The pure absorptive in-

or antiphase doublets, with splittings due solely to the desired one-bond couplings, allow the direct and accurate determination of the scalar coupling constants. To investigate their potential use for RDC measurement, we have also tested the performance of the new sequences on the same model compound (2) but this time dissolved in a weakly-orienting liquid crystalline phase of ether/alcohol mixture, as proposed by Rückert and Otting [11]. The high quality of the spectra and the selected carbon traces, with pure absorptive in- or antiphase doublets, shown in Fig. 4 demonstrates selleck the good performance of these experiments, and promises the reliable measurement of RDCs, as exemplified for selected multiplets of C5. It should be mentioned here that E7080 in vitro the undesired extra signals marked by asterisks (*) in Fig. 4, which arise from the weakly orienting phase in the anisotropic sample, show considerably reduced intensity in the broadband proton-decoupled spectra, but this is simply due to T2 relaxation during the extended acquisition scheme of the decoupled sequences. It is also important to note that following the IPAP-approach, as proposed earlier [16] (that is, adding and subtracting CLIP- and

CLAP-HSQC spectra) allows quantitative extraction of one-bond coupling constants even in the case of complete overlap of α and β components of different doublets. With a slight modification of the CLIP-HSQC sequence described above, a new method for generating broadband proton-decoupled (pure shift) HSQC (PS-HSQC) spectra is proposed. Such spectra have hitherto required a different experimental approach [24]. The PS-HSQC sequence depicted in Fig. 5 starts with the CLIP-HSQC block of the sequence in Fig. 1, but here the last purging carbon 90° pulse (which becomes superfluous when X-decoupling is used during detection) is omitted. In addition, the acquisition scheme detailed in the HSP90 previous section is extended with two

elements: (1) an appropriately-positioned carbon inversion 180° pulse (shown in gray) is needed to refocus the evolution of one-bond heteronuclear coupling between the detected FID chunks; and (2) composite pulse X-decoupling is turned on during FID acquisition s(t3) to remove the undesired heteronuclear coupling interactions and so to obtain a fully decoupled, pure shift (PS) X–1H correlation spectrum. The beneficial features of the PS-HSQC sequence presented are illustrated in Fig. 6, which compares the HSQC spectra of d-sucrose and representative F2 traces recorded with the standard non-decoupled and decoupled experiments. It is evident from the spectra presented that the removal of proton–proton splittings from X–1H correlation spectra yields a considerable resolution improvement, making unambiguous spectral assignments and automated analyses feasible even in crowded spectra.