Fluorescence switching, spectroscopic

To gain a better understanding of the vase-kite transition the Diederich group subsequently synthesized quinoxaline-bridged velcrands bearing one or two (48, Fig. 9.19) fluorescent (BODIPY) labels for single molecule spectroscopic studies [127]. The introduction of the BODIPY labels had little effect on the switching... 

Many enzymes exhibit a pH optimum of their activity. Working in a solution outside that optimum, an electrolysis of solution components involving H+ or OH at the microelectrode can induce a local pH shift toward the pH optimum of the enzyme activity, thereby switching on enzyme activity locally. The product of the enzymatic reaction may be collected at the microelectrode tip after applying the detection potential to it. This event would mark the end of the electrolysis causing the local pH shift. The locally changed pH will dissipate rapidly and switch off the enzyme activity. This principle has been demonstrated with fluorescence spectroscopic observation of the enzyme activity [100] and may soon find other applications as microelectrode-induced localized pH shifts have also been utilized in SECM microfabrication techniques (see Chapter 15). It remains to be found whether interesting enzyme systems exist which can be manipulated by rather small pH... 

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