A considerable degree of variability exists in the way that H-1, C-13
and N-15 chemical shifts are reported and referenced for biomolecules.
In this article we explore some of the reasons for this situation and
propose guidelines for future chemical shift referencing and for conv
ersion from many common H-1, C-13 and N-15 chemical shift standards, n
ow used in biomolecular NMR, to those proposed here.