Comparison of several hetero-nuclear dipolar recoupling NMR methods to be used in MAS HMQC/HSQC.
We compare several hetero-nuclear dipolar recoupling sequences available for HMQC or HSQC experiments applied to spin-1/2 and quadrupolar nuclei. These sequences, which are applied to a single channel, are based either on the rotary resonance recoupling (R3) irradiation, or on two continuous rotor-synchronized modulations (SFAM1 and SFAM2), or on four symmetry-based sequences (R2(1)1,SR4(1)2,R12(3)5,R20(5)9), or on the REDOR scheme. We analyze systems exhibiting purely hetero-nuclear dipolar interactions as well as systems where homo-nuclear dipolar interactions need to be canceled. A special attention is given to the behavior of these sequences at very fast MAS. It is shown that R3 methods behave poorly due to the narrowness of their rf-matching curves, and that the best methods are SR4(1)2 and SFAM (SFAM1 or SFAM2 if homo-nuclear interactions are not negligible). REDOR can also recouple efficiently hetero-nuclear dipolar interactions, provided the sequence is sent on the non-observed channel and homo-nuclear dipolar interactions are negligible. We anticipate that at ultra-fast spinning speed, SFAM1 and SFAM2 will be the most efficient methods.
Hu
B
B
UCCS, CNRS-8181, Lille University, Fr-59652 Villeneuve d'Ascq Cedex, France.
Trébosc
J
J
Amoureux
J P
JP
D002247:Carbon Isotopes; D003198:Computer Simulation; D005998:Glycine / Q000737:chemistry*; D006639:Histidine / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods*; D009587:Nitrogen Isotopes
D002247:Carbon Isotopes; D009587:Nitrogen Isotopes; D006639:Histidine; D005998:Glycine