blog.imaging-git.com » molecules

To Study Biological Molecules and Structures

birgitwashburn — Mon, 31 Aug 2009 09:19:25 +0000

Researchers in the United States and Spain have discovered that a tool widely used in nanoscale imaging works differently in watery environments, a step toward better using the instrument to study biological molecules and structures.

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. 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. 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.

Original Publication:

Melcher J, Carrasco C, Xu X, Carrascosa JL, Gómez-Herrero J, José de Pablo P, Raman A. (2009): Origins of phase contrast in the atomic force microscope in liquids. Proc Natl Acad Sci U S A. 2009 Aug 18;106(33):13655-60. Epub 2009 Aug 5.

Researchers in the United States and Spain have discovered that an atomic force microscope - a tool widely used in nanoscale imaging - works differently in watery environments, a step toward better using the instrument to study biological molecules and structures. The researchers demonstrated their new understanding of how the instrument works in water to show details of the mechanical properties of a virus called Phi29. The images in "a" and "c" show the topography, and the image in "b" shows the different stiffness properties of the balloonlike head, stiff collar and hollow tail of the Phi29 virus, called a bacteriophage because it infects bacteria. (C. Carrasco-Pulido, P. J. de Pablo, J. Gomez-Herrero, Universidad Autonoma de Madrid, Spain)

http://news.uns.purdue.edu

Methods and Applications of Fluorescence

aszerdi — Fri, 14 Aug 2009 07:16:35 +0000

The 11th International Conference on Methods and Applications of Fluorescence: Spectroscopy, Imaging and Probes will be held in Budapest, Hungary, from September 6-9, 2009. The venue of the Conference is the Congress Center of the oldest Hungarian University, the Eötvös Loránd University.
The meeting will cover the following scientific topics:

- Fluorescence Spectroscopy (Theory and Applications)
- Fluorescence Correlation and Single Molecule Spectroscopy
- Fluorescence in Biology/Medicine: Bioassays, Biophysics
- Special Fluorescent Imaging Techniques: Multi-Photon, Live Cell and Single Molecule Imaging
- Novel Fluorescent Probes, Sensors, Fluorescent Proteins, Quantum Dots, Nanomaterials and their Applications
- Special Fluorescence Techniques: Upconversion, Delayed Fluorescence, Fast Fluorescence Kinetics FRET, etc.
- Fluorescence Microscopy: Towards Higher Spatial and Temporal Resolution
- Fluorescence in Systems Biology High Throughput Screening Assays, Arrays, Micro-chip

www.maf11.hu

Budapest, Hungary

3D Movies of Microscopic Systems

aszerdi — Wed, 29 Jul 2009 12:51:26 +0000

Physicists at New York University (NYU), US have developed a technique to record three-dimensional movies of microscopic systems, such as biological molecules, through holographic video. The technique, developed in the laboratory of NYU Physics Professor David Grier, is comprised of two components: making and recording the images of microscopic systems and then analyzing these images. To generate and record images, the researchers created a holographic microscope. It is based on a conventional light microscope, which uses a collimated laser beam instead of on an incandescent illuminator.
When an object is placed into path of the microscope’s beam, the object scatters some of the beam’s light into a complex diffraction pattern. The scattered light overlaps with the original beam to create an interference pattern reminiscent of overlapping ripples in a pool of water. The microscope then magnifies the resulting pattern of light and dark and records it with a conventional digital video recorder. Each snapshot in the resulting video stream is a hologram of the original object. Unlike a conventional photograph, each holographic snapshot stores information about the three-dimensional structure and composition of the object that created the scattered light field. The recorded holograms appear as a pattern of concentric light and dark rings.
For analyzing the images the researchers based their work on a quantitative theory, the Lorenz-Mie theory, which maintains that the way light is scattered can reveal the size and composition of the object that is scattering it.
The application of the technique ranges from research in fundamental statistical physics to analyzing the composition of fat droplets in milk.
www.nyu.edu

In the microscope, a laser beam illuminates the sample. Light scattered by the sample creates an interference pattern which is magnified and recorded. Then measurements of the particle’s position, size, and refractive index are obtained.

Molecular Light Switches for Higher Resolution

aszerdi — Fri, 29 May 2009 14:02:09 +0000

The “Superresolution” research network, founded by the German Ministry of Education and Sciences, demonstrated a new widefield microscopy technology with resolutions better than 20 nanometers. The method is based on special dyes, which’s fluorescence can be optically and reversibly switched on and off in aqueous solutions. The dyes are bond to cellular structures by using a functional group. By switching the dyes on and off, the fluorescence emission is separated in time until only those dye molecules fluoresce that have enough distance to allow their localization as single molecules. After several thousand switching cycles, a total image is constructed (dSTORM – direct stochastic optical reconstruction microscopy). Involved in the project were the work groups of Prof. Dr. M. Sauer and Prof. Dr. J. Mattay (University of Bielefeld, Germany ), Prof. Dr. K.-H. Drexhage (University of Siegen, Germany), Prof. Dr. J. Enderlein (University of Goettingen, Germany), and Prof. Dr. S. Hell (Max Planck Institute of Biophysical Chemistry, Goettingen, Germany).
www.biophotonik.org

Cytoskeleton of a fixed cell. Left: Fluorescence image at standard conditions. Right: dSTORM image using molecular switches.

Workshop on Single Molecule Spectroscopy

aszerdi — Thu, 26 Mar 2009 10:17:11 +0000

For the 15^th time now, PicoQuant is hosting the International Workshop on Single Molecule Spectroscopy and Ultrasensitive Analysis in the Life Sciences. The workshop will take place from Sep. 15-18, 2009 in Berlin-Adlershof, WISTA campus, Germany. Topics that will be covered during the talks and a poster session are: Fluorescence Lifetime Correlation Spectroscopy (FLCS), Pulsed Interleaved Excitation (PIE) and Stimulated Emission Depletion Spectroscopy (STED), two-photon excitation, new and robust fluorophores such as quantum dots, metalfluorophore interactions, analysis of living cells, investigation of protein folding and biological function studies of macromolecules and Foerster Resonance Energy Transfer (FRET).
www.picoquant.com/_workshop.htm

European Biophysics Congress

aszerdi — Tue, 24 Mar 2009 09:29:00 +0000

The 7^th European Biophysics Congress will take place in Genoa, Italy from July 11-15, 2009. The congress is organized on behalf of the Italian Society of Pure and Applied Biophysics (SIBPA) and the European Biophysics Societies Association (EBSA). It address to representatives from academic and industrial institutions.

Conference topics include:

1. Single molecule biophysics
2. Lipid biophysics
3. Folding/unfolding of proteins
4. Multiscale simulation
5. Chromatin, nucleosomes and molecular machines
6. Glycobiophysics
7. Biomolecular self-assembly
8. Photosensory biophysics
9. Structure-function relationships (channels, pumps, exchangers)
10. Live cell imaging
11. Protein-ligand interactions
12. Membrane microdomains and signalling
13. Biological motility and molecular motors
14. Interaction and recognition of DNA
15. Biomaterials and drug delivery
16. Single molecule fluorescence
17. Imaging and spectroscopy
18. Fluorescent proteins
19. Solar energy conversion and photosynthesis
20. Statistical, soft matter and biological physics
21. Condensed colloidal phase in biology
22. Ion channels in channelopathies and cancer
23. RNA world
24. Stem cells

www.ebsa2009.org

3D Single Molecule Imaging

aszerdi — Fri, 20 Mar 2009 14:02:35 +0000

A team of researchers led by professor Rafael Piestun of the department of electrical and computer engineering at the University of Colorado and William E. Moerner, professor of chemistry at Stanford University, have demonstrated for the first time a method for three-dimensional optical imaging of objects smaller than 20 nanometers over a wide spatial range. Optical imaging at these scales is of great interest in biomedical sciences and nanotechnology. The new findings, which provide a powerful tool for the super resolution of single molecules, have implications for characterizing defects in materials, the characterization of nanostructures, and the three-dimensional, biophysical and biomedical imaging of tagged molecules inside and outside of cells.
www.stanford.edu
www.colorado.edu

3D single molecule imaging

The Smallest Periscope

aszerdi — Wed, 11 Mar 2009 07:00:26 +0000

A team of Vanderbilt scientists have invented the world’s smallest version of the periscope and are using it to look at cells and other microorganisms from several sides at once. The researchers have dubbed their devices “mirrored pyramidal wells.” They consist of pyramidal-shaped cavities molded into silicon whose interior surfaces are coated with a reflective layer of gold or platinum. They are in dimension about the width of a human hair and can be made in a range of sizes to view different-sized objects. When a cell is placed in such a well and viewed with a regular optical microscope, the researcher can see not only the top of the cell, but several sides simultaneously. “This is something biologists almost never see,” says team member Chris Janetopoulos, assistant professor of biological sciences.
The Vanderbilt group is not the first to make microscopic pyramidal wells, but it is the first to apply them to make 3D images of microorganisms. In 2006, a group of scientists in England created pyramidal micromirrors and applied them to trapping atoms. And last spring researchers at the National Institute of Standards and Technology used similar structures to track nanoparticles.
www.vanderbilt.edu

Sunflower pollen, taken by Kevin Seale, Vanderbilt Institute for Integrative Biosystems Research and Education