The doubly-selective ge-1D NOESY-NOESY (NONO) experiment permit to obtain high-quality artefact-free 1D NOESY spectra on specific protons resonating in overlapped regions where typical on-resonance selective excitation is not feasible. It can be used for tracing the spin-diffusion pathways in macromolecules.

Easy implementation on AVANCE spectrometers equipped with pulsed field gradients and selective excitation using shaped pulses.

The basic scheme of the selective ge-1D NOESY-NOESY experiment consists basically of two selective ge-1D NOESY blocks concatenated by a selective 180º pulse on a second spin. The following steps must be considered:

Selective excitation of the selected resonance using the SPFGE block or the DPFGE block.

Mixing period to achieve in-phase polarization transfer to other spins via NOE (see NOESY Block). . This mixing time is divided in two different periods separated by a selective inversion pulse on a second spin.

Proton detection as usual.

Gradients can be incorporated only to suppress unwanted magnetization and, therefore, there is no sensitivity losses due to coherence selection ( 97JMR248-126 ). Excellent spectral quality is obtained using a four-step phase cycle.

The selective ge-1D NOESY-NOESY experiment can be run with minor changes from a predefined parameter set. The best option is the version which uses a SPFGE or DPFGE scheme as a selective excitation and the refocusing gradient is omitted. Important parameters to consider are:

Selectivity of the first selective inversion pulse: the user must define the shape, the duration and the power level needed for a defined excitation profile.

Optimization of the first part of the mixing time.

Selectivity of the second selective inversion pulse: the user must define the shape, the duration and the power level needed for a defined excitation profile.

Optimization of the second part of the mixing time.

The final spectrum of a doubly-selective ge-1D NOESY-NOESY experiment is a clean 1D NOESY spectrum showing an specific NOE transfer mechanism of the selected two spins. This experiment can be used to identify and assign specific spin diffusion pathways.