Hardy synthetic patterned after nature - protein synthesized to maximize hydrophobic stabilization - Biochemistry - Brief Article

Science News, March 8, 1997 by Paul Smaglik

Taking a cue from microorganisms that thrive in near-boiling water on the ocean floor, chemists are learning how to build tough synthetic proteins that may pave the way for lab-made molecules with potentially far-reaching applications.

"These organisms have proteins in them that make them very stable," says Ramy S. Farid, a chemist at Rutgers University in Newark, N.J. "I wanted to understand what is so special about these proteins."

One clue to their properties is hydrophobic interaction, the same phenomenon that keeps gasoline and water from mixing. In the string of molecular units that makes up any protein, hydrophilic segments attract water molecules, while hydrophobic segments repel them. Robust ocean floor microorganisms-called archaeons-have proteins with long hydrophobic segments, which twist away from water until the protein becomes a ball with a tightly packed core. This packaging leaves open a small surface area of hydrophilic elements (SN: 3/11/95, p. 150).

Because these proteins are dense, high energy-for example, high heat-is required to unravel the string, Farid says. So he and his colleagues wrote a computer program to design an even more tightly packed protein. They then devised a procedure to synthesize this protein. Rather than re-create the archaeon protein exactly, Farid and his colleagues Xin Jiang and Edmund J. Bishop used a chemical backbone not found in the microorganisms, they report in the Jan. 29 Journal of the American Chemical Society. The computer program simulates evolution by first designing a simple protein based on that backbone and then adding onto it to model a larger, more complicated protein.

The results would have been interesting, but not groundbreaking, if the scientists had stopped at the design stage, says biochemist Mike Adams of the University of Georgia in Athens. However, they made the protein based on their design, tested it, and found that it remained tightly coiled at temperatures approaching 80#161#C. "There is no natural example of a protein like this," Adams says.

Taking the next step-creating industrial catalysts, medicines that remain stable in heat, and enzymes based on robust synthetic proteins-could be tricky: Natural proteins may not work when reengineered to maximize hydrophobic stabilization. Also, Adams cautions, other, undiscovered forces could help stabilize the archaeon protein. "Nature has been at this business a lot longer than we have"