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Microscopy Unit

Transmission Electron Microscopy Laboratory

Transmission Electron Microscope Transmission Electron Microscope

Transmission Electron Microscopy has contributed significantly to the knowledge of the cell. Using a thin beam of accelerated electrons as a light source, gives the high resolution of the Electron Microscopy. This makes it an indispensable tool in many fields of Biology, Medicine and Materials Science.

Basics of the technique

Electrons have both wave and particle properties (as demonstrated by Louis-Víctor de Broglie), and their wave-like properties mean that a beam of electrons can in some circumstances be made to behave like a beam of radiation. The wavelength is dependent on their energy, and so, can be tuned by adjustment of accelerating fields, and can be much smaller than that of light, yet they can still interact with the sample due to their electrical charge. Therefore, a beam of electrons accelerated at high speed by application a high potential difference, passes through the sample, the electrons will be dispersed in different trajectories as a function of the ultrastructure characteristics of the material observed. Placing a physical barrier with small opening angle below the sample, electrons scattered by certain angles will be removed. The image formed will be more intense in those areas corresponding to a greater mass. The image is enlarged and projected onto a screen fluorescent display in real time and can digitally acquired by a CCD.

Sample preparation
Biological studies in the transmission electron microscope require elaborate preparation, whose aim is the slicing of cells and tissues in sections of a thickness of about 60 nanometers, called ultra-thin sections, which are easily traversed by the narrow beam of electrons. Obtaining such sections requires the embbeding of the sample in resins that will provide the hardness and support for slicing.
Generally, and in order to improve the interaction between the biological sample and the electron beam, we need a process of contrast with heavy metals.
The powdered material samples for study in the transmission electron microscope requires the dilution of a very small amount of sample in an organic harmless solvent, usually dichloroethane, acetone or water. It is necessary to achieve maximum dispersion by immersing the solution in an ultrasonic bath and finally, place a drop of it on a carbon grid and be directly observed in the microscope.

Applications

Transmission electron microscopy possibilities:

• Cell characterization.
• Ultrastructure cell’s in plant and animals tissue studies.
• Localization and identification of specified biological substance at the ultrastructural level by inmunocytochemistery.
• Viruses reconigtion
• Nanoparticles size determination


Operation of the laboratory

Service provided a biological sample preparation laboratory. A variety of special techniques and methods are available for fixation, processing, embedding (epoxy and acrylic resins), curing and sectioning (thin and ultrathin as well).

Previously all users have to contact with the laboratory stuff and indicate the guidelines work. Finally if the sample is suitable for processing, the conditions to hand in and storage it will be established by both parts. It is very important advertising to stuff for dangerous samples (biological and toxics risks).

For exclusive use of electron microscope the user has to report all the characteristics sample to determinate the microscope suitability issue.

To use the electron microscopy service a registration is necessary in web @LIMS by the user to apply for a session.