PROTON AFFINITY OF AMINO ACIDS - THEIR INTERPRETATION WITH DENSITY FUNCTIONAL THEORY-BASED DESCRIPTORS

摘要

The calculation of group electronegativity and hardness for amino acid ''functional groups,'' considered as a biradical taken out of their protein environment, is performed for both the alpha-helix and beta-sheet geometry of these amino acids. Group electronegativity and hardness are then used to interpret the experimental gas-phase proton affinity sequence of the amino acids. Group hardness was found to play the dominant role, whereas group electronegativity only had a minor influence on the sequence, thereby stressing the importance of the charged form in the acid-base equilibrium. An explanation for the deviations, seen for some of the amino acids, from the correlation between these group properties and the proton affinity was sought. (C) 1996 John Wiley & Sons, Inc. [References: 52]