SCIENTISTS CREATE NEW PROTEIN BASED MATERIAL WITH SOME NERVE
Scientists at the
University of California, Berkeley, have taken proteins from nerve cells and
used them to create a "smart" material that is extremely sensitive to
its environment. This marriage of materials science and biology could give
birth to a flexible, sensitive coating that is easy and cheap to manufacture in
large quantities.
The work, to be
published Oct. 14, in the journal Nature Communications,
could lead to new types of biological sensors, flow valves and controlled drug
release systems, the researchers said. Biomedical applications include
microfluidic devices that can handle and process very small volumes of liquid,
such as samples of saliva or blood, for diagnostics.
"This work
represents a unique convergence of the fields of biomimetic materials,
biomolecular engineering and synthetic biology," said principal
investigator Dr. Sanjay Kumar, UC Berkeley associate professor of
bioengineering. "We created a new class of smart, protein-based materials
whose structural principles are inspired by networks found in living
cells."
Kumar's research
team set out to create a biological version of a synthetic coating used in
everyday liquid products, such as paint and liquid cosmetics, to keep small
particles from clumping together. The synthetic coatings are often called
polymer brushes because of their bristle-like appearance when attached to the
particle surface.
To create the
biological equivalent of a polymer brush, the researchers turned to
neurofilaments, pipe cleaner-shaped proteins found in nerve cells. By acting as
tiny, cylindrical polymer brushes, neurofilaments collectively assemble into a
structural network that helps keep one end of the nerve cell propped open so
that it can conduct electrical signals.
"We co-opted
this protein and turned it into a polymer brush by cloning a portion of a gene
that encodes one of the neurofilament bristles, re-engineering it such that we
could attach the resulting protein to surfaces in a precise and oriented way,
and then expressing the gene in bacteria to produce the protein in large, pure
quantities," said Kumar. "We showed that our 'protein brush' had all
the key properties of synthetic brushes, plus a number of advantages."
Kumar noted that
neurofilaments are good candidates for protein brushes because they are
intrinsically disordered proteins, so named because they don't have a fixed 3-D
shape. The size and chemical sequence of these hair-like proteins are far
easier to control when compared with their synthetic counterparts.
"In biology,
precision is critical," said Kumar. "Proteins are generally
synthesized with the exact same sequence every time; the length and biochemical
order of the protein sequence affects all of its properties, including
structure and the ability to bind to other molecules and catalyze biochemical
reactions. This kind of sequence precision is difficult if not impossible to
achieve in the laboratory using the tools of chemical synthesis. By harnessing
the precision of biology and letting the bacterial cell do all the work for us,
we were able to control the exact length and sequence of the bristles of our
protein brush."
The researchers
showed that the protein brushes could be grafted onto surfaces, and that they
dramatically expand and collapse in reaction to changes in acidity and
salinity. Materials that are environmentally sensitive in this way are often
referred to as "smart" materials because of their ability to
adaptively respond to specific stimuli.
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