A study of the conformational stability of poly(l-alanine), poly(d-alanine), poly(l-isoleucine), polyglycine and poly(l-valine) and their polypeptide blends in the solid-state by 13C CP/MAS NMR

13C CP/MAS NMR and 1H T1ρ experiments on homopolypeptides obtained from d- and l-alanines, l-isoleucine, glycine and l-valine, and on their polypeptide blends have been carried out, in order to elucidate the conformational stability of the polypeptides in the solid-state. These polypeptide blends were prepared by adding trifluoroacetic acid (TFA) solutions of the polypeptides containing a 2.0% (w/w) amount of sulfuric acid (H2SO4) to alkaline water. From these experimental results, it was clarified that the conformations of the polypeptides in their blends are strongly influenced by intermolecular hydrogen bonding interactions which cause their miscibility at the molecular level.