Detection of Single Biological Molecules

It is therefore possible to observe single molecules through a microscope with the naked eye and follow its path due to diffusion through the liquid (Fig. 10.44). With sensitive detectors, such as photomultipliers, even photon numbers of A = 100 can be readily detected. 

In particular suited for single molecule detection is the green fluorescence molecule (Fig. 10.6), which has a large quantum efficiency and which can be attached to bacteria and vimses. When these bacteria penetrate into living cells, their path can be followed in detail due to the detection of the fluorescing molecule [1532]. 

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