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The cell and tissues
Published in Peate Ian, Dutton Helen, Acute Nursing Care, 2020
The molecules that make up the lipid bilayer are phospholipids. Phospholipids are neutral fats that have had one of the three fatty acids replaced by phosphate (PO43−), which is anionic and is therefore compatible with water. The consequence of this is that the molecules have a hydrophilic (water-attracting phosphate) end and a hydrophobic (water-repelling fatty acid) end. On both layers, the hydrophilic end is on the outer face, with the hydrophobic, fatty acid end on the inside of the layer. This means that the outside of the membrane is compatible with the aqueous medium, both inside and outside the cell, but, because of the hydrophobic nature of the interior of the bilayer, water and electrolytes cannot cross the lipid sections of the membrane. The movement of electrolytes through the membrane is facilitated by protein channels.
Features of Lipid Metabolism in Diabetes Mellitus and Ischemic Heart Disease
Published in E.I. Sokolov, Obesity and Diabetes Mellitus, 2020
The cholesterol/phospholipid ratio in all biological membranes is 1. The phospholipids in a membrane are present in approximately the following proportion: PC — 30%, PEA — 28%, and SM — 25%. As already indicated, the lipid bilayer of a membrane is its basic structural unit and maintains its liquid-crystalline state. Physiological studies showed that a lipid bilayer of an erythrocyte membrane simultaneously has fluidity and order of the structure. Owing to the order of its structure, an erythrocyte carries out a number of processes occurring between the membrane and its surroundings (the reception of information, an exchange of energy and substances). Changes in the surroundings affect the composition of an erythrocyte membrane, the degree of its “adhesion” to the endothelium of the vessels changes, and the aggregative ability is disturbed.
Structures and Properties of Self-Assembled Phospholipids in Excess Water
Published in E. Nigel Harris, Thomas Exner, Graham R. V. Hughes, Ronald A. Asherson, Phospholipid-Binding Antibodies, 2020
The integral membrane proteins or glycoproteins usually have one or more segments of hydrophobic amino acid residues penetrating the lipid bilayer.6 Within the lipid bilayer, these residues are almost exclusively arranged as a-helices with an orientation nearly perpendicular to the bilayer surface. The dynamics and mobility of these bilayer-spanning proteins or glycoproteins must, therefore, be subject to modulation by the organization and polymorphism of the lipid bilayer. Consequently, the functional states of bilayer-spanning proteins or glycoproteins in biological membranes may be correlated with the physical state of the lipid bilayer. The function of lipid bilayers should, therefore, be considered not only to serve as a barrier separating two aqueous compartments, but also to modulate the activity of membrane proteins. Hence, studies of phospholipids and other membrane lipids in the form of a bilayer are of great importance in understanding the functional control of bilayer-spanning proteins in biological membranes and for providing basic information explaining the dynamic regulation of membrane activities in general.
Rationale utilization of phospholipid excipients: a distinctive tool for progressing state of the art in research of emerging drug carriers
Published in Journal of Liposome Research, 2023
Koilpillai Jebastin, Damodharan Narayanasamy
High drug entrapment allows for a smaller total volume/excipient for formulation administration. The thermodynamic and kinetic properties of the lipid bilayer membrane are valuable indications of its fluidity and uniformity. Cholesterol functions as a fluidity buffer and can be integrated into the phospholipid membrane as a high molecular weight component and at high concentrations in the 1:1 or 2:1 molar ratio of cholesterol to phosphatidylcholine (Kirby et al. 1980, Collins and Phillips 1982). The half-life of lipid-based drug products depends on vesicle diameter, negative surface charge, density, and fluidity of the bilayer membrane. A high dispersity index indicates a proclivity for aggregation. Osmolarity determines the tendency of the supra molecular structure to rupture or contract, allowing for the prediction of drug leakage from the entrapped vesicle. Mean particle size, polydispersity index, osmolality, zeta-potential, and stability of the entrapped drug in the supramolecular structure of the liposome are thus the essential critical quality attributes (CQAs) that establish the product specifications for liposomal products (Chemin et al. 2009, Bhattacharyya et al. 2019).
Protein transduction domain of translationally controlled tumor protein: characterization and application in drug delivery
Published in Drug Delivery, 2022
Biological membranes consist of lipid bilayers in which proteins are embedded. These membranes separate the cytoplasm from the extracellular milieu by regulating the movement of molecules across the membrane. These selectively permeable barriers limit the internalization of external molecules such as specific medications and drugs, unless specific mechanisms such as endocytosis are involved (Joliot & Prochiantz, 2004). As the target molecules for specific medications need to enter the interior of the cells to be effective, there has been great research interest in vehicles that enable the efficient intracellular delivery of therapeutic macromolecules. The discovery of peptide moieties that can translocate into the cells opens up new ways to deliver various types of potential medicinal cargoes, such as small and large molecules including chemicals, peptides, proteins, antisense nucleotides, and liposomes. These peptide moieties are generally called protein transduction domains (PTDs) or cell-penetrating peptides (CPPs).
Systematic review on activity of liposomal encapsulated antioxidant, antibiotics, and antiviral agents
Published in Journal of Liposome Research, 2022
Reshna K. R, Preetha Balakrishnan, Sreerag Gopi
Essentially, a liposome is an area of aqueous solution enclosed inside a hydrophobic membrane. Chemicals that are hydrophobic may be dissolved into lipid membranes, allowing liposomes to transport both hydrophilic and hydrophobic molecules at the same time. While the extent to which the drug is distributed will be determined by its physiochemical features and lipid composition, the extent to which the drug is distributed will be determined by its physiochemical qualities. The fusion of lipid bilayers with other bilayers of the cell (cell membrane) allows the release of the liposomal content, which is important for the delivery of necessary drug molecules to the site of action. The adsorption of liposomes to cell membranes results in the formation of a contact between the liposome and the cell membrane. After adhesion of liposomes to cell surface membranes, followed by engulfment and internalization into liposomes, and fusion of lipoidal cell membranes with liposome lipid bilayers through the process of laminar diffusion and lipid intermingling, the liposomal contents are delivered directly to the cytoplasm. Because the liposomal lipid membrane is identical to the phospholipids found in the cell membrane, lipid transfer proteins found in the cell membrane have an easy time recognizing liposomes and causing lipid exchange. Liposomes containing antioxidants, antibiotics, or antiviral medicines are released from their capsular shells when the gut pH is raised. It will enhance in the absorption of antioxidants, antivirals, and antibiotics to their greatest potential (Torres et al.2012). The mechanism shown in Figure 9.