Photoactive Pchlide-POR-NADPH complexes were reconstituted using protochlorophyllide (Pchlide) and recombinant light-dependent protochlorophyllide oxidoreductase (POR) proteins, His₆-PORA, His₆-PORB and His₆-PORC, from Arabidopsis thaliana. We did not observe any differences in the kinetics of the protochlorophyllide photoreduction at room temperature among the PORA, PORB and PORC proteins. In contrast, the PORC protein showed lower yield of Chlide formation than PORA and PORB when preincubated in the dark for 30 min and then illuminated for a short time. The most significant observation was that reconstituted Pchlide-POR-NADPH complexes showed fluorescence maxima at 77 K similar to those observed for highly aggregated Pchlide-POR-NADPH complexes in prolamellar bodies (PLBs) in vivo. Homology models of PORA, PORB and PORC of Arabidopsis thaliana were developed to compare predicted structures of POR isoforms. There were only slight structural differences, mainly in the organisation of helices and loops, but not in the shape of whole molecules. This is the first comparative analysis of all POR isoforms functioning at different stages of A. thaliana development.

Application of a high electric field causes an electric shock to the heart. This is utilized in defibrillation to reestablish normal contraction rhythms during dangerous arrhythmias or in cardiac arrest. If shock-induced transmembrane potentials are large enough, they can cause tissue destruction due to irreversible electroporation (EP). Also electrochemotherapy of nearby tissues may have an adverse effect on the heart. Herein, we present experimental data on effects of electroporation in culture of cardiac cells (H9C2). The electric field was applied in short pulses of 25-3250 V/cm, 50 µs each. The viability of cells was tested by MTT assay after 24 hours. For detection of DNA fragmentation, associated with apoptosis, alkaline and neutral comet assays were performed after EP. Additionally phase contrast images of cells obtained directly after EP were analyzed. Although cell images indicated disruption of cell membranes after EP with high intensities, only a few percent of apoptotic cells and no necrotic effects in the cell nucleus could be observed in comet assay tests performed 2 hours post EP. MTT viability test showed that pulse intensities above 375 V/cm are destructive for myocytes viability.

In Angiosperms, the reduction of protochlorophyllide (Pchlide) to chlorophyllide (Chlide), a penultimate reaction of chlorophyll biosynthesis, is catalyzed by a photoenzyme Pchlide oxidoreductase (POR) and completely inhibited in darkness. This reaction plays also a regulatory role in plant morphogenesis. In the case of dark-grown Angiosperms, Pchlide is accumulated, mainly in the form of complexes with NADPH and POR but also as an unbound pigment. Etioplasts that develop in the place of chloroplasts in the dark contain a highly organized lipid structure termed prolamellar body (PLB), which is the main site of accumulation of the ternary Pchlide:POR:NADPH complexes. An illumination triggers the photoreduction of Pchlide molecules which are bound to the ternary complexes. This is followed by a set of biochemical reactions and structural changes leading to Chl synthesis that can be monitored with fluorescence techniques. This chapter describes the application of low-temperature fluorescence spectroscopy and fluorescence lifetime measurements for monitoring the Pchlide to Chlide conversion in isolated prolamellar bodies. These techniques enable the analysis of heterogeneity of accumulated pigments: Pchlide and Chlide that reflect the different organization of pigment-protein complexes.