Molten globule

A molten globule (MG) is an intermediate state in the folding pathway of a protein that has some secondary and tertiary structure, but lacks the well packed amino acid side chains that characterize the native state (N) of a protein. The transition from a denatured (U) state to a molten globule may be a two state process

U ↔ MG

Or it may be a continuous transition, with no cooperativity and no apparent "switch" from one form to the other. In any event, a model that can be used in some proteins is a three step process:

U ↔ MG ↔ N

That the products of de novo protein design have been found to be molten globules instead of native state proteins is an issue in the design of purely synthetic proteins.

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Further information

Is the molten globule a third phase of proteins?

http://www.stanford.edu/group/pandegroup/papers/MGpnas.pdf