Scientists design protein filaments that assemble – GeekWire



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Protein filament
This molecular visualization shows how proteins are assembled as building blocks. (UW illustration)

Researchers have created molecular building blocks that can be woven into long protein threads.

Well, maybe not all this long. Each protein-based building block is only one nanometer long and the self-assembled filaments have a length of up to 10,000 nanometers. It would take more than 2,500 of these filaments, placed end to end, to have a total length of one inch. Nevertheless, the feat described in this week's issue of the journal Science demonstrates the power and beauty of protein design.

"Being able to create protein filaments from scratch – or de novo – will help us better understand the structure and mechanisms of natural protein filaments and will also enable us to create entirely new materials, unparalleled in nature" David Baker of the University of Washington said today in a press release.

Baker is a biochemist at the UW School of Medicine and a director of UW's Institute for Protein Design, a pioneer in the field of protein folding for years.

Proteins are complex molecules whose structure generally determines their function. In nature, protein filaments provide scaffolding for cells and connect bone, cartilage, skin and other tissues of the body.

Assembly of filaments
The computer-designed proteins self-assemble like Lego blocks into filaments over 1000 times thinner than the hair. (UW illustration)

Researchers such as Baker take advantage of the meandering protein molecules to create artificial forms. There is even a computer program called Rosetta and a video game called Foldit to help protein designers make virtual amino acids in the desired form.

The Baker team used Rosetta to design small proteins with surface amino acids that fit into each other in a predetermined manner. The small molecules assembled, row by row, into an elongated helix.

"We were finally able to design proteins that would bind as Legos," said Hao Shen, Ph.D., a candidate in molecular engineering. The lead authors of the study are biochemists Jorge Fallas and Eric Lynch of Shen and UW.

Researchers have found ways to encourage the growth or disassembly of filaments by tinkering with protein concentration levels in the solution or by adding styling units on a molecular scale to inhibit the building process.

Theoretically, proteins could be woven into artificial fiber strands equal to or greater than the resistance of spider silk, which is stronger than steel nanometer by nanometer. But do not expect to see this app so soon, except perhaps in Spider-Man movies. According to Baker, custom designed protein filaments are more likely to serve as scaffolds for new types of diagnostic tests or nanoelectronic circuits.

In addition to Hao Shen, Fallas, Lynch and Baker, William Sheffler, Bradley Parry, Nicholas Jannetty, Justin Decarreau, Michael Wagenbach, Jesus Juan Vicente, Jiajun Chen, and Lei Wang, Quinton Dowling, Gustav Oberdorfer, Lance Stewart, Linda Wordeman, James De Yoreo, Christine Jacobs-Wagner and Justin Kollman.

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