Reverse DEPT and reverse INEPT experiments can be used to measure 13-C relaxation with polarization transfer to the much stronger proton signals. In a direct measure of the 13-C relaxation, the methyl quartet has the characteristic 1:3:3:1 ratio of peak heights. In straight forward polarization transfer experiments on amino acids in the slow motion regime, however, the experimental ratios of peak heights differed considerably from the above, e.g. -1:11:11:-1 in one case. The theory of reverse DEPT and reverse INEPT experiments was developed to explain these results and the predictions of those theories were verified experimentally. The theory was then used to show how the 1:3:3:1 ratio could be obtained, thereby providing an accurate substitute for the 13-C direct observe experiment. The theory also showed how the experiment could be performed in order to minimize errors due to the multi-exponential relaxation.
