TROSY transverse relaxation optimized

The cross-correlation effects between the DD and CSA interactions also influence the transverse relaxation and lead to the phenomenon known as differential line broadening in a doublet [40], cf Figure Bl.13.8. There is a recent experiment, designed for protein studies, that I wish to mention at tire end of this section. It has been proposed by Pervushin etal [4T], is called TROSY (transverse relaxation optimized spectroscopy) and... 

TNO—Netherlands Organisation for Applied Scientific Research TROSY—transverse relaxation-optimized spectroscopy... 

Thus we cannot escape the depressing reality that 7 2 will get shorter and linewidth will get bigger as we increase the size of the protein studied. The reduced T2 is not only a problem for linewidth, but also causes loss of sensitivity as coherence decays during the defocusing and refocusing delays (1/(2J)) required for INEPT transfer in our 2D experiments. The only ray of hope comes in the form of a new technique called TROSY (transverse relaxation optimized spectroscopy), which takes advantage of the cancellation of dipole-dipole relaxation by CSA relaxation to get an effectively much longer 7 2 value we will briefly discuss TROSY at the end of this chapter. 

A number of recently developed methods offer the potential for improving the quality of NMR structures and for increasing the size of proteins that will be examined. In particular, the use of residual dipolar couplings and of anisotropic contributions to relaxation provide new kinds of restraints that promise to lead to more accurate NMR structures.78 80 The recently developed TROSY (transverse relaxation optimized spectroscopy) method81 exploits relaxation phenomena to produce spectra with narrow lines, and promises to significantly expand the size of protein targets that can be examined by NMR from the current limit of 35 kDa to perhaps 150 kDa. 

R 148 R. Riek, TROSY Transverse Relaxation - Optimized Spectroscopy , p. 227... 

With the adaptation of NMR techniques for larger molecules, it becomes possible to analyze proteins with molecular weights reaching 50 kDa. These techniques include H-, N-TROSY (transverse relaxation-optimized spectroscopy, with the mutual cancellation of H-, N-dipole-dipole coupling and the N chemical shift anisotropy) and CRINEPT (Cross-correlated Relaxation-Enhanced Polarization Transfer, combining insensitive nuclei enhanced by polarization transfer (INEPT) transfer with cross-correlated relaxation-induced polarization transfer). They are used in conjunction with the N-, c-labeling of the protein for increased sensitivity. 

TROSY (transverse relaxation-optimized spectroscopy) and CRIPT (cross-correlated relaxation-induced polarization transfer) or CRINEPT (cross-correlated relaxation-enhanced polarization transfer) for the two-dimensional (2D) NMR analysis of N-. H-labeled homo-oligomeric macromolecules with masses ranging from 110-800 kDa. Practical applications of these methods are, for instance analyses of intermolecuiar interactions in supramolecular complexes or conformational changes of a single macromolecule upon interactions with other molecules. 

---