Chemistry Reference
In-Depth Information
3
2.5
2
1.5
1
0.5
0
-0.5
-1
-1.5
-2
-2.5
3
5
7
9
11
13
|log K
OH
|
3
2.5
2
1.5
1
0.5
0
-0.5
-1
-1.5
-2
-2.5
0.05
0.07
0.09
0.11
0.13
0.15
0.17
0.19
σ
p
FIGURE 1.6
In vitro inhibition of enzyme activity by metal ions is correlated
with the absolute value of the logarithm of the first hydrolysis constant (i.e., K
OH
for
M
n+
+ H
2
O → MOH
n−1
+ H
+
) and the softness index (σ
p
). Inhibition data for these three
enzymes were produced by Christensen (1971/1972) and Christensen and Tucker (1976).
White diamonds = catfish carbonic anhydrase IC
50
, grey squares = white sucker lactic
dehydrase IC
20
and black triangles = white sucker glutamic oxaloacetic transaminase IC
20
.
McCloskey 1996), and fungal germination (Somers 1961) (
Figure 1.7
top panel).
Weltje (2002) found similar trends for bacterial bioluminescence inhibition by a
series of lanthanides.
Some central themes can be underscored by comparing the McCloskey
et al. (1996) and Weltje (2002) data. Modeling trends for bacterial bioluminescence
inactivation by divalent metal ions, Newman and McCloskey (1996) found that the
|log K
OH
| metric produced the best fitting model of a series of candidate models.
This suggested that intermetal differences in inactivation were related to differ-
ences in affinity for intermediate ligands. This research was expanded (McCloskey
et al. 1996) by exploring trends for twenty mono-, di-, and trivalent cations that
included class (a), intermediate, and class (b) metals. Although an adequate model
was produced by using σ
p
alone, the best model for describing the intermetal
inactivation trends incorporated both χ
2
r
and |log K
OH
|. Together, the degree of cova-
lency in metal-ligand bonds and metal affinity for intermediate ligands influenced
inactivation.
