n→π* interactions in poly(lactic acid) suggest a role in protein folding

Chem Commun (Camb). 2013 Sep 11;49(70):7699-701. doi: 10.1039/c3cc44317e.


Poly(lactic acid) (PLA) is a versatile synthetic polyester. We noted that this depsipeptide analog of polyalanine has a helical structure that resembles a polyproline II helix. Using natural bond orbital analysis, we find that n→π* interactions between sequential ester carbonyl groups contribute 0.44 kcal mol(-1) per monomer to the conformational stability of PLA helices. We conclude that analogous n→π* interactions could direct the folding of a polypeptide chain into a polyproline II helix prior to the formation of hydrogen bonds between backbone amides.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, U.S. Gov't, Non-P.H.S.

MeSH terms

  • Hydrogen Bonding
  • Lactic Acid / chemistry*
  • Peptides / chemistry
  • Polyesters
  • Polymers / chemistry*
  • Protein Folding
  • Proteins / chemistry*
  • Proteins / metabolism
  • Quantum Theory


  • Peptides
  • Polyesters
  • Polymers
  • Proteins
  • polyproline
  • Lactic Acid
  • poly(lactide)