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The 2D ROESY (Rotating-frame Overhauser SpectroscoPY) experiment (also called CAMELSPIN (Cross-relaxation appropriate for Minimolecules Emulated by Locked SPINs) experiment) offers a simple way to obtain NOE information in a molecule by a single experiment and without prior knowledgment of the spectral assignment or molecular structure. In ROESYexperiment, cross-relaxations are carried out in the rotating-frame with spin-locked magnetization and this means that NOE in the transverse plane (ROE) is always positive (no nulling condition as in NOESY-type experiments) and, in addition, chemical exchange can always be distinguished.REQUIREMENTS
Easy implementation on any AVANCE spectrometer.VERSIONS
The basic pulse sequence of the ROESY experiment ( 84JACS811 and 85JMR207-63 ) follows the same principles of the homonuclear 2D experiments. After an excitation 90º 1H pulse, transverse magnetization evolves during a free variable evolution t1 period. An spin-lock period, usually low-power continuous wave, is applied during the mixing time and, finally, proton resonances are detected as usual. A z-filtered ROESY experiment was also proposed ( 87JMR557-74 ). The ROESY pulse sequence can also be combined with some solvent suppression scheme:EXPERIMENTAL DETAILSSome theoretical descriptions have been published ( 88JMR470-80 ).
Several variants to removing undesired J cross-peaks ( 87JMR261-75 , 88JMR524-77 , 92JACS3157 , 92MRCS24 , and 97JMR183-126 ) and spin diffusion effects ( 95JMRB76-109 ) have been published (see T-ROESY block).
The use of off-resonance RF irradiation ( 94PROG295 and 96ENC4167 ) allows to reduction of the coherent magnetization transfer due to scalar coupling (TOCSY contribution) and of the off-resonance effects (see Off-resonance ROESY block) ( 94JMRA43-111 , 94JMRA219-108 , 95JMRA307-117 and 89JMR628-81 ). Several approaches have been proposed to remove them ( 95JMRA144-112 , 95JMRA47-113 and 96JMRB198-110 ) and conditions for the quantitative measurement of ROESY intensities have been reported ( 96JMRA230-122 , 97JMRA70-128 , 98MRC801 and 99JMR189-140 ).
Pulsed field gradients can also be incorporated in the ROESY experiment (see ge-2D ROESY experiment).
The 2D ROESY can be recorded in routine/automation modes. The most important parameter to consider is the length of the mixing time. On the other hand, the mixing process must be optimized to minimize possible TOCSY contributions. Some practical details on the ROESY implementation have been discussed ( 90JMR608-89 )SPECTRAMore details on practical implementation of 2D ROESY 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
Cross-peaks appearing in a ROESY spectrum are basically due to chemical exchange and cross-relaxation effects. However, other coherence transfer mechanisms can take place, and undesirable signals can arise.
RELATED TOPICS
Signal type Phase Properties Observations Diagonal positive in-phase absorption - ROE negative in-phase absorption - Exchange positive in-phase absorption False cross-peak COSY anti-phase absorption False and distorted cross-peak ZQC mixed-mode anti-phase False and distorted cross-peak TOCSY positive in-phase absorption False and distorted cross-peak TOCSY-ROE negative in-phase absorption Indistinguishable false cross-peak Multiple-step ROE positive (2 step) or negative (3 step) False and distorted cross-peak Exchange-ROE negative in-phase absorption Indistinguishable false cross-peak
General Reading:Relaxation effects of chemical exchange ( 96ENC4157 ) NOE connectivites can also be established using the 2D NOESY experiment.
Related experiments:
2D homonuclear experiments 2D gradient-based homonuclear experiments
