HOHAHA 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 ... 

Noroxohomoyessotoxin (noroxohomoYTX, 10, Eigure 13.1), a new addition to the class of YTXs, was reported in 2001. It was isolated from the digestive glands of mussels collected in 1998 from the northern Adriatic coast of Italy. The polycyclic skeletal structure was mainly assigned on the basis of homonuclear 2D NMR spectral data obtained from correlation spectroscopy (COSY) and HOmonuclear HArtmann HAhn (HOHAHA) experiments negative ion EAB MS/MS provided further valuable information to confirm the structure. 

Total correlation spectroscopy (TOCSY) also known as homonuclear Hartmann-Hahn (HOHAHA) experiment provides all relayed connectivities within a spin system [453, 454). The primary intention in TOCSY as in other relayed experiments is to establish connectivities in less crowded spectral regions to facilitate the assignment of spin systems. 

Tamura, H., Hayashi, Y., Sugisawa, H., Kondo, T., Stmcture determination of acylated anthocyanins in Muscat Bailey A grapes by homonuclear Hartmann-Hahn (HOHAHA) spectroscopy and liquid chromatography-mass spectrometry, Phytochem. Anal., 1994, 5, 190-196. 

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

Homonuclear Hartmann-Hahn Spectroscopy or Total Correlation Spectroscopy 269 HOHAHA 20 ms HOHAHA 40 ms... 

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. 

The combination of homonuclear Hartmann-Hahn transfer with homonuclear double- or zero-quantum spectroscopy yields the so-called DREAM experiment (double-quantum relay enhancement by adiabatic mixing Berthault and Perly, 1989) and the zero-quantum-(ZQ) TOCSY experiment (Kessler et al., 1990a), respectively. Multiplet-edited HOHAHA spectra can be obtained by adding a spin-echo sequence to the Hartmann-Hahn mbdng period (Davis, 1989a). 

One of these popular experiments, for example, is the homonuclear Hartmann-Hahn experiment. It is used widely in both small molecule and protein NMR for proton resonance assignment purposes. We call it HOHAHA [Bax, A. Davis, D. G. J. Ma n. Reson. 1985, (53, 207]. It turned out that Richard Ernst had developed a similar experiment called TOCSY, well before us [Braunschweiler, L. Ernst, R. R. /. Ma n. Reson. 1983, 53, 521]. His theory for TOCSY is fully applicable to our experiment. The original TOCSY experiment didn t work very well for technical reasons and the technique had not caught on. 

An essentially identical experiment has also been referred to as Homonuclear Hartmann-Hahn spectroscopy [50,51] or HOHAHA (the two differ only in some technical details in the originally published sequences). This name arises from its similarity with methods used in solid-state NMR spectroscopy for the transfer of polarisation from proton to carbon nuclei (so-called crosspolarisation), which are based on the Hartmann-Hahn match described below. For the same reason, the transfer of magnetisation during the TOCSY sequence is sometimes referred to as homonuclear cross-polarisation. Throughout this text the original TOCSY terminology is used, although TOCSY and HOHAHA are now used synonymously in the chemical literature. 

HOHAHA Homonuclear Hartmann-Hahn spectroscopy (aka TOCSY) 5.7... 

NMR is the tool most widely used to identify the structure of triterpenes. Different one-dimension and two-dimension techniques are usually used to study the structures of new compounds. Correlation via H-H coupling with square symmetry ( H- H COSY), homonuclear Hartmann-Hahn spectroscopy (HOHAHA), heteronuclear multiple quantum coherence (HMQC), heteronuclear multiple bond correlation (HMBC), distortionless enhancement by polarisation transfer (DEPT), incredible natural abundance double quantum transfer experiment (INADEQUATE) and nuclear Overhauser effect spectroscopy (NOESY) allow us to examine the proton and carbon chemical shift, carbon types, coupling constants, carbon-carbon and proton-carbon connectivities, and establish the relative stereochemistry of the chiral centres. 

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