One-dimensional exchange spectroscopy by sideband

CRAMPS NMR [138]. The differences in the intermolecular distances of the carboxylic acid groups involved in different types of hydrogen bonding have been visualised using ODESSA (one-dimensional exchange spectroscopy by sideband alteration) and 2D EXSY (exchange spectroscopy). The ODESSA technique [139] can measure internuclear distances (up to 9 A) between chemically equivalent nuclei with the same isotropic chemical shift. Potential applications of this approach are widespread. 

The pulse sequence used by these authors is ODESSA (one-dimensional exchange spectroscopy by sideband alternation) [48], The experiment is based on the fact that intermolecular distances between chemically equivalent nuclei differ significantly in racemates and enantiomers according to slight but substantial... 

For low-frequency motions (10 -10 s), the 2D exchange experiments are useful techniques (19). Other exchange experiments are also informative, e.g., the one-dimensional exchange spectroscopy by sideband alternation (ODESSA) (151), time-reversed ODESSA (152), and centerband-only detection of exchange (CODEX) (153). Many advanced techniques are given in a recent, excellent review by Brown and Spiess (14). 

The ultraslow motions can be observed by exchange NMR experiments. There are a number of techniques, performed in ID and 2D modes which are based on the manipulation of spinning sidebands under MAS. The first of them, applied to study of solid peptides was ODESSA (one-dimensional exchange spectroscopy by sideband-alternation) [76] and next the time-reversed ODESSA [77] (tr-ODESSA). The interesting modification, which represents this group of sequences is CODEX (centreband-only detection of exchange) introduced by Schmidt-Rohr and coworkers [78]. CODEX can be executed at any MAS speed, while ODESSA and tr-ODESSA... 

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