Light induced activation irradiation

Presently photodynamic therapy (PDT) is considered as a perspective way for therapy of different diseases, including cancer. PDT is a method based on the local light-induced activation of photosensitizers able to accumulate selectively in energy-deficient cells (malignant or dysplastic ones) not influencing the remaining normal cells of the body (Pass, 1993). Upon the action of irradiation of certain wavelength characteristic for individual photosensitizer, photochemical reaction occurs... 

The work done in Ziegler s laboratory has shown that irradiation of green leaves and isolated chloroplasts causes a rapid and reversible increase (up to 4,5-fold) in the activity of the NADP-dependent GAld3P dehydrogenase. The in vivo light-induced activation of the enzyme is closely connected with the operation of the non-cyclic electron flow of photosynthesis, as shown by experiments with inhibitors. NADPH causes a specific activation (up to about 10-fold) of the inactive dark-enzyme , and ATP is also a similarly eflFective activating agent in vitro. Anderson has achieved the conversion of one electrophoretic-... 

Photonic activation of redox enzymes results in the light-induced bioelectrocataly-tic activation of an enzyme cascade. This permits application of photoswitchable enzymes as amplifiers of weak photonic signals. Alternatively, sensitive actino-meters, measuring low irradiation doses, might be envisaged. 

Photoisomerizable polymers have been well investigated and applied in various systems to allow physical properties to be reversibly controlled by irradiation.24-31 Accordingly, the encapsulation of proteins in photoisomerizable polymers could provide a general strategy for photoregulating enzymes by means of light-induced permeability of the substrate across the polymer membrane. Willner et a/.43 reported the photoregulation of the activity of a-chymotrypsin encapsulated in a photoisomerizable polymer. They chose azobenzene-, leuco-hydroxide-, and spiropyran-attached acrylamides 4-6 as photoisomerizable copo-... 

With this probe, the investigators also studied the light-induced sampling of PKC activity in HeLa cells in vivo. Exposure of cells to phorbol ester (TPA) normally induces PKC activity. HeLa cells microinjected with the caged probe at an estimated concentration of 20 pM failed to display a fluorescent response to TPA, while a robust response was recorded as a result of a concomitant TPA treatment and UV irradiation (365 nm at 1J cm 2). 

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