Inductive effects in amino acids and peptides: Ionization constants and tryptophan fluorescence

LARA-POPOCA, JESÚS; THOKE, HENRIK S.; STOCK, ROBERTO P.; RUDINO-PINERA, ENRIQUE; BAGATOLLI, LUIS A.

Biochemistry and Biophysics Reports

Elsevier B.V.

Año: 2020 vol. 24

lthough inductive effects in organic compounds are known to influence chemical properties such as ionization constants, their specific contribution to the properties/behavior of amino acids and functional groups in peptides remains largely unexplored. In this study we developed a computationally economical algorithm for ab initio calculation of the magnitude of inductive effects for non-aromatic molecules. The value obtained by the algorithm is called the Inductive Index and we observed a high correlation (R2 = 0.9427) between our calculations and the pKa values of the alpha-amino groups of amino acids with non-aromatic side-chains. Using a series of modified amino acids, we also found similarly high correlations (R2 > 0.9600) between Inductive Indexes and two wholly independent chemical properties: i) the pKa values of ionizable side-chains and, ii) the fluorescence response of the indole group of tryptophan. After assessing the applicability of the method of calculation at the am