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pH regulation of calcium recognition by an amino acid containing acyclic ionophore
Author(s) -
Spisni A.,
Franzoni L.,
Corradini R.,
Marchelli R.,
Dossena A.
Publication year - 1989
Publication title -
journal of molecular recognition
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.401
H-Index - 79
eISSN - 1099-1352
pISSN - 0952-3499
DOI - 10.1002/jmr.300020207
Subject(s) - ionophore , chemistry , amide , calcium , stereochemistry , carbon 13 nmr , organic chemistry
Calcium ion recognition by a dicarboxylic ionophore containing two (S)‐phenylalanine residues joined via an amide bond by a flexible tri‐oxa‐undecanoyl bridge (Phe‐3‐O) has been investigated in a wide pH range (from pH 2 to 12). Experiments were performed in methanol and chloroform by 1 H and 13 C NMR, relaxation times and 2D NMR (COSY, NOESY and J‐resolved experiments). Recognition is shown to be regulated by pH, as it occurs in at least three different coordination modes according to the experimental conditions. Even at low pH (pH 2) the ion is already complexed in the compartment created by the ethereal oxygens and the amide carbonyls. At higher pH, it becomes fully encapsulated in a pseudo‐cyclic structure and at very basic pH it is localized between the amide carbonyls and the carboxylates. For these peculiar properties Phe‐3‐O appears to be a very promising ionophore in a transmembrane pH gradient system.