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Abstract
The molecular recognition properties of hemicucurbit[6]uril (HemiCB[6]) and hemicucurbit[12]uril (HemiCB[12]) towards a series of amino acid native and methyl esters (L-phenylalanine, L-leucine, L-valine, L-cysteine, L-tryptophan, L-isoleucine, L-phenylalanine methyl ester hydrochloride (L-PheOMe), L-tyrosine methyl ester hydrochloride (L-TyrOMe), L-valine methyl ester hydrochloride (L-ValOMe), L-leucine methyl ester hydrochloride (L-LeuOMe), L-serine methyl ester hydrochloride (L-SerOMe) and L-cysteine methyl ester hydrochloride (L-CysOMe) were investigated. In this respect, by means of liquid–liquid extraction, a series of amino acid native and methyl esters were extracted from an aqueous phase (pH = 5.5) into a chloroform phase as ion pairs in the presence of tropaeolin 00 as counterion. Based on results obtained in extraction experiments, the active transport assisted by pH gradient of amino acids as ion pairs through chloroform liquid membrane employing HemiCB[6] as carrier was performed. Both receptors used in experiments exhibited extractability towards amino acids under study. From the results obtained, one can observed the good affinity of both receptors, hemiCB[6, 12], towards hydrophobic amino acids (L-PheOMe, L-LeuOMe and L-ValOMe)). It was emphasised that the structure of hemicucurbiturils and amino acids together with the anion nature, and pH have influenced the experimental results.
Acknowledgements
This work was supported by the Elena Iulia Cucolea is grateful for financial support to strategic [grant number POSDRU 159/1.5/S/133652], Project “Support for Doctoral students and Postdoctoral researchers” cofinanced by the European Social Found within the Sectorial Operational Program Human Resources Development 2007–2013.
Disclosure statement
No potential conflict of interest was reported by the authors.