To hunt for the plastic-preferring peptide, Sanghvi and Miller added a solution containing bacteriophages that displayed different peptides to a container with polypyrrole stuck on its inner surface. The bacteriophages that didn't wash away when exposed to conditions that hinder attachment were retested on a new polypyrrole-coated container, a process that was repeated four more times.
The sticky peptide selected, known as T59, is a string of 12 amino acids. To make certain that something else on the outer surface of the bacteriophage virus wasn't responsible for its perceived stickiness, the researchers demonstrated that T59 by itself could attach to immobilized polypyrrole, using synthetic copies of it made at the university's Institute for Cellular and Molecular Biology. In addition, they determined that a certain amino acid, aspartic acid, had to be a part of T59 for it to attach well to the plastic.
Aspartic acid carries a negative charge, which in T59 appeared to be drawn to the positively charged surface of the polypyrrole the way magnets of opposite charges cling together. Yet other peptides containing aspartic acid didn't attach to polypyrrole, leading the researchers to speculate that something contributed by the other amino acids in T59 influenced its 3-dimensional shape in a way that augmented its plastic preference.
"This aspartic acid is just one piece of the puzzle," Sanghvi said. "There are still more pieces to put together." The researchers also evaluated how well T59 clings to polypyrrole. They attached copies of the peptide to the tip of an atomic force microscope at the university's Center for Nano- and Molecular Science and Technology. The tip of this specialized microscope is normally passed across the surface of a material
Source:University of Texas at Austin