Proton-detected solid-state NMR spectroscopy of natural-abundance peptide and protein pharmaceuticals.

The natural way: A sensitive NMR spectroscopic method is developed to obtain well-resolved two-dimensional spectra ((15)N-(1)H and (13)C-(1)H) for natural-abundance (that is, without the need for isotopic enrichment) large-molecule samples, such as biopharmaceuticals. This method gives structural insights on two lyophilized aprotinin samples and three insulin samples in lyophilized, microcrystalline suspension formulation (red; see picture) and fibril (green) forms.