Closed transportable fluorescence microscope

• Subject Area: Geology and Palaeontology ; Zoology
• Term: Funded in 2024
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 553503612

Fluorescence microscopy is a standard method in many fields of biology, in which light of a specific wavelength is used to illuminate a specimen. Filters in the beam block out this specific wavelength, so that no reflected light gets into the objective and the camera. Furthermore, the applied light induces fluorescence in the object or in parts of it. Fluorescence light always has a longer wavelength than the excitation light and is therefore not blocked by the filter in the beam, hence a selective visualisation is possible. Often epi-fluorescence microscopy is combined with specific fluorophores, which are coupled to certain structures via antibody staining and used for selective visualisation, for example in the fields of neuroanatomy or developmental biology, or for investigating intracellular processes. Often autofluorescence occurs during these investigations, which means that areas not marked with fluorophores show fluorescence. This effect is often disturbing, but can also be used for several applications, for example when documenting fossil specimens or extant historical and valuable museum material, which should not be stained. If these specimens exhibit autofluorescence, they can be documented with epi-fluorescence microscopy and allow insights not possible with regular transmitted or reflected light microscopy. The combination of fluorescence with composite imaging is especially useful. For this purpose, each image frame is documented with an image stack, with a focus shift by a determined distance after each image. As many structures are larger than the depth of field of the optical system, it is only in this way possible to get an entirely sharp image. The image stacks are then used to calculate an entirely sharp image. Furthermore, adjacent image details are combined to panorama images to be able to document entire animals. Further image adjustment can be achieved by using different light settings (HDR) for each image, which avoids over- or underexposure of certain areas of the composite image. Also surface structures can be documented with autofluorescence microscopy, with the resulting images resembling scanning electron microscopic images, but without the labor-intense preparation. Also the documentation in liquid without further preparation is possible. ESEM (Environmental Scanning Electron Microscopy), which does not require much preparation or none at all, is in many cases not better suitable, as specimens in liquid need to be taken out for documentation. The here applied for closed transportable fluorescence microscope allows to work in normally lit rooms. The transport function of the microscope is relevant for the use directly in museum collections.

• DFG Programme: Major Research Instrumentation
• Major Instrumentation: Geschlossenes transportables Fluoreszenzmikroskop
• Instrumentation Group: 5000 Labormikroskope
• Applicant Institution: Ludwig-Maximilians-Universität München
• Leader: Professor Dr. Joachim Tobias Haug