A predominant conformational isomer of non-native α-lactalbumin (α-LA) has been purified by thermal denaturation of the native α-LA using the technique of disulfide scrambling. This unique isomer retains a substantial content of α-helical structure. It is stabilized by two native disulfide bonds within the α-helical domain and two scrambled non-native disulfide bonds at the β-sheet domain. This denatured isomer of α-LA exhibits structural characteristics that are consistent with the well-documented molten globule state. The ability to prepare a stabilized and structurally defined molten globule provides a useful model for studying the folding and unfolding pathways of proteins.
