Mobility of water in NaCl and brain heart infusion (BHI) solutions as studied by O-17 NMR

The molecular dynamic behaviour of water molecules in aqueous solution has been determined by oxygen-17 NMR according to the anisotropic reorientation , two-correlation-time model for bound water. Solutions of brain heart infu sion (BHI), NaCl and their 1:1 mixture have been analysed. The anisotropic water population was distinguished into a slow(tau (s)(bw)) and a fast (tau (f)(bw)) relaxing component. The slow relaxing component was affected by t he nature of the solute, while the fast relaxing component was not. NaCl wa s found to bind water molecules more strongly (higher tau (s)(bw)) than BHI . Water was more bound in the 1: 1 mixture than in the solution containing only BHI. The population of bound water (P-bw) was concentration dependent and increased with increasing solids content. BHI, at the suspension point, bound similar to 50% of the total water, while NaCl at saturation bound on ly similar to 10%. The 1: 1 mixture bound water in a synergistic manner tha t resulted in a slightly higher P-bw than in BHI at each solid concentratio n. The P-bw correlated well with the amount of unfreezable water (as measur ed by DSC) present in the BHI samples.