A Novel Composite 90° Pulse Sequence Which Provides Distortionless NMR Spectra and Suppresses without Destroying the Water Magnetization

International audienceA novel 90 degrees composite pulse sequence which allows one to record 1D and 2D NMR spectra without disturbing the water magnetization is described. A home-written program was used to optimize the pulse angles for which the pulse sequence response fitted best the desired excitation profile, producing a neat and distortionless spectrum with a broad null excitation at the carrier frequency. The resulting pulse sequence was first evaluated using the simulation program "PENCIL" and then tested on two protein samples. A 3.5 degrees phase shift of the last pulse was required to cancel correctly the water signal. The pulse scheme was appended to a NOESY pulse sequence. Inspection of the water cross section revealed interactions between water and some protons of drosomycine, a small insect antifungal protein