Liquid-Liquid Extraction and Transport of Amino Acids through Membrane by Cucurbit[6]uril and its Derivatives

Abstract

Molecular recognition phenomenon of cucurbit[6]uril (R1) and its derivatives perhydroxy cucurbit[6]uril (R2), diphenylcucurbit[6]uril (R3) and hemicucurbit[6]uril (R4) towards aliphatic amino acids was studied. This article highlights the use of these macrocyclic receptors having variations in structure and shape for extraction and transport of amino acids using liquid membrane system. These receptors interact with amino acids by ion-dipole interaction. The observed sequence in supported liquid membrane (SLM) experiments for transport efficiency of different receptors for amino acids is serine > arginine > lysine > glycine by R1, arginine ≈ serine > glycine > lysine by R2, serine > glycine > lysine > arginine by R3 and glycine > arginine > lysine > serine by R4. In bulk liquid membrane (BLM) experiments the sequence of extraction and transport efficiency observed for amino acids using receptor R4 is glycine > lysine > serine ≈ arginine. Receptor R2 containing hydroxyl group at the outer surface of cucurbituril, increases ion dipole interaction between receptor and substrate and receptor R4 having flexible cavity, emphasized better transport efficiency. Various parameters such as pH, time, concentration of amino acids and receptors were studied for extraction and transport of amino acids.