No Karplus relationship has been defined.

As a general trend, large (>1.7 Hz) and small (<1 Hz) values indicate trans and gauche conformations. Thus, values of 2.1 Hz have been reported for Val and Ile residues in trans conformation and 0.5 Hz for gauche conformation.

Two different NMR methods based on the so-called quantitative J correlation methodology have been described to measure ³J_N,Cg coupling constants:

A simple 2D ¹H-¹⁵N{¹³Cg} spin-echo difference experiment was proposed to measure ³J_N,Cg coupling constants on methyl carbons ( 93JACS5334 and 97JACS1803 ). A more sensitive version has been reported ( 97JB323 ).

Alternatively, these coupling constants can also be measured from 3D HNCG or related HN(CO)CG ( 00JMR126-146 ) experiments.

Measurement of 3J(N-CG) in methyl groups using methyl-TROSY J-quantitative experiment ( 04JACS9827 )

Application of in the study of side-chain conformation in an unfolded protein ( 99JMB705 ).