title: Intramolecular ditryptophan crosslinks enforce two types of antiparallel beta structures.
abstract: BACKGROUND
  Two types of biaryl crosslinks can be formed with natural protein sidechains: ditryptophan and dityrosine. Biaryl crosslinks have the same topology as disulfide crosslinks, yet little is known about their effect on local peptide structure.
  
  
  RESULTS
  Three ditryptophan-linked peptide dimers based on the sequence Ac-Leu-Trp-Ala-COX were prepared. The tripeptide dimer with -CONH(2) termini was too insoluble to study, but the tripeptide dimer with -COOMe termini crystallized from methanol/chloroform as an antiparallel beta-sheet. The tripeptide dimer with a -CONMe(2) termini adopted a slipped antiparallel beta structure in methanol/chloroform.
  
  
  CONCLUSIONS
  These results suggest that intermolecular ditryptophan crosslinks that join the middle of peptide chains can confer a preference for antiparallel beta-sheet structure. The effect is most dramatic when both the inside and outside edges of the dimer can form hydrogen bonds as in the crystal structure of dimer 3b.
authors.affiliation: Department of Chemistry, University of California, Irvine, CA 92697-2025, USA.
authors.forename: J H
authors.initials: JH
authors.lastname: Matthews
authors.forename: T D
authors.initials: TD
authors.lastname: Dinh
authors.forename: P
authors.initials: P
authors.lastname: Tivitmahaisoon
authors.forename: J W
authors.initials: JW
authors.lastname: Ziller
authors.forename: D L
authors.initials: DL
authors.lastname: Van Vranken
mesh_terms: D003460:Crystallization; D018360:Crystallography, X-Ray; D019281:Dimerization; D006860:Hydrogen Bonding; D008958:Models, Molecular; D009842:Oligopeptides / Q000737:chemistry*; D017433:Protein Structure, Secondary; D012995:Solubility; D014364:Tryptophan / Q000378:metabolism*
chemical_list: D009842:Oligopeptides; D014364:Tryptophan