1H-13C HSQC
This experiment provides correlation between the aliphatic carbon and its attached protons. The constant time (CT) version of this experiment is normally used. The "constant time" refers to the entire evolution period between the two INEPT steps which is kept constant in this experiment. If this evolution period is set to be the inverse of the J-coupling constant, then the sign of the magnetization of those carbons with an odd number of aliphatic carbon attached will be opposite to those with an even number. For example, if the Cβ of leucine appears as a positive peak (2 aliphatic carbons attached), then the Cγ (3 aliphatic carbons attached) and Cα (1 aliphatic carbons attached) would appear negative.
Read more about this topic: Heteronuclear Single Quantum Coherence Spectroscopy, HSQC in Protein NMR