Hartmann-Hahn transfer combination experiments

Zuiderweg, 1995). In the case of a linear ISQ system, concatenated cross-polarization (CCP Majumdar and Zuiderweg, 1995) is more efficient than two sequential double-resonance (DCP) Hartmann-Hahn transfer steps. The CCP scheme is a combination of a DCP and TCP experiment with optimized mixing times Tj and Tj that depend on the magnitudes of and J Q (Majumdar and Zuiderweg, 1995). 

One-dimensional subspectra also may be obtained by combining selective excitation and broadband homonuclear Hartmann mixing with het-eronuclear polarization-transfer steps like INEPT, DEPT (distortionless enhancement by polarization transfer), or heteronuclear Hartmann-Hahn transfer (Doss, 1992 Gardner and Coleman, 1994 Willker et al., 1994). Related experiments with multiple-step selective Hartmann-Hahn mixing in combination with heteronuclear coherence transfer were used by Kupce and Freeman (1993a). 

The combination of HOHAHA transfer with cross-relaxation in the rotating frame leads to TOCSY-ROESY (TORO) or ROESY-TOCSY (ROTO) experiments (Kessler et al., 1988a Williamson et al., 1992). Two-dimensional hetero-TOCSY-NOESY experiments (Kellogg et al., 1992 Kellogg and Schweitzer, 1993), which combine heteronuclear Hartmann-Hahn transfer with a homonuclear NOESY mixing step, have been used for a P-driven assignment strategy of RNA and DNA spectra. 

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). 

The addition of a HOHAHA mixing step to a heteronuclear multiple-quantum correlation (HMQC) experiment (Bax et al., 1983) yields two-dimensional HMQC-HOHAHA experiments (Lerner and Bax, 1986 Davis, 1989b Oh et al., 1989 Gronenborn et al., 1989b John et al., 1991 Willker et al., 1993a). Domke and McIntyre (1992) combined heteronuclear Hartmann-Hahn transfer with multiplicity editing techniques. 

For the qualitative and quantitative determination of coupling constants, Hartmann-Hahn transfer can be of assistance and also provides a number of new approaches. These approaches are based on Hartmann-Hahn transfer functions or on the efficient transfer of coherence in one subset of the spin system while the polarization of a second subset of spins remains untouched (E.COSY principle). Furthermore, in combination with other experiments, the in-phase multiplets of Hartmann-Hahn experiments can be used as a reference in an iterative fitting of coupling constants in antiphase multiplets. 

In multidimensional NMR experiments that contain several evolution and mixing periods, even more combinations are possible (Griesinger et al., 1987b). In these experiments, Hartmann-Hahn mixing periods with in-phase coherence transfer are of particular advantage, because the resolution is often limited in the indirectly detected frequency dimensions. 

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