Chemical structure of lipids

Fig. 2.—Chemical structure of lipid A of the Escherichia coli Re mutant strain F515. The hydroxyl group at position 6 constitutes the attachment site of Kdo. The numbers in circles indicate the number of carbon atoms present in the fatty acyl chains. The 14 0(3-OH) residues possess the (Reconfiguration. The glycosylic phosphate group may be substituted by a phosphate group (see Table I) (46,65,69).

Fig. 4.—Chemical structure of lipid A of the Salmonella minnesota Re mutant strain R595. For details see the text. See also the legend to Fig. 2. For substituents of the phosphate groups see Table I.

Fig. 7.—Chemical structure of lipid A of Rhodobacter capsulatus. Dashed lines indicate nonstoichiometric substitution. The anomeric a configuration of phosphates and the configuration (Zor ) of the double bond in A5-12 1 are assigned only tentatively (89). For substituents of the phosphates see Table I. 

Of the lipid portions of bacterial macromolecular amphiphi-les, that of lipopolysaccharides is the structurally most complex. For its designation the term lipid A has been coined. More specifically, it was suggested that the lipid, as it is present in intact lipopolysaccharide, should be called lipid A, while the lipid in a separated form should be termed free lipid A (10,11). This nomenclature will be used throughout this paper. In the following, ways and methods will be described which have been used to elucidate the chemical structure of lipid A. The present discussion will deal in more detail with the elucidation of the structure of Salmonella lipid A. Relative to this structure, chemical features of other lipid A s will then be discussed. 

Subsequent to the first structural proposals, our views on the chemical structure of lipid A have changed considerably. Today, a quarter of a century later, certain principles of the lipid A... 

The chemical structure of lipid II is shown, and the binding sites of vancomycin and nisin are indicated. 

Suda, Y., Ogawa, T., Kashihara, W., Oikawa, M., Shimoyama, T., Hayashi, T., Tamura, T., Kusumoto, S. Chemical structure of lipid A from Helicobacter pylori strain 206-1 lipolysac-charide. J Biochem (Tokyo) 121 (1997) 1129-1133. 

Fig. 2. Chemical structures of lipid peroxidation inhibitors shown to be protective in models of brain...

Zahringer U, Lindner B, Rietschel ET (1999) Chemical structure of lipid A. In Brade H, Morrison DC, Opal S, Vogel S (eds) Endotoxin in health and disease. M Dekker Inc., New York, p93... 

There are two aspects pertinent to chemical compatibility and the design and the realization of reactions inside vesicles. The first concerns the chemical structure of lipids (or fatty acids, or other co-surfactants, as ammonium salts, derivatized lipids, or sterols), the second is related to the preparation method. 

Types of lipidations Chemical structures of lipids modifications Biological lipidated processes catalysed by Modification sites Reversibility Cell localizations of lipidated proteins Protein examples... 

Describe the chemical structures of lipids and phospholipids. Why can phospholipids form a bilayer in water ... 

The chemical structure of lipid A of lipopolysaccharide isolated from Comamonas testosteroni was recently determined by lida et al. (1996) by means of methylation analysis, mass spectrometry and NMR. The lipid A backbone was found to consist of 6-0-(2-deoxy-2-amino-P-D-glucopyrano-syl)-2-deoxy-2-amino-alpha-D-glucose which was phosphorylated in positions 1 and 4. Hydroxyl groups at positions 4 and 6 were unsubstituted, and position 6 of the reducing terminal residue was identified as the attachment site of the polysaccharide group. Fatty acid distribution analysis and ES/MS of lipid A showed that positions 2,2, 3 and 3 of the sugar backbone were N-acylated or O-acylated by R-3-hydroxydecanoic acid and that the hydroxyl groups of the amide-linked residues attached to positions 2 and 2 were further O-acylated by tetradecanoic and dodecanoic acids, respectively. 

Figure 1. Chemical structures of lipid A-diphosphate (A) and two antagonistic lipid A-diphosphate molecules, (B and C). Lipid A-diphosphate from E. coli is a 1,4-di-phosphorylated P-1,6-linked D-glucosamine disaccharide with four residues of amide-and esterified R-(-)-3-hydroxy fatty acids ( denotes the chiral centers in the hydroxy fatty-acid esters, apart form the chiral and epimeric carbons in the disaccharide moieties which are not marked). The antagonistic lipid A-diphosphate molecules shown in (B) and (C) contain the same disaccharide as in (A) however, they differ in the number anchored carbohydrate positions and the number of chiral fatty-acid chains but the chain lengths is the same (C J. The corresponding monophosphate of lipid A is only phosphorylated at the reducing end of the disaccharide.

Fig. 1.1. Chemical structure of lipids commonly found in biological membranes.

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