New method for imaging molecules inside cells

ScienceDaily (June 29, 2011) — Using a new sample holder, researchers at the University of Gothenburg have further developed a new method for imaging individual cells. This makes it possible to produce snapshots that not only show the outline of the cell's contours but also the various molecules inside or on the surface of the cell, and exactly where they are located, something which is impossible with a normal microscope.

Individual human cells are small, just one or two hundredths of a millimeter in diameter. As such, special measuring equipment is needed to distinguish the various parts inside the cell. Researchers generally use a microscope that magnifies the cell and shows its contours outline, but does not provide any information on the molecules inside the cell and on its surface.

"The new sample holder is filled with holds cells in solution," says Ingela Lanekoff, one of the researchers who developed the new method at the University of Gothenburg's Department of Chemistry. "We then rapidly freeze the sample down to -196°C, which enables us to get a snapshot of where the various molecules are at the moment of freezing. Using this technique we can produce images that show not only the outline of the cell's contours, but also the molecules that are there, and where they are located."

Important to measure chemical processes in the body

So why do the researchers want to know which molecules are to be found in a single cell? Because the cell is the smallest living component there is, and the chemical processes that take place here play a major role in how the cell functions in our body. For example, our brain has special cells that can communicate with each other through chemical signals. This vital communication has been shown to be dependent on the molecules in the cell's membrane.

Imaging the molecules in the membrane of single individual cells's membrane enables researchers to measure changes. Together with previous results, Lanekoff's findings show that the rate of communication in the studied cells studied is affected by a change of less than one per cent in the quantities abundance of a specific molecule in the membrane. This would suggest that communication between the cells in the brain is heavily dependent on the chemical composition of the membrane of each individual cell,. This could be an important part of the puzzle which could go some way towards explaining the mechanisms behind learning and memory.

The thesis, Analysis of phospholipids in cellular membranes with LC and imaging mass spectrometry, has been successfully defended at the University of Gothenburg. Supervisors: Andrew Ewing and Roger Karlsson. Download the thesis at: hdl.handle.net/2077/25279

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by University of Gothenburg.

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Imaging of surface plasmons may be a lot easier than previously thought

ScienceDaily (June 6, 2011) — An unusual observation turned into a scientific breakthrough when K.U.Leuven researchers investigating the optical properties of nanomaterials discovered that so-called surface plasmons leave imprints on the surface of the nanostructures. This led to a new type of high resolution microscopy for imaging the electric fields of nanostructures.

Nanomaterials, consisting of extremely small particles or thin layers, tend to acquire unexpected properties. Optical nanomaterials are a class of materials that have emerged over the last ten years and that have quickly become a hot topic in material science due to their counterintuitive optical behavior and revolutionary potential applications. Optical nanomaterials are mainly based on surface plasmon resonances -- the property whereby, in metallic nanostructures, light can collectively excite surface electron waves. These electron waves have the same frequency as light, but much shorter wavelengths, which allow their manipulation at the nanoscale. In other words, with the help of plasmons, light can be captured, modified and even stored in nanostructures. This emerging technology finds applications in surprising areas, ranging from cancer treatment (by targeting cancer cells with nanoparticles that will produce heat when excited) to invisibility (by causing light to follow a trail of nanoparticles, that acts as an invisibility cloak to whatever is underneath them).

The imaging of surface plasmons provides a direct way to map and understand the local electric fields that are responsible for the unusual electromagnetic properties of optical nanomaterials. However, the imaging of surface plasmons is quite challenging. While there are methods to image plasmons with high resolution, they come at a considerable increase in both cost and complexity. But now, Ventsislav K. Valev and his colleagues have demonstrated a powerful and user friendly method for imaging plasmonic patterns in nanostructures.

"We were performing routine characterization of freshly grown samples, when I asked Yogesh, one of our Ph.D. students, to look at a sample that had already been studied. There was absolutely no reason to do this; I just had a hunch," sais Ventsislav Valev. "Surprisingly, this sample appeared to be decorated and I immediately recognized the pattern. Somehow, the optical properties have been imprinted on the surface of the nanostructures."

The scientists indeed found out that upon illuminating nanostructures made of nickel or palladium, the resulting surface plasmon pattern is imprinted on the structures themselves. This imprinting is done through displacing material from the nanostructure to the regions where the plasmon enhancements are the largest. In this manner, the plasmons are effectively decorated, allowing for subsequent imaging with standard surface probe techniques, such as scanning electron microscopy or atomic force microscopy. The imprinting method is quite unique, combining aspects of both imaging and writing techniques.

This research is described in an upcoming paper in the journal Physical Review Letters.

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The above story is reprinted (with editorial adaptations by ScienceDaily staff) from materials provided by Katholieke Universiteit Leuven, via AlphaGalileo.

Journal Reference:

V. Valev, A. Silhanek, Y. Jeyaram, D. Denkova, B. De Clercq, V. Petkov, X. Zheng, V. Volskiy, W. Gillijns, G. Vandenbosch, O. Aktsipetrov, M. Ameloot, V. Moshchalkov, T. Verbiest. Hotspot Decorations Map Plasmonic Patterns with the Resolution of Scanning Probe Techniques. Physical Review Letters, 2011; 106 (22) DOI: 10.1103/PhysRevLett.106.226803

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