HOHAHA Hartmann-Hahn spectroscopy

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... 

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. 

Heteronuclear Multiple Quantum Correlation) and HMBC (Heteronuclear Multiple Bond Correlation). Application of nuclear Overhauser effect (nOe) difference spectroscopy and nuclear Overhauser effect spectroscopy (NOESY) complete the analysis, giving atomic spatial relationships. Sensitivity problems can be alleviated using Homo Hartmann-Hahn spectroscopy (HOHAHA or TOCSY, Total Correlation Spectroscopy). For weak nOes a rotating frame experiment, i.e. ROESY (Rotating frame Overhauser Effect Spectroscopy) is useful, and may be the best experimental method to sequence chains of sugars [5]. 

HOHAHA (Homonuclear Hartmann-Hahn Spectroscopy). This method is based on spin propagation (Braunschweiler and Ernst 1983 Summers et al. 

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). 

HOHAHA HHPA Homonuclear Hartmann-Hahn Spectroscopy Higher Random Phase Approximation... 

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 value of COSY stems from its dependence on the presence of spin coupling between the nuclei involved in the correlation. As we have seen, such coupling for protons is usually limited to three or four chemical bonds, hence provides some specificity that is helpful for structure elucidation. On the other hand, useful complementary information can be obtained from longer range interactions among a set of coupled nuclei. The standard method for obtaining such information is described by two acronyms—TOCSY (for total correlated spectroscopy, which best describes the aim of the experiment) and HOHAHA (for fiomonu-clear Hartmann-Hahn, which better describes the mechanisms employed). 

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). 

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. 

Other two-dimensional techniques, such as correlation spectroscopy (COSY) (118), DEPT (119), Homonnclear Hartmann-Hahn (HOHAHA), sohd state (120), etc, give var5nng degrees of snccess when applied to the structure-property relationship of cellnlose triesters. The recent application of H—multiple-bond correlation (HMBC) spectroscopy for the imambiguous assignment of cellulose mixed esters has successfully demonstrated the utility of NMR for the structiu-e elucidation of complex cellnlose esters (121). It is this unique abihty to provide detailed information on intermolecular interactions of cellulose esters in coatings (115) or in polymeric blends that continues to put NMR spectroscopy well ahead of other analytical techniqnes. 

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. 

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