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Normally, inorganic materials like silica are unwelcome in biological
systems, since they disrupt the form and function of proteins.
“We wanted to reverse the thinking and try to design proteins that
take on their function only after encountering an inorganic surface,”
says Bengt-Harald Jonsson, professor of molecular biotechnology.
He directs the research team that is now presenting its findings in
Angewandte Chemie.
The team designed a peptide (a short protein) with a specific
distribution of positive charges. The peptide was mixed into a
solution of spherical silica particles, about 9 nanometers (billionths
of a meter) across. When the peptide was free in the solution it had
no structure whatsoever, but when it connected with the negatively
charged silica ball it assumed the form of a helix. The result was a
complex of a silica particle and a functional protein.
When the researchers added amino acids to their peptide, the complex
took on the properties of a catalyst, a function similar to that of
enzymes in living cells.
The method has several possible fields of application:
- recognition of organic molecules
- catalyzing of chemical reactions with precise control
- target-seeking particles for medical uses
But the Linköping University scientists’ successful experiment may
also shed light on the eternal question of the origin of life.
Particles of clay containing silica in the ‘primeval soup’ may have
attracted unstructured peptides with amino acids attached and given
rise to the first functional proteins.
“We know that RNA (which plays a decisive role in the transfer of
information in cells) can bind with clay particles whose surfaces have
negative charges. The probability of peptides with amino acids having
formed well-defined structures with the clay at an early stage of
development is considerably greater, since they are more diversified
than RNA is,” says Bengt-Harald Jonsson.
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