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Query: UMLS:C1832526 (PCC)
 5,967 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

The electron-transport machinery in photosynthetic membranes is known to be very sensitive to heat. In this study, the rate of electron transport (ETR) driven by photosystem I (PSI) and photosystem II (PSII) during heat stress in the wild-type Synechocystis sp. strain PCC 6803 (WT) and its ndh gene inactivation mutants DeltandhB (M55) and DeltandhD1/ndhD2 (D1/D2) was simultaneously assessed by using the novel Dual-PAM-100 measuring system. The rate of electron transport driven by the photosystems (ETR(PSs)) in the WT, M55, and D1/D2 cells incubated at 30 degrees C and at 55 degrees C for 10 min was compared. Incubation at 55 degrees C for 10 min significantly inhibited PSII-driven ETR (ETR(PSII)) in the WT, M55 and D1/D2 cells, and the extent of inhibition in both the M55 and D1/D2 cells was greater than that in the WT cells. Further, PSI-driven ETR (ETR(PSI)) was stimulated in both the WT and D1/D2 cells, and this rate was increased to a greater extent in the D1/D2 than in the WT cells. However, ETR(PSI) was considerably inhibited in the M55 cells. Analysis of the effect of heat stress on ETR(PSs) with regard to the alterations in the 2 active NDH-1 complexes in the WT, M55, and D1/D2 cells indicated that the active NDH-1 supercomplex and mediumcomplex are essential for alleviating the heat-induced inhibition of ETR(PSII) and for accelerating the heat-induced stimulation of ETR(PSI), respectively. Further, it is believed that these effects are most likely brought about by the electron transport mediated by each of these 2 active NDH-1 complexes.
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PMID:The response of electron transport mediated by active NADPH dehydrogenase complexes to heat stress in the cyanobacterium Synechocystis 6803. 1909 81

Photosynthetic algae and cyanobacteria have been proposed for producing biofuels through a direct photoconversion process. To accelerate the efforts of discovering and screening microbes for biofuel production, sensitive and high throughput methods to measure photosynthetic activity need to be developed. Here we report the development of new ratiometric optical oxygen and pH dual sensors with three emission colors for measuring photosynthetic activities directly. The dual sensor system can measure oxygen (O(2)) generation and pH increase resulted from carbon dioxide (CO(2)) consumption simultaneously. The sensor was prepared by a copolymerization of three monomeric probes, an intra-reference probe (IRP) which does not respond to pH or O(2), a probe for pH sensing (pHS), and an O(2) probe for O(2) sensing (OS) with 2-hydroxyethyl methacrylate (HEMA) and acrylamide (AM). After polymerization, the three probes were chemically immobilized in an ion and O(2) permeable poly(2-hydroxyethyl methacrylate)-co-polyacrylamide (PHEMA-co-PAM) matrix. The resulted sensing films (membranes) exhibited three emission colors with well separated emission spectra, covering blue, green, and red emission windows, under 380 nm light excitation. Responses of the sensors to pH and dissolved O(2) were investigated in buffers and cyanobacterial cell cultures (Synechocystis sp. PCC 6803). In spite of the strong autofluorescence from cyanobacteria, the sensors were able to determine the pH values and dissolved O(2) concentrations accurately and reproducibly. The measured results using the optical sensors were well in accordance with measurements using electrodes with minimal experimental variations. The sensors were further applied for evaluation of photosynthetic activities of Synechocystis sp. PCC 6803 at the exponential and stationary phases. The results were consistent with biological observation that the photosynthetic activity in the exponential phase was higher than that in the stationary phase.
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PMID:New ratiometric optical oxygen and pH dual sensors with three emission colors for measuring photosynthetic activity in Cyanobacteria. 2312 83