Millisecond Time Resolved Photo-CIDNP NMR Reveals a Non-Native Folding Intermediate on the Ion-Induced Refolding Pathway of Bovine α-Lactalbumin

Aspects of the structure of the intermediate populated after 200 ms in the Ca2+-induced refolding of α-lactalbumin have been derived by time-resolved photo-CIDNP NMR methods. Refolding at constant denaturant concentration was initiated by laser-induced ion release from photolabile chelators. The NMR data demonstrated that part of the polypeptide chain in the β-domain of α-lactalbumin samples adopt non-native conformations while a hydrophobic core of the α-domain is already formed (see picture).