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Polymer passage takes time
Date:7/29/2010

's been known for some time that polymers don't just fly through a pore, even when they find the opening. They start. They stop. They start again. And once the leading end has entered a pore, it can back out. Polymers often jitter backward and forward as they progress through a pore, constantly reconfiguring themselves.

"Previous theorists thought that as soon as the leading end reached the channel, the whole polymer would go through," he said. "We're saying it goes back and forth many times before it finally passes."

The key to an accurate description of polymer translocation with single-molecule precision is measuring electric currents that go through the pore. "When the current is high, there's no polymer in the channel. When the current is down, it's in the pore and blocking the flux," he said.

Experiments indicate typical DNA and RNA molecules could pass through a membrane in a few milliseconds, depending on the strength of the electric field driving them. But even that, he said, is much longer than researchers previously thought.

Kolomeisky said the new method works for pores of any geometry, whether they're straight, conical or made of joined cylinders of different sizes, like the hemolysin biological channel they simulated in their research.

The calculations apply equally to natural or artificial pores, which he said would be important to scientists making membranes for drug delivery, biosensors or water purification processes, or researching new methods for sequencing DNA.


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Contact: Jade Boyd
jadeboyd@rice.edu
713-348-6778
Rice University
Source:Eurekalert

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