"This was weird," Parthasarathy said. "Like-charged objects aren't supposed to attract each other. People have seen like-charge attraction in a few other colloidal systems in the last 10 or 15 years, but still no one understands it. Here, we've got the first system in which like-charge attraction can be controlled, simply by the incorporation of molecules from biological membranes. We can tune attraction or repulsion over the entire spectrum simply by changing the composition of the membrane. This is useful both for technological applications, and for illuminating the fundamental mechanisms behind colloidal interactions."
The observations were made using an inverted microscopy technique in which the glass spheres were placed in a 655-nanometer diode laser beam, an approach developed in Parthasarathy's lab by former undergraduate biophysics student Greg Tietjen, now a doctoral student at the University of Chicago.
The findings of the National Science Foundation-funded research, he said, suggest that specially tweaked biological membranes applied to artificially produced materials may serve as specialty control knobs that direct materials to do very specific things.
Controlling molecular orientation from cell membranes
In a paper appearing online in the Journal of the American Chemical Society (JACS) in early July, Parthasarathy teamed with organic chemists at the University of California, Berkeley, to study how molecules are oriented on their cell membranes to allow for cell-to-cell interactions.
The six-member research team built tiny artificial molecules that mimic brush-like membrane proteins and contain tiny fluorescent probes at the outer end. These miniscule polymers were incorporated into artificial membranes placed on a silicon wafer that acts like a mirror, allowing precise optical measurements of the orie
|Contact: Jim Barlow|
University of Oregon