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The 3D HBHANH experiment is specifically designed to correlate the 1H and 15N amide resonances of one residue with both 1HA and 1HB resonances of the same residue and of its preceding residue via the intervening 13CO, 13CA and 13CB spins by means of the 1J(NH), 1J(N,CA) (and 2J(N,CA)), 1J(CA,CO), 1J(CH) and optional 1J(CA,CB) coupling constants. This experiment is an extension of the 3D CBCANH experiment and is closelr related to the 3D HBHA(CO)NH experimentREQUIREMENTS
Implementation on AVANCE spectrometers equipped with a third channel. Improved versions using pulsed field gradients (PFGs) are also available and, therefore, in such cases gradient technology is required.VERSIONSThe experiment is applied on 15N,13C-labeled proteins. Because the amide (NH) protons are involved, the 3D HBHANH experiment must be recorded in H2O.
The original 3D HBHANH pulse sequence ( 94JMRB196-105 ) consisted of the following steps:EXPERIMENTAL DETAILS
- After a 90º 1H pulse, 1H chemical shift evolution takes place during a variable t1 period.
- Antiphase 1H magnetization with respect to 13C is also allowed to evolve and polarization transfer is achieved by applying two simultaneous 90º 1H and 13C pulses. Then, After evolution of 13CA-13CB couplings, a 90º 13C pulse transfers magnetization from 13CB to 13CA.
- Fixed evolution delay to achieve antiphase 13CA magnetization with respect to 13CO via 1J(CA,CO) followed by magnetization transfer to 13CO by simultaneous 90º 13C and 13CO pulses.
- Fixed evolution delay to achieve antiphase 13CO magnetization with respect to 15N via 1J(N,CO) followed by magnetization transfer to 15N by simultaneous 90º 15N and 13CO pulses.
- 15N chemical shift evolution during the constant-time t2 period. Magnetization is finally transferred back to the NH protons by a retro-INEPT pulse train and proton acquisition is recorded under 15N decoupling.
Several versions have been proposed incorporating the following modifications:
- Use of WATERGATE:
- Similar 3D H(CCO)NH or 3D H(C)(CO)NH-TOCSY experiments use isotropic 13C mixing instead of a 90º COSY-type pulse to transfer magnetization from the aliphatic 13C to 13CA.
- A 4D HCC(CO)NH experiment has also been proposed ( 93JB349 ).
More details on practical implementation of the 3D HBHANH experiment on AVANCE spectrometers can be found in the corresponding Tutorial 3D HBHANH experimentSPECTRA
The HBHANH experiment affords a 3D spectrum in which 1H, 15N and 1HA/1HB chemical shifts are displayed in three independent dimensions. Intra-residue and sequential connectivities are due to 1J(NH) + 1J(N,CA) + 1J(CA,CO) + 1J(CH) + optional 1J(CA,CB) and 1J(NH) + 2J(N,CA) + 1J(CA,CO) + 1J(CH) + optional 1J(CA,CB)RELATED TOPICS
See list of 3D triple-resonance NMR experiments for doubly-labeled proteins.