Forum for Science, Industry and Business

Sponsored by:     3M 
Search our Site:


Twisting molecules by brute force: A top-down approach

Molecules that are twisted are ubiquitous in nature, and have important consequences in biology, chemistry, physics and medicine.

Some molecules have unique and technologically useful optical properties; the medicinal properties of drugs depend on the direction of the twist; and within us – think of the double helix – twisted DNA can interact with different proteins.

This twisting is called chirality and researchers at Case Western Reserve University have found they can use a macroscopic brute force to impose and induce a twist in an otherwise non-chiral molecule.

Their new "top-down" approach is described in the Dec. 2 issue of Physical Review Letters.

"The key is that we used a macroscopic force to create chirality down to the molecular level," said Charles Rosenblatt, professor of physics at Case Western Reserve and the senior author on the paper. Rosenblatt started the research with no application in mind. He simply wanted to see if it could be done — essentially scientific acrobatics.

But, he points out, since antiquity chirality has played a role in health, energy, technology and more — but until now, chirality always has been a bottom-up phenomenon. This new top-down approach, if it can be scaled up, could lead to custom designed chirality - and therefore desired properties - in all kinds of things.

Rosenblatt worked with post-doctoral researcher Rajratan Basu, graduate student Joel S. Pendery, and professor Rolfe G. Petschek, of the physics department at Case Western Reserve, and Chemistry Professor Robert P. Lemieux of Queen's University, Kingston, Ontario.

Chirality isn't as simple as a twist in a material. More precisely, a chiral object can't be superimposed on its mirror image. In a "thought experiment", if one's hand can pass through a mirror (like Alice Through the Looking Glass), the hand cannot be rotated so that it matches its mirror image. Therefore one's hand is chiral.

Depending on the twist, scientists define chiral objects as left-handed and right-handed. Objects that can superimpose themselves on their mirror image, such as a wine goblet, are not chiral.

In optics, chiral molecules rotate the polarization of light – the direction depends on whether the molecules are left-handed or right-handed. Liquid crystal computer and television screen manufacturers take advantage of this property to enable you to clearly see images from an angle.

In the drug industry, chirality is crucial.

Two drugs with the identical chemical formula have different uses. Dextromethorphan, which is right-handed, is a cough syrup and levomethorphan, which is lefthanded, is a narcotic painkiller.

The reason for the different effects? The drugs interact differently with biomolecules inside us, depending on the biomolecules' chirality.

After meeting with Lemieux at a conference, the researchers invented a method to create chirality in a liquid crystal at the molecular level.

They treated two glass slides so that cigar-shaped liquid crystal molecules would align along a particular direction. They then created a thin cell with the slides, but rotated the two alignment directions by approximately a 20 degree angle.

The 20-degree difference caused the molecules' orientation to undergo a right-handed helical rotation, like a standard screw, from one side to the other. This is the imposed chiral twist.

The twist, however, is like a tightened spring and costs energy to maintain. To reduce this cost, some of the naturally left-handed molecules in the crystal became right-handed. That's because, inherently, right-handed molecules give rise to a macroscopic right-handed twist, Rosenblatt explained. This shift of molecules from left-handed to right-handed is the induced chirality.

Although the law of entropy suggests there would be nearly identical numbers of left-handed and right-handed molecules, in order to keep total energy cost at a minimum, the right-handed molecules outnumbered the left, he said.

To test for chirality, the researchers applied an electrical field perpendicular to the molecules. If there were no chirality, there would be nothing to see. If there were chirality, the helical twist would rotate in proportion to the amount of right-handed excess.

They observed a modest rotation, which became larger when they increased the twist.

"The effect was occurring everywhere in the cell, but was strongest at the surface," Rosenblatt said.

Scientists have built chirality into optical materials, electrooptic devices, and more by starting at the molecular level. But the researchers are not aware of other techniques that use a macroscopic force to bring chiralty down to molecules.

The researchers are continuing to investigate ways this can be done.

Kevin Mayhood | EurekAlert!
Further information:

More articles from Physics and Astronomy:

nachricht Novel light sources made of 2D materials
28.10.2016 | Julius-Maximilians-Universität Würzburg

nachricht OU-led team discovers rare, newborn tri-star system using ALMA
27.10.2016 | University of Oklahoma

All articles from Physics and Astronomy >>>

The most recent press releases about innovation >>>

Die letzten 5 Focus-News des innovations-reports im Überblick:

Im Focus: Novel light sources made of 2D materials

Physicists from the University of Würzburg have designed a light source that emits photon pairs. Two-photon sources are particularly well suited for tap-proof data encryption. The experiment's key ingredients: a semiconductor crystal and some sticky tape.

So-called monolayers are at the heart of the research activities. These "super materials" (as the prestigious science magazine "Nature" puts it) have been...

Im Focus: Etching Microstructures with Lasers

Ultrafast lasers have introduced new possibilities in engraving ultrafine structures, and scientists are now also investigating how to use them to etch microstructures into thin glass. There are possible applications in analytics (lab on a chip) and especially in electronics and the consumer sector, where great interest has been shown.

This new method was born of a surprising phenomenon: irradiating glass in a particular way with an ultrafast laser has the effect of making the glass up to a...

Im Focus: Light-driven atomic rotations excite magnetic waves

Terahertz excitation of selected crystal vibrations leads to an effective magnetic field that drives coherent spin motion

Controlling functional properties by light is one of the grand goals in modern condensed matter physics and materials science. A new study now demonstrates how...

Im Focus: New 3-D wiring technique brings scalable quantum computers closer to reality

Researchers from the Institute for Quantum Computing (IQC) at the University of Waterloo led the development of a new extensible wiring technique capable of controlling superconducting quantum bits, representing a significant step towards to the realization of a scalable quantum computer.

"The quantum socket is a wiring method that uses three-dimensional wires based on spring-loaded pins to address individual qubits," said Jeremy Béjanin, a PhD...

Im Focus: Scientists develop a semiconductor nanocomposite material that moves in response to light

In a paper in Scientific Reports, a research team at Worcester Polytechnic Institute describes a novel light-activated phenomenon that could become the basis for applications as diverse as microscopic robotic grippers and more efficient solar cells.

A research team at Worcester Polytechnic Institute (WPI) has developed a revolutionary, light-activated semiconductor nanocomposite material that can be used...

All Focus news of the innovation-report >>>



Event News

#IC2S2: When Social Science meets Computer Science - GESIS will host the IC2S2 conference 2017

14.10.2016 | Event News

Agricultural Trade Developments and Potentials in Central Asia and the South Caucasus

14.10.2016 | Event News

World Health Summit – Day Three: A Call to Action

12.10.2016 | Event News

Latest News

Steering a fusion plasma toward stability

28.10.2016 | Power and Electrical Engineering

Bioluminescent sensor causes brain cells to glow in the dark

28.10.2016 | Life Sciences

Activation of 2 genes linked to development of atherosclerosis

28.10.2016 | Life Sciences

More VideoLinks >>>