Biomedical Engineering Reference
In-Depth Information
at Z 526 2 2 528. Subsequently, two more groups, that are the next
farthest away will go, and lastly, the two neighbours.
At the time, the ensemble was modelled more symmetrically, with only two
different electrostatic interaction contributions—one between neighbours and
one across the molecule (see Figure 10.4). We used a partition-function
approach since the free ligand concentration is known (pH). For example:
½
IP6
11{
½
IP6
12{
z
½
IP6
11{
z
½
IP6
10{
z
:::::
z
½
IP6
6{
f
½
IP6
11{
~
ð
10
:
18
Þ
g
11
K
12,11
A
½
H
z
~
½
H
z
2
z
::::
zK
12,11
A
½
H
z
6
1zg
11
K
12,11
A
½
H
z
zg
10
K
12,11
A
K
11,10
A
K
11,10
A
K
10,9
A
K
9,
A
K
8,
A
K
7,6
A
whereK
i,
A
are the H
+
association constants for the step i-?j-, and where g
i
are
the number of possible configurations for each charged species.
Figure 10.4
Partition-function approach for the proton-binding configurations of
IP6. Illustrated are the configurations with two protons. Values in
parentheses indicate the number of species. The electrostatic interaction
between the sites shown as occupied in configurations 2c and 2g is
different from the site-site interactions in the other configurations, and
forms the basis for the semi-equivalence points in the titration. Adapted
from ref. 11.
