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Design of peptides using α,β-dehydro-residues: Synthesis, crystal structure and molecular conformation of Boc-L-Val- ΔPhe-ΔPhe-L-Val-OCH3

✍ Scribed by Sharmistha Dey; Shome Nath Mitra; Tej P. Singh

Publisher
Wiley (John Wiley & Sons)
Year
1998
Tongue
English
Weight
591 KB
Volume
39
Category
Article
ISSN
0006-3525

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✦ Synopsis

The peptide BOC-L-Val-APhe-APhe-L-Val-OCH3 was synthesized by the azlactone method in solution phase, and its crystal and molecular structures were determined by x-ray diffraction method. Single crystals were grown by slow evaporation from a methanol/water solution at 6°C. The crystals belong to an orthorhombic space group P2,2'2' with a = 10.478 ( 6 ) 2, b = 13.953 ( I ) , c = 24.347 ( 2) and Z = 4. The structure was determined by direct methods and refined by least squares procedure to an R value of 0.052. The structure consists of a peptide and a water molecule. The peptide adopts two overlapping @-turn conformations of Types 11 and I' with torsion angles:

= 130.5 (4), $2 = 65.8 (5), $2 = 12.8 ( 6) , C$3 = 79.4 (5), $3 = 3.9 ( 7)". The conformation is stabilized by intramolecular hydrogen bonds involving Boc CO and NH of APhe' and CO of Val' and NH of Val4. The molecules are tightly packed in the unit cell. The crystal structure is stabilized by hydrogen bonds involving NH ofAPhe2 and CO ofa symmetry related (xf, fy , -z) APhe2. The solvent-water moleculeforms two hydrogen bonds with peptide molecule involving NH of Val' as an acceptor and another with CO ofa symmetry related ( Ix, y -3, fz) APhe3 as a donor. These studies indicate that a tetrapeptide with two consecutive APhe residues sequenced with valines on both ends adopts t wo overlapping &turns of Types II and 1'. = -54.8 (6).

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