The researchers demonstrated their new understanding of how the instrument - the atomic force microscope - works in water to show detailed properties of a bacterial membrane and a virus called Phi29, said Arvind Raman, a Purdue professor of mechanical engineering.
"People using this kind of instrument to study biological structures need to know how it works in the natural watery environments of molecules and how to interpret images," he said.
An atomic force microscope uses a tiny vibrating probe to yield information about materials and surfaces on the scale of nanometers, or billionths of a meter. Because the instrument enables scientists to "see" objects far smaller than possible using light microscopes, it could be ideal for studying molecules, cell membranes and other biological structures.
The best way to study such structures is in their wet, natural environments. However, the researchers have now discovered that in some respects the vibrating probe's tip behaves the opposite in water as it does in air, said Purdue mechanical engineering doctoral student John Melcher.
Purdue researchers collaborated with scientists at three institutions in Madrid, Spain: Universidad Autónoma de Madrid, Instituto de Ciencia de Materiales de Madrid and the Centro Nacional de Biotecnología.
Findings, which were detailed in a paper appearing online last week in the U.S. publication Proceedings of the National Academy of Sciences, are related to the subtle differences in how the instrument's probe vibrates. The probe is caused to oscillate by a vibrating source at its base. However, the tip of the probe oscillates slightly out of synch with the oscillations at the base. This difference in oscillation is referred to as a "phase contrast," and the tip is said to be out of phase with the base.
Although these differences in phase contrast reveal information about the composition of the material being studied, data can't be properly interpreted unless researchers understand precisely how the phase changes in water as well as in air, Raman said.
If the instrument is operating in air, the tip's phase lags slightly when interacting with a viscous material and advances slightly when scanning over a hard surface. Now researchers have learned the tip operates in the opposite manner when used in water: it lags while passing over a hard object and advances when scanning the gelatinous surface of a biological membrane.
Researchers deposited the membrane and viruses on a sheet of mica. Tests showed the differing properties of the inner and outer sides of the membrane and details about the latticelike protein structure of the membrane. Findings also showed the different properties of the balloonlike head, stiff collar and hollow tail of the Phi29 virus, called a bacteriophage because it infects bacteria.
"The findings suggest that phase contrast in liquids can be used to reveal rapidly the intrinsic variations in local stiffness with molecular resolution, for example, by showing that the head and the collar of an individual virus particle have different stiffness," Raman said.
The research was funded by the National Science Foundation and was conducted at the Birck Nanotechnology Center in Purdue's Discovery Park. The biological membrane images were taken at Purdue, and the virus studies were performed at the Universidad Autónoma de Madrid.
The paper was authored by Melcher; Carolina Carrasco, a postdoctoral researcher at Universidad Autónoma de Madrid and the Instituto de Ciencia de Materiales de Madrid; Purdue postdoctoral researcher Xin Xu; José L. Carrasco, a researcher at Departmento de Estructura de Macomoléculas, Centro Nacional de Biotecnología, Consejo Superior de Investigaciones Científicas; Julio Gómez-Herrero and Pedro José de Pablo, both researchers from Universidad Autónoma de Madrid; and Raman.
Related Web sites:Arvind Raman:
Abstract on the research in this release is available at: http://news.uns.purdue.edu/x/2009b/090811RamanWatery.html
Emil Venere | EurekAlert!
Ion treatments for cardiac arrhythmia — Non-invasive alternative to catheter-based surgery
20.01.2017 | GSI Helmholtzzentrum für Schwerionenforschung GmbH
Seeking structure with metagenome sequences
20.01.2017 | DOE/Joint Genome Institute
An important step towards a completely new experimental access to quantum physics has been made at University of Konstanz. The team of scientists headed by...
Yersiniae cause severe intestinal infections. Studies using Yersinia pseudotuberculosis as a model organism aim to elucidate the infection mechanisms of these...
Researchers from the University of Hamburg in Germany, in collaboration with colleagues from the University of Aarhus in Denmark, have synthesized a new superconducting material by growing a few layers of an antiferromagnetic transition-metal chalcogenide on a bismuth-based topological insulator, both being non-superconducting materials.
While superconductivity and magnetism are generally believed to be mutually exclusive, surprisingly, in this new material, superconducting correlations...
Laser-driving of semimetals allows creating novel quasiparticle states within condensed matter systems and switching between different states on ultrafast time scales
Studying properties of fundamental particles in condensed matter systems is a promising approach to quantum field theory. Quasiparticles offer the opportunity...
Among the general public, solar thermal energy is currently associated with dark blue, rectangular collectors on building roofs. Technologies are needed for aesthetically high quality architecture which offer the architect more room for manoeuvre when it comes to low- and plus-energy buildings. With the “ArKol” project, researchers at Fraunhofer ISE together with partners are currently developing two façade collectors for solar thermal energy generation, which permit a high degree of design flexibility: a strip collector for opaque façade sections and a solar thermal blind for transparent sections. The current state of the two developments will be presented at the BAU 2017 trade fair.
As part of the “ArKol – development of architecturally highly integrated façade collectors with heat pipes” project, Fraunhofer ISE together with its partners...
19.01.2017 | Event News
10.01.2017 | Event News
09.01.2017 | Event News
20.01.2017 | Awards Funding
20.01.2017 | Materials Sciences
20.01.2017 | Life Sciences