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. 1996 Oct;5(10):2074–2079. doi: 10.1002/pro.5560051013

Detection and characterization of an ovine placental lactogen stable intermediate in the urea-induced unfolding process.

G D Cymes 1, C Grosman 1, J M Delfino 1, C Wolfenstein-Todel 1
PMCID: PMC2143276  PMID: 8897607

Abstract

The urea-induced equilibrium unfolding of ovine placental lactogen, purified from ovine placenta, was followed by size-exclusion chromatography, far-UV CD, and intrinsic tryptophan fluorescence. The data obtained by each of these methods showed a poor fit to a two-state model involving only a native and an unfolded form. A satisfactory fit required, instead, a model that involved a stable, partially folded form in addition to the native and unfolded ones. The results obtained from the best-fitting theoretical curves for the three-state model indicated that this intermediate state, which is the predominant species in solution at 3.6 M of urea activity, is compact, largely alpha-helical, and changes considerably the native-like tertiary packing around its tryptophan residues. These findings suggest that this stable intermediate exhibits properties similar to those that characterize the molten globule state.

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Selected References

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