Selective observation of Asp and Glu resonances in 13CO detected experiments

We present a filter element to observe exclusively the resonances of Asp and Glu residues in several ¹³C detected experiments, CACO, CBCACO, and CCCO. As in these experiments the carboxylate resonances appear in the directly detected dimension, it is possible to measure their chemical shifts with a high precision. Therefore, the experiments can be of great utility in the accurate determination of the pK_a's of these residues. Furthermore, the experiments can be applied in the study of deuterated proteins, where the usual experiments for pK_a determination cannot be used. Finally, the good resolution with which the carboxylate spectrum is obtained allows observing the coupling between the carboxyl carbon and the backbone CO in Asp residues, what provides information on their side chain conformation. Copyright © 2011 John Wiley & Sons, Ltd.