More accurate 1JCH coupling measurement in the presence of 3JHH strong coupling in natural abundance

► One-bond heteronuclear C-H couplings and RDCs may contain systematic errors. ► 1H-1H strong coupling causes these errors, which distort peak position. ► The errors are found in both 1H and 13C dimensions of a 2D HSQC. ► The errors are not due to digital resolution. ► Accurate coupling constants and RDCs should be obtained from fitting to simulated spectra where the effects of strong coupling are taken into account.