Sterics and Stereoelectronics in Aza-Glycine: Impact of Aza-Glycine Preorganization in Triple Helical Collagen.

We previously demonstrated aza-glycine can serve as a reliable and general replacement of glycine in triple helical collagen. Aza-glycine considerably improves collagen's thermal stability and self-assembly properties without changing collagen's natural triple helix topology. We provided a firm structural basis for this stabilization with an atomic resolution crystal structure of collagen containing aza-glycine which revealed new cross-strand H-bonds within the triple helix interior. Here, using computational analysis, we show the enhanced properties of aza-glycine is a result of noncovalent forces (H-bonding) and backbone preorganization. The interplay of steric repulsion and hyperconjugative interactions in aza-glycine's backbone directly preorganizes the collagen peptide main-chain (φ, ψ) dihedrals for triple helical assembly. The synergy of multiple structural and electronic changes which originate at the residue level in the aza-glycine backbone and culminate at the macromolecular level of the triple helix lead to increased stability and faster refolding of collagen peptides containing aza-glycine.