The Water Permeability of Intact Subcellular Organelles
Gheorghe Benga in Water Transport in Biological Membranes, 1989
A second natural organelle that has been subjected to water permeability studies is the thylakoid membrane of chloroplasts. Thylakoid membranes form substructures of surpassing complexity within algal cells and within the chloroplasts of higher plants, where they contain the pigments and electron-transport apparatus of the light reactions of photosynthesis. The topology of these structures is still not completely understood, although the electron microscopic work in serial section of Paolillo and co-workers44–48 has provided considerable structural insight. Basically, the thylakoids are organized as layered stacks of flattened, osmotically tight vesicles (the grana stacks), in which are embedded the pigments and electron transport proteins which catalyze the following reactions:
Inter- and Intracellular Signaling in Plant Cells with Participation of Neurotransmitters (Biomediators)
Akula Ramakrishna, Victoria V. Roshchina in Neurotransmitters in Plants, 2018
Cholinesterase activity of organelles may be a marker of the presence of acetylcholine and its participation in the information transfer and regulation the reactions occur within the cellular compartments. The cholinesterase activity is located within the cell too—as has been shown first in root cell cytoplasm and plasmalemma of Phaseolus aureus (Fluck and Jaffe 1974c, 1976), nucleus of P. sativum (Maheshwary et al. 1982), and chloroplasts (Roshchina and Mukhin 1984, 1986, 1987; Gorska-Brylass et al. 1990; Gorska-Brylass and Smolinski 1992). Perhaps, the contacts between organelles include the enzyme. When the hydrolysis of acetylcholine by the chloroplasts of pea P. sativum and common nettle U. dioica was analyzed (Roshchina and Mukhin 1984, 1987a), it has been shown that the highest hydrolyzing activity is concentrated in chloroplasts and is inhibited by specific inhibitors of animal cholinesterases neostigmine and physostigmine. The cholinesterase activity has been found in fractions of outer membranes and thylakoids (Roshchina 1989). Moreover, the activity of the enzyme in thylakoids was approximately seven-fold higher than in chloroplast envelope. The concentration curves of the rate of hydrolysis of cholinic esters in a dependence on substrate show that the chloroplast cholinesterase hydrolyzes acetylcholine with a higher rate than butyrylcholine, and the excess of substrate to depress the cholinesterase activity (Roshchina and Mukhin 1984).
Carotenoids
Ruth G. Alscher, John L. Hess in Antioxidants in Higher Plants, 2017
Illumination of leaf tissues, chloroplasts, or thylakoids with high light intensities under aerobic conditions may result in the rapid bleaching of photosynthetic pigments. Such bleaching reflects oxidative damage in these systems.56 The photobleaching of chlorophyll in the light-harvesting complexes can be considered to be a self-sensitized type II reaction.52 These bleaching processes are highly dependent on the presence of oxygen, and can be controlled through the action of various scavengers of singlet oxygen and promoted in the presence of D2O (which extends the life time of singlet oxygen). Under anaerobic conditions, bleaching of pigments is minimal, i.e., it is the combination of light and oxygen that is most damaging.
Mechanism of long-term toxicity of CuO NPs to microalgae
Published in Nanotoxicology, 2018
Xingkai Che, Ruirui Ding, Yuting Li, Zishan Zhang, Huiyuan Gao, Wei Wang
The PsbO protein is the core protein of OEC and was detected with thylakoid membranes of the treated algae by Western blot. For thylakoid membranes preparation, 50mL algae medium was centrifugated (8000rpm, 5min) and then the supernatants were removed. The remaining algal pellet was homogenized in an ice-cold isolation buffer (100mM sucrose, 50mM HEPES, pH 7.8, 20mM NaCl, 2mM EDTA, and 2mM MgCl2) and filtered through three layers of pledget. The filtrate was centrifuged at 3000g for 10min. The sediments were washed with isolation buffer, re-centrifuged, and finally suspended in an isolation buffer. The thylakoid membrane proteins were then denatured and separated using 12% polyacrylamide gradient gel. The denatured protein complexes in the gel were then electro-blotted to PVDF membranes, probed with PsbO antibody, and visualized by the enhanced chemi-luminescence method.
Biomimetic phototherapy in cancer treatment: from synthesis to application
Published in Drug Delivery, 2021
Yifan Zhao, Cuixia Shi, Jie Cao
Apart from animal cell membranes, it should be noted that plant cell membranes, such as powerful chloroplast thylakoids, H2O2 will gradually accumulate in chloroplasts under the influence of low temperature or high salt environment. In order to reduce the damage caused by high oxidative stress, plant leaves have evolved to form a powerful antioxidant system in the body. For example, the hydrogen peroxide decomposing enzyme on the thylakoid membrane can break down H2O2 into O2. Furthermore, the photosynthesis of green plants can release O2, and chlorophyll itself is a kind of fluorescent PS (Sewelam et al., 2014; Wang et al., 2017). Based on this inspiration, Ouyang et al. (2018) designed biomimetic plant thylakoids for PDT guided by fluorescence imaging of tumors. They firstly extracted the functional thylakoid cell membrane from spinach and then squeezed by the extruder successfully prepared the nanothylakoids (NTs), the membrane with a particle size of 50 nm. H2O2 decomposing enzyme can catalyze the decomposition of tumor endogenous H2O2 and effectively alleviate the problem of hypoxia. Under the irradiation of the near-infrared laser, the energy level transition of fluorescent dye chlorophyll occurs, which transfers the energy to O2 and then produces 1O2, which realizes the PDT guided by fluorescence imaging of tumor.
Use of an immobilised thermostable α-CA (SspCA) for enhancing the metabolic efficiency of the freshwater green microalga Chlorella sorokiniana
Published in Journal of Enzyme Inhibition and Medicinal Chemistry, 2020
Giovanna Salbitani, Sonia Del Prete, Francesco Bolinesi, Olga Mangoni, Viviana De Luca, Vincenzo Carginale, William A. Donald, Claudiu T. Supuran, Simona Carfagna, Clemente Capasso
The analysis of the genome belonging to different microalgal species evidences a very variegated pattern of CA classes. It is possible to identify seven of the eight CA-classes discovered up to now in these organisms. The different classes can coexist or have different localizations inside the cells, such as the cell wall, plasma membrane, cytosol, mitochondria, chloroplast stroma, and chloroplast thylakoid lumen73–75. Besides, for each enzyme class, many isoforms were reported to exist74. In the present manuscript, the interest was focussed on the freshwater green microalga Chlorella sorokiniana as it can be useful in many fields, such as photosynthesis research, pharmaceuticals for humans, aquaculture foods, and wastewater treatment. In 1998, a soluble form of CA belonging to the α-class76 was purified and characterised from C. sorokiniana. Other CA-classes appear to be encoded by this green microalga genome although they have not yet been characterised76.
Related Knowledge Centers
- Chloroplast
- Cyanobacteria
- Electron Tomography
- Phospholipid
- Photosynthesis
- Photosynthetic Pigment
- Stroma
- Endoplasmic Reticulum
- Galactolipid
- Lumen