Glycine Solution Research Articles

Light-induced effects in glycine aqueous solution studied by Fourier transform infrared-emission spectroscopy and ultraviolet-visible spectroscopy

Although amino acids are insensitive to visible light, as is generally accepted, we show that particular light-matter interaction can break this obviousness. Using sensitive (FT-IR)-technique in a combination of a broadband visible light source, we registered emission spectra of glycine in the range 2500-500 cm−1. Sensitivity of the infrared emission spectrum to the exciting power –induced changes in the glycine structure was demonstrated experimentally.Vibrational spectra of glycine displayed the prominent spectral features of CH2, COO-, COOH, NH+3 groups in the “fingerprint region”. Simultaneous appearance of ionised COO- and unionised COOH forms of glycine in solution at neutral pH clearly indicated that visible light induces the partial protonation of COO- groups; if so, visible light irradiation should lead to occurrence of dimers or dimeric hydrogen - bonded structures. Spectroscopic and microscopic evidence of visible light-mediated formation of aggregates and nucleus in aqueous solution was presented.Electronic absorption/emission spectra of glycine in aqueous solution were primarily characterized in the near ultraviolet-visible region (240-600 nm). Negligible absorption near 270 nm was observed for a 1.0 M solution and dramatically enhanced with its “aging”. Moreover, an extension of the absorption edge into the region above 400 nm could be seen. Due to the visible light irradiation, we observed modification of electronic structure or occurrence of additional species causing changes in absorption of glycine amino acid. For “aged” solution, it was shown that excitation spectra corresponding to the different emission wavelengths were entirely different, at that each excitation-spectral band had a characteristic emission band.Communicated by Ramaswamy H. Sarma

Fast, facile synthesis method for BAL-mediated PVP-bismuth nanoparticles

Bismuth is a water-insoluble non-toxic metallic element used in a wide array of pharmaceutical products, cosmetics, and catalysts, among others. Yet, the research regarding the use of bismuth nanoparticles (BiNPs) for antimicrobial treatments is scarce. Most of the current protocols for synthesizing BiNPs suitable for medical uses cannot be easily replicated in non-specialized laboratories. The objective of this work is to provide a fast, facile and economical method for synthesizing BiNPs. Bismuth nanoparticles were synthesized by a chemical reduction process, in less than 1 h, in a heated alkaline glycine solution; by the chelation and reduction of the bismuth (III) ions using dimercaptopropanol (BAL) and sodium borohydride respectively, and then coated and stabilized by polyvinylpyrrolidone (PVP). The resulting PVP-BiNPs were characterized by UV–Vis spectrophotometry and transmission electron microscopy (TEM).• We describe a simple, rapid and inexpensive method for the synthesis of bismuth nanoparticles.• This method allows synthesizing small nanoparticles with an aspect ratio close to one.• Bismuth nanoparticles have antimicrobial properties, this easy-to-replicate protocol may further the research on bismuth nanoparticles for biomedical applications.

Hydration and aggregation of a simple amino acid: The case of glycine

Glycine is the smallest and simplest amino acid with several applications in the chemical and pharmaceutical industries. To date, a wide conflicting literature about the hydration and aggregation of glycine is available. The aim of the present work is to study the hydration and the aggregation properties of glycine in aqueous solution as a function of glycine concentration and temperature. These features are determined at atomistic level, by neutron diffraction with isotopic H/D substitution, augmented by a Monte Carlo simulation. Concerning the glycine-glycine aggregation, the coexistence of direct and water-mediated interactions is demonstrated. In particular, chains or cyclic dimers are preferred, depending on concentration and temperature. Finally, the perturbation of the water network, induced by glycine, is reported and described in detail. Present results give relevant information about formation of polymers and crystallization seeds in glycine solutions.

Amino Acid as a Novel Wettability Modifier for Enhanced Waterflooding in Carbonate Reservoirs

SummaryReservoir wettability plays an important role in waterflooding, especially in fractured carbonate reservoirs since oil recovery from the rock matrix is inefficient because of their mixed wettability. This paper presents the first investigation of amino acids as wettability modifiers that increase waterflooding oil recovery in carbonate reservoirs.All experiments used a heavy-oil sample taken from a carbonate reservoir. Two amino acids were tested, glycine and β-alanine. Contact angle experiments with oil-aged calcite were conducted at room temperature with deionized (DI) water, and then at 368 K with three saline solutions: 243 571-mg/L salinity formation brine (FB), 68 975-mg/L salinity injection brine 1 (IB1), and 6898-mg/L salinity injection brine 2 (IB2). IB2 was made by dilution of IB1.The contact angle experiment with 5-wt% glycine solution in FB (FB-Gly5) resulted in an average contact angle of 50°, in comparison to 130° with FB, at 368 K. Some of the oil droplets were completely detached from the calcite surface within a few days. In contrast, the β-alanine solutions were not effective in wettability alteration of oil-aged calcite with the brines tested at 368 K.Glycine was further studied in spontaneous and forced imbibition experiments with oil-aged Indiana limestone cores at 368 K using IB2 and three solutions of 5 wt% glycine in FB, IB1, and IB2 (FB-Gly5, IB1-Gly5, and IB2-Gly5). The oil recovery factors from the imbibition experiments gave the Amott index to water as follows: 0.65 for FB-Gly5, 0.59 for IB1-Gly5, 0.61 for IB2-Gly5, and 0.33 for IB2. This indicates a clear, positive impact of glycine on wettability alteration of the Indiana limestone cores tested.Two possible mechanisms were explained for glycine to enhance the spontaneous imbibition in oil-wet carbonate rocks. The primary mechanism is that the glycine solution weakens the interaction between polar oil components and positively charged rock surfaces when the solution pH is between glycine's isoelectric point (pI) and the surface's point of zero charge (pzc). The secondary mechanism is that the addition of glycine tends to decrease the solution pH slightly, which in turn changes the carbonate wettability in brines to a less oil-wet state.The amino acids tested in this research are nontoxic and commercially available at relatively low cost. The results suggest a new method of enhancing waterflooding, for which the novel mechanism of wettability alteration involves the interplay between amino acid pI, solution's pH, and rock's pzc.

Extraction of copper and the co-leaching behaviour of other metals from waste printed circuit boards using alkaline glycine solutions

Waste printed circuit boards (WPCBs) are a complicated and valuable fraction of electric and electronic waste. The recycling of them is critical to avoid environmental pollutions and to reuse resources. In particular, the e-waste import bans have been implemented in many traditional waste-importing countries in recent years, which is making the sustainable recycling essential and crucial for the advanced economies. In this study, a sustainable approach using alkaline glycine solution for the extraction of copper (Cu) from WPCBs, and the leaching behaviour of other metals (Ni, Al, Fe, Pb, Sn, Co, Zn, Au, Ag and Pd) is presented. Various leaching parameters, including initial pH, glycine concentration, solid content, oxidant, particle size, temperature and time were investigated. A maximum Cu extraction of 96.5 % was achieved, with high co-extraction of base metals (BMs). The extraction of BMs was dependent on the pH of leaching solution, which was highly correlated with other variables. BMs extraction was largely influenced by glycine concentration and solid content, while the sensitivity to H2O2, temperature, and particle size was insignificant. SEM-EDS analysis of leaching residue indicated that the unleached Cu may be locked in inert layers, e.g. Sn/solder materials. The kinetic analysis showed that the extraction of Cu from WPCBs (100 % <2 mm) at room temperature with ambient O2 in air as an oxidant was mainly controlled by internal diffusion.

Comparative study of equilibrium characteristics of Cu|Cu(II), Cu(I), glycine system containing sulfate or perchlorate as a supporting electrolyte

The distribution of species in Cu(II)-glycine solutions, containing sulfate or perchlorate as a supporting electrolyte, is considered. Substantial differences are observed at pH &lt; 4.5, where the molar fraction of monoligand complex (associate) CuSO4 reaches up to 20 percent of the total Cu(II) concentration. Cu(I)-containing species are generated at the Cu|solution interface. These are Cu+ aqua-complexes (acid media) or mono- and bidentate Cu(I)-glycine complexes (alkaline media). The addition of sulfate reduces the content of Cu+ ions, but practically does not affect the distribution of Cu(I) complexes. The study of acidbase equilibria involving Cu+ ions shows that the thermodynamic probability of Cu2O formation remains low in both perchlorate and sulfate media. HSO4– ions formed in acid media should be treated as rather labile proton donors. This is quantitatively confirmed by experimental data, according to which the rate of hydrogen evolution increases correspondingly when perchlorate is replaced by sulfate in glycine solutions.

Volumetric Properties of Amino Acids in Aqueous Solutions of Glucosamine Hydrochloride at T = 293.15–313.15 K

The densities (ρ) of glycine, L-alanine, L-serine, and L-threonine solutions in 0.05, 0.10, 0.15, 0.20, and 0.30 mol kg–1 aqueous solutions of D-glucosamine hydrochloride have been measured at T = 293.15, 298.15, 303.15, 308.15, and 313.15 K. The apparent molar volumes (Vϕ), limiting partial molar volumes ($$V_{\phi }^{0}$$) of the amino acids have been calculated from the density data. Transfer partial molar volumes (∆tr$$V_{\phi }^{0}$$) and hydration numbers from water to the aqueous solutions of D-glucosamine hydrochloride were also obtained. These parameters of volumetric properties can help to understand the mixing effects and interactions between amino acids and D-glucosamine hydrochloride aqueous solution.

Cu adsorption behaviours onto chelating resins from glycine-cyanide solutions: Isotherms, kinetics and regeneration studies

A method is presented to remove and recover copper from copper-gold glycinate solutions using an iminodiacetic functionalized resin with subsequent regeneration. The adsorption/desorption approach was evaluated for a glycine leaching process which was shown to be effective for the dissolution of gold and copper from different gold-copper ores and concentrates. In this process, glycine is the lixiviant in the presence of very low cyanide concentration as a synergistic reagent. The copper species in glycine-cyanide process are mainly present as cupric glycinate and a low concentration of cuprous dicyanide and no free cyanide. While cupric glycinate does not load well onto activated carbon, cuprous dicyanide is problematic due to its high carbon affinity and co-loading with gold onto activated carbon, thereby requiring the removal of most of the copper prior to the gold recovery. In this study, the use of ion-exchange resins as one of the possible downstream recovery processes for gold and copper from glycine-cyanide solutions was tested. The isotherms and kinetics of gold and copper (cupric copper (Cu2+)) adsorb onto the chelating resin (Puromet MTS9300) from their alkaline glycinate and cyanide complexes were studied. Results show that the [CNT−]: [CuT] molar ratio has significant effects on the adsorption of CuT, due to the change in Cu2+/Cu+ ratio in the solutions, where [CN−T] is the total cyanide in the system (free cyanide being zero). The results show that the chelating resin is selectively adsorbed cupric (Cu2+) over cuprous (Cu+) ions. The adsorption results were fitted to both the Freundlich and Langmuir isotherm models, while the Langmuir model shows a better correlation. The adsorption kinetic data of Cu2+ is well fitted to the pseudo-second-order model. Alkaline glycine solutions in the presence of NaCl was selected as the main eluent for the resin elution study. The multi-cycle adsorption/desorption tests showed that the resin adsorption and regeneration efficiencies are not significantly changed after five cycles of adsorption/desorption. Microscopic visual analysis by using scanning electron microscopy (SEM) showed that there is no significant change in shape and size of the resins, although more cracks were observed after the 5 cycles of adsorption/desorption.

Leaching and ion exchange based recovery of nickel and cobalt from a low grade, serpentine-rich sulfide ore using an alkaline glycine lixiviant system

The paper presents the outcomes of exploratory research relating to the atmospheric pressure and ambient temperature leaching of nickel and cobalt from a Western Australian low grade, disseminated, nickel-cobalt sulfide ore, and the subsequent recovery using ion exchange (IX) using alkaline glycine solutions in mildly oxidizing environments. The results present a foundation for a direct leach approach at ambient conditions, particularly if upstream opportunities are considered (heap leach, in-situ leach, or vat leach, or bulk ore leach) from low grade Ni-Co resources. The results for cobalt are particularly exciting given the low recovery of cobalt in most smelting operations and the loss of cobalt to converter slags in conventional approaches. In addition, significant nickel losses are often incurred to flotation cleaner tailings to make a smeltable concentrate at an acceptable level of magnesium. The study showed that even though glycine-based leach rates for Ni and Co are slow, no passivation was observed and about 83.5% Ni and 76.3% Co were extracted at room temperature using conventional bottle rolls over a 672 h period using a multistage extraction (i.e. leachate decant and reagent refresh with either new reagent or recycled barren raffinate). The ore contained cobalt-bearing pentlandite as the predominant Ni-Co mineralization, with Kaolinite-serpentine group, magnesite and hydrotalcite the predominant oxide and pyrrhotite as the predominant sulfide gangue minerals. The effects of glycine concentration, pH and temperature have been studied. It was found that leaching at pH 10.0 gave significant better leach Ni and Co extraction than operating at higher pH of 11.5. In glycine leach campaigns, the dissolution of iron, magnesium, silicon, manganese and other impurities were insignificant. This is particularly important for iron removal which would normally have posed a significant solid-liquid separation and waste disposal cost and magnesium, given the very high levels of magnesium that would normally have dissolved from such ores in acidic systems. Excellent recovery of Ni and Co from leach solutions was achieved by a selected ion exchange resin (Purolite S930Plus) and high Ni and Co dissolution was achieved using recycle glycine solutions after metals adsorption and pH adjustment.

Viscometric and Conductometric Studies of Doxycycline Hyclate in Water, Aqueous Glycine and L-Alanine Solutions at Different Temperatures

To investigate the behaviour of doxycycline hyclate in water, aqueous glycine and aqueous L-alanine solutions, the viscometric and conductometric studies have been conducted at different temperatures. Viscosity data has been used to derive the Jones-Dole viscosity B-coefficient, temperature derivative of B-coefficient (dB/dT), viscosity B-coefficient of transfer (ΔtrB), free energy of activation of viscous flow per mole of solvent (Δμ1 o*) and solute (Δμ2o*) respectively, activation entropy (ΔS2o*) and activation enthalpy (ΔH2o*). Conductance data has been used to compute Walden product (Λm oηo) and temperature coefficient of Walden product (dΛmoηo/dT) for doxycycline hyclate in water, and in aqueous glycine and aqueous L-alanine solution. The positive values of B-coefficient, ΔtrB indicate the prevailing of hydrophilic-ionic interactions in the systems under examination. The negative values of dB/dT and positive values of temperature coefficient of Walden product infer structure maker tendency of doxycycline hyclate in water, and in aqueous glycine and aqueous L-alanine solution. Transfer energy parameters indicate the breaking of intermolecular bonds in transition state which means that formation of activated complex is unfavourable

Viscosity–Composition Properties of Glycine and L-Alanine Solutions in Aqueous Solutions of Tributylmethylphosphonium Methylsulfate Ionic Liquid at 303–333 K

Densities and viscosities of glycine and L-alanine solutions in aqueous solutions of tributylmethylphosphonium methylsulfate were measured at 303–333 K under atmospheric pressure. These data were used to calculate apparent molar volume ( $${{\phi }_{V}}$$ ), standard partial molar volume ( $$\phi _{V}^{0}$$ ), standard isobaric partial molar expansibility ( $$\phi _{E}^{0}$$ ) and its temperature dependence, the viscosity B-coefficient and solvation number ( $${{S}_{n}}$$ ). Viscosity B-coefficients were used to calculate the free energies of activation of viscous flow. The results were discussed in terms of solute–solute and solute–solvent interactions on the basis of cosphere overlap model and transition state theory.

Fabrication of Liquid Crystal Droplet Patterns for Monitoring Aldehyde Vapors.

A sensing method based on the pattern of liquid crystal droplets was developed for detecting and monitoring low levels of organic aldehyde vapors. Exposure of the LC droplet pattern covered with glycine solution to aldehyde vapors induced an optical signal transition from a bright fan shape to a dark cross appearance, as observed by polarized light microscopy. Aldehyde and glycine react at the air/solution interface to form a Schiff-base compound, which controls the orientation of the LCs and induces a change in the optical signals of the LC droplet pattern. The results show that the glycine/LC droplet pattern system is particularly sensitive and selective to aldehydes. In the actual environment, the sensor is exposed to the aldehyde and the signal transition is completed within a few minutes (2-7 min). The LC-based method has the advantages of simple construction, easy operation, convenient data reading, and shows excellent prospects for real-time detection of aldehyde vapors.

An Alkaline Glycine-Based Leach Process of Base and Precious Metals from Powdered Waste Printed Circuit Boards

Electronic waste (E-waste) is accumulating rapidly globally and pose a significant environmental challenge. One of the ways to cover the cost of waste processing (in addition to reducing the costs associated with landfill) is through recovery of metals. In addition, toxic and dangerous metals can and must be removed prior to repurposing, incineration or pyrolysis of the plastic substrates. E-waste is usually either transported to landfills or processed by pyrometallurgical and hydrometallurgical processes. Recently, a number of hydrometallurgical approaches have been considered in metals recovery from different electronic components. In this study, glycine (amino acetic acid) or its salts is considered as a lixiviant in an alkaline environment for base and precious metals recovery from shredded and ground printed circuit boards (PCBs). It was found that alkaline glycine solutions selectively dissolve copper, zinc, and lead over precious metals. Gold and silver were then recovered in a subsequent leaching step using glycine and small amounts of cyanide (at starvation levels, implying no free cyanide is present). The leach system remains alkaline throughout both stages of processing. In the two-stage glycine leaching system, gold, silver, zinc, lead and copper recoveries were 92.1%, 85.3%, 98.5%, 89.8%, and 99.1% respectively. The recoveries of precious and base metals by direct cyanidation, single stage glycine–cyanide leaching, and ammonia leaching were lower than the recoveries of these metals using the two-stage glycine and glycine–cyanide systems.

Detection of Giardia spp. with formalin/ether concentration in Brassica oleracea (cabbage) and Lactuca sativa (lettuce)

Methods to detect protozoa are needed for food safety monitoring. We evaluated protocols to recover Giardia spp. cysts in Brassica oleracea (cabbage) and Lactuca sativa (lettuce) and then detection was performed by concentrating with formalin/ether solutions and microscopy or immunofluorescence or DNA amplification via PCR. To evaluate this methodology, G. duodenalis cysts were inoculated in triplicate (10 cysts) in 35-g samples of lettuce and cabbage. The method obtaining the highest percentage of recovery in cabbage was sulfamic acid solution plus stirring with stomacher (47.7% ± 7.5). For lettuce, the best method was glycine solution plus stirring with stomacher (46.6% ± 5.3). Inter-observer agreement was of 0.99. Giardia was detected by amplifying specific sequences for the DNA coding SSU rRNA. In 27 lettuce samples and 27 cabbage samples, obtained from supermarkets and street vendors, two lettuce samples (7.4%) and one cabbage sample (3.7%) were positive for Giardia via PCR assay and were sequenced, determining that they were two of assemblage B and one of lettuce to assemblage E. This method is proposed to detect Giardia in vegetables by PCR detection, enabling public health authorities to identify genotypes circulating in food, which will help to establish measures that reduce outbreaks of parasitic diseases associated with contaminated food.

Solution growth of γ-glycine from cadmium sulphate as solvent for frequency doubling applications

Monocrystal nonlinear optical material γ-glycine was synthesized from glycine and cadmium sulphate in 3:1 mol ratio at ambient temperature by using the slow solvent evaporation experiment. Monocrystal γ-glycine crystallized in trigonal crystal structure with non-centrosymmetric space group P32. The signature peak of γ-glycine was confirmed by x-ray powder diffraction examination. Chemical shift and Infrared studies exhibited the presence of chemical group species, resonance signal chemical shifts and functional groups present in the gamma glycine powdered samples. The existence of cadmium Cd element concentration in gamma glycine solution was quantified by inductively coupled plasma optical emission spectrometry (ICP-OES) instrument. Optical information and other parameters of γ-glycine such as crystal transparency, energy band gap, refractive index, electrical susceptibility, extinction coefficient, optical conductivity, electrical conductivity, optical reflectance, transmittance and absorbance was determined using UV–visible-NIR spectrophotometer. Thermal information such as weight-loss profile, thermal stability, decomposition temperature point, melting point and phase transition temperature were determined from TG-DTG and TG-DSC thermograms. The improved phase transition temperature in the TG-DSC thermogram established that suitability of the grown γ-glycine crystal for optoelectronic device fabrication applications. Green colour fluorescence emission was emitted from the crystal. The existence of frequency doubling in the grown γ-glycine crystal was examined.

Investigation of molecular and mesoscale clusters in undersaturated glycine aqueous solutions

In this work DLS, NTA, SAXS and NMR were used to investigate populations, size distributions and structure of clusters in undersaturated aqueous solutions of glycine. Molecular and colloidal scale (mesoscale) clusters with radii around 0.3-0.5 nm and 100–150 nm, respectively, were observed using complementary experimental techniques. Molecular clusters are consistent with hydrated glycine dimers present in equilibrium with glycine monomers in aqueous solutions. Mesoscale clusters previously observed in supersaturated glycine solutions appear to be indefinitely stable, in mutual equilibrium within mesostructured undersaturated solutions across all glycine concentrations investigated here, down to as low as 1 mg/g of water.

Effect of 1-Octyl-3-Methylimidazolium Salicylate as an Active Pharmaceutical Ingredient (API-IL) on the Thermodynamic Behavior of Aqueous Glycine Solutions at T= 298.15 K

Background: The thermophysical properties of 1-octyl-3-methylimidazolium salicylate as an active pharmaceutical ingredient based on ionic liquid have been investigated in the presence of aqueous solutions of glycine. Therefore, the scope of this article was to determine these properties by measuring the densities, speeds of sound, viscosities, electrical conductances and refractive indices for ternary (glycine + 1-octyl-3-methylimidazolium salicylate + water) soloutions at T = 298.15 K. Methods: A commercial density and speed of sound measurement apparatus was used to measure the density and speed of sound data. Viscosities, electrical conductivities and refractive indices of the studied solutions were measured using digital viscometer, conductivity meter and refractometer, respectively. Results: Variety of properties such as partial molar volume of transfer ∆traV0ϕ, partial molar isentropic compressibility of transfer ∆traK0ϕ, viscosity B-coefficients of transfer ∆traB, ion association constants (KA) and molar refraction RD were determined to investigate the solute-solute and solute-solvent interactions in these systems. Conclusion: The positive values of transfer properties including partial molar volume of transfer (∆traV0ϕ), partial molar isentropic compressibility of transfer (∆traK0ϕ), and viscosity B-coefficients of transfer (∆traB) indicated that in these systems, the ion-polar and polar-polar interactions are dominant. The calculated hydration number showed that dehydration of glycine occurs in presence of this ionic liquid.

A Field Procedure To Screen Soil for Hazardous Lead.

Soils retain lead contamination from possible sources such as mining, smelting, battery recycling, waste incineration, leaded gasoline, and crumbling paint. Such contamination is often concentrated in toxic hot spots that need to be identified locally. To address this need, a simple field procedure was designed to screen soil for hazardous Pb for use by the general public. The procedure is a modification of the in vitro soil Pb extraction described by Drexler and Brattin (Hum. Ecol. Risk Assess.2007, 13, 383) and EPA Method 1340, and uses a 0.4 M glycine solution at pH 1.5. A higher soil-to-solution ratio of 1:10 allows for classifying soil samples based on extractable Pb concentrations of <200 mg/kg (low), 200–400 mg/kg (medium), and >400 mg/kg (high) using sodium rhodizonate as a color indicator. The 1:10 soil-to-solution ratio also makes it possible to measure Pb concentrations in the glycine extract solutions on a continuous scale using a portable X-ray fluorescence analyzer. The procedure rather consistently extracts about one-third of the Pb extracted by the standard method across a wide range of Pb concentrations. Manufacturing the kit in larger quantities could reduce the cost of the materials well below the current $5/test.

Selective crystallization of gamma glycine for NLO applications using magnesium sulfate (MgSO4) as an additive

Abstract Crystallization of γ-glycine in the presence of selected concentration (9 g/mL) of tailor-made additive magnesium sulfate heptahydrate salt (MgSO4·7H2O) has been studied at ambient temperature by adopting slow solvent evaporation procedure. The morphological modifications of glycine crystals grown from pure aqueous solutions of glycine and from glycine solutions containing magnesium species in the amount of 0.1 g/mL to 16 g/mL have been investigated thoroughly. The crystalline nature and phase identification of the crystalline material were confirmed by X-ray powder diffraction and SXRD studies. NMR studies revealed the information about the molecular conformation in solution, phase changes, functional groups and chemical environment. FT-IR spectra revealed distinct difference between α and γ-glycine polymorphs in the region around 880 cm−1 to 930 cm−1. The grown γ-glycine crystal had a lower cut-off value at 200 nm and the bandgap value evaluated from the Tauc plot was found to be 5.83 eV. The marked differences between α and γ-polymorphs of glycine were also revealed by DSC thermograms. The mechanical strength of the γ-glycine crystal was studied with the help of Vickers microhardness instrument. Kurtz-powder NLO study proved the generation of second harmonics (i.e. green light emission) in the grown γ-glycine crystal and its efficiency was calculated as 1.44 times better than that of the reference material potassium dihydrogen phosphate.

4-Oxoproline as a Site-Specific Infrared Probe: Application To Assess Proline Isomerization and Dimer Formation.

Due to its unique structure, proline plays important structural and functional roles in proteins. However, this special amino acid lacks an adequate vibrational mode that can be exploited to probe its local electrostatic and hydration status via infrared spectroscopy. Herein, we show that the C═O stretching vibration of a proline derivative, 4-oxoproline, is sensitive to local environment and hence can be used as a site-specific infrared probe. We further validate this notion by applying this unnatural amino acid to assess the thermodynamics of proline cis-trans isomerization in a peptide environment and examine the amino acid dimer formation in concentrated proline and glycine solutions.