Stereoselective synthesis of perdeuterated phytanic acid, its phospholipid derivatives and their formation into lipid model membranes for neutron reflectivity studies.

We describe a straightforward method, for synthesis of large scale (gram quantities) of highly deuterated phytanic acid from commercially available phytol while preserving the stereochemistry around the chiral centres. The subsequent synthesis of tail-deuterated analogues of the archeabacterial membrane lipids 1,2-di(3RS,7R,11R-phytanyl)-sn-glycero-3-phosphocholine (DPEPC) and 1,2-di(3RS,7R,11R-phytanoyl)-sn-glycero-3-phosphocholine (DPhyPC) from perdeuterated phytanic acid is also described. Both lipids were employed in construction of two different model membranes, namely Langmuir monolayers and a tethered bilayer membrane (TBM) on a solid substrate, characterised by pressure area isotherm and neutron reflectometry techniques. At 10 mN/m pressure the head-group thickness of both monolayers was similar while the thickness of the tail region was significantly larger for tail-deuterated DPhyPC, which was evident from a smaller area per molecule. At 20 mN/m the thickness of the head and tail regions in both lipids was comparable, yet the area per molecule of tail-deuterated DPhyPC was 10% smaller than tail-deuterated DPEPC. In the TBM bilayer model membrane, the thickness of the lipid tails in both inner and outer leaflets was 8.2 Å, giving a total of 16.4 Å. Deuteration enabled unambiguous determination of the relative proportion of the hydrogenous tether, phospholipid and subphase.

Use of polystyrene-supported 2-isobutoxy-1-isobutoxycarbonyl-1,2-dihydroquinoline for the preparation of a hapten-protein conjugate for antibody development.

Polystyrene-supported 2-isobutoxy-1-isobutoxycarbonyl-1,2-dihydroquinoline (PS-IIDQ), a polymer-supported covalent coupling reagent, was successfully employed for the first time in the bioconjugation of an example hapten (phytanic acid derivative) to a carrier protein (bovine serum albumin (BSA)) within the context of immunogen preparation for antibody development. The ability of the prepared example phytanic acid derivative-BSA conjugate to bind an anti-phytanic acid antibody was confirmed using an enzyme-linked immunosorbent assay (ELISA).

Studies on phytanoyl-CoA 2-hydroxylase and synthesis of phytanoyl-coenzyme A.

Phytanoyl-CoA 2-hydroxylase (PAHX), an iron(II) and 2-oxoglutarate-dependent oxygenase, catalyses an essential step in the mammalian metabolism of beta-methylated fatty acids. Phytanoyl-CoA was synthesised and used to develop in vitro assays for PAHX. The product of the reaction was confirmed as 2-hydroxyphytanoyl-CoA by NMR and mass spectrometric analyses. In accord with in vivo analyses, hydroxylation of both 3R and 3S epimers of the substrate was catalysed by PAHX. Both pro- and mature- forms of PAHX were fully active.

Alpha-oxidation of 3-methyl-substituted fatty acids in rat liver.

3-Methyl-substituted fatty acids are first oxidatively decarboxylated (alpha-oxidation) before they are degraded further via beta-oxidation. We synthesized [1-14C]phytanic and 3-[1-14C]methylmargaric acids in order to study their alpha-oxidation in isolated rat hepatocytes, rat liver homogenates and subcellular fractions. alpha-Oxidation was measured as the production of radioactive CO2. In isolated hepatocytes, maximal rates of alpha-oxidation amounted to 7 and 10 nmol/min x 10(8) cells with phytanic acid and 3-methylmargaric acid, respectively. At equimolar substrate concentrations, alpha-oxidation of branched fatty acids was approximately 10- to 15-fold slower than the beta-oxidation of the straight chain palmitate. In whole liver homogenates, rates of alpha-oxidation that equaled 60 to 70% of those observed in the hepatocytes were obtained. Optimum rates required O2, NADPH, Fe3+, and ATP. Fe3+ could be replaced by Fe2+ and ATP could be replaced by a number of other phosphorylated nucleosides and even inorganic phosphate without loss of activity. NADH could substitute for NADPH but not always with full restoration of activity. A variety of other cofactors and metal ions was either inhibitory or without effect. Scavengers of reactive oxygen species, known to be formed during the NADPH-dependent microsomal reduction of ferric-phosphate complexes, were without effect on alpha-oxidation. No evidence was found for the accumulation of NADPH-dependent or Fe(3+)-dependent reaction intermediates. Subcellular fractionation of liver homogenates demonstrated that alpha-oxidation was located predominantly, if not exclusively, in the endoplasmic reticulum. alpha-Oxidation, measured in microsomal fractions, was not inhibited by CO, cytochrome c, or ferricyanide, indicating that NADPH cytochrome P450 reductase and cytochrome P450 are not involved in alpha-oxidation. Our results indicate that, contrary to current belief, alpha-oxidation is catalyzed by the endoplasmic reticulum. The cofactor requirements suggest that alpha-oxidation involves the reduction of Fe3+ by electrons from NADPH and that it is stimulated by phosphate ions and nucleotides.