Coupling Constants in Proteins
Hydrogen Bond Experiments
Multiplicity edited HMBC
The edited HMBC experiment edits into two subspectra according to the number of protons attached to 13C nuclei being odd or even.
a) Standard sequence
b) Up-down sequence
HMBC pulse sequences with a 3rd order low-pass J filter for editing into two subspectra according to the number of directly attached protons being odd or even:
Filled and open bars refer to /2 and pulses, respectively, while the dashed box represents 13C decoupling. = (2×1JCH)-1 and is the delay necessary for a gradient.
The initial four gradients of the low-pass J filter can be set an order of magnitude weaker than the other gradients for formation of heteronuclear gradient echoes.
The recommended phase cycle is:
The delays for the 3rd order low-pass J filter is
a) Standard HMBC pulse sequence where the echo is selected by the filled gradients and the antiecho by the open gradients;
b) up-down HMBC pulse sequence inverting 13CH and 13CH3 peaks relative to the standard sequence and where the echo is selected by the +5G/-5G gradients and the antiecho by the -3G /+3G gradients.
Code and procedures
Document: Edited HMBC (index.shtml)
Last modified: 2006-05-24