Correlated spectroscopy relayed COSY

The pulse methods rely on selective irradiation of a particular resonance line with a radio frequency (rf) and observation of the resulting effects in the rest of the spectrum. Among commonly employed methods are 2D correlated spectroscopy (COSY), 2D spin-echo correlated spectroscopy (SECSY), 2D nuclear Overhauser and exchange spectroscopy (NOESY), 2D J-resolved spectroscopy (2D-J), and relayed coherence-transfer spectroscopy (RELAYED-COSY) (Wutrich, 1986). 

Figure 1. Pulse sequences of some typical 2D-NMR experiments. COSY = correlation SpectroscopY, DQFCOSY = Double Quantum Filtered COSY, RELAY = RELAYed Magnetization Spectroscopy, and NOESY = Nuclear Overhauser Effect SpectroscopY.

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.)...

Oil and 0)2, and (b) 2D shift-correlation spectra, involving either coherent transfer of magnetization [e.g., COSY (Aue et al, 1976), hetero-COSY (Maudsley and Ernst, 1977), relayed COSY (Eich et al, 1982), TOCSY (Braunschweiler and Ernst, 1983), 2D multiple-quantum spectra (Braun-schweiler et al, 1983), etc.] or incoherent transfer of magnedzation (Kumar et al, 1980 Machura and Ernst, 1980 Bothner-By et al, 1984) [e.g., 2D crossrelaxation experiments, such as NOESY, ROESY, 2D chemical-exchange spectroscopy (EXSY) (Jeener et al, 1979 Meier and Ernst, 1979), and 2D spin-diffusion spectroscopy (Caravatti et al, 1985) ]. 

Coherent transfer experiments can roughly be divided into two classes pulse-interrupted free-precession experiments and Hartmann-Hahn-type experiments (Ernst et al., 1987). Examples of homo- and heteronuclear pulse-interrupted free-precession coherence transfer are COSY (correlation spectroscopy Aue et al., 1976), RELAY (relayed correlation spectroscopy Wagner, 1983), and INEPT (insensitive nucleus enhancement by polarization transfer) transfer steps (Morris and Freeman, 1979 Burum... 

Bosly J (1951) Akaloids of Strychnos holstii var. reticulata. J Pharm Belg 6 135-149 Braunschweiler L, Ernst RR (1983) Coherence transfer by isostropic mixing application to proton correlation spectroscopy. J Magn Reson 53 521-528 Briihwiler D, Wagner G (1986) Selective excitation of resonance coupled to C. Hetero-COSY and RELAY experiments with detection for a protein. J Magn Reson 69 546-551... 

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). 

Figure 5.79. (A) In heteronuclear relayed proton correlated spectroscopy (HERPECS), the coherence is transferred first from to a heteronuclear spin, X, and is then relayed and detected at the third nucleus, Hg. (B) A schematic representation of INADEQUATE, H,H-COSY, and H,C-COSY, relayed H,C-COSY, H,C-COLOC, and HERPECS experiments.

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. 

Further modifications (the addition of a spin-echo) allow the direct and relayed peaks to be differentiated through inversion of the direct correlations [38], and gradient-selected versions of these sequences without [39, 40] and with [10,41] such editing have also been proposed. Although the addition of TOCSY transfer is probably the most useful extension, any homonuclear mixing scheme can, in principle, be added, including a COSY, NOESY (NOE spectroscopy) or ROESY (ROE spectroscopy) step. 

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