Lipid types

There are no convenient databases for liposome log P values. Most measured quantities need to be ferreted from original publications [149,162,376,381-387,443], The handbook edited by Cevc [380] is a comprehensive collection of properties of phospholipids, including extensive compilations of structural data from X-ray crystallographic studies. Lipid-type distributions in various biological membranes have been reported [380,388,433]. 

Lipid Type Composition pHdon/pHacc No Sink Sink... 

Cellular membranes function as selective barriers and integral membrane protein scaffolds. Membranes allow the compartmentalization of cells, and individual organelles within cells, and are critical in energy transduction and cell signaling. In vivo membranes contain hundreds to thousands of lipid types, making characterization of particular lipid-lipid interactions challenging. 

Phase behavior of lipid mixtures is a much more difficult problem, due to nonideal mixing of lipid components. Ideal mixing implies like and unlike lipids have the same intermolecular interactions, while nonideal mixing results from differential interactions between lipid types. If the difference is too great, the two components will phase separate. While phase separation and lateral domain formation have been observed in many experiments, we lack a molecular-level physical description of the interactions between specific lipids that cause the macroscopic behavior. The chemical potential of a lipid determines phase separation, as phase coexistence implies the chemical potential of each type of lipid is equal in all phases of the system [3,4],... 

Different biological tissues are complex mixtures of various lipid types, and each one is usually represented by numerous homologs with... 

These polymer-coated liposomes showed high potency in oral delivery of peptide drugs such as insulin and calcitonin, mainly because of the mucoadhe-sion of the chitosan-coated liposomes to the intestinal tract (Takeuchi et al. 1996, 2001,2003,2005a). Similar trials have been reported by Guo et al. (2003), who investigated the effect of chitosan concentration and lipid type on the characteristics of chitosan-coated liposomes and their interactions with leupro-lide. They found that a thicker adsorptive layer could be realized by using low... 

Grubauer, G. et al. Lipid content and lipid type as determinants of the epidermal permeability barrier. Journal of Lipid Research 50(l) 89-96, 1989. 

Nonetheless, the most fascinating and complex lipid type is sterols. They have a rigid steroid ring stmcture, which is a simple hydroxyl group as their polar head and a short flexible tail at the other end of the molecule. Of the many sterols found, two sterols exist whose significance in cells is above the others. Cholesterol is abundant in eukaryotic cells, and ergosterol is abundant in fungi. The reasons why nature has chosen these two specific sterols are not well understood. One is tempted to think that the properties of all sterols should be similar,... 

In lipoproteins, one finds essentially the same types of lipids but with somewhat different concentrations. In order of decreasing numbers, low density lipoproteins contain (2) mainly cholesteryl esters, (unesterified) cholesterol, phosphatidylcholines, SM, triglycerides, and lyso-PC, and smaller numbers of PE, PI, and ceramide. In HDLs, one finds the same lipid types but in a different order, as HDLs are abundant in phospholipids and are complemented by cholesterol esters, cholesterol, and triglycerides. 

The use of animal fats by humans may well predate civilization. As the depot fats of animals are readily noticed during the butchering of a slaughtered animal, are easily harvested, and are available in the absence of plant domestication and the adoption of established agriculture, it is probable that animal fats were the hrst lipids employed as industrial and as distinct edible lipids by humans. This is evidenced by the fact that the paints used in prehistoric cave paintings were animal fat-based, as were the fuels in the lamps that illuminated the cave artists at their work. Despite a tremendous diversihcation to include other lipid types over the intervening centuries, animal fats still play a prominent role in our diets, industry, and commerce. 

Grain Fraction/Lipid Type Lipid Composition % of total lipid) Barley Oats ... 

Solvents such as isopropyl alcohol have been incorporated in daily cleaners to aid in removing lipid type of deposits. Such solvents have been reported to affect certain lens materials, especially silicone acrylate rigid gas-permeable lenses. 

Sulfoquinovosyldiacylglycerol and digalactodiacylglycerol are prominent glycolipids of plants [6,9] where they occur in the plastids however, members of both lipid types were also identified as major membrane components of bacteroids of Bradyrhizobium japonicum [11,12]. 

Several ascorbic acid derivatives were examined by Pensabene et al. (570) for their ability to inhibit nitrosation of pyrrolidine in a model system developed to simulate the lipid-aqueous-protein composition of bacon. While sodium ascorbate was quite effective in the aqueous phase, a combination of an ascorbyl ester with sodium ascorbate gave a better effect in the lipid phase (Table XX). The use of ascorbates and tocopherol as inhibitors of nitrosamine formation and oxidation in foods of the aqueous and lipid type has been reviewed by Newmark and Mergens (326). These compounds in combination could be markedly useful in preventing food contamination with nitrosamines and/or nitros-amides in cured meats such as bacon. 

Arsonoliposomes (ARSL) which are liposomes that contain arsonolipids in their membranes have shown interesting anticancer and antiparasitic activity in vitro. Their lipid composition (the specific arsonolipids and/or phospholipids used for their preparation, and the relative amounts of each lipid type) highly influences their physicochemical properties as well as their in vivo kinetics and antiparasitic activity however, their cytotoxicity towards cancer cells is minimally - if at all - modified. ARSL are prepared by a modification of the one step method followed or not by sonication (for formation of sonicated or non-sonicated ARSL, respectively). Arsonoliposomes may be composed only of arsonolipids (containing or not cholesterol) [plain ARSL], or they may contain mixtures of arsonolipids with phospholipids (with or without Choi) [mixed ARSL]. Herein, we describe in detail the preparation and physicochemical characterization of ARSL. 

The hypothesis has been advanced that changes in relative concentrations of lipid type compounds, when comparing aquatic biota and their habitat, can be explained in large part by an estimate of their tendency to partition into tissues which has been related to octanol/water partition coefficients - K s (, 22). Table Vll presents tabulated data for and water to biota bloaccumu-latlon concentration factors calculated from data in Tables III and IV. Representative data from Table Vll are plotted in Figure 6 in the manner of Mackay (21) and Chlou (22), who have reviewed data on bloaccumulatlon of neutral hydrophobic compounds in aquatic biota. The solid line Is the expected distribution of data based on Chlou s review (22) of predictability for equilibrium situations. Our data is different in an absolute sense than the data used by Mackay and Chlou, because they used concentrations in biota... 

Table 1. Content of lipid types within human stratum corneum, expressed as a percentage of the total lipid content.

In addition to subunits L, M, and H, the RCs of several purple bacteria such as Rp. viridis, Rhodocydus (Rc.) gelatinosus, and Chromatium vinosum contain a tightly bound tetraheme cyto-chrome-c subunit which donates electrons to D. In Rp. viridis, this subunit does not possess intramem-branous segments, but it has an N-terminal cysteine that is linked to a glycerol residue via a thioether bond (Weyer etal., 1987). Such a bond has also been found at the N-terminus of the major outer membrane lipoprotein of Escherichia coli (Hantke and Braun, 1973) in which the fatty acids form a lipid-type membrane anchor. 

The mechanisms of the sorption of lipophilic substances to surfaces from an aqueous solution have more to do with displacement from the body of water and solution in a lipid-type surface layer than with the classic sorptive interactions (Fbrstner, 1995). On the basis of their chemical structure and possible surface charges it is possible to distinguish between the following categories of organic environmental chemicals that are relevant to water and soil (Fbrstner, 1995) ... 

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