Relayed coherence transfer, homonuclear

The individual proton spin systems for each sugar residue were delineated by homonuclear and heteronuclear correlations as detected from COSY and multistep homonuclear relayed coherence transfer (RCT) experiments [9], In this way triple relayed correlations were detected from anomeric protons (Hi) to H5 via the intervening H2 ( direct coupling), H3 (single relayed coherence transfer) and H4 (double relayed coherence transfer). Thus, beginning from the anomeric proton (5 6.13, Glc Hi 5.68, Rha. Hi 4.89, Glc . Hi 4.70, Ara . Hi 4.68, Ara. Hi ), all 2-position protons of sugar moieties were easily located in the... 

Bax A, Davis DG (1985) MLEV-17 Based two-dimensional homonuclear magnetization transfer spectroscopy. J Magn Reson 65 355-360 Bax A, Drobny G (1985) Optimization of two-dimensional homonuclear relayed coherence transfer NMR spectroscopy. J Magn Reson 61 306-320 Bax A, Marion D (1988) Improved resolution and sensitivity in H-detected heteronuclear multiple-bond correlation spectroscopy. J Magn Reson 78 186-191 Bax A, Subramanian S (1986) Sensitivity-enhanced two-dimensional heteronuclear chemical shift correlation NMR spectroscopy. J Magn Reson 67 565-569 Bax A, Summers MF (1986) and Assignments from sensitivity-enhanced detection of heteronuclear multiple bond connectivity by 2D multiple-quantum NMR. J Am Chem Soc 108 2093-2094... 

The most commonly used 2D nmr technique applied to through-bond interactions is termed (7 ) correlated spectroscopy (COSY), others are total correlation spectroscopy (TOCSY), which allows somewhat longer-range through-bond connectivities to be observed than with COSY, spin echo coherence transfer spectroscopy (SECSY), relayed coherence transfer spectroscopy (RELAY), double quantum spectroscopy (DQNMR) and homonuclear Hartmann-Hahn spectroscopy (HOHAHA). The most commonly used 2D nmr technique applied to through-space interactions is termed nuclear Overhauser effect spectroscopy (NOESY) also used is the closely related rotating-frame NOESY (ROE-SY). 

In the relayed coherence transfer experiment the first step is an initial homonuclear magnetization transfer (i.e., from proton A to proton B). The coherence is then relayed to a third nucleus, which may be a proton (homonuclear relay) or a different nucleus (e.g., heteronuclear relay). Recently, another variation of the relay experiment has been reported which involves transfer of coherence to a heteronuclear spin as the first step ( H-X heteronuclear shift correlation). The coherence is then relayed to a third nucleus, a proton (X- H coherence transfer), which is the nucleus observed. ... 

COSY = homonuclear chemical shift correlation spectroscopy NOESY = 2D nuclear Overhauser effect (NOE) spectroscopy HMQC = heteronuclear mulltiple-quantum coherence RELAY = relayed coherence transfer COLOC = correlation via long-range coupling HMBC = heteronuclear long-range coupling INADEQUATE = incredible natural abundance double quantum transfer experiment. 

Figure 1.45 Coherence transfer pathways in 2D NMR experiments. (A) Pathways in homonuclear 2D correlation spectroscopy. The first 90° pulse excites singlequantum coherence of order p= . The second mixing pulse of angle /3 converts the coherence into detectable magnetization (p= —1). (Bra) Coherence transfer pathways in NOESY/2D exchange spectroscopy (B b) relayed COSY (B c) doublequantum spectroscopy (B d) 2D COSY with double-quantum filter (t = 0). The pathways shown in (B a,b, and d) involve a fixed mixing interval (t ). (Reprinted from G. Bodenhausen et al, J. Magn. Resonance, 58, 370, copyright 1984, Rights and Permission Department, Academic Press Inc., 6277 Sea Harbor Drive, Orlando, Florida 32887.)...

Both homonuclear and heteronuclear versions of relayed nOe experiments are known. The homonuclear relayed NOESY experiment involves both an incoherent transfer of magnetization between two spins H and H/ that are not coupled but close in space, and a coherent transfer of magnetization between two spins H(and H that are /-coupled together. The magnetization pathway may be depicted as... 

Relayed transfer of two-dimensional double-quantum coherence (2QT) has recently been described in homonuclear and heteronuclear correlated spectral system. The pulse sequence used in the relayed 2QT experiment is shown in Figure 5.88. The first three mixing pulses (90°, 180°, 90°) serve to mix double-... 

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