Fluorescence microscopy techniques

In fluorescence microscopy cellular structures are stained by fluorescent dyes; they are excited by certain wavelengths and emit fluorescent light of longer wavelength. Specific filter sets allow for observation of the emitted light on a dark background.

Staining can be used for:

• visualization of sub-resolution structures by organelle-specific dyes
• identification of visible and sub-resolution structures by organelle-specific dyes
• immuno-labelling of proteins
• fluorescence-in-situ-hybridization of DNA (FISH)
• visualization of proteins in living cells by green fluorescent protein technique (GFP)
• quantitative analysis of cell content
• measuring of physiological parameters such as membrane potential, yield of photosynthesis or respiration

Quite a few biological structures emit fluorescent light naturally upon excitation. A well known example is chlorophyll which can be excited by different wavelenghts and emits red light. This phenomenon is called autofluorescence.