studies support the interactions between solutes and L-ascorbic acid. Influence of pH variation was taken into consideration while evaluating chemical behavior and stability of L-ascorbic acid in aqueous and buffer solutions.

Effect of tartarate and citrate based food additives on the micellar properties of sodium dodecylsulfate for prospective use as food emulsifier

Citrate and tartarate based food preservatives can be used to enhance the emulsifying properties of sodium dodecylsulfate (SDS) based micellar system and thus making it appropriate for food applications. Exploration of interactions between the two species is the key constraint for execution of such ideas. In this work various micellar and thermodynamic parameters of SDS like critical micellar concentration (CMC), standard Gibbs free energy of micellization (ΔG(0)mic.) etc. have been calculated in different concentrations of disodium tartarate (DST) and trisodium citrate (TSC) in the temperature range (288.15-318.15)K from the conductivity and surface tension measurements. The parameters obtained from these studies reveal the competitive nature of both the additives with SDS for available positions at the air/water interface. TSC is found to be more effective additive in order to make SDS micellar system better for its potential applications as food emulsifier.