Conformational dependence of triton X-100 on environment studied by 2D NOESY and H-1 NMR relaxation

Conformation of Triton X-100 (TX-100) in the bulk and in aqueous solutions at concentrations higher and lower than the critical micellar concentration (cmc) was studied by NMR relaxation, two-dimensional nuclear Overhauser en hancement spectroscopy (2D NOESY), and molecular simulation by HYPERCHEM. R esults show that motion of TX-100 in dilute solution (0.5 cmc) is in the ex treme narrowing condition. Molecules are in the single molecular state with an extended polyoxyethylene chain. Tn forming micelles, these hydrophilic polyoxyethylene chains, staying in the exterior of the micellar core, coil, bend. and align along the surface of the TX-100 micellar core, forming a l ayer thick in dimension and loose in structure around the micellar core wit h a certain number of water molecules included. This hydrophilic layer is i n contact with the solvent, water, keeping the micellar solution stable. Th e micelle is spherical at 10 cmc. Motions of all of the protons of TX-100 i n the bulk, even of those on the polyoxyethylene chain, are more restricted than motions of those in the micellar core. Exponential decay of the proto n spin - spin relaxation of TX-100 in the bulk shows the absence of oriente d self-aggregation. Very short internuclear distances of the protons betwee n hydrophilic and hydrophobic parts of TX-100 bulk measured from the 2D NOE SY spectrum show that the molecules are arranged randomly, closely, and uni formly, which is the origin for the high viscosity of TX-100 bulk. Results are discussed in terms of inter- and intramolecular interactions.