NCOCX

Experiment Details

Dimensions = 3

Isotope labeling required = ¹³C and ¹⁵N

Magnetization transfer = magnetization originates on ¹H and is transferred to ¹⁵N via cross polarization and then is transferred to ¹³CO nuclei through specific CP. A DARR step is used to transfer magnetization to neighboring ¹³Cnuclei. Chemical shift evolves on ¹⁵N and ¹³CO and detected on ¹³C.

Image courtesy: www.protein-nmr.org.uk/

Pulse program:

Comment on key optimization:

CNST31 = wr; PLW14 = PLW12 found in DARR optimization; p2 = 2*p1; p22 = 2*p21;

parmode = 3D; o1p = '100'; cnst22 = '55';o2p = '3'; o3p = '115'; ZGOPTNS = '-DCDC' for constant duty cycle

Example spectrum of GB1: The spectrum is used for linking N_i to CO_i-1 and to other ¹³C nuclei. When using short mixing times, only residue "i" ¹³Care visible whereas when longer mixing times are used, then links to ¹³C nearby can be made. These links provide useful information for structure calculations.

References:

1. J. Pauli, M. Baldus, B.-J. van Rossum, H. de Groot and H. Oschkinat (2001) Chem. Biochem. 2 272-281.