Interaction of methyl benzoate as a model odorant with a series of free-base amino acids and some amino-acid hydrochlorides.
The interactions of methyl benzoate as a model odorant with a series of free-base amino acids: lysine, tryptophan, arginine, proline, histidine, cysteine, leucine, threonine and phenylalanine, were studied by gas-phase adsorption on solid amino-acid samples. DL-, D- and L-isomers were investigated for all of the amino acids with the exception of cysteine where only DL- and D- were studied. Langmuir adsorption isotherms show that the strongest interactions are with lysine. Correlation of the relative interaction strength with the chemical structures suggests that binding is strongest to the remote amino groups in the amino-acid side-chain and involves a nucleophilic attack of a lone pair of electrons on the epsilon-nitrogen of lysine to the carbon of the carbonyl group of the methyl benzoate. This suggestion is supported by studies on hydrochlorides of lysine where the side-chain amino groups are protonated and thus cannot participate in a lone-pair interaction. Arginine mono-hydrochloride was found to adsorb more methyl benzoate than even the lysine free-base, an observation which is not fully understood.
PubMed Abstracts
PubMed Abstracts