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The Cell Membrane in the Steady State
Published in Nassir H. Sabah, Neuromuscular Fundamentals, 2020
In living cells, the basic phospholipid bilayer structure is modified in several respects so as to serve the many important functions required of the cell membrane. Cell membranes have an abundance of cholesterol and protein molecules (Figure 2.2). Cholesterol is a small steroid-type molecule having a hydrophilic OH group, that aligns with the polar heads of the phospholipid molecules, and a hydrophobic portion that nestles between the fatty acid chains. On the one hand, cholesterol makes the membrane more fluid and flexible by preventing the fatty acid chains from forming a more rigid, crystal-like structure. On the other hand, the attraction to the fatty acid chains makes the membrane firmer and less permeable to small, water-soluble molecules. In addition, cholesterol plays a significant role in mechanically securing protein molecules in the membrane so that they are not adversely affected by membrane fluidity.
Electron Spin Resonance Spectroscopy
Published in Adorjan Aszalos, Modern Analysis of Antibiotics, 2020
George C. Yang, Adorjan Aszalos
In addition to the application of ESR to membrane fluidity studies, Peterson et al. [42] used ESR to measure the competitive bindings between dodecyldimethylammonium-l-oxyl-2,2,6,6-tetramethylpiperidine spin label and aminoglycoside antibiotics to gram-negative bacterial membrane lipopolysacharides. They observed that the toxicity of the different aminoglocoside antibiotics correlate to their binding ability.
Dynamic Aspects of Cell Membrane Structure
Published in Lelio G. Colombetti, Biological Transport of Radiotracers, 2020
Fedor Medzihradsky, Edward I. Cullen
Initial evidence for the relationship between membrane fluidity and transport function was provided by studies of bacterial cells grown in the presence of various fatty acids. In these cells, the transport of β-galactoside displayed a characteristic temperature dependence, reflecting the transition temperature for the fatty acid, i.e., the shift between a liquid-crystalline and a crystalline state of the lipid environment. In a given cell type identical temperature dependence was obtained, as assessed by corresponding Arrhenius plots,21 for the uptake of β-glucosides and β-galactosides occurring by two independent transport systems.22 These transport processes were also studied in a strain of Escherichia coli requiring unsaturated fatty acids for growth. By inclusion of specific unsaturated fatty acids, the membrane fluidity of these cells was altered. The results indicated partitioning of the transport proteins between ordered and fluid domains in the membrane by lateral migration.23 The partition was dependent on the lipid composition of the membrane and on the transport protein, the latter displaying a strong preference for diffusing into fluid parts of the membrane.
Mechanistic study of copper oxide, zinc oxide, cadmium oxide, and silver nanoparticles-mediated toxicity on the probiotic Lactobacillus reuteri
Published in Drug and Chemical Toxicology, 2023
Aya M. Eid, Osama M. Sayed, Walaa Hozayen, Tarek Dishisha
This interaction allows some NPs to enter the cytoplasm of bacterial cells, interacting with the components of the cell, resulting in the leaking of various vital intracellular constituents and eventually cell death. The leakage of the cellular content (protein) was confirmed by Bradford assay. The increased level of extracellular protein (compared to control) could be related to changes in membrane fluidity and an increase in passive permeability. A similar interaction with the cell membrane of bacteria was reported when Klebsiella pneumoniae were treated with AgNPs, where cytolysis and leakage of proteins and carbohydrates were observed (Rajesh et al.2015). Another study reported that treatment of Acinetobacter baumannii cells with ZnONPs disrupted cell membrane with consequent release of their cytoplasmic content by 1.4 times higher than control (Tiwari et al.2018). ZnO NPs are absorbed into the human body through cutaneous, inhalational, and oral routes. These particles can travel throughout the body and penetrate the placenta, the blood-brain barrier, and individual cells and nuclei (Kermanizadeh et al.2015).
A molecular perspective on identifying TRPV1 thermosensitive regions and disentangling polymodal activation
Published in Temperature, 2023
Dustin D. Luu, Aerial M. Owens, Mubark D. Mebrat, Wade D. Van Horn
Given the importance of the cellular membrane to ion channel stability and function, the role of lipids and other cellular membrane components in TRPV1 temperature activation has also been probed. The potential role of the membrane in TRPV1 heat activation arises naturally from the known temperature-dependence of lipid-phase transitions that ultimately define membrane fluidity. Cholesterol is a known regulator of membrane fluidity. It has been noted that cholesterol modulates bulk biological membrane phase transitions between liquid–ordered and – disordered at temperatures that overlap with the TRPV1 heat activation temperature [51]. Cellular studies of heat-evoked rTRPV1 currents show that cholesterol enrichment produces a slight rightward shift of the activation temperature (~3 °C) coupled with a modestly increased temperature sensitivity, as noted by a steeper slope of the TRPV1 thermal response [51]. Cholesterol depletion is commonly manipulated in the plasma membrane with cyclodextrins [52], and decreased cholesterol concentrations did not significantly affect TRPV1 heat activation. These studies suggest that while the membrane environment can potentially tune the TRPV1 temperature response, fundamentally, thermosensitivity is likely an intrinsic feature of the channel that is modulated by both membrane-bound and water-exposed regions.
Tinospora Cordifolia and Arabinogalactan in combination modulates benzo(a)pyrene-induced genotoxicity during lung carcinogenesis
Published in Drug and Chemical Toxicology, 2022
Yongli Chang, Diancui Zhang, Junxia Cui, Anshoo Malhotra
The membrane fluidity is crucial for optimization of membrane dynamics of a cell. In other words, membrane fluidity is the freedom of the relative motion in the membrane lipid bilayer (Li et al.2021). These dynamic features allow rotational or lateral diffusion of molecules. BP treatment revealed an increase in E/M ratio in comparison to normal control group. On the other hand, observance of the increased E/M ratio of the probe [pyrene] signified decline in membrane microviscosity. This decline in membrane viscosity leads to rise in membrane fluidity. In other words, alterations in membrane dynamics favored cancer initiation (Kaur and Sanyal 2010, Oommen et al.2016, Bhardwaj et al.2019). The above observation could be owed to rise in lateral diffusion as noticed by recording of high degree of freedom of the probe in the hydrocarbon phase. On the other hand, administration of combination of Aq.Tc and AG to BP treated rats significantly decreased the E/M ratio leading to significant decline in membrane fluidity. The observed decrease in membrane fluidity in BP treated rats could be linked with the regulatory role of combination of Aq.Tc and AG. So, it is quite clear from these observations that combination of Aq.Tc and AG are capable of regulating membrane dynamics in lung cancers cell, thereby, preventing the invasion phase of carcinogenesis.