Rapid advances have transformed the capabilities of light microscopy in recent years. Super-resolution techniques now make it possible to visualize and thus localize intracellular structures in unprecedented detail. Much of this progress has been based on the development of ever more sensitive procedures for the detection of fluorescent compounds, which can be used as markers to label specific molecules that have essential biological functions. The Deutsche Forschungsgemeinschaft (DFG) has now approved funding for the purchase of an instrument at the LMU belonging to a novel class of light microscopes. As part of an initiative designed to specifically promote “highly developed but as yet barely established technologies in the area of light microscopy”, the DFG is providing just under 1.5 million euros for the instrument. Twelve more German universities are supported with further 13 million euros. The microscope will be installed in the Core Facility Bioimaging at the Biomedical Center (BMC). Its acquisition was approved by the DFG on the basis of project proposals relating to its use, which were submitted by 10 research groups in the Biosciences.
The new instrument is specifically equipped for Fluorescence Lifetime Imaging Microscopy (FLIM). Most conventional fluorescence microscopes are designed to quantify the intensities of fluorescence signals, and allow to visualize the spatial distribution of labelled proteins. FLIM, on the other hand, measures how long the marker remains in the excited state before emitting a fluorescent signal and falling back into the ground state. The lifetime of the excited state lies in the region of a few nanoseconds (billionths of a second) and is specific for each particular marker, but it can also be modulated by physiological parameters such as the pH value, the temperature or the oxygen concentration in the sample. This makes FLIM ideal for the investigation of the physiological state of cells and tissues. “Importantly, fluorescence lifetimes are independent of factors such as the concentration of the fluorescent label, the nature of the sample or the undesirable effects of bleaching,” explains Dr. Steffen Dietzel, Head of the Core Facility Bioimaging at the BMC, so this approach promises to yield highly precise and reliable results. The latest generation of FLIM microscopes permits imaging data to be collected much faster than was previously possible. “What used to take several minutes can now be accomplished in seconds. This will allow us to observe highly dynamic processes in living cells.”