Cover image for Vol. 17 Issue 10

Editor: Meghan Campbell; Editorial Board Chairs: Thomas Carell, Donald Hilvert, Barbara Imperiali

Online ISSN: 1439-7633

Associated Title(s): ChemCatChem, ChemMedChem, ChemPhysChem, ChemSusChem

8_08/2007Cover Picture: In Vivo Screening Identifies a Highly Folded β-Hairpin Peptide with a Structured Extension (ChemBioChem 8/2007)

The cover picture shows the NMR-derived structure of a β-hairpin peptide that was identified through a fluorescence-based screen in live cells. A Petri dish covered in colonies of E. coli expressing recombinant fluorescent proteins was illuminated by ultraviolet light. Each bacterial colony expresses a single protein composed of a tandem fusion of a cyan (CFP) and a yellow (YFP) fluorescent protein. As shown in ribbon representations, peptide sequences are fused between these CFP and YFP units. Peptides that fold into β-hairpin structures tend to bring the two fluorescent proteins into closer proximity, and thus a higher FRET signal is observed. Residues in the green portions of the peptides were randomized to create libraries of many hundreds of variants, and the peptide sequence that provided the highest FRET efficiency was identified by FRET-based screening of bacterial colonies. The 3D structure of this peptide revealed that the selected residues participated in a cross-strand cation–π interaction that held the ends of the peptide closer together. More details can be found in the article by Robert E. Campbell et al. on p. 880 ff. (Image credit: Annie Tykwinski and R.E.C.)

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