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Finding a Target
Published in Nathan Keighley, Miraculous Medicines and the Chemistry of Drug Design, 2020
Most of the specific functions carried out by the plasma membrane are conducted by membrane proteins. As such, the type and quantities of these proteins in plasma membranes varies a great deal, depending on the function of that membrane. In myelin membranes, which function as the electrical insulators in nerve cells, less than 25% of the membrane mass is protein. By contrast, in the inner membranes of mitochondria, which are involved in energy transduction, are about 75% protein, by mass. Typically, cell membranes will have approximately 50% of their mass being proteins. Proteins molecules are much larger than the lipid molecules that comprise the bilayer, so there are many more lipid molecules in the membrane than there are proteins. The membrane proteins on the cell exterior will often have oligosaccharide (carbohydrate) molecules attached to them, which form a coat on the cell surface.
Basic Microbiology
Published in Philip A. Geis, Cosmetic Microbiology, 2020
Plasma membrane—A phospholipid bilayer which creates a semi-permeable barrier and delineates the boundaries of the cell. This is the location of many important membrane-associated proteins including receptors and enzymes as well as transport proteins designed to internalize desired extracellular components and to extrude cellular contents such as waste.
Airway Repair and Adaptation to Inhalation Injury
Published in Jacob Loke, Pathophysiology and Treatment of Inhalation Injuries, 2020
S. F. Paul Man, William C. Hulbert
The molecular mechanisms by which oxidizing gases cause cellular injury are not completely understood; however, the formation of free radicals by these agents is postulated to play a pivotal role. These mechanisms have been reviewed (Reck nagel and Glende, 1977; Pryor, 1982; Menzel, 1984). The gases, O3, NO2, and SO2 are strong oxidants that can react with many biochemical moieties to form free radicals. Free radicals formed by these interactions adversely affect the structure and function of cellular components such as proteins, especially enzymes containing sulfhydryl groups (SH), nucleic acids, and, more importantly, the cellular plasma membrane. The plasma membrane provides the containment of all cellular and organelle contents, and its permeability characteristics regulate the molecular species that enter and exit the cell and its organelles. The membrane is composed of lipoproteins rich in polyenoic long-chain fatty acids that are prone to undergo rancid or peroxidation decomposition under certain conditions. Free radicals, once formed, can react readily with molecular oxygen to form organic peroxy free radicals. When a peroxy free radical reacts with a phospholipid fatty acid side chain, it not only denatures the molecule but also produces another new organic free radical; this process is known as linear propagation of lipid hydroperoxide formation. Furthermore, new free radicals can be produced by the decomposition of organic peroxide via a number of cellular biochemical mechanisms (see Recknagel and Glende, 1977, for review).
Modulating insulin secretion and inflammation against sodium arsenite toxicity by levosimendan as a novel pancreatic islets’ protector
Published in Toxin Reviews, 2023
Marzieh Daniali, Mona Navaei-Nigjeh, Maryam Baeeri, Soheyl Mirzababaei, Mahdi Gholami, Mahban Rahimifard, Mohammad Abdollahi
Regarding the insulin secretion pathway, it should be noted that insulin is produced in the endoplasmic reticulum and stored and transported in vesicles. Insulin is released from β-cells by exocytosis involving the attachment of secretory vesicles to the plasma membrane by a group of proteins called SNARE. The interaction of these proteins with the plasma membrane forms a stable complex that prepares the membrane for attachment and fusion to the granule. The exocytosis of vesicles is also regulated by Ca2+ concentration. Some studies also showed that as insulin granules become acidic, structural changes occur in the SNARE protein, facilitating its attachment to the membrane. By acting on the insulin gene transcription promoter, NaAsO2 toxin causes the cell to lose sensitivity to extracellular glucose concentrations and alter the stability of insulin mRNA, which is typically affected by glucose concentrations (Meloni et al.2013).
There and back again: a dendrimer’s tale
Published in Drug and Chemical Toxicology, 2022
Barbara Ziemba, Maciej Borowiec, Ida Franiak-Pietryga
If we consider dendrimers as tools in nanomedicine, their ability to cross the cell membrane is a crucial requirement. The cell membrane has two function. Firstly, it is a barrier keeping the constituents of the cell inside and unwanted substances outside, and secondly it is a gate that enables the transport of essential nutrients into the cell and the movement of metabolic products from the cell. The lipid bilayer which is largely made up of phospholipids and cholesterol, strewn with proteins and other biomolecules, results in an overall negative charge of the plasma membrane. It is also characterized by several cationic domains and selective permeability to ions, molecules, and nanoparticles (Cooper 2000). The crucial issue is to know how nanoparticles (including dendrimers) enter cells as the underlying uptake pathways determine the nanoparticle’s function, intracellular fate, and biological response (Donahue et al.2019).
Graphene 2D platform is safe and cytocompatibile for HaCaT cells growing under static and dynamic conditions
Published in Nanotoxicology, 2022
Iwona Lasocka, Elzbieta Jastrzębska, Agnieszka Zuchowska, Ewa Skibniewska, M. Skibniewski, Lidia Szulc-Dąbrowska, Iwona Pasternak, Jakub Sitek, Marie Hubalek Kalbacova
In the plasma membrane, some proteins serve as structural links that connect the membranes of adjacent cells. E-cadherin is one of them. This cell-cell adhesion protein is crucial for tissue integrity, cell migration and wound healing (Ekanem and Udoh 2018; van Roy and Berx 2008) and its normal expression could be visible in Figure 8. Graphene as a ground substrate does not cause abnormalities in the formation of E-cadherin adhesion between adjacent cells (Figure 8(A)). Clusters consisting of 2, 3, 4, 6, 10 and more cells were analyzed, and none of them showed any abnormalities in the visualization of E-cadherin. The last image with a scale in Figure 8(A,B) presents that when more cells are touching, the clusters become denser and the E-cadherin connections are localized all around the whole cell.