Homonuclear Hartmann-Hahn

The ID homonuclear Hartmann-Hahn (HOHAHA) experiment is an excellent way to determine complete coupled spin networks (18). The following pulse sequence is used ... 

Because of the complexity of the polyether antibiotics tittle progress has been made in stmcture determination by the chemical degradation route. X-ray methods were the techniques most successfully applied for the early stmcture elucidations. Monensin, X206, lasalocid, lysocellin, and salinomycin were included in nineteen distinct polyether x-ray analyses reported in 1983 (190). Use of mass spectrometry (191), and H (192) and nmr (141) are also reviewed. More recently, innovative developments in these latter techniques have resulted in increased applications for stmcture determinations. Eor example, heteronuclear multiple bond connectivity (hmbc) and homonuclear Hartmann-Hahn spectroscopy were used to solve the stmcture of portimicin (14) (193). East atom bombardment mass spectrometry was used in solving the stmctures of maduramicin alpha and co-factors (58). 

Homonuclear Hartmann-Hahn Spectroscopy or Total Correlation Spectroscopy 267... 

HOMONUCLEAR HARTMANN-HAHN SPECTROSCOPY (HOHAHA), OR TOTAL CORRELATION SPECTROSCOPY (TOCSY)... 

We now want to turn to another experiment which, we must make clear at the start, does not have any relationship in theory to NOE experiments. In fact the theory is so complicated that we shall not say anything about it at all, but just refer you to one of the books in the Appendix. We are including this experiment because of its unique advantages when the spectrum has overlapping multiplets. It is called TOCSY, which stands for Total Correlation SpectroscopY (it has a second, more amusing name HOHAHA, standing for HOmonuclear HArtmann-HAhn), and is of particular use when oligosaccharides or peptides are under study. 

Homology modeling, 20 837 Homomenthyl salicylate, 22 16 physical properties of, 22 14t Homonuclear Hartmann-Hahn spectroscopy, 20 137 Homopolymerization, 10 183 of a-olelins, 16 110 ethene, 16 102-103 propene, 16 104-110 of VDC, 25 695-697 Homopolymers... 

Hirota and coworkers41 reported a planar structure of new polyene macrolide antibiotic YS-822A (65), which they isolated. XH and 13C NMR spectra of 65 showed a number of broad and overlapping signals, but the 1H-1H and 13C- H COSY spectra implied the existence of a mycosamine moiety and several other partial structures. The connectivity of these partial structures was established by extensive 2D NMR experiments, including homonuclear Hartmann-Hahn and heteronuclear multiple-bond connectivity measurements, which led to the determination of the gross planar structure of 65. 

These intermolecular correlation peaks mean that intermolecular cross polarization (CP) occurs between the carbon and proton of intermolecular -interacting polypeptides in blend. There may be two pathways for the observed intermolecular CP. One is that a direct transfer from proton to carbon exists, and another is that a change in the magnetization by spin diffusion (homonuclear Hartmann Hahn transfer) exists. It is thought that the former is much more efficient than the latter because the former comes from only one magnetization transfer process, but the latter comes from two... 

As demonstrated by Hartmann and Hahn (1962), energy-matched conditions can be created with the help of rf irradiation that generates matched effective fields (see Section IV). Although Hartmann and Hahn focused on applications in the solid state in their seminal paper, they also reported the first heteronuclear polarization-transfer experiments in the liquid state that were based on matched rf fields. A detailed analysis of heteronuclear Hartmann-Hahn transfer between scalar coupled spins was given by Muller and Ernst (1979) and by Chingas et al. (1981). Homonuclear Hartmann-Hahn transfer in liquids was first demonstrated by Braunschweiler and Ernst (1983). However, Hartmann-Hahn-type polarization-transfer experiments only found widespread application when robust multiple-pulse sequences for homonuclear and heteronuclear Hartmann-Hahn experiments became available (Bax and Davis, 1985b Shaka et al., 1988 Glaser and Drobny, 1990 Brown and Sanctuary, 1991 Ernst et al., 1991 Kadkhodaei et al., 1991) also see Sections X and XI). 

Various authors have used different names for Hartmann-Hahn-type experiments that emphasize distinct experimental or theoretical aspects. For example, heteronuclear Hartmann-Hahn transfer in liquids has been called coherence transfer in the rotating frame (Muller and Ernst, 1979), J cross-polarization (JCP Chingas et al., 1981), heteronuclear crosspolarization (Ernst et al., 1991), HEHAHA (heteronuclear Hartmann-Hahn transfer Morris and Gibbs, 1991), and hetero TOCSY (total correlation spectroscopy Brown and Sanctuary, 1991). Homonuclear Hartmann-Hahn transfer has been referred to as TOCSY (Braunschweiler... 

Although in general, only one multiple-pulse sequence is applied to homonuclear spin systems, it can be useful to apply different multiple-pulse sequences to several nuclear species at the same time by using separate rf channels. In heteronuclear Hartmann-Hahn experiments, the same multiple-pulse sequence is usually applied simultaneously to two or more nuclear species. However, some selective homonuclear Hartmann-Hahn experiments are also based on the simultaneous irradiation of a multiple-pulse sequence at two or more different frequencies (see Section X). If only a single homonuclear rf channel is used, this can be achieved experimentally by adding an amplitude or phase modulation to the sequence, in order to create appropriate irradiation sidebands (Konrat... 

For the practical implementation of Hartmann-Hahn experiments, the type of multiple-pulse sequence can be important (see Section III). Continuous wave (CW) irradiation represents the simplest homonuclear Hartmann-Hahn mixing sequence (Bax and Davis, 1985a). Simultaneous CW irradiation at the resonance frequencies of two heteronuclear spins is the simplest heteronuclear Hartmann-Hahn mixing sequence (Hartmann and Hahn, 1962). 

Isotropic effective /-coupling tensors (/) with a scaling factor s 1 are characteristic for ideal homonuclear Hartmann-Hahn experiments and, in particular, for homonuclear isotropic mixing experiments (see Section X). Isotropic effective /-coupling tensors can also be created between heteronuclear spins i and m (see Section XI) however, this results in a reduced effective coupling constant with a scaling factor i 1/3 [see Eq. (115)]. 

Sjj 1/2) are also characteristic for many selective homonuclear Hartmann-Hahn experiments based on doubly selective rf irradiation (see Section X.C). 

Homonuclear Hartmann-Hahn transfer functions for off-resonant CW irradiation have been derived for two coupled spins 1 /2 (Bazzo and Boyd, 1987 Bothner-By and Shukla, 1988 Elbayed and Canet, 1990) and for the AX 2 spin system (Chandrakumar et al., 1990). In the multitilted frame, Hartmann-Hahn transfer functions under mismatched effective fields are related to polarization- and coherence-transfer functions in strongly coupled spin systems (Kay and McClung, 1988 McClung and Nakashima, 1988 Nakai and McDowell, 1993). Numerical simulations of homonuclear... 

Mohebbi and Shaka (1991b) also developed selective homonuclear Hartmann-Hahn experiments based on zero-quantum analogs of DANTE sequences (Bodenhausen et al., 1976 Morris and Freeman, 1978) and binomial solvent suppression methods (Plateau and Gueron, 1982 Sklenaf and Starcuk, 1982 Hore, 1983) (see Section X.C). 

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