Aqueous Solutions Of Glycine Research Articles

Solution thermodynamics of sodium pyruvate in aqueous glycine solutions at T 298.15-313.15 K

In this study we investigated the effects of sodium pyruvate on the solution thermodynamics of glycine in terms of the solute-solute and solute-solvent interactions in aqueous solutions. Measured density and viscosity were used to derive apparent molar volumes (?V), standard partial molar volumes (?V0) and viscosity B-coefficients at 298.15, 303.15 K, 308.15, and 318.15 K under ambient pressure. The interactions are further discussed in terms of ion-dipolar, hydrophobic- hydrophobic, hydrophilic-hydrophobic group interactions. The activation parameters of viscous flow were also discussed in terms of transition state theory. The overall results indicated that ion-hydrophilic and hydrophilic-hydrophilic group interactions are predominant in the ternary solutions.

Electroanalytical characterization of Zn (II) complexes with D-mannosamine and Glycine in aqueous solutions

A detailed study of Zn(II)-D-mannosamine and mixed ligand complex Zn(II)-D-mannosamine-glycine in aqueous solution (θ=25°C, Ic=0.55molL⿿1) was carried out by voltammetry and potentiometry, allowing their characterization. Redox process of the [ZnManN]2+ complex was registered at Ep ⿼ ⿿1.01V, [ZnGly]+ at ⿿1.02V, ZnGly2 at ⿿1.18V, while [ZnManNGly]+ at ⿿1.12V (pH=8.0). Stoichiometry and stability constants of Zn (II) complexes were determined by potentiometric titrations. Calculated stability constants were found to be: log⿿βZnManN2+=2.7, log⿿βMaNZnGly+=7.7 and log⿿βMaNZnGlyH⿿1=⿿0.15. Voltammetric and potentiometric data were in good agreement, both indicating formation of two different ternary complexes, i.e. [ZnGlyManN]+ and [ZnGlyManNH⿿1]. Calculated speciation revealed the presence of the [ZnManN]2+ complex, as well as ternary complexes ([ZnManNGly]+) in significant amount. This study was the first attempt to quantify complexation processes of Zn (II) with naturally occurring amino sugar and mixed complex with amino acid, important for bioavailability of zinc (II) in seawater.

Volumetric, acoustic and viscometric behaviour of dipotassium hydrogen phosphate and disodium hydrogen phosphate in aqueous solution of N-acetyl glycine at different temperatures

Densities, speeds of sound and viscosities of dipotassium hydrogen phosphate (DPHP) and disodium hydrogen phosphate (DSHP) in aqueous solutions of N-acetyl glycine (AcGly) are reported at different temperatures. Densities and speeds of sound have been used to calculate apparent molar volume, apparent molar isentropic compression, partial molar volume, partial molar isentropic compression, partial molar volume of transfer, partial molar isentropic compression of transfer and partial molar expansivity. Pair and triplet interaction coefficients have also been calculated. Experimental viscosities have been used to determine B-coefficients. Further pair and triplet interaction coefficients have also been calculated. The results are discussed in terms of solute–solvent interactions.

Effect of potassium phosphate buffer on volumetric behavior of glycine in aqueous solutions at different temperatures

The apparent molar volume (V∅) of glycine in water and in 100, 500 and 1000mM aqueous potassium phosphate buffer (KPB) solutions have been obtained from density measurements at different temperatures (288.15 to 328.15K, including physiological temperature) and at different pH values (1.00, 7.40 and 14.00) by using vibrating-tube digital density meter. The estimated partial molar volumes at infinite dilution (V2o) have been used to obtain the corresponding transfer volume (∆trV2o) from water to aqueous potassium phosphate buffer solutions. Interaction parameters have been calculated from ∆trV2o data. The partial molar expansibilities (∂V2o|∂T)P at infinite dilution and (∂2V2o|∂T2)P values have also been determined from the V2o data at different temperatures. The hydration numbers (nH) of glycine at pH7.4 have been determined from the V2o data in the presence of KPB at different temperatures. The results have been discussed in terms of various interactions operating in these systems.

Formation of 4(5)-Methylimidazole in Aqueous d-Glucose-Amino Acids Model System.

The International Agency for Research on Cancer (IRAC) has classified 4(5)-methylimidazole (4-MeI) as a group 2B possible human carcinogen. Thus, how 4-MeI forms in a D-glucose (Glu) amino acids (AA) model system is important, as it is how browning is affected. An aqueous solution of Glu was mixed individually in equimolar amounts at 3 concentrations (0.05, 0.1, and 0.15 M) with aqueous solutions of L-Alanine (Ala), L-Arginine (Arg), Glycine (Gly), L-Lysine (Lys), and L-Serine (Ser). The Glu-AA mixtures were reacted at 60, 120, and 160 °C for 1 h. The 4-MeI levels were measured by gas chromatography-mass spectrometry after derivatization with isobutylchloroformate. No 4-MeI was formed at 60 °C for any treatment combination; however, at 120 °C and 0.05 M, Glu-Arg and Glu-Lys produced 0.13 and 0.14 mg/kg of 4-MeI. At 160 °C and 0.05 M all treatment combinations formed 4-MeI. At 160 °C and 0.15 M, the observed levels of Glu-Ala, Glu-Arg, Glu-Gly, Glu-Lys, and Glu-Ser were 0.21, 1.00, 0.15, 0.22, and 0.16 mg/kg. The AA type, reactant concentrations, and temperature significantly affected (P < 0.001) formation of 4-MeI as well as browning. Glu-Lys treatment in all combinations produced the most browning, but Glu-Arg produced the most 4-MeI. This method showed that foods processed using low temperatures may have reduced levels of 4-MeI.

Control of X-ray Induced Electron and Nuclear Dynamics in Ammonia and Glycine Aqueous Solution via Hydrogen Bonding.

Recently, a new family of autoionization processes has been identified in aqueous phases. The processes are initiated by core-electron ionization of a solute molecule and involve proton transfer along the solute-solvent hydrogen bond. As a result, short-lived singly charged cations form with structures sharing a proton between solute and solvent molecules. These molecular transients decay by autoionization, which creates reactive dicationic species with the positive charges delocalized over the entire molecular entity. Here, we investigate the ultrafast electron and nuclear dynamics following the core ionization of hydrated ammonia and glycine. Both molecules serve as models for exploring the possible role of the nonlocal relaxation processes in the chemical reactivity at the interface between, for instance, a protein surface and aqueous solution. The nature of the postionization dynamical processes is revealed by high-accuracy Auger-electron spectroscopy measurements on liquid microjets in vacuum. The proton-transfer-mediated processes are identified by electron signals in the high-energy tail of the Auger spectra with no analogue in the Auger spectra of the corresponding gas-phase molecule. This high-energy tail is suppressed for deuterated molecules. Such an isotope effect is found to be smaller for aqueous ammonia as compared to the hydrated H2O molecule, wherein hydrogen bonds are strong. An even weaker hydrogen bonding for the hydrated amino groups in glycine results in a negligibly small proton transfer. The dynamical processes and species formed upon the nitrogen-1s core-level ionization are interpreted using methods of quantum chemistry and molecular dynamics. With the assistance of such calculations, we discuss the conditions for the proton-transfer-mediated relaxation processes to occur. We also consider the solvent librational dynamics as an alternative intermolecular ultrafast relaxation pathway. In addition, we provide experimental evidence for the umbrella-type motion in aqueous ammonia upon core ionization. This intramolecular channel proceeds in parallel with intermolecular relaxation processes in the solution.

Potentiometric, Raman spectroscopy and DFT study of pentaaqua glycine aluminum(III) complex in aqueous solution

Aluminum ion bioaccumulation is associated with the formation of β-amyloid peptide, a main microscopic characteristic of Alzheimer’s disease. β-amyloid affects glucose transport and consequently limits glycine synthesis. Glycine is an important amino acid in several body functions and it acts as an inhibitory neurotransmitter in the central nervous system. Moreover, aluminum glycinate salt is used as medication. The complex formed by aluminum(III) and glycine in aqueous solution at metal-to-ligand ratio of 1:1 has been studied by potentiometry, Raman spectroscopy and quantum chemical calculations (DFT:B3LYP/6-311++G**). Atomic charges, electrostatic potential contour surface, electrostatic potential map and donor–acceptor second order perturbative energies were examined. Potentiometry data revealed complexion formation. Distributions of species pointed out the better value to perform the Raman analyses. Raman data was used to confirm complexion formation and indicated coordination mode adopted by the ligand. Quantum chemical calculations provided data about structure, normal modes, charge distribution and delocalization. Glycine should act as a monodentate ligand through the oxygen of the carboxylate group in pentaaqua glycine aluminum(III). The other positions in the octahedral arrangement are occupied by coordinated water molecules.

Thermodynamics and structure of aqueous electrolyte solutions of glycine at different temperatures

The enthalpies of dissolution of glycine in aqueous electrolyte solutions are measured by calorimetry at temperatures of 288 K, 298 K, and 313 K in the molality range from 0.25 mol/kg to 6 mol/kg NaCl and to 4.5 mol/kg KCl. The enthalpy and heat capacity parameters are determined for the pair and triple interactions of glycine with electrolyte in water. Special (singular) points are discovered on the concentration dependences of the heats of dissolution of glycine in aqueous electrolyte solutions and in urea solutions at different temperatures. At these points, such a structurally sensitive property as the entropy of dissolution is temperature independent and the partial heat capacity of glycine is equal to that of the crystalline amino acid. The position of the singular point on the concentration axis is identical for NaCl and KCl solutions; in the case of urea solutions, the singular point is achieved at a much higher concentration of urea.

Cyclic voltabsorptometry of copper nanofoil in aqueous glycine solutions

Real time detection of the electrode products as a function of potential during the electrolysis is desirable for fundamental analyses of the electrode processes. In the present work, cyclic voltabsorptometry was used to investigate the electrochemical behavior of copper in glycine solutions at acidic, neutral and alkaline pH levels. A long-optical-path thin-layer cell was used for the spectroelectrochemical measurements. Electro-oxidation of the deposited copper nanofoil leads to formation of Cu(I)–glycine complex with high electrochemical stability. At a high concentration of glycine, all the deposited copper can be directly converted into soluble Cu(I)–glycine complex in the KCl-containing solutions without accumulation of the intermediate CuClads. The Cu(I)–glycine complex is also evidenced to be an intermediate in the cupric complex reduction to copper. This Cu(I) complex can be destroyed at relatively positive potentials where the evolution of chlorine occurs, especially in acidic and neutral solutions. This work proves that cyclic voltabsorptometry is adaptable for the analysis of the potential-dependent formation and conversion of the light-absorbing metal complexes.

Effect of mixing, concentration and temperature on the formation of mesostructured solutions and their role in the nucleation of dl-valine crystals

We report investigations on the formation of mesostructured solutions in DL-valine-water-2-propanol mixtures, and the crystallization of DL-valine from these solutions. Mesostructured liquid phases, similar to those previously observed in aqueous solutions of glycine and DL-alanine, were observed using Dynamic Light Scattering and Brownian microscopy, in both undersaturated and supersaturated solutions below a certain transition temperature. Careful experimentation was used to demonstrate that the optically clear mesostructured liquid phase, comprising colloidal mesoscale clusters dispersed within bulk solution, is thermodynamically stable and present in equilibrium with the solid phase at saturation conditions. Solutions prepared by slow cooling contained mesoscale clusters with a narrow size distribution and a mean hydrodynamic diameter of around 200 nm. Solutions of identical composition prepared by rapid isothermal mixing of valine aqueous solutions with 2-propanol contained mesoscale clusters which were significantly larger than those observed in slowly cooled solutions. The presence of larger mesoscale clusters was found to correspond to faster nucleation. Observed induction times were strongly dependent on the rapid initial mixing step, although solutions were left undisturbed afterwards and the induction times observed were up to two orders of magnitude longer than the initial mixing period. We propose that mesoscale clusters above a certain critical size are likely to be the location of productive nucleation events.

Interactions of Saccharides in Aqueous Glycine and Leucine Solutions at Different Temperatures of (293.15 to 313.15) K: A Viscometric Study

The results of viscosity measurements of ribose, maltose, and raffinose at molalities ranging from (0.050 to 0.100) mol·kg–1 in aqueous solutions of glycine and leucine of (0.025, 0.050, and 0.100) mol·kg–1, respectively, over a wide temperature range of (293.15 to 313.15) K, have been reported. The viscosity data have been used to calculate the viscosity B-coefficients by employing the Jones–Dole equation at different temperatures. The temperature derivative of B-coefficients, dB/dT, the viscosity B-coefficient of transfer, ΔtrB, free energy of activation of viscous flow per mole of solvent, Δμ1o*, and solute, Δμ2o*, respectively, activation entropy, ΔS2o*, and activation enthalpy, ΔH2o* for saccharides in aqueous amino acid solutions have been estimated from viscosity B-coefficient data. These parameters have been discussed in terms of saccharide–amino acid interactions, structure-making behavior of saccharides, and formation of transition state in the presence of amino acids. We have also attempted to investigate the temperature and concentration dependence of these outcomes.

Influence of Controlled Fluid Shear on Nucleation Rates in Glycine Aqueous Solutions

The nucleation of glycine was investigated in supersaturated aqueous solutions exposed to well-controlled fluid shear under isothermal conditions. Shear rates between 25 s–1 and 1000 s–1 were studied using Couette and capillary flow devices. Induction times were obtained from imaging, transmission and scattering measurements, or visual monitoring. Great care was taken to eliminate any seeding in order to avoid secondary nucleation preceding formation of first crystals through primary nucleation. The observed induction times of sheared solutions were considerably lower than those of unsheared solutions. Increasing the average shear rate was found to reduce the mean induction time through a power law relationship. A detailed statistical analysis showed that the number of experimental repetitions used was sufficient to obtain statistically significant trends for the system studied. Induction times appeared to closely follow a probability distribution based on a previously published model of Jiang and ter Hor...

Synthesis of pure-phase Sr2MgMoO6 nanostructured powder by the combustion method

Abstracts Pure-phase Sr2MgMoO6 (SMMO) nanopowder was obtained by combustion synthesis (CS) from an aqueous solution of metal nitrates, glycine and ammonium nitrate and subsequent treatment in air at 900 °C. The morphological and structural characterization was performed by X-Ray diffraction (XRD), N2 physisorption and scanning electron microscopy (SEM). This nanostructured powder presents average crystallite size of ~150 nm and a sponge-like morphology composed of highly interconnected crystallites and an effective specific area of 5.6 m2/g. EIS measurements indicate ASR values as low as 0.07 Ω cm2 at 800 °C.

Effect of temperature on solvation behaviour of diclofenac sodium salt in aqueous glycine and l-proline solutions

Apparent molar volume (V2,ϕ) and apparent molar isentropic compressibility (Ks,2,ϕ) of diclofenac sodium salt (DSS) drug within the concentration range of (0.001 to 0.008)mol·kg−1 in (0.01, 0.03 and 0.05)mol·kg−1 aqueous glycine and l-proline solutions are computed from the experimental density (ρ) and speed of sound (u) values at T=(293.15 to 313.15)K and atmospheric pressure. Derived parameters such as partial molar properties, transfer partial molar properties, hydration numbers and Hepler’s constant are computed from the data of V2,ϕ and Ks,2,ϕ. These parameters have been used to understand the effect of temperature on interactions between DSS drug and aqueous glycine/l-proline solution. Furthermore, the structure making and breaking ability of DSS drug in probed solutions are analysed at experimental conditions.

Conductivity and fluorescence studies on the micellization properties of sodium cholate and sodium deoxycholate in aqueous medium at different temperatures: Effect of selected amino acids

In order to add to the existing knowledge of aqueous solution behavior of bile salts in presence of amino acids, the micellization properties of sodium cholate (NaC) (1 to 20)mmol·kg−1, and sodium deoxycholate (NaDC) (0.5 to 10)mmol·kg−1 in 0.1mol·kg−1 aqueous solution of glycine, leucine, methionine, and histidine have been investigated at different temperatures (293.15 to 318.15)K at intervals of T=5K by using conductivity and fluorescence probe studies. The critical micelle concentration (CMC) values have been determined and elucidated in terms of hydrophobicity as well as hydrophilicity of NaC and NaDC in aqueous solution of these additives. Thermodynamic parameters of micellization viz. standard Gibbs free energy (ΔmicGo), standard enthalpy (ΔmicHo), and standard entropy (ΔmicSo) have also been calculated to extract information regarding the nature of micellization of bile salts in aqueous solutions. The (enthalpy+entropy) compensation plots have been interpreted to the contribution of chemical part towards micellization or stability of the micelle formed.

Density, viscosity, and refractive index of mono-, di-, and tri-saccharides in aqueous glycine solutions at different temperatures

Density, ρ, viscosity, η, and refractive index, nD of glucose, sucrose, and raffinose have been measured in 0.015 m aqueous glycine at 298.15, 303.15, 308.15, and 313.15K. From these experimental data, apparent molar volumes, Vϕ, apparent specific volumes, Vϕ,sp as a function of the concentration of solutes, the standard partial molar volume, Vϕ0, transfer volume from water to aqueous glycine solutions, ΔVϕ(tr)0, and partial molar expansibility of solute, Eϕ0 have been calculated for glucose, sucrose and raffinose in aqueous glycine solutions. Falkenhagen coefficient A and Jones–Dole coefficient B, free energies of activation of viscous flow per mole of solvent, Δμ10#, and solute, Δμ20#, enthalpy, ΔH0#, and entropy, ΔS0# of activation of viscous flow have been evaluated by using viscosity data. The molar refraction has been calculated by using measured refractive index data. Results have been explained in terms of solute–solute and solute–solvent interactions.

Viscosity and viscometric properties of Glycine in aqueous solutions of Sodium Thiosulfate Pentahydrate (Na2S2O3 .5H2O) at different temperatures

Flowing times of Glycine in aqueous solutions Sodium Thiosulfate Pentahydrate (0.01-2.0 mol kg-1) using an AMVn Anton Paar viscometer at temperatures of (283.15; 288.15; 293.15; 298.15; 303.15; 308.15, 313.15 and 318.15) K and 101.1 Kpa.From the data obtained, the absolute viscosity, viscosity B-coefficients, slope ( dB/dT ),the ΔB tr ,adjustable parameters of the equation of Out and Los (B E , B S , K) , activation parameters of viscous flow (ΔG° ≠ , ΔH° ≠ , ΔS° ≠ ) were calculated , the values obtained for these parameters were discussed in terms of the interactions present in solution.

Dual Approach to Vibrational Spectra in Solution: Microscopic Influence of Hydrogen Bonding to the State of Motion of Glycine in Water.

We have proposed a new theoretical methodology to clarify the microscopic nature of the vibrational properties in solution, which consists of a combination of the vibrational frequency analyses (VFAs) with two kinds of Hessian matrices, that is, the effective Hessian on the free energy surface (free energy Hessian: "FE-Hessian") and the instantaneous one (instantaneous normal mode Hessian: "INM-Hessian") within QM/MM framework. In these VFAs, the Hessians were obtained by the analytical approach, having the advantages from the aspect of both the computational efficiency and accuracy in comparison to those obtained by the numerical one. In the present study, we have applied them to the glycine aqueous solution. First, by using the VFA with the FE-Hessian (VFA-FEH), we estimated the vibrational frequency shifts induced by solvent water molecules. The calculated values were quantitatively in agreement with experimental ones. It was clearly demonstrated that such vibrational shifts are attributed to not only the structural relaxation but also the explicit solute-solvent interactions (i.e., interatomic interactions). Second, by using the VFA with the INM-Hessian (VFA-INMH), the vibrational spectra in solution were investigated through the vibrational INM densities of states (DOS). By the comparison between the spectroscopic features and the microscopic solvation structure around glycine molecule, it was found that the frequency shifts and bandwidths in IR spectra are closely correlated with the hydrogen bonding (HB) network formations. In particular, the instantaneous changes of vibrational states of the hydroxyl group and carbonyl one, showing apparently inverse tendency on the strength of the HB interaction, can be explained very well on the basis of two different mechanisms, that is, the direct change of electron density in the bonding orbitals and the indirect one due to hyperconjugation between the lone electron pair and the antibonding orbitals, respectively. In conclusion, the present dual VFA approach is a quite useful strategy to interpret the microscopic origin of the experimental vibrational spectra.

Infrared spectrum analysis of the dissociated states of simple amino acids

In this work, we present detailed analyses of the dissociation of dilute aqueous solutions of glycine and of lysine over the range 1<pH<12. Using appropriate spectrum subtraction methods, we obtained ATR-IR spectra of the solvated species as a function of pH. Discernible changes in the ionic species were identified in the absorption region between 1800 and 1100cm−1. By applying peak deconvolution techniques to the spectra, we correctly interpret the apparent peak shift from 1615 to 1600cm−1 as being due to the receding NH3+ asymmetric deformation alongside the appearing COO− asymmetric stretching. The effect of aqueous solution environment was also investigated in terms of 10 and 100mmol/L NaCl. Salt solution spectra at each pH were also subtracted from each solution phase spectrum. Analysis of the deconvoluted peak areas due to CO and COO− at pH ranges<4.5 and those due to NH2 and NH3+ for pH>8 resulted in consistent pKa values for the amino acids.

Water Activity in Aqueous Amino Acid Solutions Containing Ammonium Sulfate at 298.2 K

Water activity in aqueous solutions of dl-alanine, glycine, or l-serine, with ammonium sulfate, molality ranging from 0.5 to 5.0, have been measured at 298.2 K. The new experimental data was correlated using three different theoretical schemes such as Zdanovskii–-Stokes–Robinson, its extension, or the Clegg–Seinfeld–Brimblecombe approach, with global average absolute deviations in the calculation of the osmotic coefficient of 3.46 %, 0.93 % and 1.95 %, respectively. The extended Zdanovskii–Stokes–Robinson method also enabled the prediction of unsymmetric molal activity coefficients of the electrolyte, in fair agreement with the experimental values found from literature measured by an electrochemical method. It is evidenced the usefulness of the experimental ternary data measured to extend the capabilities of thermodynamic models to higher salt and amino acid concentrations.