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Aromatic-Aromatic Interactions in Crystal Structures of Helical Peptide Scaffolds Containing Projecting Phenylalanine Residues

Aravinda, Subrayashastry and Shamala, Narayanaswamy and Das, Chittaranjan and Sriranjini, Arumugam and Karle, Isabella L and Balaram, Padmanabhan (2003) Aromatic-Aromatic Interactions in Crystal Structures of Helical Peptide Scaffolds Containing Projecting Phenylalanine Residues. In: Journal of the American Chemical Society, 125 (18). pp. 5308-5315.

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Aromatic-aromatic interactions between phenylalanine side chains in peptides have been probed by the structure determination in crystals of three peptides: Boc-Val-Ala-Phe-Aib-Val-Ala-Phe-Aib-OMe, I; Boc-Val-Ala-Phe-Aib-Val-Ala-Phe-Aib-Val-Ala-Phe-Aib-OMe, II; Boc-Aib-Ala-Phe-Aib-Phe-Ala-Val-Aib-OMe, III. X-ray diffraction studies reveal that all three peptides adopt helical conformations in the solid state with the Phe side chains projecting outward. Interhelix association in the crystals is promoted by Phe-Phe interactions. A total of 15 unique aromatic pairs have been characterized in the three independent crystal structures. In peptides I and II, the aromatic side chains lie on the same face of the helix at ii+ 4 positions resulting in both intrahelix and interhelix aromatic interactions. In peptide III, the Phe side chains are placed on the opposite faces of the helix, resulting in exclusive intermolecular aromatic interactions. The distances between the centroids of aromatic pair ranges from 5.11 to 6.86 Å, while the distance of closest approach of ring carbon atoms ranges from 3.27 to 4.59 Å. Examples of T-shaped and parallel-displaced arrangements of aromatic pairs are observed, in addition to several examples of inclined arrangements. The results support the view that the interaction potential for a pair of aromatic rings is relatively broad and rugged with several minima of similar energies, separated by small activation barriers.

Item Type: Journal Article
Publication: Journal of the American Chemical Society
Publisher: American Chemical Society
Additional Information: Copyright for this article belongs to American Chemical Society
Department/Centre: Division of Biological Sciences > Molecular Biophysics Unit
Division of Physical & Mathematical Sciences > Physics
Division of Chemical Sciences > Inorganic & Physical Chemistry
Date Deposited: 28 Aug 2004
Last Modified: 19 Sep 2010 04:14
URI: http://eprints.iisc.ac.in/id/eprint/1219

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