Dissociation Of Glycine Research Articles

Review of effect of temperature and thermodynamic quantities upon acidic dissociation of Glycine in 10, 20 and 30% dioxane (m/m) in dioxane-water system at 288.15K, 298.15K, 308.15K and 318.15K by e.m.f. measurement

<p>For study of effect of temperature and thermodynamic quantities upon acidic dissociation of Glycine in 10, 20, and 30% dioxane(m/m) content in dioxane-water system at 288.15K, 298.15K, 308.15K, and 318.15K, the following types of cell has been set up:</p> <p>H<sub>2</sub>(Pt) | Glycine, HCl, X% Dioxane, Hg<sub>2</sub>Cl<sub>2 </sub>| Hg</p> <p>m<sub>1 </sub> m<sub>2</sub> (C-1)</p> <p>in 10, 20, and 30% dioxane in dioxane-water system at 288.15K to 318.15K at an interval of 10K, and e.m.f. of the cell was given by:</p> <p>E = E<sup>0</sup> - (2.303RT/F) (log m<sub>H</sub><sup>+</sup> m<sub>Cl</sub><sup>_</sup> + log Ɣ<sub>H</sub><sup>+</sup> Ɣ<sub>Cl</sub><sup>_</sup>) (1)</p> <p>where,</p> <p>log Ɣ<sub>H</sub><sup>+</sup> Ɣ<sub>Cl</sub><sup>_</sup> = - (2A`√μ/(1+√μ) ) + b<sub>1</sub>μ (2) </p> <p>log K<sub>1</sub> - b<sub>1</sub>μ = log K<sub>1</sub>(A) – (2A`√μ/(1+√μ)) (3)</p> <p>The equation (2) is called Modified Davies equation given by B. Prasad<sup>1</sup> for calculating activity coefficient in the system.</p> <p>From equation (3), acidic dissociation constant of glycine was calculated<sup>2-5</sup> by extrapolating the graph at μ=0 in 10, 20, and 30% dioxane (m/m) in dioxane-water system from 288.15K to 318.5K at an interval of 10K, and then standard free energy change, standard enthalpy change, and standard entropy change were calculated by thermodynamic relations:</p> <p> ΔG<sup>0</sup> = -RTlnK<sub>1</sub> (4)</p> <p>and ΔG<sup>0</sup> = ΔH<sup>0 </sup>- TΔS<sup>0 </sup> (5)</p> <p>and by least square method<sup>6</sup>.</p>

Study of Ion-Solvent Interaction during Acidic Dissociation of Glycine in 10, 20 And 30% Dioxane in Dioxane-Water System At 318.15K by Potentiometric Method

Ion solvent interaction was studied by free energy transfer during acidic dissociation of Glycine in 10,20 and 30% dioxane in dioxane-water system at 318.15K and free energy was given by the thermodynamic relation </p> <p>ΔG<sub>t</sub> = 2.303RTΔpK<sub>1</sub></p> <p>where ΔG<sub>t</sub> = free energy transfer when solvent change from water to dioxane-water.</p> <p>ΔpK<sub>1</sub> = pK<sub>s1</sub>-pK<sub>w1</sub></p> <p>where pK<sub>w1</sub> = -log K<sub>w1</sub> negative logarithmic of dissociation constant of glycine in water.</p> <p>pK<sub>s1</sub> = -log K<sub>s1</sub>negative logarithmic of acid dissociation constant of glycine in dioxane-water.</p> <p>For this purpose acidic dissociatio constant of glycine was determined potentiometrically by setting up the cell:</p> <p>H<sub>2</sub>(Pt) | Glycine, HCl, X% Dioxane, Hg<sub>2</sub>Cl<sub>2 </sub>| Hg …(C-1)</p> <p>m<sub>1 </sub>m<sub>2</sub> (100-x)% water</p> <p>and e.m.f. of the cell was given by the formula:</p> <p>E = E<sup>0</sup>- 2.303RT/F (log m<sub>H</sub><sup>+</sup> m<sub>cl</sub><sup>-</sup> + log Ɣ<sub>H</sub><sup>+</sup> Ɣ<sub>Cl</sub><sup>_</sup>) …(1)</p> <p>In the equation (1) activity coefficient of the solution has been taken into consideration to understand ion solvent interaction and activity coefficient is given by the relation:</p> <p>log Ɣ<sub>H</sub><sup>+</sup> Ɣ<sub>Cl</sub><sup>_</sup> = -2A¢√μ/(1+ √μ) +ꞵ<sub>1</sub>μ …(2)</p> <p>Equation (2) is modified Davies equation given by B. Prasad and hence acidic dissociation constant of glycine can be calculated by calculating m<sub>H</sub><sup>+</sup> as: log m<sub>H</sub><sup>+ </sup>= (E<sup>0 </sup>- E)/K - log m<sub>Cl</sub><sup>_</sup> + (2A¢√μ/(1+ √μ)) - ꞵ<sub>1</sub>μ …(3)

The Structural Basis of Negative Cooperativity between Subunits of the NMDA Receptor

NMDA receptors are crucial signaling proteins in the mammalian central nervous system and play roles in development, synaptic maturation and learning and memory. As such, the biophysical properties of these channels can profoundly shape physiological function. For example, the biophysical property of pore block by magnesium ions endows NMDA receptor with the ability to act as synaptic co-incidence detectors. Here we examine the biophysical property of negative co-operativity between the co-agonists glutamate and glycine. It has been previously reported that the glutamate bound to the GluN2A subunit speeds the dissociation of glycine from the GluN1 subunit. Using rapid perfusion methods on outside-out patches, we confirm that glycine dissociates from the GluN1 subunit roughly 3 fold faster when glutamate is bound to GluN2A then when GluN2A is unliganded. We also report that glutamate dissociates from GluN2A approximately 2 fold faster when glycine is bound compared to when GluN1 is unoccupied. We hypothesize that this co-operativity arises from long unstructured loops of amino acids, found in the upper ligand binding domain (LBD) lobes of GluN1 and GluN2, interacting between LBD dimers. To test this, we are using fluorescence labelling of unnatural amino acids and luminescence resonance energy transfer experiments to measure conformational changes between LBDs of different dimers under varying occupancy conditions. By combing these measures of conformational change with electrophysiology and mutations blocking co-operativity, we aim to elucidate the structural mechanism of negative co-operativity at NMDA receptors.

DFT periodic study of adsorption of glycine on the (0 0 0 1) surface of zinc terminated ZnO

Bio-inorganic interfaces attract attention due to numerous possible applications in industry. Following this interest, we performed a molecular modelling of glycine adsorption on Zincite (ZnO). Adsorption of neutral, zwitterionic and anionic glycine on zinc-terminated polar (0 0 0 1)-ZnO surface, was studied using a periodic Density Functional Theory based method. Several coverages were considered, from the limit of the isolated molecule to the monolayer and bilayer coverage. The interaction of each glycine function (carboxylate and amine) with the Zn–ZnO surface is investigated separately, and then the adsorption through both functions is studied. We found that glycine adsorbs on Zn–ZnO surface at low coverage preferentially in the anionic form with dissociation, in a parallel orientation to the surface. The carboxylate moiety forms a Zn–OCO–ZnO ring two surface Zn atoms, and an additional Zn–N bond is formed between the amine function and a surface Zn atom; the proton, product of dissociation, forms a hydride like Zn–H at the surface. The formation of OH groups with oxygens of the underlying layer was also considered, but is less stable. At higher coverage, (2.6 G/nm 2) the dissociation of glycine into a glycinate ion is again the most stable configuration. An organized glycinate layer is formed, in which the glycine molecules adopt the ZnO honeycomb structure. Still increasing the coverage leads to the formation of a Zn–glycinate bilayer as shown by ab initio molecular dynamics simulations. In the first layer glycine molecules adopt the honeycomb ZnO lattice. The second layer consists in a Zn–glycinate complex, with a Zn atom extracted from the surface.

Ionic dissociation of glycine, alanine, valine and proline as induced by VUV (21.21 eV) photons

Ionic fragmentation of the sublimated α-amino acids glycine, l -alanine, l -proline and l -valine has been studied using a time-of-flight mass spectrometer coupled to a He I lamp ( hν = 21.21 eV). Partial ion yields (branching ratios) and kinetic energy releases for the fragments have been determined. The spectra basically resemble available mass spectra obtained through electron impact (70 eV) demonstrating that the ionic dissociation of these compounds, induced by energetic electrons, is also dominated by processes involving low-energy valence-shell orbitals. A previously unreported fragment has been observed at m/z = 32 ( O 2 + ) in the spectra of valine and proline.

Adsorption of glycine on a NiAl(1 1 0) alloy surface

The adsorption and desorption of glycine (NH 2CH 2COOH), vacuum deposited on a NiAl(1 1 0) surface, were investigated by means of Auger electron spectroscopy (AES), low energy electron diffraction (LEED), temperature-programmed desorption, work function (Δ φ) measurements, and ultraviolet photoelectron spectroscopy (UPS). At 120 K, glycine adsorbs molecularly forming mono- and multilayers predominantly in the zwitterionic state, as evidenced by the UPS results. In contrast, the adsorption at room temperature (310 K) is mainly dissociative in the early stages of exposure, while molecular adsorption occurs only near saturation coverage. There is evidence that this molecularly adsorbed species is in the anionic form (NH 2CH 2COO −). Analysis of AES data reveals that upon adsorption glycine attacks the aluminium sites on the surface. On heating part of the monolayer adsorbed at 120 K is converted to the anionic form and at higher temperatures dissociates further before desorption. The temperature-induced dissociation of glycine (<400 K) leads to a series of similar reaction products irrespective of the initial adsorption step at 120 K or at 310 K, leaving finally oxygen, carbon and nitrogen at the surface. AES and LEED measurements indicate that oxygen interacts strongly with the Al component of the surface forming an “oxide”-like Al–O layer.

Surface-Enhanced Raman Spectroscopic Studies of Dissociative Adsorption of Amino Acids on Platinum and Gold Electrodes in Alkaline Solutions

The dissociative adsorption of amino acids on Pt and Au electrodes in 0.1 M NaOH solutions was studied by cyclic voltammetry and surface-enhanced Raman spectroscopy (SERS). The intermediate species has been determined as adsorbed cyanide, which is designated by a potential-dependent vibration band around 2110 cm-1 on both Pt and Au surfaces. The dissociation of glycine can be observed on Pt surface in a wide potential region to form cyanide, while the dissociation of serine and threonine occurs at relatively high potentials along with the oxidation of their functional groups. The onset potential of dissociation of amino acids on the Pt surface increases in the order glycine < threonine < serine. It has been revealed that the self-inhibition of amino acid oxidation is originated from the strongly adsorbed cyanide, which is oxidized at potentials above 0.2 V vs SCE. On gold surfaces, cyanide species can be formed only from anodic oxidation of amino acids. The present study reveals characteristic interaction...

Thermodynamics of dissociation of glycine in aqueous ethanol and urea solutions

The dissociation enthalpies of glycine in aqueous ethanol and urea solutions have been determined at 298.15 K by LKB-2277 BioActivity Monitor. Combined with the corresponding Gibbs free energies, the dissociation entropies have been calculated. The results have been interpreted with the point of view of structure alteration of the two solvents.

Multiple sites of action of neomycin, Mg2+ and spermine on the NMDA receptors of rat hippocampal CA1 pyramidal neurones.

1. The effects of neomycin on NMDA-evoked currents in isolated CA1 hippocampal pyramidal neurones were investigated and single channel activity was examined in outside-out patches taken from cultured hippocampal neurones. The effects of neomycin on two combinations of NMDA receptor subunits (NR1a-NR2A and NR1a-NR2B) expressed in human embryonic kidney (HEK293) cells were also studied. 2. Neomycin (0. 01-1 mM) caused a potentiation of NMDA-activated currents in all neurones examined. No evidence of a voltage-dependent depression was observed in whole-cell recordings. 3. In outside-out patch recordings relatively low concentrations (30 and 100 microM) of neomycin caused a voltage-dependent reduction in single channel current amplitude as well as a large increase in the frequency of channel opening. 4. In saturating concentrations of glycine, neomycin enhanced NMDA-activated currents and this glycine-independent enhancement was confirmed using recombinant NR1a-NR2B receptors. Neomycin substantially increased the potency of glycine for the receptor by reducing the rate of dissociation of glycine from the receptor. Neomycin demonstrated a glycine-dependent enhancement of currents mediated by the NR1a-NR2A combination of subunits but a paradoxical depression was observed in saturating concentrations of glycine. 5. Neomycin increased the rate of deactivation of glutamate-activated currents consistent with neomycin causing a reduction in the affinity of the receptor for agonist. 6. These results indicate that neomycin has multiple and complex effects on NMDA receptors.

Thermal desorption spectroscopy study of native and electron irradiated glycine overlayers on graphite(0001)

The adsorption of glycine deposited at 95 K on the graphite basal (0001) plane was studied from submonolayer to multilayer coverages by thermal desorption spectroscopy (TDS) and high- resolution electron loss spectroscopy (HREELS). At all coverages glycine adsorbs in three-dimensional (3D) clusters (no distinct monolayer formation was observed). Glycine molecules desorb around 300 K in a single desorption peak (α peak) with a binding energy of 0.85 eV, representing the cohesive energy of glycine. HREELS analysis of these overlayers is severely hampered by charging of the 3D clusters; only one vibrational feature at 26 meV was observed reproducibly. The glycine adlayers are very sensitive to electron irradiation. This effect was studied in some detail by TDS. Electrons of ∼50 eV energy cause: (i) conversion of glycine molecules from the α state to (surprisingly) a more weakly bound β state (desorption temperature ∼250 K), interpreted as 2D adsorbates, and (ii) dissociation of glycine into fragments that either desorb spontaneously or adsorb on the bare graphite surface, and desorb upon heating (γ peak) at 170 K, i.e., earlier than both the α and β peaks. The cracking pattern of the γ peak suggests that the electrons break the C–C bond in glycine, into COOH and H2N–CH2 fragments.

Multiple effects of spermine on N-methyl-D-aspartic acid receptor responses of rat cultured hippocampal neurones.

1. The modulation by polyamines of responses to N-methyl-D-aspartic acid (NMDA) was studied using a rapid perfusion system and whole-cell voltage-clamp recording from rat hippocampal neurons in dissociated culture. 2. Concentration jump responses to 100 microM NMDA in the presence of 10 microM glycine revealed potentiation by 3 mM spermine at a membrane potential of +60 mV, but depression at -120 mV; the degree of potentiation at +60 mV was variable from cell to cell while marked depression at -120 mV was observed in all cells. The depression of responses to NMDA by spermine was highly voltage dependent (z delta = 1.17) with an apparent equilibrium dissociation constant for block at 0 mV of 27 mM. 3. Analysis of spermine dose-potentiation curves for responses recorded at +60 mV in the presence of 10 microM glycine revealed a half-maximal effect at 125 microM. Under the same conditions, but at -60 mV, analysis of spermine-evoked depression was performed for cells with less than 5% potentiation at +60 mV, and revealed half-maximal inhibition at 344 microM. 4. Dose-response analysis for the glycine-sensitive activation of NMDA receptors at +60 mV revealed a 3.5-fold increase in apparent affinity for glycine in the presence of 1 mM spermine. This increase in affinity for glycine was accompanied by a 3.3-fold decrease in the rate of development of glycine-sensitive desensitization, and a 2.4-fold decrease in the rate of dissociation of glycine from NMDA receptors, while the rate constant for dissociation of NMDA was not reduced. 5. In the presence of non-saturating concentrations of glycine, spermine-induced potentiation at +60 mV developed with two exponential components: a slow glycine-sensitive component, the amplitude and time constant of which decreased with increasing glycine concentration (30 nM glycine, amplitude = 80.2 +/- 5.1%, tau = 780 +/- 79 ms; 3 microM glycine, amplitude = 22.6 +/- 7.1%, tau = 45 +/- 13 ms), and a faster component (tau < 20 ms at all concentrations of glycine), the amplitude of which varied from cell to cell, and which became larger with increase in concentration of glycine. When responses to the application of spermine were measured in the presence 10 microM L-alanine instead of 100 nM glycine, the slow component of potentiation was absent.(ABSTRACT TRUNCATED AT 400 WORDS)

Competitive antagonists and partial agonists at the glycine modulatory site of the mouse N‐methyl‐D‐aspartate receptor.

1. Kynurenate (Kyn), 7-chlorokynurenate (7-Cl-Kyn), 3-amino-1-hydroxypyrrolid-2-one (HA-966) and D-cycloserine are known to bind to the glycine site that modulates the N-methyl-D-aspartate (NMDA) response of vertebrate central neurones. The effects of these compounds were investigated with patch-clamp and fast-perfusion techniques on mouse cortical neurones in primary culture in an effort to establish whether they act as antagonists, partial agonists and/or inverse agonists of glycine. A fast drug application method allowed the study of both steady-state and transient responses. 2. The analysis of steady-state responses indicates that the main effects of Kyn and 7-Cl-Kyn are those expected from competitive antagonists of glycine, with a dissociation constant of 15 microM for Kyn, and of 0.3 microM for 7-Cl-Kyn. Concentration jumps indicate that at all concentrations of glycine, and in particular in the absence of added glycine, the blockade by Kyn and 7-Cl-Kyn develops at a rate which is close to the rate of dissociation of glycine from its binding site and is independent of antagonist concentration. 3. The main effects of D-cycloserine and of HA-966 are those of partial agonists of high and low efficacy, respectively. In the absence of added glycine, D-cycloserine always produced a potentiation, while HA-966 produced either a potentiation or an inhibition. This can be explained by assuming the presence of a variable level of contaminating glycine. With both D-cycloserine and HA-966, concentration jumps produced biphasic relaxations in which the onset rate of the slow component was, here again, close to the rate of dissociation of glycine from its binding site. 4. These results can be interpreted by assuming that (1) Kyn and 7-Cl-Kyn are competitive antagonists of glycine, (2) HA-966 and D-cycloserine are partial agonists, (3) in the absence of added glycine some glycine is present in the extracellular solution and (4) the response in the total absence of glycine is very small or negligible.

The Effects of Certain Salt Mixtures on the Dissociation of Glycine and Alanine.

ADVERTISEMENT RETURN TO ISSUEPREVArticleNEXTThe Effects of Certain Salt Mixtures on the Dissociation of Glycine and Alanine.A. C. Batchelder and Carl L. A. SchmidtCite this: J. Phys. Chem. 1939, 43, 9, 1121–1132Publication Date (Print):September 1, 1939Publication History Published online1 May 2002Published inissue 1 September 1939https://doi.org/10.1021/j150396a002RIGHTS & PERMISSIONSArticle Views28Altmetric-Citations1LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (533 KB) Get e-Alerts