Described herein is a technique and method for analyzing the protein binding affinity of a drug. The techniques and methods described herein leverage magnetic resonance techniques such as NMR and MRI to make relaxation measurements of an NMR detectable species. In some embodiments, a rubidium polarizer is used to magnetize 129Xe, which is bubbled into a protein solution. The magnetic decay of the hyperpolarized 129Xe is monitored by measuring the T1 or T2 of 129Xe through NMR spectroscopy.