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The crystal structure of Afc-containing peptides
A Lombardi1, G De Simone, S Galdiero
1Centro Interuniversitario di Ricerca su Peptidi Bioattivi, CNR, University of Napoli "Federico II" via Mezzocannone 4, I-80134 Napoli, Italy.
Biopolymers
|February 19, 2000
Summary
The 9-amino-fluorene-9-carboxylic acid (Afc) residue in peptides typically adopts an extended conformation. However, it can form a 3(10)-helical structure when flanked by Aib residues.
Area of Science:
- Peptide Chemistry
- Structural Biology
- X-ray Crystallography
Background:
- The 9-amino-fluorene-9-carboxylic acid (Afc) residue is a non-natural amino acid with unique structural properties.
- Understanding the conformational preferences of Afc in peptide backbones is crucial for designing novel peptide-based materials and therapeutics.
Purpose of the Study:
- To systematically analyze the structural behavior of the Afc residue within peptide sequences.
- To investigate the influence of neighboring residues on the conformation of Afc.
Main Methods:
- X-ray crystallography was employed to determine the crystal structures of four protected tripeptides containing Afc.
- The peptides varied in the identity of residues flanking the central Afc residue (Glycine (Gly) and Aib (C(alpha, alpha)-dimethylglycine)).
Main Results:
- The Afc residue demonstrated a strong propensity to adopt an extended conformation in most of the studied peptides.
- An exception was observed in a peptide where Afc was flanked by two Aib residues, leading to a folded conformation within a 3(10)-helical region.
- This suggests that the helical propensity of adjacent residues can override the intrinsic preference of Afc for extended structures.
Conclusions:
- The Afc residue generally favors extended conformations in peptides.
- The presence of strong helix-promoting residues like Aib can induce helical structures involving Afc.
- These findings provide valuable insights into the conformational versatility of Afc in peptide chemistry.