But one important class of proteins -- those stuck in the cell membranes -- has proven difficult to extract and study in 3-D crystals. Now an international team of scientists has developed a way to train such molecules to line up neatly on the surface of water in thin, tissue-like layers called nanofilms.
This technique should allow biochemists to better see and study the molecules and may lead to a new generation of molecular electronics and ultra-thin materials only one molecule thick.
"To the best of our knowledge, this is the first time aligned films less than a nanometer thick have been produced," say Iftach Nevo, a Marie Curie fellow at the University of Aarhus in Denmark, and Leslie Leiserowitz of the Weizmann Institute of Science in Israel. Together with their colleagues at these institutions and at the Max-Planck Institute of Colloids and Interfaces in Germany and Northwestern University in Evanston, they describe their research in the 14 April 2009 issue of The Journal of Chemical Physics, published by the American Institute of Physics.
One way of creating a nanofilm is to build it on the surface of water. First, the building blocks of the film are dissolved in a volatile substance. When a drop of this solution is splashed onto water, the solvent evaporates. The building blocks left floating on the water interact with each other and spontaneously come together -- like soap scum in a bathtub -- to create a thin crystalline layer.
The shortcoming of this technique is that the thin crystals in the film created will be a mess. Like a mob in a dance club, molecules floating on a surface tend to spin around chaotically with little regard for order. Different patches of molecules will point different, random directions. Because the orientation of these molecules dictates the electrical, magnetic, and optical properties of the final film, these jumbled regions are difficult to develop into useful technologies. They are also difficult to analyze using imaging techniques like X-ray diffraction.
To force the molecules to line up, the team blasted them with nanosecond laser pulses. These pulses create an electric field that interacts with the molecules, rotating them slowly. The electric field associated with these laser pulses is polarized, filtered so that all of the light waves vibrate in the same direction. Molecules caught in the laser feel most stable when they line up along this direction, a process analogous to the needle in a compass swinging to line up with the Earth's magnetic field. Eventually, this forms an aligned film with long range order.
The technique has not been completely perfected yet. Its success rate is about 30 percent, but the group believes that a better understanding of what is happening during the evaporation process and how the molecules interact with each other just before solidifying into a film will improve the efficiency.
When these molecules line up in a stable 2-D layer, their structures can be seen with X-ray imaging techniques normally used on 3-D crystals. "Alignment should enhance the X-ray diffraction intensity by more than two orders of magnitude allowing more detailed structure elucidations," say Nevo and Leiserowitz. The technique could be useful for studying molecules that cannot be easily crystallized in three dimensions -- cell membrane proteins are only one example.
It could also be useful for creating 3-D crystals with aligned structures. The 2-D layer can be used to seed the growth of these crystals, providing a stage on which this growth can be monitored using X-ray diffraction.
Another application is molecular electronics, like field-effect transistors, that require ordered molecules. Also interesting is an emerging class of solar cell technologies that are trying to copy nature by reverse-engineering photosynthesis. The ability to align the molecules in these devices will be important to their effectiveness, explains team member Tamar Seideman of Northwestern University.
Because the technique should work with a variety of molecules, it may pave the way for brand new kinds of self-assembling nanomaterials. "The international team that produced this paper is outstanding, and this is one of those papers that will likely spawn a number of novel applications that haven't been discovered yet," says Edward Castner of Rutgers University, Associate Editor for The Journal of Chemical Physics.
The article "Laser-Induced Self Assembly on Water Surfaces" by Iftach Nevo et al will be published online on April 14, 2009. Journalists can obtain a free copy by emailing firstname.lastname@example.org.
ABOUT THE JOURNAL
The Journal of Chemical Physics, published by the American Institute of Physics (AIP), contains concise and definitive reports of significant research in methods and applications of chemical physics. Innovative research in traditional areas of chemical physics such as spectroscopy, kinetics, statistical mechanics, and quantum mechanics continue to be areas of interest to readers of JCP. In addition, newer areas such as polymers, materials, surfaces/interfaces, information theory, and systems of biological relevance are of increasing importance. See: http://jcp.aip.org.
The American Institute of Physics (AIP) is a not-for-profit membership corporation chartered in 1931 for the purpose of advancement and diffusion of the knowledge of physics and its application to human welfare. An umbrella organization for 10 Member Societies, AIP represents over 134,000 scientists, engineers and educators and is one of the world's largest publishers of physics journals. A total-solution provider of publishing services, AIP also publishes 12 journals of its own (many of which have the highest impact factors in their category), two magazines, and the AIP Conference Proceedings series. Its online publishing platform Scitation (registered trademark) hosts more than 1,000,000 articles from more than 175 scholarly journals, as well as conference proceedings, and other publications of 25 learned society publishers.
Devin Powell | EurekAlert!
A 100-year-old physics problem has been solved at EPFL
23.06.2017 | Ecole Polytechnique Fédérale de Lausanne
Quantum thermometer or optical refrigerator?
23.06.2017 | National Institute of Standards and Technology (NIST)
An international team of scientists has proposed a new multi-disciplinary approach in which an array of new technologies will allow us to map biodiversity and the risks that wildlife is facing at the scale of whole landscapes. The findings are published in Nature Ecology and Evolution. This international research is led by the Kunming Institute of Zoology from China, University of East Anglia, University of Leicester and the Leibniz Institute for Zoo and Wildlife Research.
Using a combination of satellite and ground data, the team proposes that it is now possible to map biodiversity with an accuracy that has not been previously...
Heatwaves in the Arctic, longer periods of vegetation in Europe, severe floods in West Africa – starting in 2021, scientists want to explore the emissions of the greenhouse gas methane with the German-French satellite MERLIN. This is made possible by a new robust laser system of the Fraunhofer Institute for Laser Technology ILT in Aachen, which achieves unprecedented measurement accuracy.
Methane is primarily the result of the decomposition of organic matter. The gas has a 25 times greater warming potential than carbon dioxide, but is not as...
Hydrogen is regarded as the energy source of the future: It is produced with solar power and can be used to generate heat and electricity in fuel cells. Empa researchers have now succeeded in decoding the movement of hydrogen ions in crystals – a key step towards more efficient energy conversion in the hydrogen industry of tomorrow.
As charge carriers, electrons and ions play the leading role in electrochemical energy storage devices and converters such as batteries and fuel cells. Proton...
Scientists from the Excellence Cluster Universe at the Ludwig-Maximilians-Universität Munich have establised "Cosmowebportal", a unique data centre for cosmological simulations located at the Leibniz Supercomputing Centre (LRZ) of the Bavarian Academy of Sciences. The complete results of a series of large hydrodynamical cosmological simulations are available, with data volumes typically exceeding several hundred terabytes. Scientists worldwide can interactively explore these complex simulations via a web interface and directly access the results.
With current telescopes, scientists can observe our Universe’s galaxies and galaxy clusters and their distribution along an invisible cosmic web. From the...
Temperature measurements possible even on the smallest scale / Molecular ruby for use in material sciences, biology, and medicine
Chemists at Johannes Gutenberg University Mainz (JGU) in cooperation with researchers of the German Federal Institute for Materials Research and Testing (BAM)...
19.06.2017 | Event News
13.06.2017 | Event News
13.06.2017 | Event News
23.06.2017 | Physics and Astronomy
23.06.2017 | Physics and Astronomy
23.06.2017 | Information Technology