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Environmental pH and Glu364 to Gln mutation in the chlorophyll-binding CP47 protein affect redox-active TyrD and charge recombination in Photosystem II
摘要： In Photosystem II, loop E of the chlorophyll-binding CP47 protein is located near a redox-active tyrosine, YD, forming a symmetrical analog to loop E in CP43, which provides a ligand to the oxygen-evolving complex (OEC). A Glu364 to Gln substitution in CP47, near YD, does not affect growth in the cyanobacterium Synechocystis sp. PCC 6803; however, deletion of the extrinsic protein PsbV in this mutant leads to a strain displaying a pH-sensitive phenotype. Using thermoluminescence, chlorophyll fluorescence, and flash-induced oxygen evolution analyses, we demonstrate that Glu364 influences the stability of YD and the redox state of the OEC, and highlight the effects of external pH on photosynthetic electron transfer in intact cyanobacterial cells.
关键词： TyrD,oxygen-evolving complex,cyanobacteria,YD,CP47,Synechocystis sp. PCC 6803,Photosystem II
更新于2025-09-09 09:28:46
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Micro-patterned cell orientation of cyanobacterial liquid-crystalline hydrogels
摘要： Control of cell extension direction is crucial for the regeneration of tissues, which are generally composed of oriented molecules. The scaffolds of highly-oriented liquid crystalline polymer chains were fabricated by casting cyanobacterial mega-saccharides, sacran, on parallel-aligned micrometer bars of polystyrene (PS). Polarized microscopy revealed that the orientation was in transverse direction to the longitudinal axes of the PS bars. Swelling behavior of the micro-patterned hydrogels was dependent on the distance between the PS bars. The mechanical properties of these scaffolds were dependent on the structural orientation; additionally, the Young’s moduli in the transverse direction were higher than those in the parallel direction to the major axes of the PS bars. Further, fibroblast L929 cells were cultivated on the oriented scaffolds to be aligned along the orientation axis. L929 cells cultured on these scaffolds exhibited uniaxial elongation.
关键词： Cell orientation,Liquid crystal hydrogels,Micropatterned scaffolds,Cyanobacteria,Sulfated polysaccharides
更新于2025-09-09 09:28:46
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Fluorescence spectra predict microcystin-LR and disinfection byproduct formation potential in lake water
摘要： Disinfection byproducts (DBPs) and algal toxins can be expensive to monitor and represent significant potential risks to human health. DBPs, including haloacetic acids and trihalomethanes, are possible or probable human carcinogens. Microcystin-LR—produced by cyanobacteria—is linked with various adverse health effects. Here we show that fluorescence spectra predict both microcystin-LR occurrence and DBP formation potential (DBPfp) in lake water. We compared models with either fluorescence spectra or a suite of water quality predictors as inputs. A regularized logistic regression model with fluorescence spectral inputs correctly classified 94% of test data with respect to microcystin-LR occurrence, with a 96% probability of correctly ranking a detect/non-detect pair. Regularized linear regression predicted DBPfp based on fluorescence inputs with a combined R2 of 0.83 on test data. A gradient-boosted classifier with seven water quality inputs was comparable in detecting microcystin-LR (91% correct), as was UV254 in predicting DBPfp (combined test R2 = 0.84), but no single parameter matched fluorescence spectra over both predictive tasks. Results highlight the potential for multiparameter monitoring via fluorescence spectroscopy, extending previous work on predicting DBPs alone. As a high-frequency monitoring tool, this approach could supplement mass spectrometric methods that may only be applicable at low frequency due to resource limitations.
关键词： cyanobacteria,MC-LR,trihalomethanes,elastic net,EEM,classification,gradient boosting,haloacetic acids,lasso
更新于2025-09-04 15:30:14