Lipid backbone

In the bilayer or upon interaction with detergent micelles, a structural reorganization of pardaxin aggregates takes place, in which the polar side chains interact with themselves and the hydrophobic residues are externally oriented in the pardaxin aggregate, therefore allowing interactions with the lipid backbone hydrocarbons. 

Glycerolipids are derivatives of glycerol and fatty acids 34 In sphingolipids, the long-chain aminodiol sphingosine serves as the lipid backbone 37... 

Fig. 1. Lipid substitution patterns for the polymerization of lipid bilayers, featuring polymerization of the lipid tails at (A) the chain terminus, (B) near the lipid backbone or polymerization of reactive groups (C) covalently or (D) electrostatically associated with the hydrophilic headgroup.

To deduce the location of the double bond within the lipid backbone, the mixture (500 ng) was subjected to consecutive bisthiomethylation of the alkene85 and O-methyloxime formation (Equation 3). GC—MS study of the fragmentation of these derivatives (e.g., see 31, derived from 24) allowed simultaneous determination of the cleavage site (between C24 and C25) and of which portion contained the original ketone (i.e., the odd versus even mass fragments of 17 3 and 426 for 31). All of the monounsaturated lipid ketones had the alkene in the same downstream location in other words, they varied in the number of methylene units between the ketone and alkene functional groups but were constant in their -octyl terminal alkyl moiety. The four most major components (24, 25, 27, and 28) were prepared by chemical synthesis and used to confirm their identity in the natural pheromone and their pheromonal activity both alone and in admixtures. 

If step (2) results in an enhanced rate of transbilayer movement of the functional lipid because of the raised temperature, one would expect, upon bringing the pH back to 8 [step 3], to detect a new fast process accounting for the ester lipid that has moved from the interior to the exterior of the vesicles. This is in fact what the authors were able to monitor. By repetition of cycles (l>-(3), all the ester surfactant is eventually cleaved. By variation of the incubation time, a lifetime of the flip-flop process could be determined. The ti/2 data are reported in Table 3. Scrutiny of this table reveals that apart from the above-mentioned temperature of phase transition, the flip-flop process is also affected by the structure of the lipid backbone. For instance, dialkylammonium amphiphiles are much more mobile than those featuring a glycerolUke backbone increasing the length of the chain decreased the rate of... 

Table 3 Influence of the lipid backbone on the transbilayer and permeation kinetics of functional lipids (17a)-(17i), as measured by Moss and coworkers...

The diacylglycerol backbone in eubacteria and eukaryotes is sn-3-glycerol esterified at positions 1 and 2 with long-chain fatty acids (Fig. 2). In archaebacteria (Fig. 3), the opposite isomer sn-1-glycerol forms the lipid backbone and the hydrophobic domain is composed of phytanyl (saturated isoprenyl) groups in ether linkage at positions 2 and 3 (an archaeol)... 

Lipid peroxidation implies that one or more oxygen atoms has been added to a lipid backbone, usually accompanied by changes in the number and/or the position of double bonds. Before discussing methods for quantifying oxidized lipids, the process of product formation will be discussed. Two factors that are essential for understanding peroxidation are the strength of the radical and lability of the attacked species. 

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