Tarlok S. Banipal

Partial Molar Volumes of Transfer of Some Amino Acids from Water to Aqueous Glycerol Solutions at 25°C

Apparent molar volumes of glycine, DL-α-alanine, L-valine, L-leucine, and L-phenylalanine in 0.5, 1.0, 2.0, 3.5, and 5.0 mB (mol-kg−1) aqueous solutions of glycerol have been obtained from solution densities at 25°C using precise vibrating-tube digital densimeter. The estimated partial molar volumes at infinite dilution Vo2 have been used to obtain the corresponding transfer volumes ΔtrV2o from water to different glycerol–water mixtures. The transfer volumes are positive for glycine and DL-α-alanine, and both positive and negative for the other amino acids over the concentration range studied. Interaction coefficients have been obtained from McMillan–Mayer approach and the data have been interpreted in terms of solute–cosolute interactions.

How PEO-PPO-PEO Triblock Polymer Micelles Control the Synthesis of Gold Nanoparticles: Temperature and Hydrophobic Effects

Aqueous micellar solutions of F68 (PEO(78)-PPO(30)-PEO(78)) and P103 (PEO(17)-PPO(60)-PEO(17)) triblock polymers were used to synthesize gold (Au) nanoparticles (NPs) at different temperatures. All reactions were monitored with respect to reaction time and temperature by using UV-visible studies to understand the growth kinetics of NPs and the influence of different micellar states on the synthesis of NPs. The shape, size, and locations of NPs in the micellar assemblies were determined with the help of TEM, SEM, and EDS analyses. The results explained that all reactions were carried out with the PEO-PPO-PEO micellar surface cavities present at the micelle-solution interface and were precisely controlled by the micellar assemblies. Marked differences were detected when predominantly hydrophilic F68 and hydrophobic P103 micelles were employed to conduct the reactions. The UV-visible results demonstrated that the reduction of gold ions into nucleating centers was channeled through the ligand-metal charge-transfer complex (LMCT) and carried out by the surface cavities. Excessive hydration of the surface cavities in the case of F68 micelles produced a few small NPs, but their yield and size increased as the micelles were dehydrated under the effect of increasing temperature. The results concluded that the presence of well-defined predominantly hydrophobic micelles with a compact micelle-solution interfacial arrangement of surface cavities ultimately controlled the reaction.

Partial molal adiabatic compressibilities of transfer of some amino acids and peptides from water to aqueous sodium chloride and aqueous glucose solutions

Abstract Partial molal adiabatic compressibilities at infinite dilution have been determined for glycine, dl -alanine, diglycine and triglycine in water, 1 M aqueous sodium chloride and 1 M aqueous glucose solutions by measuring sound velocities at 298.15 K. In the case of water, our results show a non-linear relationship between the partial molal adiabatic compressibility at inifinite dilution ( K ⊖ s,2 ) and the number n of glycyl units for n = 1–3, and the results have been compared with the literature values. The data have been used to derive partial molal adiabatic compressibilities of transfer at infinite dilution ( K ⊖ S,2,tr ) from water to 1 M aqueous sodium chloride and to 1 M aqueous glucose solutions. All transfer values are found to be positive which in the case of sodium chloride results from the dominant interactions between the ions of sodium chloride and the charged centres of amino acids or peptides. However, in the case of glucose these have been discussed in terms of the interactions between ions (charged centres), hydrophilic groups (OH and CONH) and hydrophobic groups.

Biomineralization of Gold Nanoparticles by Lysozyme and Cytochrome c and Their Applications in Protein Film Formation

Lysozyme (Lys) and cytochrome c (Cyc,c) proteins were used as mild reducing and stabilizing agents to synthesize gold nanoparticles (NPs) at precisely 40 and 80 degrees C. All reactions were monitored simultaneously by UV-visible measurements to determine changes in the nature of the protein during the course of reaction. The synthesis of Au NPs caused the simultaneous denaturation of protein due to the formation of bioconjugate NPs, and the denaturation temperature decreased with the number of NPs. Lys entrapped NPs in a typical gel state, and Cyc,c carried them on well-defined micelles at 80 degrees C or in the form of long fibrils or strands at 40 degrees C. The shape, size, and arrangement of bioconjugate NPs were characterized by atomic force microscopy and transmission electron microscopy measurements. Purified bioconjugate NPs were further used in zein protein film formation. The resulting films were characterized by photophysical and mechanical measurements. The induction of bioconjugate NPs made protein films isotropic and relatively more brittle (with a greater effect for Cyc,c than for Lys conjugate NPs) than in their absence and was considered to be well suited for biomedical applications.

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.

Densities and Partial Molar Volumes of Some Amino Acids and Diglycine in Aqueous n-Propanol Solutions at 25°C

Apparent molar volumes, Vφ, of glycine, DL-α-alanine, DL-α-amino-n-butyric acid, L-valine, L-leucine, and diglycine in water and in 1.0, 2.0, 3.0, 4.0, 5.0, and 6.0 mB [molality of n-propanol in water (mol-kg−1)] aqueous solutions of n-propanol have been obtained from densities of their solutions at 25 °C measured by using a precise vibrating-tube digital densimeter. The calculated partial molar volumes of amino acids and diglycine at infinite dilution, V2,mo, have been used to obtain the corresponding transfer volumes, ΔtrV2,mo, from water to different n-propanol–water mixtures. ΔtrV2,mo values are positive for glycine, DL-α- alanine, and diglycine (except at lower concentration ∼1.0 mB), negative for L-valine, and both positive and negative for the remaining amino acids over the concentration range studied. The side-chain contributions and hydration numbers have been calculated from V2,mo data. Interaction coefficients have also been obtained from the McMillan–Mayer approach and the data have been interpreted in terms of various 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.

Nanoparticle Surface Specific Adsorption of Zein and Its Self-assembled Behavior of Nanocubes Formation in Relation to On–Off SERS: Understanding Morphology Control of Protein Aggregates

Zein, an industrially important protein, is characterized in terms of its food and pharmaceutical coating applications by using surface enhanced Raman spectroscopy (SERS) on Au, Ag, and PbS nanoparticles (NPs). Its specific surface adsorption behavior on Ag NPs produced self-assembled zein nanocubes which demonstrated on and off SERS activity. Both SERS characterization as well as nanocube formation of zein helped us to understand the complex protein aggregation behavior in shape controlled morphologies, a process with significant ramifications in protein crystallization to achieve ordered morphologies. Interestingly, nanocube formation was promoted in the presence of Ag rather than Au or PbS NPs under in situ synthesis and discussed in terms of specific adsorption. Zein fingerprinting was much more clear and enhanced on Au surface in comparison to Ag while PbS did not demonstrate SERS due to its semiconducting nature.