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Electron Microscopy Core Laboratory
Instrumentation
The instrumentation in the Core is sophisticated, expensive and in many cases the only equipment of its type at MCG. To protect the Department’s and Institution’s investment in the facility and to insure the Core can provide its services to the entire research community, use of the facilities and instrumentation is restricted to Core staff and investigators trained and certified by the Core staff. The majority of investigators prefer to receive results in a timely and cost-effective manner rather than learn how to process specimens and operate the equipment that provides those results. However, the staff will train investigators or members of their laboratory in all phases of specimen preparation and the use of the equipment when investigators determine that is preferable. There are fees associated with this training. Institutional policy prohibits use of the Core facilities except during normal work hours (8 am – 4:30 pm, Monday through Friday) when a member of the Core staff is available to assist if that becomes necessary.
The laboratory is equipped with instrumentation necessary for most types of biological specimen preparation and imaging for scanning and transmission electron microscopic ultrastructural analysis. When an investigator’s research requires more specialized equipment, the Core staff will attempt to locate facilities that have the equipment. The Core's major equipment includes the following:
- Reichert UltraCut T Ultramicrotome
- Leica UC6 Ultramicrotome
- Samdri-790 Critical Point Dryer
- Technics Hummer Sputter Coater
- FEI XL30 FEG Scanning Electron Microscope
- JEOL JEM 1230 Transmission Electron Microscope
- Gatan UltraScan 4000 Imaging System
Reichert Ultracut T and Leica UC6 ultramicrotomes are used for ultrathin sectioning resin-embedded specimens for transmission electron microscopy. The Leica ultramicrotome is on an anti-vibration air table in a specially designed enclosure and equipped with a digital camera and remote monitoring system to permit serial sectioning of specimens up to approximately 200 sections. Serial section images are typically used to create 3D reconstructions. Investigators who use these ultramicrotomes must provide their own diamond knives.
The critical point dryer and sputter coater are used to dehydrate and metal coat specimens for scanning electron microscopy. Both instruments are available to experienced users for a modest fee to cover the cost of consumable supplies.
The FEI XL30 field emission gun scanning electron microscope is controlled by a computer workstation running under Microsoft Windows. The field emission electron source offers high-resolution secondary electron imaging at high magnifications and accelerating voltage. In addition to the secondary electron detector the instrument has a solid state backscattered electron detector for mean atomic number imaging. Samples must be compatible with high vacuum, i.e. clean and dry, and conductive for normal observation. Uncoated or non-conductive sample can be imaged a low (1kV) accelerating voltage. Relatively large samples (150 mm diameter x 50 mm high) will fit into the specimen chamber but because of the limited movement of the specimen stage samples that fit on a 12 or 24 mm stub and have a maximum height of less than 15 mm are recommended. Magnification range is 100x to 106x with 2 nm resolution at 30kV. Digital images are saved in TIF format at resolutions of 484 x 712 to 1936 x 2576 pixels.
The JEOL JEM-1230 is a high performance, high contrast, 40-120kV transmission electron microscope with excellent imaging capabilities suitable for biological, polymer and materials science applications. Imaging modes include bright and dark field and electron diffraction. The electron gun is a standard tungsten filament. The instrument is capable of magnifications from 50x to 600,000x and resolution at 120 kV is 0.2 nm. Single specimen holder rods permit ± 30° tilt or ± 110° rotation with ± 15° tilt. Digital images are collected with a 16 megapixel (4k x 4k pixel) Gatan UltraScan 4000 camera using Gatan’s DigitalMicrograph (DM) software. The camera is Peltier cooled and offers 16 bit dynamic range in the image. The DM software runs on a high performance Dell workstation interfaced with the JEM 1230 computer and controls operations of the TEM including optimum focusing, astigmatism correction and other aspects of lens alignment. Images are initially saved in DM’s proprietary format that records user-selected information about the specimen and microscope operating conditions in addition to the image. The huge (65 MB) file is retained permanently by the Core. Full resolution (2000 pixels/in) image-only jpeg (5 MB) or Tiff (16 MB) files are provided to Core users.The Core does not provide or use sheet film in the JEM-1230.