Simultaneous alpha/beta spin-state selection for (13)C and (15)N from a time-shared HSQC-IPAP experiment.

Two novel HSQC-IPAP approaches are proposed to achieve alpha/beta spin-state editing simultaneously for (13)C and (15)N in a single NMR experiment. The pulse schemes are based on a time-shared (TS) 2D (1)H,(13)C/(1)H,(15)N-HSQC correlation experiment that combines concatenated echo elements for simultaneous J(CH) and J(NH) coupling constants evolution, TS evolution of (13)C and (15)N chemical shifts in the indirect dimension and heteronuclear alpha/beta-spin-state selection by means of the IPAP principle. Heteronuclear alpha/beta-editing for all CH( n ) (n = 1-3) and NH( n ) (1-2) multiplicities can be achieved in the detected F2 dimension of a single TS-HSQC-F2-IPAP experiment. On the other hand, an alternative TS-HSQC-F1-IPAP experiment is also proposed to achieve alpha/beta-editing in the indirect F1 dimension. Experimental and simulated data is provided to evaluate these principles in terms of sensitivity and performance simultaneously on backbone and side-chain CH, CH(2), CH(3), NH, and NH(2) spin systems in uniformly (13)C/(15)N-labeled proteins and in small natural-abundance peptides.