Navigation Links
Polymer passage takes time
Date:7/29/2010

HOUSTON (July 29, 2010) Polymer strands wriggle their way through nanometer-sized pores in a membrane to get from here to there and do their jobs. New theoretical research by Rice University scientists quantifies precisely how long the journey takes.

That's a good thing to know for scientists studying the transport of RNA, DNA and proteins -- all of which count as polymers -- or those who are developing membranes for use in biosensors or as drug-delivery devices.

Researchers led by Anatoly Kolomeisky, an associate professor of chemistry and of chemical and biomolecular engineering, have come up with a theoretical method to calculate the time it takes for long-chain polymers to translocate through nano-sized channels in membranes, like the one that separates the nucleus of a cell from surrounding cytoplasm. RNA molecules have to make this intracellular trip, as do proteins that pass through a cell's exterior membrane to perform tasks in the body.

Primary author Kolomeisky reported the findings this month in the Journal of Chemical Physics. Study co-authors include Aruna Mohan, a former postdoctoral research associate at Rice and now a researcher at Exxon-Mobil, and Matteo Pasquali, professor in chemical and biomolecular engineering and chemistry.

The team studied the translocation of a long polymer molecule, which roughly resembles beads on a string, through two types of nanopore geometries: a cylinder and a two-cylinder composite that resembled a large tube connected to a small tube. Not surprisingly, they found a polymer passed more quickly when entering the composite through the wide end.

"We assume the polymer is relatively large in comparison with the size of the pore, which is realistic," Kolomeisky said of the process, which is akin to threading a rope through a peephole. "A typical strand of DNA could be a thousand nanometers long, and the pore could have a length of a few nanometers."

It'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.


'/>"/>

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

Related biology news :

1. New polymer coatings prevent corrosion, even when scratched
2. Novel polymer could improve protein-based drugs
3. A step toward better brain implants using conducting polymer nanotubes
4. How RNA polymerase II gets the go-ahead for gene transcription
5. Multifunctional polymer neutralizes both biological and chemical weapons
6. To improve lung cancer diagnosis, good medicine is a polymer pill
7. Polymer-based filter successfully cleans water, recovers oil in Gulf of Mexico test
8. Pitt researcher says simple polymer-based filter successfully cleans water, recovers oil in Gulf of Mexico tests
9. UM scientists demonstrate role of RNA polymerase in gene transcription
10. Seemingly suicidal stunt is normal rite of passage for immune cells
11. Technology improves salmon passage at hydropower dams
Post Your Comments:
*Name:
*Comment:
*Email:
(Date:3/31/2016)... -- Genomics firm Nabsys has completed a financial  restructuring under ... M.D., who returned to the company in October 2015. ... including Chief Technology Officer, John Oliver , Ph.D., ... Vice President of Software and Informatics, Michael Kaiser ... Bready served as CEO of Nabsys from 2005-2014 and ...
(Date:3/23/2016)... 23, 2016 ... Gesichts- und Stimmerkennung mit Passwörtern     ... MESG ), ein führender Anbieter digitaler ... mit SpeechPro zusammenarbeitet, um erstmals dessen Biometrietechnologie ... die Möglichkeit angeboten, im Rahmen mobiler Apps ...
(Date:3/22/2016)... OTTAWA, Ontario , PROVO ... 2016 Newborn Screening Ontario (NSO), which operates ... for molecular testing, and Tute Genomics and ... process management technology respectively, today announced the launch of ... new next-generation sequencing (NGS) testing panel. ...
Breaking Biology News(10 mins):
(Date:4/29/2016)... , April 29, 2016 Elekta ... latest update to its industry-leading treatment planning software, is ... Monaco version 5.11 provides significant ... attain calculation speeds up to four times faster than ... With the industry,s gold standard Monte Carlo ...
(Date:4/28/2016)... (PRWEB) , ... April 28, 2016 , ... ... and ongoing support for Connecticut's innovative, growing companies, today announced the launch of ... and financial technology (fintech) companies. , “VentureClash looks to attract the ...
(Date:4/28/2016)... ... 28, 2016 , ... Morris Midwest ( http://www.morrismidwest.com ), a ... at its Maple Grove, Minnesota technical center, May 11-12. The event will ... Almost 20 leading suppliers of tooling, accessories, software and other related technology will ...
(Date:4/27/2016)... ... 27, 2016 , ... The Pittcon Organizing Committee is pleased to announce that ... volunteer member of Committee since 1987. Since then, he has served in a number ... was chairman for both the program and exposition committees. In his professional career, Dr. ...
Breaking Biology Technology: