Reciprocity of Steric and Stereoelectronic Effects in the Collagen Triple Helix
摘要:
In previous work, we demonstrated that 4-fluoroproline residues can contribute greatly to the conformational stability of the collagen triple helix, and that this stability arises from stereoelectronic effects that fix the pucker of the pyrrolidine ring and thereby preorganize the backbone properly for triple-helix formation. Here, we take a reciprocal approach, demonstrating that the steric effect of a 4-methyl group confers stability similar to that from a 4-fluoro group in the opposite configuration. Such fundamental interplay between steric and stereoelectronic effects is heretofore unknown in proteins-natural or synthetic-and provides a new means to modulate conformational stability.
Novel collagen mimics are disclosed with a tripeptide unit having the formula (Xaa-Yaa-Gly)
n
, where one of the positions Xaa or Yaa is a bulky, non-electron withdrawing proline derivative. By substituting a proline derivative at either the Xaa or Yaa position in the native collagen helix, the stability of the helix is increased due solely to steric effects relative to prior known collagen-related triple helices. Methods are also disclosed for making the novel collagen mimics.