Recent developments in the characterization of water interacting with proteins by O-17 NMR

Transverse and longitudinal O-17-water relaxation rates were detected in di fferent samples of BSA solutions after one-quantum and triple-quantum-filte red NMR sequences. Another contribution other than quadrupolar relaxation w as found for transverse relaxation, which did not change significantly with the concentration and hence could not correspond to agglomeration of prote ins. This was interpreted as chemical exchange between different types of O -17-water in fast motion; probably free water and water weakly bound to the proteins. At lower BSA concentrations, two peaks were detected for water; this was in agreement with thus hypothesis. The interactions between BSA an d lactic acid were also studied. It was shown that at a sufficient concentr ation of lactic acid, the number of strongly bound water molecules detected diminishes. On the other hand, the weakly bound water properties do not ch ange significantly. (C) 2001 Academic des sciences/Editions scientifiques e t medicales Elsevier SAS.