Lipids physicochemical properties

Bioconcentration, Bio accumulation and Biomagnification. These aspects are determined by the physicochemical properties of a chemical, an organism s ability to excrete the chemical, the organism s lipid content and its trophic level. Bioconcentration relates to the difference between the environmental concentration and that of the body tissues. A high bioconcentration factor (BCF) predisposes to bioaccnmulation. The upper limit of bioaccnmulation is determined by lipid levels in the organism s tissues. Whether the resultant body burden causes biomagnification in the food chain depends upon the metabolic capabilities of the exposed organism. 

Liposomes are members of a family of vesicular structures which can vary widely in their physicochemical properties. Basically, a liposome is built of one or more lipid bilayers surrounding an aqueous core. The backbone of the bilayer consists of phospholipids the major phospholipid is usually phosphatidylcholine (PC), a neutral lipid. Size, number of bilayers, bilayer charge, and bilayer rigidity are critical parameters controlling the fate of liposomes in vitro and in vivo. Dependent on the preparation procedure unilamellar or multilamellar vesicles can be produced. The diameter of these vesicles can range from 25 nm up to 50 ym—a 2000-fold size difference. 

The SUM was covered by a polymer film with an orifice of approximately 0.3 mm in diameter on each side, and subsequently a folded BLM was generated from a DPhPC/l,2-dipalmitoyl-in-glycero-3-phosphatidic acid (DPPA) monolayer on the side facing the SUM (Fig. 19). Interestingly, no pretreating of the orifice with any alkane or lipid was required, as is imperative for all other BLM techniques. Thus, an accumulation of such compounds could be excluded, and the physicochemical properties of the membrane and... 

Lipophilicity is the measure of the partitioning of a compound between a lipidic and an aqueous phase [1]. The terms lipophilicity and hydrophobicity are often used inconsistently in the literature. Lipophilicity encodes most of the intramolecular forces that can take place between a solute and a solvent. Hydrophobicity is a consequence of attractive forces between nonpolar groups and thereby is a component of lipophilicity [2]. Lipophilicity is one of the most informative physicochemical properties in medicinal chemistry and since long successfully used in quantitative structure-activity relationship (QSAR) studies. Its... 

There are several reports concerning the modification of the physicochemical properties of biomembranes by the presence of a carotenoid within the lipid phase. Under physiological conditions, all of... 

In this study a ten year model simulation with the fully coupled ocean-atmosphere GCM [Roeckner et al (2003), Marsland et al (2003), Maier-Reimer et al (2005), Lammel et al (2001)] was performed. The insecticide DDT was chosen because it is one of the most studied of all synthetic organic chemicals and because of its physicochemical properties. It has a low water solubility, high lipid solubility and it is semi-... 

Tetraalkylleads are highly lipid, soluble, rapidly metabolized and readily cross the blood-brain barrier. These physicochemical properties make the central nervous system the main site of the toxic action of the alkyllead species138. The earliest symptoms include insomnia, which may be followed by lack of appetite, nausea, vomiting, diarrhea hallucinations, delusions, delirium and ultimately death141. Continuing exposure may lead to complaints associated with central nervous system disturbances141. 

The physicochemical properties of both PCDD/PCDFs and coplanar PCBs enable these compounds to be readily absorbed by organisms. The high lipid solubility and low water solubility of all congeners lead to the retention of the compounds in... 

A new quality in the analysis of hydrophobically post-translational modified proteins could be achieved by the construdion of lipidated proteins in a combination of bioorganic synthesis of activated lipopeptides and bacterial expression of the protein backbone as described before. The physicochemical properties of such artificial lipoproteins differ substantially from those of the corresponding lipopeptides. The pronounced dominance of the hydrophilic protein moiety (e.g. for the Ras protein 181 amino acids) over a short lipopeptide with one or two hydrophobic modifications keeps the construct soluble up to 1CT4 M, while the biotinylated or fluorescence labeled lipopeptides exhibit low solubility in aqueous solutions and can be applied in the biophysical experiments only in vesicle integrated form or dissolved in organic solvent. 

Pseudo-glycolipids. The interest for glycolipids is connected with their occurrence in biological systems, as well as their physicochemical properties, the two viewpoints being sometimes correlated. For example in membranes, lipid rafts are sub-domains which contain liquid-ordered phases.73... 

This permeability barrier shows selectivity in that small hydrophobic molecules can partition into and diffuse across the lipid bilayer of the cell membrane, whereas small hydrophilic molecules can only diffuse between cells (i.e., through the intercellular junctions). In addition, the presence of uptake and efflux transporters complicates our ability to predict intestinal permeability based on physicochemical properties alone because transporters may increase or decrease absorptive flux. The complexity of the permeability process makes it difficult to elucidate permeability pathways in complex biological model systems such as animals and tissues. For this reason, cultured cells in general, and Caco-2 cells in particular, have been used extensively to investigate the role of specific permeability pathways in drug absorption. 

Therefore, extensive characterization is required, as the physicochemical properties of lipid nanodispersions influence not only drug incorporation and release but also the physical stability of the preparation for example, drug localization in the matrix. Several methods have to be combined for characterization to allow detection of dynamic processes such as changes in lipid modifications, particle aggregation, and the formation of nanostructures of other kinds. 

Bakan DA, Weichert JP, Longino MA, Counsel RE (2000) Polyiodinated triglyceride lipid emulsions for use as hepatoselective contrast agents in CT effects of physicochemical properties on bio distribution and imaging profiles. Invest Radiol 35 69... 

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