Featured Research

from universities, journals, and other organizations

New Molecular Force Probe Stretches Molecules, Atom By Atom

Date:
April 1, 2009
Source:
University of Illinois at Urbana-Champaign
Summary:
Chemists have created a simple and inexpensive molecular technique that replaces an expensive atomic force microscope for studying what happens to small molecules when they are stretched or compressed.

Chemists at the University of Illinois have created a simple and inexpensive molecular technique that replaces an expensive atomic force microscope for studying what happens to small molecules when they are stretched or compressed.

The researchers use stiff stilbene, a small, inert structure, as a molecular force probe to generate well-defined forces on various molecules, atom by atom.

"By pulling on different pairs of atoms, we can explore what happens when we stretch a molecule in different ways," said chemistry professor Roman Boulatov. "That information tells us a lot about the properties of fleeting structures called transition states that govern how, and how fast, chemical transformations occur."

Boulatov, research associate Qing-Zheng Yang, postdoctoral researcher Daria Khvostichenko, and graduate students Zhen Huang and Timothy Kucharski describe the molecular force probe and present early results in a paper accepted for publication in Nature Nanotechnology. The paper is to be posted on the journal's website on March 29.

Similar to the force that develops when a rubber band is stretched, restoring forces occur in parts of molecules when they are stretched. Those restoring forces contain information about how much the molecule was distorted, and in what direction.

The molecular force probe allows reaction rates to be measured as a function of the restoring force in a molecule that has been stretched or compressed.

This information is essential for developing a chemomechanical kinetic theory that explains how force affects rates of chemical transformations.

Such a theory will help researchers better understand a host of complex phenomena, from the operation of motor proteins that underlie the action of muscles, to the propagation of cracks in polymers and the mechanisms by which living cells sense forces in their surroundings.

"Localized reactions offer the best opportunity to gain fundamental insights into the interplay of reaction rates and molecular restoring forces," Boulatov said, "but these reactions are extremely difficult to study with a microscopic force probe."

Microscopic force probes, which are utilized by atomic force microscopes, are much too large to grab onto a single pair of atoms. Measuring microns in size, the probe tips contact many atoms at once, smearing experimental results.

"By replacing microscopic force probes with small molecules like stiff stilbene, we can study the relationship between restoring force and reaction rate for localized reactions," Boulatov said. "The more accurately we know where our probe acts, the better control we have over the distortion, and the easier it is to interpret the results."

Using conventional methods, Boulatov and his students first attach stiff stilbene to a molecule they wish to study. Then they irradiate the resulting molecular assembly with visible light. The light causes the stilbene to change from a fully relaxed shape to one that exerts a desired force on the molecule. The chemists then measure the reaction rate of the molecule as a function of temperature, which reveals details of what caused the reaction to accelerate.

One type of chemical transformation the researchers studied is the breaking of one strong (covalent) chemical bond at a time. The experimental results were sometimes counterintuitive.

"Unlike a rubber band, which will always break faster when stretched, pulling on some chemical bonds doesn't make them break any faster; and sometimes it's a bond that you don't pull on that will break instead of the one you do pull," Boulatov said. "That's because experiences in the macroscopic world do not map particularly well to the molecular world."

Molecules do not live in a three-dimensional world, Boulatov said. Molecules populate a multi-dimensional world, where forces applied to a pair of atoms can act in more than three dimensions.

"Even small molecules will stretch and deform in many different ways," Boulatov said, "making the study of molecular forces even more intriguing."

Funding was provided by the National Science Foundation, the U.S. Air Force Office of Scientific Research, the American Chemical Society Petroleum Research Fund and the U. of I. The National Center for Supercomputing Applications and the U.S. Department of Defense High-Performance Computing Modernization Program provided computational resources.


Story Source:

The above story is based on materials provided by University of Illinois at Urbana-Champaign. Note: Materials may be edited for content and length.


Cite This Page:

University of Illinois at Urbana-Champaign. "New Molecular Force Probe Stretches Molecules, Atom By Atom." ScienceDaily. ScienceDaily, 1 April 2009. <www.sciencedaily.com/releases/2009/03/090329143318.htm>.
University of Illinois at Urbana-Champaign. (2009, April 1). New Molecular Force Probe Stretches Molecules, Atom By Atom. ScienceDaily. Retrieved September 19, 2014 from www.sciencedaily.com/releases/2009/03/090329143318.htm
University of Illinois at Urbana-Champaign. "New Molecular Force Probe Stretches Molecules, Atom By Atom." ScienceDaily. www.sciencedaily.com/releases/2009/03/090329143318.htm (accessed September 19, 2014).

Share This



More Matter & Energy News

Friday, September 19, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

MIT BioSuit A New Take On Traditional Spacesuits

MIT BioSuit A New Take On Traditional Spacesuits

Newsy (Sep. 19, 2014) The MIT BioSuit could be an alternative to big, bulky traditional spacesuits, but the concept needs some work. Video provided by Newsy
Powered by NewsLook.com
Virtual Reality Headsets Unveiled at Tokyo Game Show

Virtual Reality Headsets Unveiled at Tokyo Game Show

AFP (Sep. 18, 2014) Several companies unveiled virtual reality headsets at the Tokyo Game Show, Asia's largest digital entertainment exhibition. Duration: 00:48 Video provided by AFP
Powered by NewsLook.com
Apple's iOS8 Includes New 'Killswitch' To Curb Theft

Apple's iOS8 Includes New 'Killswitch' To Curb Theft

Newsy (Sep. 18, 2014) Apple's new operating system, iOS 8, comes with Apple's killswitch feature already activated, unlike all the models before it. Video provided by Newsy
Powered by NewsLook.com
Stocks Hit All-Time High as Fed Holds Steady

Stocks Hit All-Time High as Fed Holds Steady

AP (Sep. 17, 2014) The Federal Reserve signaled Wednesday that it plans to keep a key interest rate at a record low because a broad range of U.S. economic measures remain subpar. Stocks hit an all-time high on the news. (Sept. 17) Video provided by AP
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