Fluorescence spectroscopy voltage

A conventional set-up to characterize synthetic ion channels and pores by fluorescence spectroscopy in vesicles uses large unilamellar vesicles (LUVs) that are labeled with one or more internal (Pi), external (Pe) or membrane-bound (Pm) fluorescent probes (Fig. 11.5a). Internal probes such as HPTS, ANTS or CF are most common to determine activity, external probes are used to reveal specific characteristics (e.g. the voltage-sensitive safranin O, Section 11.3.4), membrane-bound probes are mainly but not exclusively used for structural studies (Section 11.4). 

Electrochemical experiments to measure cell voltage and current efficiency are simple, direct, and usefiil for the investigation of membrane performance. Visual and microscopic observations are indispensable. Visual inspection is the principal method used for determining the soundness of the membrane surface. SEM is quite useful for the inspection of morphology of the surface or cross-sections. It can be used to identify deposits of impurities. XRD and X-ray fluorescence spectroscopy (XRF) are useful for the semiquantitative determination of impurity accumulation and distribution [126]. Table 4.8.10 [ 132] sununarizes the reconunended methods for detecting the physical and chemical damage to membranes. 

The operation and application of streak cameras in fluorescence lifetime spectroscopy has been reviewed previously (see, e.g., Refs. 91 and 92). Streak cameras are useful in 2-D time-resolved imaging applications such as microscopy or multiwavelength array fluorometry. The operating principle is based on converting an optical pulse into a photoelectron pulse and spatially dispersing the electron image on a phosphor by means of a synchronized deflection voltage across two plates. 

The detector is usually built around the capillary tube which must remain unbroken so that the voltage can draw the desired components through the detection region. Detection is usually accomplished by passing a beam of light directly through the capillary tube and observing UV absorbance or fluorescence (16,20,21). Other detection systems are based on conductivity [22] and mass spectroscopy [23]. 

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