Nonhydroxylated fatty acids

In P. aeruginosa PAO, the degree of hydroxylation, that is, lipid A heterogeneity with respect to hydroxylated [12 0(2-OH)] and nonhydroxylated (12 0) fatty acids, was found to be mainly influenced by the growth temperature. With increasing temperature, the proportion of the nonhydroxylated fatty acids (12 0 and 16 0) was decreased at the expense of such hydroxylated ones as 12 0(2-OH)(144). Asimilar finding was made with Salmonella species (142). 

Specified. ABA shown here is stereospecific as ot-ABA. The regiospecific analysis of TAGs ABA and AAB containing only common fatty acids (nonhydroxyl fatty acids) is described here by ESl-MS of lithiated adducts. We have used this method to quantify the regiospecific ABA and AAB in extra virgin olive oil. 

Different lipid molecules associate together to form membrane structures with very different overall curvatures. When liposomes are made in the presence of sufficient concentrations of nonhydroxylated fatty-acid galactoceramides (NFA-GalCer) they form nanotubes (Wilson-Kubalek et al, 1998). We have used these preformed lipid nanotubes to examine the effect of GTP hydrolysis on the conformation of a dynamin helix (Marks et al, 2001 Stowell et al, 1999). Indeed, in the absence of GTP hydrolysis, purified dynamin aggregates to form helices and, as seen above, can tubulate liposomes. Also, dynamin interacts with lipid nanotubes to form ordered arrays with a diameter similar to the constricted necks of clathrin-coats pits observed in vivo (Stowell et al, 1999 Takei et al, 1995), suggesting that the nanotube acts as a good mimic of the neck of a vesicle. 

FIGURE 1.20 a-Hydroxylated and nonhydroxylated ceramides. a is the first carbon after the carbonyl group of the acyl chain (it corresponds to A2 in the A numbering system of fetty adds). HFA refers to a-hydroxylated fatty add, and NFA to nonhydroxylated fatty acid. 

FIGURE 4.4 Two versions of ceramides coexist in the brain. HFA, a-hydroxylated acyl chain (ceramide-HFA for a-hydroxylated fatty acid) NFA, nonhydroxylated acyl chain (ceramide-NFA for nonhydroxylated fatty acid). These two distinct types of ceramides are represented in tube (A) or spheres (B). The aOH group of ceramide-HFA is indicated by an arrow. 

Nonhydroxylated and hydroxylated fatty acids (C10-C18) comprise the hydrophobic region of lipid A s. Among these, cyclopropane and, in general, unsaturated fatty acids are lacking. In the following, procedures are described which were applied for the determination of the nature, quantity and binding site of fatty acids present in Salmonella lipid A (39). 

Sulfatides are readily deprotonated to form [M-H] ions and upon CAD they yield an abundant HS04 ion (m/z 97), which allows convenient analysis of sulfatides by precursor ion scanning. Identification of the long-chain base and the fatty acyl constituents is also feasible, since a daughter ion diagnostic of the acyl moiety can be detected. The method allows identification of isobaric species and those containing a-hydroxylated fatty acid substituents as well [102,103]. Alternatively, the LC-MS method can be used [19,104]. Notably, LC-MS provides a clear distinction between the a-hydroxylated and nonhydroxylated species and thus their accurate quantitation. 

Hydroxy fatty acid (HFA) A fatty acid with a OH group linked to carbon C2 (also referred to as a). Ceramide with a hydroxyacyl chain is referred to as ceramide-HFA. If the acyl chain is nonhydroxylated, the ceramide is referred to as ceramide-NFA. 

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