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HMBC-RELAY experiment

Figure 22 Pulse sequence of the HMBC-RELAY experiment. Filled and open bars represent 90° and 180° pulses, respectively. All other phases are set as x, excepted otherwise stated. A two-phase cycle x, —x is used for the pulse phases (j>, and Figure 22 Pulse sequence of the HMBC-RELAY experiment. Filled and open bars represent 90° and 180° pulses, respectively. All other phases are set as x, excepted otherwise stated. A two-phase cycle x, —x is used for the pulse phases (j>, and <p2 and the receiver phase. In order to separate the 2JCH and the nJCn spectra, two FIDs have to be acquired for each tn increment with the phase </)n set as x, — x and — x, x, respectively (interleaved mode of detection) and have to be stored separately. By using a composite 90°x — 180°y — 90°x pulse instead of a single 180° x H pulse, artefacts arising from misadjusted H pulse lengths are suppressed. The delays are calculated according to t/2 = [0.25/Vch]. 8 = [0.25/3Jhh] and A = [O.S/nJCH], The, 3C chemical shift evolution delay t, must be equal for both evolution periods.
The HMBC-RELAY experiment has merit, but suffers from several deficiencies. First, 2/ch signals for quaternary carbons are missing since the transfer of coherences from carbon to protons is restricted to protonbearing carbons. This is also the drawback of the 2/,3/-HMBC experiment. [Pg.328]

Fig. 2. Pulse sequence for the HMBC-RELAY experiment proposed by Sprang and Bigler to differentiate V from "i (n = 3, 4) long-range heteronuclear correlations. Ibises are represented as solid (90°) or open (180°) bars. All pulses are x except for the y pulse in the composite pulse and the last 90° proton pulse. A two step phase cycle, x, —x is used for the pulse phases i, 2, and the receiver phase. Two FIDs are recorded for each increment of the evolution time, ti with the phase i set as X, —X and —x, x, respectively (interleaved detection) with the data stored separately. Delays are set as D4=1/[4Vch]. D6 = 1/[4 /hh]> and D5 = y2["AH]- The evolution delay, DO, must remain equal for both evolution periods. The gradient ratio optimized for is 4, 4,... Fig. 2. Pulse sequence for the HMBC-RELAY experiment proposed by Sprang and Bigler to differentiate V from "i (n = 3, 4) long-range heteronuclear correlations. Ibises are represented as solid (90°) or open (180°) bars. All pulses are x except for the y pulse in the composite pulse and the last 90° proton pulse. A two step phase cycle, x, —x is used for the pulse phases <I>i, <I>2, and the receiver phase. Two FIDs are recorded for each increment of the evolution time, ti with the phase <I>i set as X, —X and —x, x, respectively (interleaved detection) with the data stored separately. Delays are set as D4=1/[4Vch]. D6 = 1/[4 /hh]> and D5 = y2["AH]- The evolution delay, DO, must remain equal for both evolution periods. The gradient ratio optimized for is 4, 4,...
Figure 23 HMBC-RELAY spectra recorded on cyclosporine. Top experiment optimized for yHH = 6 Hz. Bottom experiment optimized for fHH = 8 Hz. Figure 23 HMBC-RELAY spectra recorded on cyclosporine. Top experiment optimized for yHH = 6 Hz. Bottom experiment optimized for fHH = 8 Hz.
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. [Pg.156]

See other pages where HMBC-RELAY experiment is mentioned: [Pg.293]    [Pg.326]    [Pg.328]    [Pg.329]    [Pg.5]    [Pg.8]    [Pg.8]    [Pg.9]    [Pg.293]    [Pg.326]    [Pg.328]    [Pg.329]    [Pg.5]    [Pg.8]    [Pg.8]    [Pg.9]    [Pg.297]    [Pg.96]    [Pg.256]    [Pg.207]    [Pg.367]    [Pg.26]   


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