Study of the structure of Triton X-100 micelles in polyacrylamide aqueous solution by 2D heteronuclear Overhauser enhancement spectroscopy

Two-dimensional nuclear Overhauser enhancement (2D NOESY) and two-dimension al heteronuclear Overhauser enhancement (2D HOESY) experiments were perform ed on Triton X-100 (TX-100-polyacrylamide (PAAM) aqueous solution at concen trations of 104 gl(-1) TX-100 and 40 gl(-1) PAAM. The absence of the NOESY cross peaks between the protons of TX-100 and PAAM and their presence among TX-100 molecules significantly imply that interaction among the protons of TX-100 molecules is far stronger than that between the protons of TX-100 m olecules and PAAM even at very high concentration. There are no HOESY cross peaks of protons of the system with either the carbonyl or the carboxylic carbon nuclei of PAAM. Therefore, there is no evidence for either hydrophob ic (by 2D NOESY) or hydrophilic interaction (by 2D HOESY) between TX-100 an d PAAM in aqueous solution. The appearance of cross correlation peaks betwe en hydrophobic protons and hydrophilic carbon nuclei and Vice versa of the same pairs of groups in the 2D HOESY map gives strong evidence for the coil ed and folded feature of the loosely packed hydrophilic chain of TX-100 upo n micellization. This suggests that the conformation of the hydrophilic pol yoxyethylene chain remains unchanged as the concentration of TX-100 increas es even up to about 104 gl(-1). Copyright (C) 2001 John Wiley & Sons, Ltd.