Physicochemical properties of lipids

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. 

It is interesting that work on the internal motions of the molecules that produce lyotropic mesophases is more advanced. This is mainly because of the importance of the microscopic properties of these systems in solubilization and interfacial problems, problems which are encountered in industry as well as in cell membrane biology. The structural and functional roles of lipid molecules in biomembranes are much discussed investigations of the physicochemical properties of lipid media thus might provide orientations for biological studies. Moreover, the findings on the flexibility of the paraffinic chains in lyotropic mesophases might also be relevant to similar problems in thermotropic mesophases. 

The obligatory steps in TAG absorption are hydrolysis and solubilization of the hydrolytic products. Based on the physicochemical properties of lipids and luminal mucosal membranes, one can predict that (1) TAG and DAG may not permeate the absorptive mucosal membrane and that (2) only 2-MAG and primarily protonated FA can pass through the membrane by diffusion as free monomers in the aqueous phase near the luminal membrane. The efficiency of fat digestion is assured by an excess of pancreatic lipase. Lipase is secreted to the duodenum in about 1000-fold excess. Thus, under optimal conditions, 100 kg TAG could be hydrolyzed in 24 hours instead of the ingested 100 g fat in a normal diet. 

The surface-active properties of phospholipids (PL) are widely used for the formation of liposomes, which are a model of biomembranes and also a technique for the study of cells and exposure to them [1,2], Earlier it has been established the substantial role of lipids which contain in biosorbents for the regulation of properties of lipids in medium [3], It was also foimd that scale and character of interrelations between the different fractions in lipids of the mice tissue had a dependence on physicochemical properties of lipids [4, 5], and the physicochemical properties and composition of natural lipids have an influence on those of liposomes formed from them [6]. Besides, earlier it was shown the existence of physicochemical regulatory system of the lipid peroxidation (LPO) both a membrane and organ levels [7, 8]. It allows us to suggest the existence of a uniform mechanism of the regulatory in the LPO system both on the membrane and the organ levels. 

Earlier it was found that the PL composition and physicochemical properties of lipids from the liver of the laboratory mice significantly differ depending on the season [4-6, 16], Lecithin (L) is a mixture of the natural lipids among which PC is the main fiaction of PL (86-90%), however, the different samples of L also have not identical composition of lipids [9], In this connection it is necessary to note the presence of the substantial differences between the initial lipid composition and lipids of the formed liposomes [6,9], As seen from data presented in Table 1, there are the reliable changes both the ratio of the sums of the more easily oxidizable to the more poorly oxidizable fi actions of PL which characterize the ability of lipids to fhe oxidation and the PC to PE ratio (PC/PE) which is one of the parameters characterizing the membrane stmctural state between the initial and formed liposome lipids [6, 7],... 

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. 

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... 

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... 

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. 

Drugs may be formulated as their salt forms (i.e., hydrochloride salt for base, sodium salts for acids) that dissociate in the body, or they may be formulated as the free acid or base. The fraction of the drug absorbed can be difficult to predict, as it is influenced by many factors. The extent and rate of absorption are partly determined by the physicochemical properties of the drug. Favorable absorption is related to lipid solubility, nonpolarity, and small molecular size. Reduced absorption is often observed for highly polar, non-lipid-soluble, and large-molecular size drugs. 

The influence of physicochemical properties of liposomes, such as charge density, membrane fluidity, and epitope density, on the immune response elicited by antigens has been extensively studied [37]. In addition to antigens, other immune stimulators that are amphoteric muramyl peptides or lipid-soluble compounds, such as monophosphoryl lipid A or muramyl tripeptidyl-phosphatidylethanolamine, can also be incorporated into liposomes to increase their adjuvant effect in eliciting immune responses [34]. 

Hofmann, A.F., and A. Roda. 1984. Physicochemical properties of bile acids and their relationship to biological properties An overview of the problem. J Lipid Res 25 1477. 

The lipid solubility, degree of ionization, pKa of the drug, pH of the drug solution, presence of saliva and the membrane characteristics, molecular weight and size of the drug, various physicochemical properties of the formulation, and the presence or absence of permeation enhancers, all affect the absorption and the permeation of drugs through the oral mucosa. 

The first synthetic amphiphiles found to self-organize into bilayers, were quaternary ammonium salts bearing two long alkyl chains 1.13.47.48.49 it is interesting to note that these molecules did not contain a connector moiety between the polar and the apolar part, as in the case of the biolipids. While the physicochemical properties of these bilayers were found to be comparable to those of the biological membranes, the synthetic lipids were found to... 

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