Featured Research

from universities, journals, and other organizations

Would a molecular horse trot, pace or glide across a surface? Chemists study quadrupedal molecular machines

Date:
September 14, 2010
Source:
University of California - Riverside
Summary:
To determine how a quadrupedal molecular machine would move across a flat metal surface, chemists studied a class of molecular machines that "walk." Molecular machines can be found everywhere in nature, for example, transporting proteins through cells and aiding metabolism. To develop artificial molecular machines, however, scientists first need to understand the rules that govern mechanics at the molecular or nanometer scale.

This image shows a quadrupedal molecular machine trotting -- diagonally opposite hooves move together. The researchers found that this form of movement distorted the molecular species far too much to be viable.
Credit: Bartels lab, UC Riverside.

Molecular machines can be found everywhere in nature, for example, transporting proteins through cells and aiding metabolism. To develop artificial molecular machines, scientists need to understand the rules that govern mechanics at the molecular or nanometer scale (a nanometer is a billionth of a meter).

To address this challenge, a research team at the University of California, Riverside studied a class of molecular machines that 'walk' across a flat metal surface. They considered both bipedal machines that walk on two 'legs' and quadrupedal ones that walk on four.

"We made a horse-like structure with four 'hooves' to study how molecular machinery can organize the motion of multiple parts," said Ludwig Bartels, a professor of chemistry, whose lab led the research. "A couple of years ago, we discovered how we can transport carbon dioxide molecules along a straight line across a surface using a molecular machine with two 'feet' that moved one step at a time. For the new research, we wanted to create a species that can carry more cargo -- which means it would need more legs. But if a species has more than two legs, how will it organize their motion?"

Bartels and colleagues performed experiments in the lab and found that the quadrupedal molecules use a pacing gait -- both legs on one side of the molecule move together, followed next by the two legs on the opposite side of the molecule. The species they created moved reliably along a line, not rotating to the side or veering off course. The researchers also simulated a trotting of the species, in which diagonally opposite hooves move together, and found that this form of movement distorted the species far too much to be viable.

Having established how the molecule moves, the researchers next addressed a fundamental question about molecular machinery: Does a molecule -- or portions of it -- simply tunnel through barriers presented by the roughness it encounters along its path?

"If it did, this would be a fundamental departure from mechanics in the macroscopic world and would greatly speed up movement," Bartels said. "It would be like driving on a bumpy road with the wheels of your car going through the bumps rather than over them. Quantum-mechanics is known to allow such behavior for very light particles like electrons and hydrogen atoms, but would it also be relevant for big molecules?"

Bartels and colleagues varied the temperature in their experiments to provide the molecular machines with different levels of energy, and studied how the speed of the machines varied as a consequence. They found that a machine with two legs can use tunneling to zip through the surface corrugation. But a machine with four (or potentially more) legs is not able to employ tunneling; while such a machine can coordinate the movement of its hooves in pacing, it cannot coordinate their tunneling, the researchers found.

"Thus, even at the tiniest scale, if you want to transport cargo fast, you need a light and nimble bipedal vehicle," Bartels said. "Larger vehicles may be able to carry more cargo, but because they cannot use tunneling effectively, they end up having to move slowly. Is this discouraging? Not really, because molecular machinery as a concept is still in its infancy. Indeed, there is an advantage to having a molecule move slowly because it allows us to observe its movements more closely and learn how to control them."

Study results appear online in the Journal of the American Chemical Society, and will appear in print in an upcoming issue of the journal.

Next, the researchers plan to develop molecular machines whose motion can be controlled by light.

Currently, molecular machines are being studied intensely for their functions in biology and for their therapeutic value. For example, patients with GERD (Gastroesophageal reflux disease) are prescribed proton pump inhibitors, which slow the pumping action of biological molecular machines, thus reducing stomach acid levels.

"Generally, scientists' picture of the working of such biological molecular machinery completely disregards tunneling," Bartels said. "Our study corrects this perception, which may, in turn, lead to novel ways of controlling or correcting the behavior of biological molecular machines."

Artificial molecular machines are of interest to the microelectronic industry in its quest for smaller and smaller active elements in computers and for data storage. Artificial molecular machines potentially can also operate inside cells like their biological counterparts, greatly benefiting medicine.

Bartels's lab used the following molecules in the study: anthraquinone and pentaquinone (both bipedal); and pentacenetetrone and dimethyl pentacenetetrone (both quadrupedal).

The research was made possible by dedicated instrumentation developed and built in the Bartels lab. Bartels specializes in developing scanning tunneling microscopy instrumentation and applying it to molecular systems. Besides the Department of Chemistry, he holds appointments in the departments of physics, electrical engineering, mechanical engineering and the program in materials science and engineering.

He was joined in the study by the following researchers at UCR: postdoctoral scholar Zhihai Cheng; undergraduate student Eric S. Chu; graduate students Dezheng Sun, Daeho Kim, Yeming Zhu, MiaoMiao Luo, Greg Pawin, Kin L. Wong, Ki-Young Kwon and Robert Carp; and Michael Marsella, an associate professor of chemistry. Carp, who works in Marsella's lab, made dimethyl pentacenetetrone; the other chemicals used in the study are commercially available.

The research was supported by a Department of Energy grant to Bartels and a National Science Foundation (NSF) grant to Bartels and Marsella. The latter grant was rated in a recent review of the NSF Division of Chemistry as "an exemplar of excellence in support of the Division's investment in research, education, and infrastructure."


Story Source:

The above story is based on materials provided by University of California - Riverside. Note: Materials may be edited for content and length.


Journal Reference:

  1. Zhihai Cheng, Eric S. Chu, Dezheng Sun, Daeho Kim, Yeming Zhu, MiaoMiao Luo, Greg Pawin, Kin L. Wong, Ki-Young Kwon, Robert Carp, Michael Marsella, Ludwig Bartels. Tunability in Polyatomic Molecule Diffusion through Tunneling versus Pacing. Journal of the American Chemical Society, 2010; 100910090635005 DOI: 10.1021/ja1027343

Cite This Page:

University of California - Riverside. "Would a molecular horse trot, pace or glide across a surface? Chemists study quadrupedal molecular machines." ScienceDaily. ScienceDaily, 14 September 2010. <www.sciencedaily.com/releases/2010/09/100913141539.htm>.
University of California - Riverside. (2010, September 14). Would a molecular horse trot, pace or glide across a surface? Chemists study quadrupedal molecular machines. ScienceDaily. Retrieved April 21, 2014 from www.sciencedaily.com/releases/2010/09/100913141539.htm
University of California - Riverside. "Would a molecular horse trot, pace or glide across a surface? Chemists study quadrupedal molecular machines." ScienceDaily. www.sciencedaily.com/releases/2010/09/100913141539.htm (accessed April 21, 2014).

Share This



More Matter & Energy News

Monday, April 21, 2014

Featured Research

from universities, journals, and other organizations


Featured Videos

from AP, Reuters, AFP, and other news services

Why Did Nike Fire Most Of Its Nike FuelBand Team?

Why Did Nike Fire Most Of Its Nike FuelBand Team?

Newsy (Apr. 19, 2014) Nike fired most of its Digital Sport hardware team, the group behind Nike's FuelBand device. Could Apple or an overcrowded market be behind layoffs? Video provided by Newsy
Powered by NewsLook.com
Small Reactors Could Be Future of Nuclear Energy

Small Reactors Could Be Future of Nuclear Energy

AP (Apr. 17, 2014) After the Fukushima nuclear disaster, the industry fell under intense scrutiny. Now, small underground nuclear power plants are being considered as the possible future of the nuclear energy. (April 17) Video provided by AP
Powered by NewsLook.com
Horseless Carriage Introduced at NY Auto Show

Horseless Carriage Introduced at NY Auto Show

AP (Apr. 17, 2014) An electric car that proponents hope will replace horse-drawn carriages in New York City has also been revealed at the auto show. (Apr. 17) Video provided by AP
Powered by NewsLook.com
Honda's New ASIMO Robot, More Human-Like Than Ever

Honda's New ASIMO Robot, More Human-Like Than Ever

AFP (Apr. 17, 2014) It walks and runs, even up and down stairs. It can open a bottle and serve a drink, and politely tries to shake hands with a stranger. Meet the latest ASIMO, Honda's humanoid robot. Duration: 00:54 Video provided by AFP
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