In vitro protein folding pathway

Three folding mechanisms have been proposed 

Framework model The protein folding begins with the secondary structures. This is followed by docking of the pre-formed secondary structure units to produce the native, folded macromolecule (Kim and Baldwin, 1990). For small proteins with stable secondary structure(s), they tend to adopt a-helical and turn or P-hairpin structures. These structures may start the folding process. 

Hydrophobic collapse model The formation of hydrophobic clusters drives compaction of the protein so that the polypeptide chain folds in a confined volume narrowing the conformational search to the native state (Kim and Baldwin, 1990). The expulsion of water from the burial of nonpolar surfaces provides the hydrophobic driving force and the secondary structures are formed during hydrophobic collapse. 

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