Biology Reference
In-Depth Information
125
Table 5-2. A typical set of Cartesian coordinates for atoms C
-1,
N,
C and N
+1
.
x
y
z
C
-1
-13.351
10.195
6.742
N
-14.244
9.389
7.285
-14.271
9.077
8.721
C
-13.756
7.654
8.943
-12.711
7.340
8.199
N
+1
They are in Angstrom units, A, or 0.1 nm. The third decimal place may not
be reliable. As discussed later, the first two decimal places are generated by
the use of a standard peptide unit. To position the atom at the origin, the
above set of coordinates is translated to give the result listed in Table 5-3:
Table 5-3. Translated coordinates of atoms listed in Table 5-2, with
-atom positioned at
the origin of the new coordinates.
y
x
z
0.920
1.118
-1.979
C
-1
N
0.027
0.312
-1.436
0.0
0.0
0.0
0.515
-1.423
0.222
C
1.560
-1.737
-0.522
N
+1
The vectors
C
-1,
N
,
C
and
N
+1
are thus defined by the new coordinates (Fig.
5-6). From these, we can calculate the unit normals to the three planes (Fig.
5-3),
U
,
V
and
W
, as mentioned above. We have:
