Biology Reference
In-Depth Information
In Fig. 7-11, the P atom is placed at the origin, and the P-O(-C
3
') along the
negative z-axis. The other P-O(-C
5
') bond is in the x,z-plane at
Angle is the angle between the x,z-plane and the plane defined by these
two P-O bonds. In Fig. 7-12, the C
3
' atom is placed at the origin, and the
C
3
'-O and the O-P bonds are in the x,z-plane. Angle is the angle
between the x,z-plane and the plane defined by the H
3
'-C
3
' and the C
3
'-O
bonds. In both cases, the positive value follows the right-hand rule along
the z-axis. Again, due to the relative large van der Waal radius of the P
atom, tolerance is plotted again
for P atom only in Fig. 7-13.
Figure 7-13.
Tolerance as a function of
for P atom only.
Similar to the situation for the combination of and tolerance can also
be plotted for the combination of and excluding the P atom. Symmetry
of still exists for DNA. However, the presence of the OH group attached
to the C
2
' atom on RNA makes this symmetry no longer valid (Murthy
et
al.,
1999). Fig. 7-14 illustrates tolerance as a function of and for DNA.
Thus, it is clear that the 3'-end of the nucleotide unit is more restricted due
to steric hindrance than the 5'-end.
