Influence of Dielectric constant on Protonation Equilibria of L-Cysteine and L-Methionine in 1, 4-Dioxane-Water Mixture
K. Bharath Kumar Naik, Department Of Chemistry, Dr. V. S. Krishna Govt. Degree & PG College(A), Maddilapalem Visakhapatnam
Protonation equilibria, L-Cysteine, L-Methionine, 1, 4-Dioxane
The solute-solvent interactions of L-Cysteine and L-Methionine have been studied pH metrically in various concentrations (0.0-60.0% v/v) 1, 4-Dioxane-water mixture maintaining an ionic strength of 0.16 mol L-1 at ambient conditions. The protonation constants have been calculated with the computer program MINIQUAD75 and the best fit chemical models are selected based on statistical parameters. Linear variation of step-wise protonation constants (log K) with reciprocal of dielectric constant of the solvent mixture has been attributed to the dominance of the electrostatic forces. Protonation equilibria and effect of influential parameters on the protonation constants have also been presented.
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[1] C. Jacob, I. Knight & P. G. Winyard “Aspects of the Biological Redox Chemistry of Cysteine: from Simple Redox Responses to Sophisticated Signaling Pathways” Biol. Chem., 387: p1385-1397, 2006.
[2] B. Balta, G. Monard, M. F. Ruiz-Lopez, M. Antoine, A. Gand, S. Boschi-Muller & G. Branlant “Theoretical Study of the Reduction Mechanism of Sulfoxides by Thiols” J. Phys. Chem. A, 110: p7628-7636, 2006.
[3] D. W. Martin, P. A. Mayes, V. W. Food Wells & D. W. Granner “Harper’s Review of Biochemistry” 20th Ed., Lange Medical Publishers, California, 672, 1985.
[4] B. Regland, L. Abrahamsson, K. Blennow, B. Grenfeldt & C. G. Gotlfries “Cerebrospinal fluid-methionine is elevated in psychotic patients” J. Neural Transm, 111, p631–640, 2004.
[5] M. Noji & K. Saito “Sulfur amino acids: Biosynthesis of Cysteine and Methionine, Sulphur in plants” A review, p135-144, 2003.
[6] G.N. Rao, & R.S. Rao, “Characteristics of water-organic solvent mixtures” J. Teach. Res. Chem., 2: p15-27, 1995.
[7] H. Sigel, R.B. Martin, R. Tribolet, U. K. Haring & R. M. Balakrishnan, “An estimation of the equivalent solution dielectric constant in the active-site cavity of metalloenzymes dependence of carboxylate metal ion complex stabilities on the polarity of mixed aqueous/organic solvents” Eur. J. Biochem. 152: p187-194, 1985.
[8] S.Herbert Harned & M. Clair Birdsall, ‘’ The Acidic Ionization Constant of Glycine in Dioxane-Water Solutions’’ J. Am. Chem. Soc. 65: p54-57, 1943,
[9] A. Sharma, K. D. Gupta & K. K Sexsena, ‘’The stability constants of Cu (II) complexes’’J Indian Council Chem., 19: p43-50, 2002.
[10] V. S. Rao, P. S. Rao, B. Srikanth, C. Kamala Sastry & G. N. Rao, ‘’Speciation of binary complexes of Co(II), Ni(II), Cu(II) and Zn(II) with L-aspartic acid in anionic, cationic and neutral micellar medium’’ Chem. Speciat. Bioavail. 21: p71-80, 2009.
[11] J. Hens, ‘’Structural effects on equilibria in organic chemistry’’ Wiley, New York, 1975.
[12] S. H. Herbert & M. Clair Birdsall, ‘’The Acidic Ionization Constant of Glycine in Dioxane-Water Solutions’’ J. Am. Chem. Soc., 65: p54–57, 1943.
[13] G. Gran, “Determination of the equivalence points in potentiometric titrations-Part-II” Analyst, 77: p661-671, 1952.
[14] G. Gran, “Equivalence volumes in potentiometric titrations” Anal. Chim. Acta, 206: p111-123, 1988.
[15] K. V. Santhe Devi, B. Rama Raju & G.N. Rao, “Efect of Dielectric Constant on protonation Equlibria of L-Dopa and 1, 10-Phenanthroline in Dioxan-Water Mixtures” Acta Chim. Slov., 57: p398-404, 2010.
[16] M. P. Latha, V. M. Rao, T.S Rao & G.N. Rao, “Determination of protonation constants of L-glutamic acid and L-methionine in 1, 2-propanediol-water mixtures” Acta Chim. Slov, 54: p160-165, 2007.
[17] G. N. Rao, (1989) “Complex equilibria of some biologically important metal ions in aquo-organic media” Ph. D. Thesis. Andhra University, Visakhapatnam, India.
[18] P. Gans, A. Sabatini & A. Vacca, “An improved computer program for the computation of formation constants from potentiometric data” Inorg. Chim. Acta, 18: p237-239, 1976.
[19] M. Born, “Volumes and hydratation-swarme der ionen” Z. Phys., 1: p45-48, 1920.
Paper ID: GRDJEV02I030049
Published in: Volume : 2, Issue : 3
Publication Date: 2017-03-01
Page(s): 60 - 65
Published in: Volume : 2, Issue : 3
Publication Date: 2017-03-01
Page(s): 60 - 65