Other Fluorescence Microscopic Techniques

The FRAP (fluorescence recovery after photobleaching) technique uses photobleaching to measure molecular diffusion and can be used if the material in question is confined to a specific plane (e.g., a membrane or cytoskeletal filaments adsorbed on a surface). The fluorophores 

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An unusually extensive battery of experimental techniques was brought to bear on these comparisons of enantiomers with their racemic mixtures and of diastereomers with each other. A very sensitive Langmuir trough was constructed for the project, with temperature control from 15 to 40°C. In addition to the familiar force/area isotherms, which were used to compare all systems, measurements of surface potentials, surface shear viscosities, and dynamic suface tensions (for hysteresis only) were made on several systems with specially designed apparatus. Several microscopic techniques, epi-fluorescence optical microscopy, scanning tunneling microscopy, and electron microscopy, were applied to films of stearoylserine methyl ester, the most extensively investigated surfactant. 

In addition to UV microscopy, there are other microscopic techniques for investigating the topochemistry of lignin in wood. These methods include fluorescence and electron microscopy The combination of these techniques with UV microscopy should give the best results However, when a composite technique is employed, precautions must be taken. For example, in measurements of lignin concentration by bromination/UV microscopy, a correction factor is needed to account for the difference in the reactivities of middle lamella and secondary wall lignins toward bromine (Saka et al, 1982) (see Chap, 4.4). 

Several diagnostic techniques are grouped under the term of immunofluorescence which do not correspond to measurements but rather to locate, for example by microscopic examination under ultraviolet light, of certain parts of the preparation derived from a reaction with fluoroscein isocyanate or other fluorescent derivatives. 

In this chapter we have mentioned only a few of the more important future developments which can be foreseen in colloid science. Many of these will depend on the availability of modern instrumentation and of powerful computer facilities. In addition to the techniques dealt with in this chapter, mention should also be made of the contributions from greatly improved electron microscopic techniques, ultracentrifuges, and X-ray equipment. Other techniques that will become of increasing significance include dielectric measurements, electrical birefringence, and time-resolved fluorescence. 

Other useful microscopic analytical techniques include hot stage, fluorescence, and cathodolumines-cence microscopies micro-infrared spectroscopy micro-Raman spectroscopy ultraviolet-visible microspectrophotometry and X-ray diffraction however, the discussion of these techniques is beyond the scope of this article. Briefly stated, each of these techniques can be used to ascertain additional information about characteristic properties of a material. The microscopist must be aware of all of these techniques, and others, so as to be able to extract the necessary information from a sample when the need arises. 

The previously described methods necessitate the extraction of the catecholamines from the tissue prior to assay. The histochemical fluorescence technique allows the visualization of the amines in situ, but it is not an accurate quantitative procedure. Freeze-dried sections of tissue are exposed to formaldehyde vapour at SO C for 1 hr or more. The catecholamines are thereby converted to hydroxyiso-quinoline derivatives (Fig. 1), which fluoresce strongly under U-V light in the fluorescence microscope (Fig. 1, p. 110). ADR and other secondary amines can be distinguished from NA, DA and DOPA by their slower rate of reaction with formaldehyde. 

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