H2BC for Bruker

Pulse programs

• H2BC with second order low-pass J filter (XWinNMR 2.6+):
  h2bc_cteal2
• H2BC with third order low-pass J filter (XWinNMR 2.6+):
  h2bc_cteal3
• H2BC with second or third order low-pass J filter and multiplicity editing (TopSpin 1.3):
  h2bc_two

Procedure for h2bc_two

1. Start with a HSQC parameterset rpar HSQCETGP all
2. Change pulse program to h2bc_two pulprog h2bc_two
3. Set up the acquisition parameters ased
4. Set cnst6 to 125 Hz, cnst8 to 165 Hz and cnst15 to 20 ms.
5. For a standard H2BC-experiment: set the ZGOPTNS to -DSUB and L31 to 0 ZGOPTNS -DSUB; l31 0 If this is not done two experiments will be acquired in interleaved mode for multiplicity editing and this will require som extra processing steps. Please see the procedure for edited h2bc. This point can be skipped for the pulse programs h2bc_cteal2 and h2bc_cteal3.
6. Adjust sw and/or cnst15 until the calculated parameter TD1MAX is less or equal to the current td1 (= number of increments of t₁ × 2)
7. Make sure the power for the decoupling schemes is suitable for your system.
8. Set the number of scans to ~ 4× that of a decent HSQC on the same sample. Keep the same receiver gain.
9. Start the experiment and keep an eye on the amplifiers and temperature of the sample.

Processing

1. Do two-dimesional Fourier transform XFB
2. Phase the signals to either pure absorption or pure dispersion. Weak signals will benefit from the latter.
3. Cross peaks generally correlates protons with carbons two bonds away.