Monitoring of Membrane Processes Using Fluorescence Techniques Advances and Limitations

Monitoring of Membrane Processes Using Fluorescence Techniques Advances and Limitations 

This chapter discusses the use of fluorescence techniques for the monitoring of membrane processes, making use of the intrinsic fluorescence properties of the various components involved. This chapter deals with situations where none of these components is labeled with an external reporter, a fluorescence probe, as happens in many other applications described in this book (see Chapters 3,4 and 8). 

Therefore, the use of the intrinsic ( natural ) fluorescence behavior of a given molecule may be an extremely powerful approach to investigate and monitor a specific process, because the molecule to be inspected is not labeled/altered by an external reporter. However, these techniques are restricted to the monitoring of compounds that exhibit natural fluorescence. 

One of the most interesting features of natural fluorescence results from the fact that the fluorescence response of such a molecule depends very much on its microenvironment. Take, for example, the fluorescence behavior of a tryptophan residue in a protein molecule its fluorescence response differs, depending on the position of such a tryptophan within the protein (e.g. more exposed at an outer hydrophilic environment or more buried inside a hydrophobic region of the protein). Also, for the same tryptophan example, the proximity or distance of potential quenchers influences its fluorescence response. This behavior can be explored in order to gather information about the molecular interaction between the target fluorescent compound and a membrane, as discussed in this chapter. 

This chapter introduces and discusses different fluorescence techniques that do not require the use of external labeling steady-state fluorescence (including 2D fluorescence), fluorescence anisotropy and time-resolved fluorescence and it provides illustrative examples showing how these techniques may be used for the monitoring of membrane processes. 

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