Mapping energy landscapes of a growing filamin domain reveals an intermediate associated with proline isomerization during biosynthesis

200 uM [U-13C; U-15N] FLN5, 10 mM HEPES, 30 mM ammonium chloride, 12 mM magnesium chloride,
2 mM beta-mercaptoethanol, 1 mM EDTA, 90% H2O/10% D2O