DETERMINATION OF THE BOUND WATER FRACTION IN CELLS AND PROTEIN SOLUTIONS USING O-17-WATER MULTIPLE-QUANTUM FILTERED RELAXATION ANALYSIS

Multiple-quantum filtering NMR sequences were used to study the multie xponential relaxation behavior of H-2 O-17 in the presence of macromol ecules. By this means, the fraction and the correlation time of water in slow motion, or ''bound'' water, were determined, as well as the re laxation time of bulk water in the extreme-narrowing limit. Aqueous so lutions of bovine serum albumin and intact human red blood cells were studied. The small fraction of bound water of less than 1% appeared to correspond to ''strongly bound'' water, whereas the behavior of bulk water was different from pure water and was interpreted as being due t o weak (or transient) interactions with macromolecules. The experiment s and the data analysis appeared to be reproducible, which suggests th at diverse samples might be studied this way and thus help define the properties of water in these systems. (C) 1996 Academic Press, Inc.