The ge-2D semi-selective NOESY experiment is a gradient-enhanced band-selective version of the 2D NOESY experiment. By the use of some band-selective excitation method, only part of the 1H spectrum is evolving during the conventional variable t1 period or/and the proton acquisition period. In this way, a conventional 2D NOESY spectrum is partially recorded with improved resolution and t1-noise.

Easy implementation on any AVANCE spectrometer equipped with pulsed field gradients (PFGs) and selective excitation using shaped pulses.

The most simple way to convert the classical 2D NOESY pulse sequence to a gradient-based F1-semi-selective 2D NOESY pulse sequence is replacing the initial 90º 1H pulse by a SPFGE ( 96JMRB124-110 ) or DPFGE ( 98JMR154-132 ) scheme. The SPFGE block can be prefered because minimizes sensitivity losses due short transverse relaxation times without to sacrify selectivity.

Band-selective excitation of the F2 dimension can be equally performed by replacing the last 90º 1H pulse in the NOESY pulse sequence by another SPFGE block. Both band-selective excitation schemes can be combined in a same experiment. However, in modern spectrometers equipped with digital filters, automatic selection on the F2 dimension could be accomplished without the need to include the second SPFGE block. It is important to choose a shaped selective pulse giving excelent selective inversion profile as, for instance, a RE-BURP sequence.

The experiment is acquired an processed using the same experimental conditions as described for its phase cycle counterpart. The only difference is the presence of gradients. Thus, the user needs to define the strength, duration, shape of the gradients and the recovery delay. If PFGs are not used for coherence selection, clean phase-sensitive spectra can be obtained using a eigth-step phase cycle without sensitivity losses. The inversion profile of the selected SPFGE scheme migth be checked on the same sample.

Tutorials: 2D homonuclear experiments

Tutorials: 2D gradient-based homonuclear experiments

Tutorials: 2D gradient-based homonuclear experiments in H₂O

Data is  analyzed as in a conventional 2D NOESY experiment.

Related experiments:

2D homonuclear experiments

2D gradient-based homonuclear experiments