110
R. Vijayaraghavan et al. / Journal of Molecular Structure 654 (2003) 103–110
respectively. As seen from Table 5a, the molecules in
the two structures are linked by intermolecular
hydrogen bonds involving NH of DPhe and its
carbonyl oxygen of a symmetry related molecule.
The other intermolecular hydrogen bond involves Ne1
of Trp residue as a donor and carbonyl oxygen of a
symmetry related Val residue in peptide (I) and
symmetry related Leu residue in peptide (II) as
acceptors. The packing of the molecules in these
peptides are further stabilized by van der Waals
forces (Table 5b) involving hydrophobic groups
(Fig. 2a and b).
residue at ði þ 3Þ position induces an unusual
type VIa b-turn conformation. This is a new
design rule with a DPhe at ði þ 2Þ position and
is a valuable addition to the already existing
design rules with dehydro-residues that can be
exploited to provide specific structures for useful
applications.
Acknowledgements
The authors thank Council of Scientific and
Industrial Research (CSIR), New Delhi for financial
support.
4. Conclusions
The peptide design rules with a DPhe residue at
ði þ 2Þ position are summarized below:
References
[1] T.P. Singh, P. Kaur, Prog. Biophys. Mol. Biol. 66 (1996)
141.
1. The DPhe residue has been found to adopt one out
of the three conformations belonging to the
following three sets of f; c torsion angles, 260,
1408; 80, 08 and 60, 2308 or their enantiomers [1].
2. A peptide with a DPhe residue at ði þ 2Þ position
prefers a type II b-turn conformation [1].
3. A peptide with a DPhe residue at ði þ 2Þ
position and a branched b-carbon residue (Val) at
ði þ 3Þ position adopts a distorted b-turn II
conformation [8].
[2] R. Vijayaraghavan, P. Kumar, S. Dey, T.P. Singh, J. Pep. Res.
52 (1998) 89.
[3] G.M. Shedrick, SHELX 86, A Program for the Determination of
Crystal Structures, Anorganisch-Chemisches Institut der Uni-
¨ ¨
versitat, Gottingen, Germany, 1986
[4] G.M. Shedrick, SHELX 76, A Program for the Determination of
Crystal Structures, Anorganisch-Chemisches Institut der Uni-
¨ ¨
versitat, Gottingen, Germany, 1976
[5] D.T. Cromer, J.B. Mann, Acta Crystallogr. A24 (1968) 321.
[6] R.F. Stewart, E.R. Davidson, W.T. Simpson, J. Chem. Phys. 42
(1965) 3175.
4. A peptide having a DPhe residue at ði þ 2Þ
position with branched b-carbon residues on its
both sides, adopts a characteristic unfolded S-
shaped conformation with the values of f; c
torsion angles in which their signs change
alternately [9,10].
[7] J.S. Richardson, Adv. Protein Chem. 34 (1981) 167.
[8] (a) T.P. Singh, M. Haridas, V.S. Chauhan, A. Kumar, D.
Viterbo, Biopolymers 26 (1987) 816. (b) T.P. Singh, M.
Haridas, V.S. Chauhan, A. Kumar, D. Viterbo, Biopolymers 27
(1987) 1333.
[9] S.N. Mitra, S. Dey, S. Bhatia, T.P. Singh, Int. J. Biol. Marcol.
19 (1996) 103.
5. As observed in the present case, a peptide with
a DPhe residue at ði þ 2Þ position and a Trp
[10] S. Dey, S.N. Mitra, T.P. Singh, Int. J. Peptide Protein Res. 48
(1996) 123.
Vijayaraghavan
