Lipid membranes overview

The confusion between these two characteristics is common in medicinal chemistry. It comes from the usual empirical measurement of the lipophilicity, which is the logarithm of the partition coefficient between 1-octanol and water (log P). This parameter gives a representative overview of a compound absorbed by a lipidic membrane, an essential datum in medicinal chemistry. It is often considered that the higher the log P value is, the more lipophilic the compound is. Acmally, the log P value is only a measurement of relative solubility. Considering that the solubility of a fluorinated substance decreases more in water than in octanol, this measurement leads one to think that fluorinated compounds are more lipophilic. Actually, this represents the relative lack of affinity of fluorinated compounds for both phases. 

Oxygen-Activating Enzymes, Chemistry of GC-MS of Lipids Membranes, Fluidity of Natural Products An Overview Organic Chemistry in Biology... 

In this chapter, we will review methods to characterize the activity of synthetic transport systems in translocating molecules across otherwise impermeable membranes for beginners in the field. The following two sections briefly introduce methods with bulk membranes (U-tube experiments) and planar or black lipid membranes (BLMs), and close with a more comprehensive overview of methods involving liposomes, in particular large unilamellar vesicles (LUVs). The fourth section will then focus on how to apply... 

This chapter has given an overview of the structure and dynamics of lipid and water molecules in membrane systems, viewed with atomic resolution by molecular dynamics simulations of fully hydrated phospholipid bilayers. The calculations have permitted a detailed picture of the solvation of the lipid polar groups to be developed, and this picture has been used to elucidate the molecular origins of the dipole potential. The solvation structure has been discussed in terms of a somewhat arbitrary, but useful, definition of bound and bulk water molecules. 

General anesthetics are usually small solutes with relatively simple molecular structure. As overviewed before, Meyer and Overton have proposed that the potency of general anesthetics correlates with their solubility in organic solvents (the Meyer-Overton theory) almost a century ago. On the other hand, local anesthetics widely used are positively charged amphiphiles in solution and reversibly block the nerve conduction. We expect that the partition of both general and local anesthetics into lipid bilayer membranes plays a key role in controlling the anesthetic potency. Bilayer interfaces are crucial for the delivery of the anesthetics. 

Huckins, J.N. Prest, H.F. Petty, J.D. Lebo, J.A. Hodgins, M.M. Clark, R.C. Alvarez, D.A. Gala, W.R. Steen, A. Gale, R.W Ingersoll, C.G. 2004, Overview and comparison of lipid-containing semipermeable membrane devices (SPMDs) and oysters (Crassostrea gigas) for assessing chemical exposure. Environ. Toxicol. Chem. 23 1617-1628. 

Huckins J.N. Prest H.F Petty J.D. R0e T.I. Meadows J.C. Echols K.R. Lebo J.A. Clark R.C. 1998, A Overview of the Results of Several Comparisons of Lipid-containing Semipermeable Membrane Devices (SPMDs) and Biomonitoring Organisms for Assessing Organic Chemical Exposure. Abstracts of the 19th Annual National Meeting SETAC Charlotte, NC November 15-19, 1998 p 215. 

Cell membranes are two-dimensional fluids that exhibit a wide range of dynamic behaviors. Recent technical advances have enabled unprecedented views of membrane dynamics in living cells. In this technical review, we provide a brief overview of three well-studied examples of membrane dynamics lateral diffusion of proteins and lipids in the plane of the membrane, vesicular trafficking between intracellular compartments, and exchange of proteins on and off membranes. We then discuss experimental approaches to monitor membrane protein and lipid dynamics, and we place a special emphasis on the use of genetically encoded fluorescent probes and live cell-imaging techniques. 

Figure 1 Overview of different lipidation motifs found on membrane binding proteins.

Similar to the oq-ARs, our knowledge of the cellular trafficking properties of the oq-AR family is not as nearly refined as that for the P-ARs. Three oq-ARs (oqA, oqB, and oqc) have been isolated, cloned, and characterized. An overview of the nature of the oq-AR subtypes, their localization, and their cellular trafficking properties has been published (58). Reminiscent of the oq-ARs, subtypes of the oq-ARs are differentially localized within the cell. Indeed, results from studies conducted with polarized Madin-Darby canine kidney cells showed that the oq-ARs are selectively expressed on the basolateral surface (exposed to the blood) as opposed to the apical aspect (exposed to urine) of these renal cells (59,60). In investigating the mechanism forthis differential localization, Wozniak and Limbird (60) noted that oqA-AR is inserted directly and selectively into the basolateral membrane. The targeting of this receptor to the basolateral aspect is determined by a sequence as yet poorly defined near the lipid—oqA- AR interface ... 

In Chapter 11 the structure and function of each major type of lipid is described. The lipoproteins, complexes of protein and lipid that transport lipids in animals, are discussed. Chapter 11 ends with an overview of membrane structure and function. In Chapter 12 the metabolism of several major lipids is described. 

A FIGURE 18-1 Overview of synthesis of major membrane lipids and their movement into and out of cells. Membrane lipids (e.g., phospholipids, cholesterol) are synthesized through complex multienzyme pathways that begin with sets of water-soluble enzymes and intermediates in the cytosol (D) that are then converted by membrane-associated enzymes into water-insoluble products embedded in the membrane (B), usually at the interface between the cytosolic leaflet of the endoplasmic reticulum (ER) and the cytosol. Membrane lipids can move from the ER to other organelles (H), such as the Golgi apparatus or the mitochondrion, by either vesicle-mediated or other poorly defined mechanisms. Lipids can move into or out of cells by plasma-membrane transport proteins or by lipoproteins. Transport proteins similar to those described in Chapter 7 that move lipids (0) include sodium-coupled symporters that mediate import CD36 and SR-BI superfamily proteins that can mediate... 

In Chapter 5 the Penn State group of K. V. Damodaran and Kenneth M. Merz Jr. review lipid systems. Merz s research in computational chemistry spans the range from applied bonding theory of small organic molecules to simulations of biophysical processes. Membranes are an important component of living systems and are now the focus of much research. An overview of computer simulation of lipid systems is warranted. It is to be noted that this is the first chapter in Review in Computational Chemistry that discusses a class of molecules rather than a technique of computation. As time progresses we will... 

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