Abstract
The impact of cationic micelles on the protonation equilibria of L-glutamine and chemical speciation of its complexes with Co(II), Ni(II) and Cu(II) have been studied by monitoring hydrogen ion concentration pH metrically at 303 K and at an ionic strength of 0.16 M. The protonation constants and binary stability constants have been calculated with the computer program MINIQUAD75. The best fit chemical models are selected based on standard deviations in the model parameters and residual analysis using crystallographic R-factor and sum of squares of residuals in all mass-balance equations. The trend in the variation of stability constants of the complexes with mole fraction of the surfactant is attributed to the compartmentalization of complexation equilibria. Distribution of species and effect of influential parameters on chemical speciation have also been presented. KEY WORDS: Chemical speciation, complex equilibria, L-glutamine, cationic micelles Bull. Chem. Soc. Ethiop. 2012, 26(3), 383-394.DOI: http://dx.doi.org/10.4314/bcse.v26i3.7
Highlights
In humans, glutamine (Gln) is the most abundant amino acid in the extra and intracellular compartments, contributing to greater than 50% of the free amino acid pool in muscle [1, 2]
Secondary formation functions like average number of moles of protons bound per mole of ligand, nH, and number of moles of alkali consumed per mole of ligand (a) are useful to detect the number of equilibria
Secondary formation functions are used in detecting the number of equilibria and in guessing the approximate constants
Summary
Glutamine (Gln) is the most abundant amino acid in the extra and intracellular compartments, contributing to greater than 50% of the free amino acid pool in muscle [1, 2]. Two half integrals (1.5 and 0.5) of glutamine (Figure 1) emphasize the presence of two protonation-deprotonation equilibria in the pH range of present study. The best fit models containing the type of species and log values of overall formation constants (log β) along with some of the important statistical parameters of the present study are given in Tables 2 and 3.
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