2D 13C-13C DARR and ASSET spectra of the amino acid mixture WYIEN (a–c) and tripeptide MLF (d–f). (a, d) Full DARR spectra showing all cross peaks. (b, e) Spectra with tarom = 0, where most Cα and Cβ cross peaks are suppressed. (c, f) ASSET spectra with tarom = 10 ms, which exhibit mostly aromatic Cα and Cβ cross peaks. The spectra in (c) and (f) are reproduced in red in (a) and (d) to compare with the full DARR spectra.