110
A. Bagaria and S. Ramakumar
Table 5 Backbone Torsion angles (°) for two conformers A and B of L -Valyl-α,
βdehydrophenylalanine (VF) and for l-Valyl-l-phenylalanine
Torsion angle
(VF) A
(VF) B
VF (Form 1)
ψ1 = N1–C1α–C1 -N2
145.95 (31)
127.36 (30)
151.35 (11)
ω1 = C1α–C1 –N2 C2α
178.75 (29)
−174.01 (27)
172.31 (11)
φ2 = C1 –N2–C2α–C2
58.36 (41)
53.41 (39)
48.55 (16)
T1 = N2–C2α–C2 –OT1
23.26 (50)
25.84 (48)
48.4 (10)
T2 = N2–C2α-C2 -OT2
−158.48 (34)
−157.17 (33)
−136.3 (14)
θ = C1β–C1αL C2α–C2β
22.2
40.4
19.97
3.2.5 Crystal Packing
The dipeptide VF (Fig. 12) was crystallized by controlled slow evaporation in
methanol–water mixture. There are two crystallographically independent conformers in the asymmetric unit. The two conformers of VF, have |θ| = C
β
1
–
C α
1
LC α
2
–C
β
2
= 22.23° and 40.4° (Table 5) respectively, thereby exhibiting conformation with both side chains located on the same side of the plane defined by
the peptide bond.
In VF, four peptide molecules constitute the circumference of the rectangular channel. The crystal packing can be seen in Fig. 12. The interior of this
channel is hydrophilic due to the presence of CONH moieties and NH 3 + and
−OOC groups, while the exterior is hydrophobic as it is occupied by the side
Fig. 12 The crystal packing of the dipeptide II as seen down the b axis, It can be seen that four
dipeptide molecules aggregate to form a rectangular channel with water molecules (♦) trapped
inside
A. Bagaria and S. Ramakumar
Table 5 Backbone Torsion angles (°) for two conformers A and B of L -Valyl-α,
βdehydrophenylalanine (VF) and for l-Valyl-l-phenylalanine
Torsion angle
(VF) A
(VF) B
VF (Form 1)
ψ1 = N1–C1α–C1 -N2
145.95 (31)
127.36 (30)
151.35 (11)
ω1 = C1α–C1 –N2 C2α
178.75 (29)
−174.01 (27)
172.31 (11)
φ2 = C1 –N2–C2α–C2
58.36 (41)
53.41 (39)
48.55 (16)
T1 = N2–C2α–C2 –OT1
23.26 (50)
25.84 (48)
48.4 (10)
T2 = N2–C2α-C2 -OT2
−158.48 (34)
−157.17 (33)
−136.3 (14)
θ = C1β–C1αL C2α–C2β
22.2
40.4
19.97
3.2.5 Crystal Packing
The dipeptide VF (Fig. 12) was crystallized by controlled slow evaporation in
methanol–water mixture. There are two crystallographically independent conformers in the asymmetric unit. The two conformers of VF, have |θ| = C
β
1
–
C α
1
LC α
2
–C
β
2
= 22.23° and 40.4° (Table 5) respectively, thereby exhibiting conformation with both side chains located on the same side of the plane defined by
the peptide bond.
In VF, four peptide molecules constitute the circumference of the rectangular channel. The crystal packing can be seen in Fig. 12. The interior of this
channel is hydrophilic due to the presence of CONH moieties and NH 3 + and
−OOC groups, while the exterior is hydrophobic as it is occupied by the side
Fig. 12 The crystal packing of the dipeptide II as seen down the b axis, It can be seen that four
dipeptide molecules aggregate to form a rectangular channel with water molecules (♦) trapped
inside