Aqueous Solutions Of Glycine Research Articles

Preparation and stability analysis of glycine water-based phase change materials modified with potassium sorbate for cold chain logistics

Organic water-based phase change material (PCM) shows great potential for cold chain logistics below 0 °C. However, its poor stability limits its application. The purpose of this study is to develop an organic water-based PCM with high latent heat and melting temperature of −4 °C to −6 °C based on solving the problem of poor stability. Glycine and mannitol aqueous solution were selected as the base PCM, and the static stability was improved effectively with 0.1 wt% potassium sorbate modification. The prepared 6-PCM5 composed of 6 wt% glycine, 1.5 wt% mannitol, and 0.1 wt% potassium sorbate, demonstrated moderate thermal conductivity of 0.6017 W/(m·K) and a suitable melting temperature of −5.78 °C as well as an enthalpy of fusion of 292.64 J/g. After 100 thermal cycles, the melting temperature, enthalpy of fusion, and thermal conductivity were −5.91 °C, 290.66 J/g, and 0.5886 W/(m·K), which decreased only by 2.24%, 0.68%, and 2.18%, respectively. Furthermore, the cold storage performances of 6-PCM5 and ice were compared and evaluated by loading strawberries. Compared with ice storage, the pre-cooling time and average temperature of strawberries in the cold storage box with 6-PCM5 was reduced by 68.4% and 2.55 °C, and the effective cold storage time was lasted for 22.83 h at a temperature range of 0.45 °C to 3 °C, which effectively improved the cold storage quality of strawberries. Overall, the developed 6-PCM5 cold storage material possesses good static and cyclic stability, providing an effective solution for pre-cooling and short-distance cold chain transportation of perishable food.

Volumetric, Compressibility and Viscometric Approach to Study the Interactional Behaviour of Sodium Cholate and Sodium Deoxycholate in Aqueous Glycyl Glycine.

Viscosity, speed of sound (u), and density (ρ) have been measured in aqueous glycyl glycine solution over a temperature range from 293.15 to 313.15 K with a 5 K interlude to evaluate the volumetric and compressibility properties of bio-surfactants, namely sodium cholate (NaC; 1-20 mmol∙kg-1) and sodium deoxycholate (NaDC; 1-10 mmol∙kg-1). Density and viscosity findings provide information on both solute-solute and solute-solvent types of interactions. Many other metrics, such as apparent molar adiabatic compression (κS,φ), isentropic compressibility (κS), and apparent molar volume (Vφ), have been calculated from speed of sound and density measurements, utilising experimental data. The results show that the zwitterionic end group in the glycyl glycine strongly interacts with NaDC and NaC, promoting its micellization. Since the addition of glycyl glycine causes the bio-surfactant molecules to lose their hydrophobic hydration, the observed concentration-dependent changes in apparent molar volume and apparent molar adiabatic compression are likely attributable to changes in water-water interactions. Viscous relaxation time (τ) increases significantly with a rise in bio-surfactant concentration and decreases with increasing temperature, which may be because of structural relaxation processes resulting from molecular rearrangement. All of the estimated parameters have been analysed for their trends with regard to the different patterns of intermolecular interaction present in an aqueous glycyl glycine solution and bio-surfactant system.

Tuning Interfacial Concentration Enhancement through Dispersion Interactions to Facilitate Heterogeneous Nucleation.

Classical molecular dynamics simulations were used to investigate how dispersion (van der Waals) interactions between non-polar, hydrophobic surfaces and aqueous glycine solutions affect the solution composition, molecular orientation, and dynamics at the interface. Simulations revealed that dispersion interactions lead to a major increase in the concentration of glycine at the interface in comparison with the bulk solution, resulting from a competition between solute and solvent molecules to be or not to be near the interface. This can then lead to kinetic and/or structural effects facilitating heterogeneous nucleation of glycine at non-polar surfaces, in agreement with recent observations for tridecane, graphene, and polytetrafluoroethylene. A novel parameterization process was developed to map a model surface with tunable dispersion interactions to heptane, tridecane, and graphite materials. The model surface was capable of reproducing the solution structure observed in fully atomistic simulations with excellent agreement and also provided good agreement for dynamic properties, at a significantly reduced computational cost. This approach can be used as an effective tool for screening materials for heterogeneous nucleation enhancement or suppression, based on non-specific dispersion interactions based on bulk material molecular properties, rather than interfacial functional groups, templating or confinement effects.

Solvation properties of 1-butyl 2, 3-dimethyl imidazolium chloride ionic liquid in aqueous and aqueous glycine solutions at different temperatures using volumetric and compressibility parameters

Volumetric and compressibility approaches were employed in this investigation to analyse the intermolecular interactions of 1-Butyl-2,3-dimethyl imidazolium chloride in aqueous, in 0.05 mol.kg−1 aqueous glycine and 0.1095 mol.kg−1 aqueous glycine solutions over the concentration range 0.01 to 0.13 mol.kg−1 at different temperatures i.e., T= (288.15,293.15, 298.15, 303.15, 308.15, 313.15 and 318.15) K and atmospheric pressure by measuring density(ρ) and speed of sound(u) data. Various thermophysical parameters such as apparent molar volume of solute(Vϕ), limiting apparent molar volume of solute(Vϕ0), transfer limiting apparent molar volume of soluteΔtrVϕ0, Hepler's constant (∂2Vϕ0/∂T2), isentropic compressibility (κS), apparent molar isentropic compression of solute (KS,ϕ), partial molar isentropic compression of solute(KS,ϕ0) and partial molar isentropic compression of transfer of solute ΔtrKS,ϕ0 have been calculated using the corresponding thermophysical data at studied temperatures. In addition, the temperature dependence of apparent molar volume of solute has been used to determine isobaric expansivity or thermal expansion coefficient(α), apparent molar expansivity of solute Eϕ and limiting apparent molar expansivity solute Eϕ0 parameters of binary and ternary systems. The findings were described in terms of solute–solute and solute–solvent interactions.

Molecular Dynamics Investigation of Clustering in Aqueous Glycine Solutions.

Recent experiments with undersaturated aqueous glycine solutions have repeatedly exhibited the presence of giant liquid-like clusters or nanodroplets around 100 nm in diameter. These nanodroplets re-appear even after careful efforts for their removal and purification of the glycine solution. The composition of these clusters is not clear, although it has been suggested that they are mainly composed of glycine, a small and very soluble amino acid. To gain insights into this phenomenon, we study the aggregation of glycine in aqueous solutions at concentrations below the experimental solubility limit using large-scale molecular dynamics simulations under ambient conditions. Three protonation states of glycine (zwitterion = GLZ, anion = GLA, and cation = GLC) are simulated using molecular force fields based on the 1.14*CM1A partial charge scheme, which incorporates the OPLS all-atom force field and TIP3P water. When initiated from dispersed states, we find that giant clusters do not form in our simulations unless salt impurities are present. Moreover, if simulations are initiated from giant cluster states, we find that they tend to dissolve in the absence of salt impurities. Therefore, the simulation results provide little support for the possibility that the giant clusters seen in experiments are composed purely of glycine (and water). Considering that strenuous efforts are made in experiments to remove impurities such as salt, we propose that the giant clusters observed might instead result from the aggregation of reaction products of aqueous glycine, such as diketopiperazine or other oligoglycines which may be difficult to separate from glycine using conventional methods, or their co-aggregation with glycine.

Multi-technique approach to explore the mixed micellization behavior of promazine hydrochloride drug and cetyltrimethylammonium bromide surfactant in aqueous glycine, glycylglycine (dipeptide) and glycylglycylglycine (tripeptide) solutions

The aggregation properties of amphiphiles and their mixtures are of theoretical and applied importance. Therefore, mixed micellization behavior of promazine hydrochloride (PMZ) drug and cetyltrimethylammonium bromide (CTAB) surfactant at different mole fractions, α PMZ = (0.2, 0.4, 0.6 and 0.8) has been scrutinized in water and (0.025, 0.050 and 0.100) mol·kg −1 aqueous solutions of glycine, glycylglycine (dipeptide) and glycylglycylglycine (tripeptide) at T = (298.15 to 318.15) K, by means of multiple techniques. Thermodynamic parameters of micellization (ΔG°m, ΔH°m, and ΔS°m) along with excess Gibbs free energy of mixing (ΔG m ex), the molecular interaction parameter (β int), and the degree of ionization (α), have been attained from the conductivity measurements. The partial specific volumes (φ v), partial specific isentropic compression (φ κ) as well as isentropic compressibilities (κ s) were computed from the measured density and speed of sound data. UV-Visible absorption, fluorescence emission and proton (1H) NMR spectra were recorded for the pure PMZ and mixed (PMZ + CTAB) system in the presence of glycine(aq), glycylglycine(aq) and glycylglycylglycine(aq) solutions. Dynamic light scattering (DLS) study was carried out to measure the hydrodynamic diameters (D H) of mixed micellar systems. The prevalence of hydrophobic-hydrophobic interactions amid the hydrophobic groups of PMZ drug (tricyclic scaffolding), CTAB (–C16H33), glycine, di- and tri-peptides (–CH2), and electrostatic interactions amid the hydrophilic/ionic groups of PMZ{tertiary amine part and +NH (CH3)2, Cl−}, CTAB (–N (CH3)3 +, Br‒) and glycine, di- and tri-peptides {zwitterion (NH3 +, COO−} have been depicted from the aforementioned studies.

Synthesis of carbon-encapsulated metal-based nanoparticles by gas/liquid interfacial plasma under high pressure

Carbon-encapsulated TiO2, Ag and Fe3O4 NPs are synthesized by pulse arc discharge plasma over glycine aqueous solution under high pressures, which is a novel plasma technique to fabricate metal-based NPs/C nanocomposites in one step. The carbon coatings are formed by utilizing glycine as a carbon precursor and confirmed to be amorphous carbon. While TiO2, Ag and Fe3O4 NPs are generated instantaneously via the erosion of the metal electrodes and reaction with the active oxidation radicals and molecular produced during the plasma generation over gas/liquid interface. It was found that the NPs are produced in the uniform size only under high operating pressure and the average size of the TiO2, Ag and Fe3O4 NPs were around 10.2 nm, 6.6 nm and 9.6 nm, respectively. The pulse arc discharge plasma was performed in different pressures, glycine concentrations and pulse times to investigate the effect of the influential factors on the formation of the carbon-encapsulated NPs in this plasma system. The carbon-encapsulated NPs are later annealed at 800 °C under Ar gas to construct the porous structure. In the MB degradation test, the porous carbon-encapsulated TiO2 NPs exhibit good adsorption capacity and improved photocatalytic activity.

A Metastable Amorphous Intermediate Is Responsible for Laser-Induced Nucleation of Glycine.

Laser-induced crystal nucleation through optical tweezing, and in particular polymorph selection through laser polarization, promises unprecedented control over crystallization. However, in the absence of a nearby liquid-liquid critical point or miscibility gap, the origin of the required mesoscale clusters remains unclear. A number of recent studies of so-called nonclassical nucleation have suggested the presence of large amorphous clusters. Here, we show that supersaturated aqueous glycine solutions form metastable intermediate particles that are off the direct path to crystal nucleation. Laser-induced crystal nucleation only occurs when the laser "activates" one of these particles. In situ low-frequency Raman spectroscopy is used to demonstrate their amorphous or partially ordered character and transformation to various crystal polymorphs. The requirement for solution aging in many previously reported laser-induced crystal nucleation experiments strongly suggests that the presence of amorphous intermediates is a general requirement.

Orientation-controlled crystallization of γ-glycine films with enhanced piezoelectricity.

Glycine, the simplest amino acid, is considered a promising functional biomaterial owing to its excellent biocompatibility and strong out-of-plane piezoelectricity. Practical applications require glycine films to be manufactured with their strong piezoelectric polar 〈001〉 direction aligned with the film thickness. Based on the recently-developed solidification approach of a polyvinyl alcohol (PVA) and glycine aqueous solution, in this work, we demonstrate that the crystal orientation of the as-synthesized film is determined by the orientation of glycine crystal nuclei. By controlling the local nucleation kinetics via surface curvature tuning, we shifted the nucleation site from the edge to the middle of the liquid film, and thereby aligned the 〈001〉 direction vertically. As a result, the PVA-glycine-PVA sandwich film exhibits the highest aver-age piezoelectric coefficient d33 of 6.13 ± 1.13 pC N-1. This work demonstrates a promising kinetic approach to achieve crystallization and property control in a scalable biocrystal manufacturing process.

Peculiarities of mineral change under action of aqueous glycine solutions

Peculiarities of mineral change under action of aqueous glycine solutions

Enthalpic Characteristics of the Dissociation of Glycylglycine and Glycine in Aqueous Solutions of Dimethylsulfoxide: Calculations and Experiments

Enthalpic Characteristics of the Dissociation of Glycylglycine and Glycine in Aqueous Solutions of Dimethylsulfoxide: Calculations and Experiments

Iron(II) reactions with glycine – suitable biomineralization model?

The reactions of Mohr’s salt with amino acid glycine in aqueous solution and aerobic conditions were studied and obtained samples consist of different compounds. The obtained products were characterized by elemental analysis, infrared spectroscopy and the iron determination also and exhibited very low organic matter content – the sum of N, C, H and S content less than 20 % and Fe content around 40 %. Prepared samples consist of iron(II) amino acid complex [Fe(glyH)(SO4)]n, known as iron food supplement (FeGS) as the only sulphur containing compound. Its content varies from 26 % up to 46 %. Ferrous glycinate was obtained in the samples collected initially after the reaction in very low content < 7 %. Iron(III) hydroxy-oxide FeO(OH) was obtained in the range 40 – 65 %. The FeO(OH) content increased with the decreasing FeGS content. Formation of inorganic FeO(OH) suggest the ongoing redox reaction under aerobic condition therefore, it is suggested as a biomineralization reaction model.

Effect of glycine on aggregation of citrate-functionalised gold nanoparticles and SERS measurements

Surface enhanced Raman Scattering (SERS) can be used as a novel way of probing local liquid composition and structure at solid-liquid interfaces. This is particularly important for understanding the mechanism of heterogeneous nucleation from solution, where solutes are present at relatively high concentrations. To obtain information about the solution composition and structure near a gold nanoparticle (AuNP) surface, which facilitates SERS, it is thus necessary to understand the role of the analyte in AuNP aggregation, and its effect on the SERS signal and the Raman signal from the bulk. We have used dynamic light scattering and UV-Vis spectroscopy to investigate how glycine influences the aggregation of citrate-functionalised gold nanoparticles (AuNPs), and thus the SERS response, in glycine aqueous solutions. At pH 4 the AuNP suspensions in aqueous solutions (without glycine) did not aggregate due to the electrostatic stabilisation by negatively charged citrate functional groups. However, the addition of glycine promoted aggregation of the AuNPs, concomitantly increasing the strength of the SERS signal. Under these conditions glycine is zwitterionic, and its effect on the colloidal stability of AuNPs is most likely due to its association with citrate, affecting its charge state, resulting in reduction of the electrostatic stabilisation of the AuNPs. Using SERS as a solid-liquid interface probe provides a window into an interplay of interfacial and colloidal phenomena in the AuNP suspensions.

Mixed Micellization Behavior of (Chlorpromazine Hydrochloride + Cetyltrimethylammonium Bromide) System in Aqueous Solutions of Glycine

AbstractWe have examined the mixed micellar behavior of {amphiphilic drug; chlorpromazine hydrochloride (CPZ) + cationic surfactant; cetyltrimethylammonium bromide (CTAB)} at varying mole fractions of CPZ (αCPZ = 0.2, 0.4, 0.6, and 0.8) in (0.1, 0.3, and 0.5) mol kg−1 glycine(aq) solutions at 298.15, 308.15, and 318.15 K, by using conductometric, volumetric, isentropic compressibility, UV–visible absorbance, fluorescence, and dynamic light scattering (DLS) techniques. The critical micelle concentration (CMC) values obtained from above measurements have been utilized to calculate the thermodynamic parameters (ΔG°m, ΔH°m, and ΔS°m) and degree of ionization (α) at studied temperatures and concentrations. The partial specific volume (φv), partial specific isentropic compression (φκ), and isentropic compressibility (κs) have been calculated from the experimental density and speed of sound measurements and the results have been used to elucidate different interactions occurring in these systems. These results are further supported by UV–visible absorbance and fluorescence spectroscopic studies. The hydrodynamic diameters (Dh) of the mixed micellar system have been measured from the DLS studies. Thermodynamic and spectroscopic studies depict the dominance of hydrophobic/hydrophilic‐hydrophobic interactions between the alkyl (R = C16H33) chain of CTAB or hydrophobic tricyclic scaffolding of CPZ/Br−/N+‐CH3 group of CTAB or hydrophilic group i.e., tertiary amine portion of CPZ with hydrophobic group of glycine.

Molecular Interaction Studies of Doxycycline Hyclate in Aqueous Glycine or l-Alanine by Using Volumetric and Ultrasonic Parameters

The intermolecular interactions of the antibiotic drug doxycycline hyclate in water, aqueous solutions of glycine and aqueous solutions of l-alanine were determined by using volumetric and acoustic methods at four different temperatures (305.15, 310.15, 315.15 and 320.15) K. The limiting partial molar volume $$(V_{\phi }^{{\text{o}}} )$$ , limiting standard partial molar volume of transfer $${(}\Delta_{{{\text{tr}}}} V_{\phi }^{{\text{o}}} )$$ , limiting partial molar adiabatic compressibility ( $$\kappa_{\phi ,s}^{{\text{o}}} )$$ and limiting partial molar adiabatic compressibility of transfer $${(}\Delta_{{{\text{tr}}}} \kappa_{\phi ,s}^{{\text{o}}} )$$ were calculated from the density and ultrasonic velocity data at different temperatures and the results suggest strong solute–solvent interactions. The caging effect of doxycycline hyclate in water and in aqueous solutions of glycine and aqueous solutions of l-alanine was studied using the positive values of $$\left( {E_{\phi }^{{\text{o}}} = \frac{{{\updelta }V_{\phi }^{{\text{o}}} }}{{{\updelta }T}}} \right)$$ . The structure making behavior of doxycycline hyclate in water, aqueous solutions of glycine and aqueous solutions of l-alanine was analyzed from the positive values of Hepler’s constant i.e. $$\left( {\frac{{{\updelta }^{2} V_{\phi }^{{\text{o}}} }}{{{\updelta }T^{2} }}} \right)$$ . The limiting isobaric thermal expansion coefficient $$\left( {\alpha^{{\text{o}}} { } = \frac{{E_{\phi }^{{\text{o}}} }}{{V_{\phi }^{{\text{o}}} }}} \right)$$ , intermolecular free length (Lf) and acoustic impedance (Z) of doxycycline hyclate in water, aqueous solutions of glycine and aqueous solutions of l-alanine were also calculated at the studied temperatures.

Probing Local Electrostatics of Glycine in Aqueous Solution by THz Spectroscopy

AbstractBased upon precise terahertz (THz) measurements of the solvated amino acid glycine and accompanying ab‐initio molecular‐dynamics simulations, we show that the N‐C‐C‐O open/close mode at 315 cm−1 serves as a sensitive, label‐free probe for the local protonation of the amide group. Experimentally, we can show that this holds not only for glycine but also for diglycine and valine. The approach is more general, since the changes due to protonation result in intensity changes which can be probed by THz time domain (0–50 cm−1) as well as by precise THz‐FT spectroscopy (50–400 cm−1). A detailed analysis allows us to directly correlate the titration spectra with pKa values. This demonstrates the potential of THz spectroscopy to probe the charge state of a natural amino acid in water in a label‐free manner.

Probing Local Electrostatics of Glycine in Aqueous Solution by THz Spectroscopy.

Based upon precise terahertz (THz) measurements of the solvated amino acid glycine and accompanying ab‐initio molecular‐dynamics simulations, we show that the N‐C‐C‐O open/close mode at 315 cm−1 serves as a sensitive, label‐free probe for the local protonation of the amide group. Experimentally, we can show that this holds not only for glycine but also for diglycine and valine. The approach is more general, since the changes due to protonation result in intensity changes which can be probed by THz time domain (0–50 cm−1) as well as by precise THz‐FT spectroscopy (50–400 cm−1). A detailed analysis allows us to directly correlate the titration spectra with pK a values. This demonstrates the potential of THz spectroscopy to probe the charge state of a natural amino acid in water in a label‐free manner.

Volumetric and acoustic studies of glycine in aqueous solutions of sulphathiazole drug at T=(288.15 to 308.15) K

The densities (ρ) and speeds of sound (u) for glycine in aqueous solutions of (0.01, 0.02, 0.03, and 0.04) mol·kg -1 sulphathiazole drug have been measured at T = (288.15, 293.15, 298.15, 303.15 and 308.15) K, using vibrating tube digital densimeter and sound analyser Anton–Paar Model DSA - 5000. The apparent molar properties like apparent molar volume ( ), apparent molar adiabatic compressibility ( ) and the apparent molar volume ( 0 ) and adiabatic compressibility at infinite dilution ( 0 ) of glycine have been determined in water as well as in ternary mixtures containing sulphathiazole drug at different concentrations and at different temperatures from experimental data of densities and speeds of sound under atmospheric pressure. These data were also used to calculate the transfer parameters. Transfer parameters have been explained from the point of view of concentration dependence of solute-solute and solute-solvent interactions. The limiting apparent molar expansibility ( ) values for glycine in aqueous solutions of drug have been calculated. The calculated values of thermal expansion coefficient ( ) have small and positive values. These results are explained on the basis of drug-amino acid - water interactions and hydrophobic –hydrophilic interactions.

Investigations of (solute-solute) and (solute-solvent) interactions in ternary {amino acids + 1-dodecyl-3-methylimidazolium bromide [C12mim] [br] + water} mixtures at different temperatures

Density and speed of sound of an aqueous solution of glycine and L-valine containing 1-dodecyl-3-methylimidazolium bromide, [C12mim] [Br], have been determined at T= (288.15 K to 308.15 K). From experimental density, the apparent molar volumes (Vϕ), the apparent molar volumes at infinite dilution (Vϕ0) and partial molar volume of transfer ΔVϕ0have been calculated. The values of apparent molar volumes (Vϕ) are positive for both glycine and L-valine and increase with the increase in temperature and concentration of 1-dodecyl-3-methylimidazolium bromide. On the other hand speed of sound data have been used to determine partial molar isentropic compression (Kϕ,s), partial molar isentropic compression at infinite dilution (Kϕ,s0) and partial molar isentropic compression of transfer ΔKϕ,S0. The obtained volumetric and acoustic parameters will be helpful to understand mixing effects, structural changes and other complex biological processes between head and side-chain groups of glycine or L-valine and ionic liquid [C12mim] [Br] in aqueous medium.

Molecular interactions studies of doxycycline hyclate in water, aqueous L-phenylalanine and glycyl glycine at different temperatures by using volumetric, ultrasonic and viscometric parameters

The density, sound velocity and viscosity of doxycycline hyclate in water, aqueous solution of L-phenylalanine and aqueous solution of glycyl glycine have been determined at different temperatures (305.15, 310.15, 315.15 and 320.15) K. The calculated values of partial molar volume (V_ϕ^o), standard partial molar volume of transfer (〖Δ_tr V〗_ϕ^o), partial molar adiabatic compressibility (κ_(ϕ,s)^o) and partial molar adiabatic compressibility of transfer (〖Δ_tr κ〗_(ϕ,s)^o) for doxycycline hyclate in water, aqueous solution of L-phenylalanine and aqueous solution of glycyl glycine infer the dominance of ion-hydrophilic interactions over hydrophobic-hydrophobic interactions. The Jones-Dole viscosity B-coefficient, viscosity B-coefficient of transfer (ΔtrB), free energy of activation of viscous flow per mole of pure solvent (〖Δμ〗_1^(o*)) and solute (〖Δμ〗_2^(o*) ), respectively, activation entropy (〖ΔS〗_2^(o*)) and activation enthalpy (〖ΔH〗_2^(o*)) of doxycycline hyclate in water, aqueous solution of L-phenylalanine and aqueous solution of glycyl glycine also have been calculated using viscosity data. The structure making and breaking behaviour of doxycycline hyclate in water, aqueous solution of L-phenylalanine and aqueous solution of glycyl glycine are obtained from the values of Hepler’s constant i.e.((δ^2 V_ϕ^o)/(δT^2 )) and (dB/dT). The presence and absence of caging effect has been studied with the help of partial molar adiabatic expansibility (E_ϕ^o). The isobaric thermal expansion coefficient (α^o= (E_ϕ^o)/(V_ϕ^o )), intermolecular free length and acoustic impedance for doxycycline hyclate in water, aqueous solution of L-phenylalanine and aqueous solution of glycyl glycine also have been determined.