27 May 2005
27 May 2005
The simple marine sponge is inspiring cutting-edge research following the discovery of how glass is biologically made by researchers at the University of California.
The research is undertaken by Daniel E. Morse, professor of molecular, cellular and developmental biology at UCSB, and director of the Institute for Collaborative Biotechnologies, and his research group.
The simple sponge fits into the palm of your hand, and proliferates in the ocean next to the UCSB campus, said Morse. ""When you remove the tissue you're left with a handful of fibreglass needles as fine as spun glass or cotton. This primitive skeleton supports the structure of the sponge, and we've discovered how this glass is made biologically.""
The research team developed a method for coupling small, inexpensive synthetic molecules (that duplicate those found at the active centre of the bio-catalyst of the marine sponge) onto the surfaces of gold nanoparticles. They showed that when two populations of these chemically modified nanoparticles, each bearing half of the catalytic site, are brought together, they function just as the natural biological catalyst does to make silica at low temperatures.
Morse explained that his research group discovered that the centre of the sponge's fine glass needles contains a filament of protein that controls the synthesis of the needles. By cloning and sequencing the DNA of the gene that codes for this protein, they found that the protein is an enzyme that acts as a catalyst –– a surprising discovery. Never before had a protein been found to serve as a catalyst to promote chemical reactions to form the glass or a rock-like material of a biomineral. From that discovery, the researchers learned that this enzyme actively promotes the formation of the glass while simultaneously serving as a template to guide the shape of the growing mineral (glass) that it produces.
These discoveries are significant because they represent a low temperature, biotechnological, catalytic route to the nanostructural fabrication of valuable materials. Nature produces silica on a scale of gigatons –– thousands of millions of tons –– thousands-fold more than man can produce, said Morse. ""This biosynthesis is remarkable because this nanoscale precision can't be duplicated by man.""
Although the reported research, featured in the Advanced Materials magazine, marks an important step forward, Morse believes that the use of these biological methods to control such syntheses would be impractical on an industrial scale. The high cost of the purification of these proteins, the requirement of the proteins for a watery environment, and their instability, all make their incorporation into electronic devices impractical. Furthermore, the presence of proteins would be incompatible with the high electronic performance required for today's device applications.
Instead, the scientists expect that by learning the fundamental mechanism used in nature, that mechanism could be translated into a practical and low-cost manufacturing method. Such a ""biomimetic"" approach will eventually be used in industry, said Morse.
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