title: Self-assembly of left- and right-handed molecular screws.
abstract: Stereoselectivity is a hallmark of biomolecular processes from catalysis to self-assembly, which predominantly occur between homochiral species. However, both homochiral and heterochiral complexes of synthetic polypeptides have been observed where stereoselectivity hinges on details of intermolecular interactions. This raises the question whether general rules governing stereoselectivity exist. A geometric ridges-in-grooves model of interacting helices indicates that heterochiral associations should generally be favored in this class of structures. We tested this principle using a simplified molecular screw, a collagen peptide triple-helix composed of either l- or d-proline with a cyclic aliphatic side chain. Calculated stabilities of like- and opposite-handed triple-helical pairings indicated a preference for heterospecific associations. Mixing left- and right-handed helices drastically lowered solubility, resulting in micrometer-scale sheet-like assemblies that were one peptide-length thick as characterized with atomic force microscopy. X-ray scattering measurements of interhelical spacing in these sheets support a tight ridges-in-grooves packing of left- and right-handed triple helices.
authors.affiliation: Center for Advanced Biotechnology and Medicine, Department of Biochemistry and Molecular Biology, Robert Wood Johnson Medical School, Rutgers University , Piscataway, New Jersey 08854, United States.
authors.forename: Fei
authors.initials: F
authors.lastname: Xu
authors.forename: I John
authors.initials: IJ
authors.lastname: Khan
authors.forename: Kenneth
authors.initials: K
authors.lastname: McGuinness
authors.forename: Avanish S
authors.initials: AS
authors.lastname: Parmar
authors.forename: Teresita
authors.initials: T
authors.lastname: Silva
authors.forename: N Sanjeeva
authors.initials: NS
authors.lastname: Murthy
authors.forename: Vikas
authors.initials: V
authors.lastname: Nanda
mesh_terms: D018625:Microscopy, Atomic Force; D046529:Microscopy, Electron, Transmission; D012542:Scattering, Radiation; D012995:Solubility; D013237:Stereoisomerism