NCO

Experiment Details

Dimensions = 2

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.

Chemical shift evolves on ¹⁵N and detected on ¹³C.

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

Pulse program: hNCO.dcp

Parameters:

p1 : C 90 at pl1

p2 : C 180 at pl1

p3 : H 90 at pl2

p17 : NCO CP at pl6 (f3,N), sp51 (f1,C), pl34 (f2,H)

p25 : HN CP at sp43 (f3,N) and sp42 (f2,H)

pl1 : C pulse power

pl2 : H pulse pwpower

pl6 : N NCO CP power

pl12 : H dec power

pl34 : H dec power during NCO CP

sp42 : H HN CP power

sp43 : N HN CP power

sp51 : C NCO CP power

d0 : incremented delay (t1)

d1 : recycle delay; 1 to 5 times T1

d30 : extra time for constant duty cycle

pcpd2 : H dec pulse cpdprg2

cpdprg2 : Decoupling file cw, tppm (at pl12)

spnam42 : H ramp use e.g. ramp.10070 for variable amplitude CP

spnam43 : N ramp use e.g. square.100 for square pulse CP

spnam51 : CO ramp use e.g. tcn for amplitude modulated tangential pulse CP

cnst10 : Frequency reset to Carrier(o1, usually ~100 ppm)

cnst21 : Frequency offset for CO (~175 ppm)

cnst30 : expected td1 for use in constant duty cycle (-DCDC)

cnst31 : MAS rotation rate in Hz

inf1: 1/SW(N) = 2 * DW(N)

in0 : = inf1

in30: = inf1

l0 : loopcounter for F1

ZGOPTNS : -DCDC : for constant duty cycle or blank

FnMODE: TPPI, States or States-TPPI

ns: MIN. 4 (full:8)

Comment on key optimization:

parmode = 1D; o1p = '175'; cnst22 = '175'; o2p = '3'; o3p = '115'; p2 = 2*p1;

Example spectrum of GB1: Recorded with 3.2 mm rotor and MAS@ 17587Hz.

The spectrum gives ¹⁵N -¹³CO correlation.

References:

1. Baldus, M.; Petkova, A. T.; Herzfeld, J. H.; Griffin, R. G. Mol. Phys. 1998,95, 1197-1207.

2. M. Hong and R.G. Griffin; J. Am. Chem. Soc. 120, 7113-7114.

3. J. Lewandowski, G. De Pape, and R. G. Griffin; J Am Chem Soc. 129(4): 728-29.