Featured Research

from universities, journals, and other organizations

Physicists control chemical reactions mechanically

Date:
October 4, 2010
Source:
University of California -- Los Angeles
Summary:
Physicists have taken a significant step in controlling chemical reactions mechanically, an important advance in nanotechnology.

Giovanni Zocchi, UCLA professor of physics (right), and UCLA graduate student Hao Qu.
Credit: Reed Hutchinson/UCLA

UCLA physicists have taken a significant step in controlling chemical reactions mechanically, an important advance in nanotechnology, UCLA physics professor Giovanni Zocchi and colleagues report.

Chemical reactions in the cell are catalyzed by enzymes, which are protein molecules that speed up reactions. Each protein catalyzes a specific reaction. In a chemical reaction, two molecules collide and exchange atoms; the enzyme is the third party, the "midwife to the reaction."

But the molecules have to collide in a certain way for the reaction to occur. The enzyme binds to the molecules and lines them up, forcing them to collide in the "right" way, so the probability that the molecules will exchange atoms is much higher.

"Instead of just watching what the molecules do, we can mechanically prod them," said Zocchi, the senior author of the research.

To do that, Zocchi and his graduate students, Chiao-Yu Tseng and Andrew Wang, attached a controllable molecular spring made of DNA to the enzyme. The spring is about 10,000 times smaller than the diameter of a human hair. They can mechanically turn the enzyme on and off and control how fast the chemical reaction occurs. In their newest research, they attached the molecular spring at three different locations on the enzyme and were able to mechanically influence different specific steps of the reaction.

They published their research in the journal Europhysics Letters, a publication of the European Physical Society, in July.

"We have stressed the enzyme in different ways," Zocchi said. "We can measure the effect on the chemical reaction of stressing the molecule this way or that way. Stressing the molecule in different locations produces different responses. If you attach the molecular spring in one place, nothing much happens to the chemical reaction, but you attach it to a different place and you affect one step in the chemical reaction. Then you attach it to a third place and affect another step in this chemical reaction."

Zocchi, Tseng and Wang studied the rate of the chemical reactions and reported in detail what happened to the steps of the reactions as they applied mechanical stress to the enzyme at different places.

"Standing on the shoulders of 50 years of structural studies of proteins, we looked beyond the structural description at the dynamics, specifically the question of what forces -- and applied where -- have what effect on the reaction rates," Zocchi said.

In a related second paper, Zocchi and his colleagues reached a surprising conclusion in solving a longstanding physics puzzle.

When one bends a straight tree branch or a straight rod by compressing it longitudinally, the branch or rod at first remains straight and does not bend until a certain critical force is exceeded. At the critical force, it does not bend a little -- it suddenly buckles and bends a lot.

"This phenomenon is well known to any child who has made bows from hazelnut bush branches, for example, which are typically quite straight. To string the bow, you have to press down on it hard to buckle it, but once it is bent, you need only a smaller force to keep it so," Zocchi said.

The UCLA physicists studied the elastic energy of their DNA molecular spring when it is sharply bent.

"Such a short double-stranded DNA molecule is somewhat similar to a rod, but the elasticity of DNA at this scale was not known," Zocchi said. "What is the force the DNA molecular spring is exerting on the enzyme? We have answered this question.

"We find there is a similar bifurcation with this DNA molecule. It goes from being bent smoothly to having a kink. When we bend this molecule, there is a critical force where there is a qualitative difference. The molecule is like the tree branch and the rod in this respect. If you're just a little below the threshold, the system has one kind of behavior; if you're just a little above the threshold force, the behavior is totally different. The achievement was to measure directly the elastic energy of this stressed molecule, and from the elastic energy characterize the kink."

Co-authors on this research are UCLA physics graduate students Hao Qu, Chiao-Yu Tseng and Yong Wang and UCLA associate professor of chemistry and biochemistry Alexander Levine, who is a member of the California NanoSystems Institute at UCLA. The research was published in April, also in the journal Europhysics Letters.

"We can now measure for any specific DNA molecule what the elastic energy threshold for the instability is," Zocchi said. "I see beauty in this important phenomenon. How is it possible that the same principle applies to a tree branch and to a molecule? Yet it does. The essence of physics is finding common behavior in systems that seem very different."

While Zocchi's research may have applications for medicine and other fields, he emphasizes the advance in knowledge itself.

"There is value in science that adds to our knowledge and helps us understand our world, apart from the value of future applications," he said. "I study problems that I find interesting, where I think I can make a contribution. Why study a particular problem rather than another? Perhaps for the same reason a painter chooses a particular landscape. Perhaps we see beauty there."


Story Source:

The above story is based on materials provided by University of California -- Los Angeles. The original article was written by Stuart Wolpert. Note: Materials may be edited for content and length.


Journal References:

  1. C.-Y. Tseng, A. Wang, G. Zocchi. Mechano-chemistry of the enzyme Guanylate Kinase. EPL (Europhysics Letters), 2010; 91 (1): 18005 DOI: 10.1209/0295-5075/91/18005
  2. Hao Qu, Chiao-Yu Tseng, Yong Wang, Alex J. Levine, Giovanni Zocchi. The elastic energy of sharply bent nicked DNA. EPL (Europhysics Letters), 2010; 90 (1): 18003 DOI: 10.1209/0295-5075/90/18003

Cite This Page:

University of California -- Los Angeles. "Physicists control chemical reactions mechanically." ScienceDaily. ScienceDaily, 4 October 2010. <www.sciencedaily.com/releases/2010/09/100917090844.htm>.
University of California -- Los Angeles. (2010, October 4). Physicists control chemical reactions mechanically. ScienceDaily. Retrieved July 31, 2014 from www.sciencedaily.com/releases/2010/09/100917090844.htm
University of California -- Los Angeles. "Physicists control chemical reactions mechanically." ScienceDaily. www.sciencedaily.com/releases/2010/09/100917090844.htm (accessed July 31, 2014).

Share This




More Matter & Energy News

Thursday, July 31, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Britain Testing Driverless Cars on Roadways

Britain Testing Driverless Cars on Roadways

AP (July 30, 2014) British officials said on Wednesday that driverless cars will be tested on roads in as many as three cities in a trial program set to begin in January. Officials said the tests will last up to three years. (July 30) Video provided by AP
Powered by NewsLook.com
Amid Drought, UCLA Sees Only Water

Amid Drought, UCLA Sees Only Water

AP (July 30, 2014) A ruptured 93-year-old water main left the UCLA campus awash in 8 million gallons of water in the middle of California's worst drought in decades. (July 30) Video provided by AP
Powered by NewsLook.com
Smartphone Powered Paper Plane Debuts at Airshow

Smartphone Powered Paper Plane Debuts at Airshow

AP (July 30, 2014) Smartphone powered paper airplane that was popular on crowdfunding website KickStarter makes its debut at Wisconsin airshow (July 30) Video provided by AP
Powered by NewsLook.com
U.K. To Allow Driverless Cars On Public Roads

U.K. To Allow Driverless Cars On Public Roads

Newsy (July 30, 2014) Driverless cars could soon become a staple on U.K. city streets, as they're set to be introduced to a few cities in 2015. Video provided by Newsy
Powered by NewsLook.com

Search ScienceDaily

Number of stories in archives: 140,361

Find with keyword(s):
Enter a keyword or phrase to search ScienceDaily for related topics and research stories.

Save/Print:
Share:

Breaking News:
from the past week

In Other News

... from NewsDaily.com

Science News

Health News

    Environment News

    Technology News



      Save/Print:
      Share:

      Free Subscriptions


      Get the latest science news with ScienceDaily's free email newsletters, updated daily and weekly. Or view hourly updated newsfeeds in your RSS reader:

      Get Social & Mobile


      Keep up to date with the latest news from ScienceDaily via social networks and mobile apps:

      Have Feedback?


      Tell us what you think of ScienceDaily -- we welcome both positive and negative comments. Have any problems using the site? Questions?
      Mobile: iPhone Android Web
      Follow: Facebook Twitter Google+
      Subscribe: RSS Feeds Email Newsletters
      Latest Headlines Health & Medicine Mind & Brain Space & Time Matter & Energy Computers & Math Plants & Animals Earth & Climate Fossils & Ruins