Chemistry Reference
In-Depth Information
torsion
non-bonded
Figure 8.17
Representation of effects operating in molecular mechanics (left). An example of binding of a copper
complex to a phosphate group on the backbone of a DNA strand optimised using molecular mechanics
methodology appears at right.
can be probed, for example (Figure 8.17). Modelling is set to expand its reach from a
dominant use with pure organic systems to include metal complexes, now that software
packages appropriate for dealing successfully with metal ions have been established.
Concept Keys
Biomolecules offer a range of potential donors for metal ions, including carboxylate,
amine, thiolate, phosphate and aromatic nitrogen groups.
A range of particularly the lighter metal ions from the
s
and
d
blocks find biological
roles in nonproteins, functional proteins and enzymes.
Iron, zinc and copper are the most common of the transition metal ions in the human
body, and play key roles at the active sites of electron carrier, structural and oxygen
binding proteins, as well as in cleavage and redox enzymes.
Overall, a limited number of key structural motifs are met in the molecular components
acting as ligands in metallobiomolecules. The oxygen binding proteins
myoglobin
and
hemoglobin
are examples of iron complexes of one class, unsaturated macro-
cyclic tetraamines called hemes.
Metal complexes lie at the heart of proteins involved in the vital life processes of
oxygen storage, transport and reduction in all life forms.
Polynuclear metal units are common in biomolecules, as exemplified by the ferredox-
ins, which contain up to four iron centres in an iron-sulfur cluster.
Mixed-metal polynuclear units are also met in enzymes, with each metal ion usually
playing a different role in the chemistry performed by the enzyme.
The chemistry in metalloenzymes usually occurs at the metal centre(s), and involves
effectively reactions of coordinated ligands.
Laboratory preparation of synthetic molecules that mimic the shape and/or function of
metallobiomolecules may be practicable.
Computer-based
molecular
modelling
is
finding
application
in
the
study
of
biomolecules and their interactions.
