Predictions by restraint free folding

Highly simplified models of protein structure embedded into low coordination lattices have been used for tertiary structure prediction for almost 20 years [65, 66, 75]. For example, Covell and Jemigan [64] enumerated all possible conformations of five small proteins restricted to fee and bcc lattices. They found that the nativelike conformation always has an energy within 2% of the lowest energy. Virtually simultaneously. Hinds and Levitt [28] used a diamond lattice model where a single lattice unit represents several residues. While such a representation cannot reproduce the geometric details of helices or P-sheets, the topology of native folds could be recovered with moderate accuracy. 

The pioneering work in the use of medium resolution protein models to predict protein structure ab initio is due to Levitt and Warshel [75]. They were able to obtain models of BPTI with a cRMSD from native of about 6.5 A. The significance of these predictions was later called into question by Hagler and Honig [200], who obtained comparable quality structures using a glycine and 

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