Many types of NMR experiments demand the use of frequency-selective pulses to invert magnetization within discrete frequency limits. For certain experiments, only one side of the inversion band must be sharply demarcated, in which case this transition bandwidth can be narrowed when using an asymmetric adiabatic full passage. In the present study, a highly efficient asymmetric adiabatic full passage was created from a combination of two adiabatic half passages which used different modulation functions (HS1/2 and tanh/tan). Each adiabatic half passage occupied a different amount of time in the total pulse and performed one-half of the inversion. On one side, HS1/2 produced a sharp transition between inverted and noninverted states which was approximately 2.5 times narrower than the transition bandwidth afforded by a symmetric hyperbolic secant pulse of equal length. On the other side of the narrow transition band, the tanh/tan pulse achieved broadband inversion. These asymmetric pulses were applied to select NH groups immediately adjacent to the water signal in water-flip-back HSQC experiments using a double spin echo for the reverse INEPT step.
Bibliographical noteFunding Information:
The authors thank Dr. David Shortle for providing the staphylococcal nuclease sample. The 800-MHz spectrometer at the University of Minnesota was supported by NSF Grant BIR-9601477. This research was supported by NIH Grants RR11115 (P.v.Z.) and RR08079 (M.G.), and, in part, via a subcontract of NIH STTR Grant GM55441 to Adiabatics, Inc., of which M.G. and P.v.Z. are officers. The terms of this agreement have been reviewed and approved by the Johns Hopkins University in accordance with its conflict of interest policies.
- Adiabatic full passage
- Asymmetric pulses
- Selective spin inversion