A study of conformational stability of polypeptide blends by solid state two-dimensional 13C–1H heteronuclear correlation NMR spectroscopy

The intermolecular hydrogen-bond interactions in polyglycine (PG)/poly(l-valine) (PLV) blend with a ratio of 1/1 have been studied through high-speed frequency-switched Lee–Goldburg (FSLG) 13C–1H heteronuclear correlation (HETCOR) NMR experiments, where the PG/PLV blend sample is prepared by adding trifluoroacetic acid (TFA) solution of their polypeptide mixture containing a 2.0 wt/wt% amount of sulfuric acid (H2SO4) to alkaline water. The spectral assignment of the polypeptide blend is made by using multiple proton cross-peaks, which appeared in the HETCOR spectra. Intermolecular correlation peaks between PG(β-sheet) and PLV(β-sheet) appear in the HETCOR spectra with long contact time. From these experimental results, it has been clarified that intermolecular hydrogen-bond interactions (CO⋯H–N) between the PG(β-sheet) and PLV(β-sheet) are formed and thus the PG/PLV blend with high miscibility is formed.