Abstract
A theoretical study was conducted to determine the ionization constants of N-substituted amino acid derivatives using HF, DFT, and MP2 calculation methods. The extent of compatibility of these methods was determined by discussing the theoretical variables calculated in the three methods mentioned above, the relationship between the calculated physical variables have been found to be theoretical and to determine their nature. These variables were then correlated with the known chemical values of amino acids as pK a ionization parameters. The results obtained by this relationship were found to be good. This is indicated by the results of the statistical analysis across the correlation coefficient values. The theory that gave the best agreement between the values of the theoretical and the experimental ionization parameters were the MP2 method with good correlation coefficient (0.997) and standard error (0.162). As well as the large overlap between pK a values calculated theoretically with practical values where the difference (0.008) gives the opportunity to apply these variables in other studies.
Highlights
Amino acids have a important location in biology as basic building blocks of all proteins and contribute to cellular functions.[1]The terms dissociation/protonation constants are referred to measure of acidic or alkaline force
Three types of amino acid ionization constants are defined: pKa refers to the ionization of the carboxyl group, pKb represents the ionic group ionization constant, and pKc refers to the side group R, which may contains ionizable groups, and exist in the form of zwitter ions.[3]
Calculations of the Mulliken charge were calculated for five atoms at the centre of the interaction of amino acid derivatives using the basic calculation methods (MP2, DFT and HF)
Summary
A theoretical study was conducted to determine the ionization constants of N-substituted amino acid derivatives using HF, DFT, and MP2 calculation methods. The extent of compatibility of these methods was determined by discussing the theoretical variables calculated in the three methods mentioned above, the relationship between the calculated physical variables have been found to be theoretical and to determine their nature. These variables were correlated with the known chemical values of amino acids as pKa ionization parameters.
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