Low-y Nuclei Detection Experiments for Biomolecular NMR - Recent Developments in Biomolecular NMR - page 37

While analyzing the [2- 13 C] and [1,3- 13 C]-glycerol-labelled samples sepa-
rately for clarity, one can also combine the two samples to obtain all the
information at once. In this case, however, the C a labelling rate would be 50%
for all residues. Similar data could be obtained from HMQC-type NCA
experiments. In addition, the alternate labelling provides complementary 13 C-
labelling in the C9 position when C a is not 13 C-labelled. Thus, it would also
enable recording of simple C9N correlated spectra without C a -C9 coupling,
which might be of interest for smaller systems.
Furthermore, with the alternate 13 C- 12 C-labelling scheme and using both
samples labelled with [2- 13 C] and [1,3- 13 C] glycerol, we can now run a
broadband CN-HSQC experiment, which excites both 13 C9 and 13 C a
simultaneously, transfers the coherences to nitrogen and returns them back
to the original carbon nuclei for detection (Figure 2.4). This can be achieved by
simply changing all C ali selective pulses in Figure 2.3(C) into hard pulses. One

Figure 2.4

Broadband CN HSQC spectrum. (A) Schematic representation of a broad-
band CN HSQC spectrum. (B) A broad-band CN HSQC spectrum
recorded on the alternately 13 C-labelled protein GB1 (2- 13 C glycerol
labelled). Data were recorded with carbon and nitrogen sweep widths of
145 and 34 ppm, respectively. The total experimental time was 4.5 h.