Time-Resolved Spectroscopy of Biological Processes

The combination of time-resolved laser spectroscopic techniques with a laser scanning microscope opens new possibilities for the investigation of dynamical processes with high spatial resolution. This is demonstrated in [15.143b] by time-resolved fluorescence measurements of carcinoma cells compared with normal cells. 

The application of femtosecond lasers to the investigation of important biological processes, such as the photosynthesis or the visual process, has brought a very detailed understanding of the different steps between the photoexcitation and the final product of this processes [15.144]. For example, the primary reaction of sensory rhodopsin after the excitation of the Si state is the decay with a time constant of 4 ps into a redshifted photo product, while bacteriorhodopsin decays much faster with a time constant of 500 fs. The pop- 

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