Sulphur-containing lipids

In addition to cerebroside sulphates (Section 2.4) and diacylsulphoquinovosylglycerol (Section 2.5), various other sulphur-containing lipids have been reported. These include alkyl sulphates (Mayers etal., 1969) in micro-organisms. 

Chlorosulpholipids are found in some fungi (e.g. caldariomycin (CICH2COCH2CH2COOH) and certain algae. Ochromonas danica contains particularly high amounts of chlorosulpholipids where they represent almost half of the total membrane lipids. A whole family of compounds are found with two sulphate ester functions and from one to six 

Derivative Position of substitution in 1,14-dicosane-disulphate Position of substitution in 1,15-tetracosane-disulphate 

An unusual glycolipid sulphate ester has been reported in extremely halophilic bacteria by Kates and co-workers (cf. Kates, 1972) and a glycolipid sulphate, 2,3,6,6 -tetra-acetyl-a,a -trehalose-2 -sulphate in Mycobacterium tuberculosis (Goren, 1970). 

(1970) Biochim. Biophys. Acta, 210,127. Haines, T.H. (1973) in The Biochemistry of Lipids (ed. T.W. Goodwin), MTP International Reviews of Science, Biochemistry Series 1, Butterworths, London, Vol. 4, p. 197. 

---

Sulphur-containing compounds, 474 Sulphur-containing lipids, see Sulpho-quinovosylglycerol Sulphatides Chlorosulpholipids Alkylsulphates Sulphur olive oil, 19, 52 Summary tables, fats, 98 Sunflower oil, 3,21, 51, 52,91, 92, 99,... 

In Scheuer (1973), investigations concerning sulphur-containing compounds in lipids of brown algae are reviewed which are biogenetically related to the dictyopterenes (Moore et al., 1972). The spectroscopically identified compounds belong to the classes of alkyl thioacetates, open-chain disulphides, and l,2-dithiepin-5-ones as well as organic tri- and tetra-sulphides. 

During a study of the lipids of Gluconobacter cerinus it was observed that an ornithine-containing lipid was labelled with sulphur-35 when [ S]-sulphate was added to the culture medium. 

By thin-layer chromatography this lipid was isolated and named cerilipin. On hydrolysis, it gave ornithine and a sulphur-containing component identified as taurine. By alkaline transmethylation, cerilipin was deacylated and the resulting methyl ester was found to be identical with methyl 2-hydroxyhexadecanoate (with a small amount of methyl 2-hydroxylactobacillate). Acid hydrolysis of the deacylated lipid gave a fatty acid identified as 3-hydroxyhexadecanoic acid as well as ornithine and taurine, in the molecular ratio 1 1 1. Treatment of cerilipin with dinitrofluorobenzene gave -ornithine as the only DNP derivative. From these data, structure (14) was proposed for cerilipin 45). 

Analysis of the CLA content and profile of animal tissues or biological fluids containing a mixture of lipid classes is more difficult. In order for all of the fatty acids to be methylated, a two-stage methylation procedure is recommended. Kramer et al. (1997) evaluated many different combinations of acid/base catalysts and concluded that the best compromise was the use of sodium methoxide followed by a mild acidic methylation, which resulted in the methylation of the majority of the fatty acids with minimal isomerization of the CLA isomers. However, mild boron triflouride or 1% methanolic sulphuric acid with a minimal temperature and reaction time are often used with good success. 

In addition to sulfoquinovosyldiacylglycerol, the marine diatom Nitzschia alba has been found to contain a sulfonium analog of phosphatidylcholine, phosphatidylsulfocholine (14). This lipid has two methyl groups attached to the sulphur atom, and it substitutes completely for phosphatidylcholine in Nitzschia alba. In other marine diatoms and algae, both lipids have been found (15). 

Contains FMN, nonhaem Fe, acid- abile sulphur, ubiquinone-10 and lipids (Table 3.8). The several constituent polypeptides probably include ubiquinone-binding proteins (281). 

Biochemical effects of arsenic are caused by blocking the SH-groups of proteins, which is most serious in enzymes containing sulphur (mainly hydrolases) and also by a chemical similarity between arsenic and phosphorus. Arsenic disturbs the metabolism of glycides and lipids, with considerable damage to the oxidative phosphorylation, etc. 

Isolation of the hydrocarbons from other lipids The total lipid extract may be subjected to removal of elemental sulphur by passage through an activated copper column (Blumer, 1957) and then to chromatographic separation on adsorbent columns or thin layer plates. For column chromatography, silic el is used with a short alumina bed on the top of the silic el. Both adsorbents should be partially deactivated by the addition of water (2—5%) to prevent the formation of artifacts (Blumer, 1970). Elution with a non-polar solvent such as hexane or pentane and subsequently with mixtures of non-polar and polar solvents, e.g. benzene and methanol, permits the isolation of several fractions containing saturated, unsaturated, aromatic hydrocarbons and more polar compounds (methyl esters, alcohols, acids, phenols and heterocyclic compounds). The interference from esters encountered in the isolation of aromatic hydrocarbons can be avoided prior to separation by saponification of the esters of fatty acids, which are easily removed. 

The inclusion of phosphoric acid in the mobile phase increases the potential for error in subsequent quantitation by lipid phosphorus determinations and has been replaced with a mobile phase containing acetonitrile-methanol-sulphuric acid (100 3 0.05) to provide resolution of phosphatidylinositol, phosphatidylserine, phosphatidyl-ethanolamine, phosphatidylcholine, lysophosphatidylcholine and sphingomyelin (Kaduce et al., 1983). The authors reported that a reduction in the sulphuric acid content of the mobile phase caused a broadening of the eluted peaks and an increase in the retention of phosphatidylserine, phosphatidylethanolamine and phosphatidylcholine, while if omitted, these components did not elute. It was also noted that if the methanol content of the mobile phase was increased then the retention times of all the phospholipids were decreased. Samples were therefore injected in chloroform-diethyl ether (1 1) to avoid altering the concentration of methanol in the mobile phase. 

A fourth complex connects site 1 to site 2. Thus, the first complex in the chain consists of the enzyme NADH dehydrogenase and a group of around five closely linked proteins that contain electron-rich iron-sulphur clusters. These are non-heme proteins vital to the flow of electrons through the chain. The second complex consists of the enzyme succinate dehydrogenase and its collection of iron-sulphur proteins. The third complex contains the hemoproteins cytochromes b and Cj, and one iron-sulphur protein. The final complex, the one that actually reduces oxygen to water, is called cytochrome oxidase and contains two heme groups (heme a and heme a ) and two copper centres. Ubiquinone, also known as coenzyme Q, is a lipid-soluble quinone which connects the first, second, and third complexes. Cytochrome c is the electron carrier hemoprotein that links the complexes of site 2 to cytochrome oxidase in site 3. 

The neutral lipid fraction extracted from biological materials contains among other components all the triglyceride fats. The fatty acid composition of these is sometimes of great significance, and methods for the establishment of this composition are based on the quantitative analysis of fatty acid methyl esters by gas chromatography. Initially, alkaline hydrolysis released the fatty acids, which were then extracted, concentrated and esterified, some kind of sulphuric acid/methanol procedure being widely used. However, this sequence of separate procedures has been superseded because losses may occur due to incomplete hydrolysis or side reactions such as polymerization or the alteration of unsaturated fatty adds. The preferred method is transesterification in either alkaline or add media [134]. The most recent methods use methanolic HQ, because in alkaline conditions some hydrolysis may occur as a side reaction and cause lowered yields [19, 135, 136]. There are of course effective quantitative methods for the... 

The dry matter (DM) of foods is conveniently divided into organic and inorganic material, although in living organisms there is no such sharp distinction. Many organic compounds contain mineral elements as structural components. Proteins, for example, contain sulphur, and many lipids and carbohydrates contain phosphorus. 

The ether extract (EE) fraction is determined by subjecting the food to a continuous extraction with petroleum ether for a defined period. The residue, after evaporation of the solvent, is the ether extract. As well as lipids it contains organic acids, alcohol and pigments. This procedrue is referred to as method A. In the current official method, the extraction with ether is preceded by hydrolysis of the sample with sulphuric acid and the resultant residue is the acid ether extract (method B). 

A mixture of 10—20 mg of a lipid sample containing compounds with free alcohol or amine groups and a 20% excess of a solution of acetic anhydride-1- C (specific activity 0.6 mCurie/mmole) in pyridine (1 + 10) is sealed into a glass ampoule, 5 X 150 mm. The ampoule is heated 30—60 min at 100° C. After cooling and opening, the reaction mixture is diluted with 10 ml N sulphuric acid. The acetylated lipids are extracted with several portions of ether, the combined extract washed neutral with water and dried over anhydrous sodium sulphate. 

All organisms carrying out oxygenic photosynthesis contain the plant sulphoUpid, sulphoquinovosyMacylglycerol, as a major component of their thylakoid membranes. The lipid was first discovered by Benson and co-workers, and, in some marine algae, may represent up to half of the total lipids. Thus, the plant sulpholipid is a very significant membrane component and makes a major contribution to the sulphur cycle [1,2]. 

---