T1 and T2 dispersion measurements of proton spin relaxation on aqueous solutions of bovine serum albumin as a function of both protein concentration and temperature, covering Larmor frequencies from 3 kHz to 75 MHz, will be presented as a most conclusive test for a three-phase fast-exchange relaxation model. By means of a computer curve fitting of this model to the experimental data, we were able to separate 3 distinct water environments and, in addition, the rotational tumbling of the bovine serum albumin molecules.
