heteronuclear single quantum coherence FIX:0000148 HSQC A type of heteronuclear NMR spectroscopy where a second frequency dimension is employed to disperse the signals and reveal correlations between protons and the nuclei to which they are covalently bound. In HSQC only the magnetisation of one nucleus is allowed to evolve over time. CHMO:0000604 heteronuclear two-dimensional nuclear magnetic resonance spectroscopy