Studies of the Stability of Some Amino Acid Carbamates in Neutral Aqueous Solution

Abstract Although glutamine has been considered unstable during storage and therefore difficult to quantitate, recent results suggest this amino acid is stable at low pH ranges. We evaluated the stability of glutamine in plasma and tissue extracts, using fluorometric analysis. The measured concentration of glutamine detected varied linearly up to 0.8 mmol/L for the aqueous solution (r2 = 98.7, P = 0.0001) with a mean (+/- SD) coefficient of variation of 2.41% +/- 0.79%. When glutamine was dissolved in 50 g/L trichloroacetic acid (TCA), the values were essentially unaltered. Glutamine in an aqueous solution and stored at -70 degrees C was stable for at least 16 days; glutamine in TCA was stable for 6-8 days, then decreased to a concentration significantly lower than that of the aqueous solution. The expected and observed concentrations in plasma were equal (r2 = 0.99975) for increasing amounts of added glutamine. Glutamine concentrations in plasma were stable for > 1 year when stored at -70 degrees C. The glutamine of a transplantable rat sarcoma and a normal rat liver could be extracted with 50 g/L TCA with high efficiency (88.6% +/- 1.9% and 90.2% +/- 0.04%, respectively); the extracted glutamine is stable in TCA for at least 7 days without neutralization when stored at -70 degrees C. Fluorometric analysis of glutamine required only a small quantity of plasma (25 microL) or tissue (200 mg) and is a convenient method for quantifying this important amino acid.

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The Stability and Structure of Complex Species Formed in Equilibrium Reactions of Diethyltin(IV) with N-D-Gluconylamino Acids in Aqueous Solution

Zeitschrift für Naturforschung B ◽

10.1515/znb-1995-0408 ◽

1995 ◽

Vol 50 (4) ◽

pp. 515-523 ◽

Cited By ~ 18

Author(s):

B. Gyurcsik ◽

N. Buzás ◽

T. Gajda ◽

L. Nagy ◽

E. Kuzmann ◽

...

Keyword(s):

Aqueous Solution ◽

Amino Acid ◽

Water Soluble ◽

Complex Formation Equilibria ◽

Complex Species ◽

Carboxylate Oxygen ◽

Equilibrium Reactions ◽

Formation Equilibria ◽

The Stability ◽

Ph Range

Complex formation equilibria of diethyltin(IV) with five N-D-gluconylamino acids in aqueous solution (I = 0.1 M, NaClO4) were studied and the stabilities of the species were determined by potentiometric titrations. Diethyltin(IV) complexes of α-amino acid derivatives are water-soluble in the physiological pH range, while in the presence of N-D-gluconyl-β-alanine a precipitate is formed, which dissolves with increasing pH. 13C NMR measurements showed that in the N-D-gluconyl-α-amino acid complexes the ligand is coordinated through its deprotonated carboxylate oxygen, amide nitrogen and C(2)-hydroxy group, while for the soluble N-D-gluconyl-β-alanine complex the ligand is coordinated via the deprotonated carboxylate and C(3)-, C(4)-, C(5)-hydroxy groups. Mössbauer measurements reflected the geometry of the complexes formed.

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Use of N-Carboxyanhydrides in the Synthesis of Dipeptides. Factors Affecting the Yields of Several Alanine and Valine-containing Dipeptides

Canadian Journal of Chemistry ◽

10.1139/v73-194 ◽

1973 ◽

Vol 51 (8) ◽

pp. 1284-1287 ◽

Cited By ~ 4

Author(s):

Eric M. Grovestine ◽

Jean R. Langlois ◽

Ross E. Williams

Keyword(s):

Aqueous Solution ◽

Amino Acid ◽

Side Chains ◽

Organic Base ◽

Factors Affecting ◽

The Stability

A series of dipeptides having aliphatic side chains have been prepared in aqueous solution from alanine and valine NCA. An organic base was used to establish and maintain the pH. After the reaction the amounts of unreacted amino acid nucleophile and the overall yields in the reaction were determined. Our observations have led us to propose that NCA stability, the pKa of the amino acid nucleophile and the stability of the carbamate all can play an important role in determining synthetic yields during these preparations.

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Kinetic study of permanganate oxidation of L-leucine in neutral aqueous solution

Collection of Czechoslovak Chemical Communications ◽

10.1135/cccc19880479 ◽

1988 ◽

Vol 53 (3) ◽

pp. 479-486 ◽

Cited By ~ 15

Author(s):

Enrique Brillas ◽

José A. Garrido ◽

Joaquin F. Perez-Benito ◽

Rosa M. Rodriguez ◽

Jaime de Andres

Keyword(s):

Aqueous Solution ◽

Amino Acid ◽

Kinetic Study ◽

Kinetic Data ◽

Reaction Pathways ◽

Soluble Form ◽

Permanganate Oxidation ◽

Zwitterionic Form ◽

Neutral Aqueous Solution ◽

Ph Range

The permanganate oxidation of L-leucine in aqueous phosphate buffers over the pH range 6.1 – 7.6 is autocatalyzed by the manganese reduction product, a soluble form of colloidal manganese dioxide. The kinetic data for both the non-catalytic and autocatalytic reaction pathways have been obtained, and mechanism in agreement with them proposed. The non-catalytic pathway takes place by reaction between either the anionic or the zwitterionic form of the amino acid and permanganate ion, whereas the autocatalytic pathway is realized by the permanganate oxidation of the amino acid previously adsorbed on the colloid surface.

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REMOVAL OF HEAVY METAL Cr (II), Ni (II), Cu (II), Zn (II), Cd (II), Pb (II) IONS FROM AQUEOUS SOLUTION BY MENTHA PIPERITA EXTRACT

10.32006/eeep.2020.2.1520 ◽

2020 ◽

pp. 15-20

Author(s):

Ersin Yucel ◽

Mine Yucel

Keyword(s):

Aqueous Solution ◽

Metal Ions ◽

High Efficiency ◽

Correlation Coefficients ◽

Langmuir Model ◽

Mentha Piperita ◽

Freundlich Model ◽

Biosorption Capacity ◽

Peppermint Extract ◽

The Stability

In this study, the usage of the peppermint (Mentha piperita) for extracting the metal ions [Mg (II), Cr (II), Ni (II), Cu (II), Zn (II), Cd (II), Pb (II)] that exist at water was investigated. In order to analyze the stability properties, Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherms were used at removing the metal ions and the highest correlation coefficients (R2) were obtained at Langmuir isotherm. Therefore, it is seen that the Langmuir model is more proper than the Freundlich model. However, it was found that the correlation coefficients of removing Ni and Cd is higher at Freundlich model than Langmuir and low at Dubinin-Radushkevich isotherm. It is established that the biosorption amount increase depends on the increase of biosorbent and it can be achieved high efficiency (95%) even with small amount (0.6 mg, peppermint extract) at lead ions. It is also determined that the peppermint extracted that is used at this study shows high biosorption capacity for metal ions and can be used for immobilization of metals from polluted areas.

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