Chemistry Reference
In-Depth Information
2
Fig. 7 Contour plot representations of
(
r
) of AMCHA in the plane spanned by the atoms of
the carboxylate group (
black lines
negative,
green lines
positive values). All geometries are
optimized in the respective environment
r
r
situation in the crystal and the enzyme, respectively. This allows differentiating
between the variations that arise due to different geometry from those that are due
to electrostatic influences. The ESPs are presented in Figs.
9
and
10
.
From a simple visual inspection, the differences between the p/p and c/c cases
should arise for the C-O2 and the N-H2 bonds. Their environments differ in the
kind of the bonding environment or the number of interactions. For N-H2, a salt
bridge to a neighbored carboxylate group (in crystal) is replaced by a hydrogen
bond to a solvent water molecule (in the enzyme). For C-O2, one salt bridge to an
ammonium group (in the crystal) is replaced by a similar salt bridge plus a hydrogen
bond to a phenyl group (in the enzyme). The differences are actually reflected in the
topological properties of the EDs shown in Tables
8
and
10
.The
l
3
values of
the C-O2 bond differ for the p/p and c/c calculations by about 15%, while the
corresponding difference is only about 1% for the C-O1 bond (Table
9
). For the
l
3
value of the N-H2 bond the variation is about 15% (Table
10
), while only 2-5% are
found for the other N-H bonds (Tables
11
and
12
). The corresponding changes at
the C-C bonds and C-H bonds within the molecule are smaller than 2% for the ED
