Origin of Cyanobacteria thylakoids via a non-vesicular glycolipid phase transition and impact on the Great Oxygenation Event

2021 ◽  
Author(s):  
Nolwenn Guéguen ◽  
Eric Maréchal
Keyword(s):  
Phase Transition ◽  
External Source ◽  
Oxygenic Photosynthesis ◽  
Lipid Phase ◽  
Thylakoid Biogenesis ◽  
Multiplier Effect ◽  
Evolution Of Life ◽  
Anionic Lipids ◽  
Review Reports

Abstract Appearance of oxygenic photosynthesis in Cyanobacteria is a major event in the evolution of Life. It had an irreversible impact on our planet, promoting the Great Oxygenation Event (GOE), ~2.4 b.y.a. Ancient Cyanobacteria predating the GOE were Gloeobacter-type cells, having no thylakoids. They hosted photosystems in their cytoplasmic membrane. The driver of the GOE was proposed to be the transition from unicellular to filamentous Cyanobacteria. However, the appearance of thylakoids expanded the photosynthetic surface by multiple logs: this multiplier effect would be more coherent with an impact on the atmosphere. Primitive thylakoids self-organize as concentric parietal uninterrupted multilayers. The quest for their origin resists vesicular-based scenarios. This review reports studies supporting that Hexagonal II-forming gluco- and galactolipids at the periphery of the cytosolic membrane could be turned within nanoseconds and without any external source of energy into membrane multilayers. Comparison of lipid biosynthetic pathways further shows that ancient Cyanobacteria contained only one anionic Lamellar-forming lipid, phosphatidylglycerol. Acquisition of sulfoquinovosyldiacylglycerol biosynthesis correlates with thylakoid emergence, possibly enabling a sufficient provision of anionic lipids to trigger an Hexagonal II-to-Lamellar phase transition. With this non-vesicular lipid-phase transition, a framework is also available to reexamine the role of companion proteins in thylakoid biogenesis processes.

scholarly journals The role of phospholipids in the reduction of ubiquinone analogues by the mitochondrial reduced nicotinamide-adenine dinucleotide-ubiquinone oxidoreductase complex

1978 ◽  
Vol 172 (3) ◽  
pp. 539-547 ◽  
Author(s):  
C I Ragan
Keyword(s):  
Phase Transition ◽  
Nicotinamide Adenine Dinucleotide ◽  
Chemical Nature ◽  
The Other ◽  
Lipid Phase ◽  
Ubiquinone Oxidoreductase ◽  
Nadh Ubiquinone Oxidoreductase ◽  
Reduced Nicotinamide Adenine Dinucleotide ◽  
Endogenous Lipids

The isolated NADH-ubiquinone oxidoreductase complex of bovine heart mitochondria reduces ubiquinone analogues by two pathways. One pathway is inhibited by rotenone, and reduction of quinones takes place in the lipid phase of the system. The other pathway is insensitive to rotenone and reduction takes place in the aqueous phase. The variation of rates of electron transpport with the chemical nature of the quinone analogue and the concentrations of both quinone and phospholipid can be rationalized in terms of partition of the quinone between the aqueous and lipid phases of the system. Thus one function of phospholipid associated with the enzyme appears to be to act as solvent for ubiquinone reduced by the rotenone-sensitive pathway. This proposal is supported by the kinetic behaviour of enzyme whose endogenous lipids have been replaced by (1,2)-dimyristoylsn-glycero-3-phosphocholine. Thus, under certain circumstances, the rotenone-sensitive reduction of ubiquinone-1 exhibited a substantial increase in activation energy below the phase-transition temperature of the synthetic lipid, whereas the reduction of other acceptors was unaffected.

scholarly journals The influence of phosphatidate bilayers on pig heart AMP deaminase. Crucial role of pH-dependent lipid-phase transition

1988 ◽  
Vol 255 (3) ◽  
pp. 977-981 ◽  
Author(s):  
M Woźniak ◽  
E Kossowska ◽  
J Purzycka-Preis ◽  
M M Zydowo
Keyword(s):  
Phase Transition ◽  
Competitive Inhibition ◽  
Saturated Fatty Acids ◽  
Lipid Phase ◽  
Amp Deaminase ◽  
Alkaline Ph ◽  
Lipid Phase Transition ◽  
Inhibited Enzyme

Phosphatidate bilayers composed of dilauroylphosphatidate, dimyristoylphosphatidate, dipalmitoylphosphatidate and dioleoylphosphatidate were prepared. Their interaction with AMP deaminase isolated from pig heart was investigated. Dioleoylphosphatidate bilayers were found to exert non-competitive inhibition on the AMP deaminase with a Ki of 15 x 10(-6) M. This inhibition is three orders of magnitude stronger than that exerted by orthophosphate. The phosphatidate species containing saturated fatty acids were either non-inhibitory or inhibited enzyme activity rather poorly. However, alkalinization of the medium from pH 6.5 to pH 7.9 led to the inhibition of pig heart AMP deaminase by dilauroylphosphatidate bilayers. This was accompanied by the fluidization of the saturated phosphatidate species, i.e. the lowering of their phase transition temperature in alkaline pH, as measured by light-scattering and fluorescence scans. The possible significance of these findings for the regulation of AMP deaminase activity in vivo by natural membranes is discussed.

Role of Erlotinib in Influencing the Quality of Life of Cancer Patients

2020 ◽  
Vol 07 ◽  
Author(s):  
Deepika Purohit ◽  
Parijat Pandey
Keyword(s):  
Quality Of Life ◽  
Lung Cancer ◽  
Cancer Patients ◽  
Kinase Inhibitors ◽  
Treatment Modalities ◽  
Pancreatic Cancers ◽  
Review Reports ◽  
Causes Of Deaths

Background:: Cancer is one of the significant causes of morbidity and mortality in patients globally. Lung cancer, among other cancers, remains to be one of the principal causes of deaths in both men and women. The most common type of lung cancer is the non-small-cell lung cancer (NSCLC). Apart from lung cancer, pancreatic cancer is also one of the common cancers currently. Objective:: The assessment of QoL in erlotinib-treated patients can also prove to be very useful in the establishment of this drug as the main treatment option for the patients with pancreatic and lung cancer. Methods:: Therapies that target EGFR-mediated signalling are the latest keystones for treating these two types of cancers. They comprise of two main treatment modalities: firstly, against the extracellular fields, that include monoclonal antibodies and secondly, mechanisms that create interferences in the signalling pathways, primarily the small molecule tyrosine kinase inhibitors. Results:: Quality of life (QoL) is one of the key advantages in erlotinib therapy over chemotherapy. Conclusion:: The present review reports the role of erlotinib in improving the quality of life of cancer patients especially in NSCLC and pancreatic cancers. The studies or trials establishing the relations between erlotinib and QoL are discussed in detail in this review.

scholarly journals Structural and Technological Approach to Reveal the Role of the Lipid Phase in the Formation of Soy Emulsion Gels with Chia Oil

Gels ◽  
2021 ◽  
Vol 7 (2) ◽  
pp. 48
Author(s):  
Ana M. Herrero ◽  
Claudia Ruiz-Capillas
Keyword(s):  
Raman Spectroscopy ◽  
Structural Properties ◽  
Structural Changes ◽  
Protein Secondary Structure ◽  
Lipid Phase ◽  
Α Helix ◽  
Β Sheet ◽  
Shed Light ◽  
Chia Oil

Considerable attention has been paid to emulsion gels (EGs) in recent years due to their interesting applications in food. The aim of this work is to shed light on the role played by chia oil in the technological and structural properties of EGs made from soy protein isolates (SPI) and alginate. Two systems were studied: oil-free SPI gels (SPI/G) and the corresponding SPI EGs (SPI/EG) that contain chia oil. The proximate composition, technological properties (syneresis, pH, color and texture) and structural properties using Raman spectroscopy were determined for SPI/G and SPI/EG. No noticeable (p > 0.05) syneresis was observed in either sample. The pH values were similar (p > 0.05) for SPI/G and SPI/EG, but their texture and color differed significantly depending on the presence of chia oil. SPI/EG featured significantly lower redness and more lightness and yellowness and exhibited greater puncture and gel strengths than SPI/G. Raman spectroscopy revealed significant changes in the protein secondary structure, i.e., higher (p < 0.05) α-helix and lower (p < 0.05) β-sheet, turn and unordered structures, after the incorporation of chia oil to form the corresponding SPI/EG. Apparently, there is a correlation between these structural changes and the textural modifications observed.

Fatty acyl chain structure, orientational order, and the lipid phase transition in Acholeplasma laidlawii B membranes. A review of recent 19F nuclear magnetic resonance studies

1984 ◽  
Vol 62 (11) ◽  
pp. 1134-1150 ◽  
Author(s):  
P. M. Macdonald ◽  
B. D. Sykes ◽  
R. N. McElhaney
Keyword(s):  
Phase Transition ◽  
Fatty Acids ◽  
Nuclear Magnetic Resonance ◽  
Acyl Chain ◽  
Orientational Order ◽  
Membrane Lipid ◽  
Fatty Acyl ◽  
Fatty Acyl Chain ◽  
Lipid Phase ◽  
Lipid Phase Transition

The orientational order parameters of monofluoropalmitic acids biosynthetically incorporated into membranes of Acholeplasma laidlawii B in the presence of a large excess of a variety of structurally diverse fatty acids have been determined via 19F nuclear magnetic resonance (19F NMR) spectroscopy. It is demonstrated that these monofluoropalmitic acids are relatively nonperturbing membrane probes based upon physical (differential scanning calorimetry), biochemical (membrane lipid analysis), and biological (growth studies) criteria. 19F NMR is shown to convey the same qualitative and quantitative picture of membrane lipid order provided by 2H-NMR techniques and to be sensitive to the structural characteristics of the membrane fatty acyl chains, as well as to the lipid phase transition. Representatives of each naturally occurring class of fatty acyl chain structures, including straight-chain saturated, methyl-branched, monounsaturated, and alicyclic-ring-substituted fatty acids, were studied and the 19F-NMR order parameters were correlated with the lipid phase transitions (determined calorimetrically). The lipid phase transition was the prime determinant of overall orientational order regardless of fatty acid structure. Effects upon orientational order attributable to specific structural substituents were discernible, but were secondary to the effects of the lipid phase transition. In the gel state, relative overall order was directly proportional to the temperature of the particular lipid phase transition. Not only the overall order, but also the order profile across the membrane was sensitive to the presence of particular structural substituents. In particular, in the gel state specific fatty acyl structures demonstrated a characteristic disordering effect in the membrane order profile. These various observations can be merged to provide a unified picture of the manner in which fatty acyl chain chemistry modulates the physical state of membrane lipids.

scholarly journals Antioxidant and Signaling Role of Plastid-Derived Isoprenoid Quinones and Chromanols

2021 ◽  
Vol 22 (6) ◽  
pp. 2950
Author(s):  
Beatrycze Nowicka ◽  
Agnieszka Trela-Makowej ◽  
Dariusz Latowski ◽  
Kazimierz Strzalka ◽  
Renata Szymańska
Keyword(s):  
Current Knowledge ◽  
Stress Factors ◽  
Oxygenic Photosynthesis ◽  
Ros Generation ◽  
Main Site ◽  
Storage Lipids ◽  
Abiotic Stress Factors ◽  
Cell Components ◽  
And Function

Plant prenyllipids, especially isoprenoid chromanols and quinols, are very efficient low-molecular-weight lipophilic antioxidants, protecting membranes and storage lipids from reactive oxygen species (ROS). ROS are byproducts of aerobic metabolism that can damage cell components, they are also known to play a role in signaling. Plants are particularly prone to oxidative damage because oxygenic photosynthesis results in O2 formation in their green tissues. In addition, the photosynthetic electron transfer chain is an important source of ROS. Therefore, chloroplasts are the main site of ROS generation in plant cells during the light reactions of photosynthesis, and plastidic antioxidants are crucial to prevent oxidative stress, which occurs when plants are exposed to various types of stress factors, both biotic and abiotic. The increase in antioxidant content during stress acclimation is a common phenomenon. In the present review, we describe the mechanisms of ROS (singlet oxygen, superoxide, hydrogen peroxide and hydroxyl radical) production in chloroplasts in general and during exposure to abiotic stress factors, such as high light, low temperature, drought and salinity. We highlight the dual role of their presence: negative (i.e., lipid peroxidation, pigment and protein oxidation) and positive (i.e., contribution in redox-based physiological processes). Then we provide a summary of current knowledge concerning plastidic prenyllipid antioxidants belonging to isoprenoid chromanols and quinols, as well as their structure, occurrence, biosynthesis and function both in ROS detoxification and signaling.

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