The 2D EXSY (EXchange SpectroscoPY) experiment offers a simple way to obtain information about cdynamic processes (for instance, chemical exchange) in a molecule by a single experiment and without prior knowledgment of the spectral assignment or molecular structure.

Easy implementation on any AVANCE spectrometer.

The EXSY experiment uses the basic NOESY ( 79JCP4546 ) and  ROESY ( 84JMR149-56 , and 96MRC545 ) schemes. During the mixing time, transfer polarization can be due to dipolar couplings or exchange/dynamic processes. Modified EXSY pulse sequences have been proposed to remove NOE effects (CLEAN-EXSY experiment) and to study protein hydration ( 89JACS1871 ). An excellent review on protein hydration has been recently published ( 97PROG259 ).

The 2D EXSY can be recorded in routine/automation modes. The most important parameter to consider is the length of the mixing time.

More details on practical implementation of 2D EXSY experiments on AVANCE spectrometers can be found in

Tutorials: 2D homonuclear experiments

Tutorials: 2D gradient-based homonuclear experiments

Tutorials: 2D gradient-based homonuclear experiments in H₂O

As described in 2D NOESY experiment: Diagonal peaks are positive, exchange cross-peaks are also positive and NOE cross-peaks are positive in the slow-tumbling or spin-difussion limit for large molecules (negative NOE) and negative in the extreme-narrowing limit (positive NOE). Thus, for small molecules chemical exchange and NOE effects have opposite signs and can be distinguished.

Related experiments:

2D homonuclear experiments

2D gradient-based homonuclear experiments