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Biomedical subjects

M Kates

Publications and source records attributed to M Kates.

At least 73 records · Page 4Linked to original sources
PubMed1979

Studies of the biosynthesis of C50 carotenoids in Halobacterium cutirubrum.

Cells of Halobacterium cutirubrum were grown in the presence of [14C]mevalonate with and without 3 mM nicotine. Growth of cells was inhibited to a maximum extent of 25% but overall incorporation of 14C into total, neutral, or polar lipids was only inhibited about 16% during active growth and to a much lesser extent or not at all in stationary phase. Little effect of nicotine on labelling of squalenes, vitamin MK-8, geranylgeraniol, and phytoene was observed. However, labelling of bacterioruberin and monoanhydrobacterioruberin was extensively inhibited while that of lycopene and bisanhydrobacterioruberin was increased reciprocally by growth in the presence of 3 mM nicotine. Reincubation of the labelled nicotine-grown cells in fresh cold medium without nicotine restored the 14C-labelling of bacterioruberin and monoanhydrobacterioruberin at the expense of lycopene and bisanhydrobacterioruberin. These results confirm our previous findings suggesting that the C50 bacterioruberin is made by addition of a C5-isoprene unit to each end of the C40-lycopene chain, followed by introduction of four hydroxyl groups.

Carotenoids↗
PubMed1979

Chemical synthesis of sn-3-phosphatidyl sulfocholine, a sulfonium analog of lecithin.

A sulfonium analog of lecithin has been reported to replace the ubiquitous phosphatidyl choline in a non-photosynthetic diatom, Nitzschia alba. The structure of this sulfonium analog has now been established by chemical synthesis using the following methods: (i) condensation of sn-3-phosphatidic acid (dimyristoyl-, dipalmitoyl-, distearoyl-, distearoyl-, and dioleoyl-) with sulfocholine chloride in the presence of triisopropylbenzenesulfonylchloride in chloroform-pyridine (9:1); and (ii) phosphorylation of 1,2-dipalmitoyl-sn-glycerol with monophenylphosphoryl-dichloridate followed by a reaction with sulfocholine in the presence of pyridine and finally removal of the blocking phenyl group by catalytic hydrogenolysis. The desired synthetic products were obtained in overall yields of 50-70% and 11% for methods (i) and (ii), respectively, and were characterized by elemental analyses; infrared spectroscopy, nuclear magnetic resonance spectrometry, and mass spectrometry; optical rotation; and thin-layer chromatography mobilities. Comparison of the synthetic analogs with the natural sulfolecithin showed them to be identical, except for the nature of the fatty acid chains, thus establishing the natural product as sn-3-phosphatidyl sulfocholine.

Magnetic Resonance Spectroscopy↗
PubMed1978

The lipid composition of the non-photosynthetic diatom Nitzschia alba.

The lipid composition of the non-photosynthetic marine diatom, Nitzschia alba, has been quantitatively determined. Triglycerides accounted for 20% of the cell dry weight and 87% of the total lipids. Smaller amounts of 1,2- and 1,3-diglycerides, free sterol (24-methylene cholesterol), hydrocarbons and an unknown component were the remaining neutral lipids detected. Phosphatidylsulfocholine (phosphatidyl S,S-dimethylmercaptoethanol), present in amounts of 0.8% of cell dry weight (35% of total polar lipids), was the major polar lipid component. Other phospholipids were lysophosphatidylsulfocholine, phosphatidylglycerol, phosphatidylinositol and cardiolipin, but both phosphatidylcholine and phosphatidylethanolamine were completely absent. Another novel sulfolipid, deoxyceramide sulfonic acid, as well as the sulfate ester of the free sterol, were also present. Considerable amounts of the four lipids often associated with photosynthetic organisms, mono- and di-galactosyl diglycerides, sulfoquinovosyl diglyceride and phosphatidylglycerol, were identified in N. alba. However, the fatty acid components of the glycosyl diglycerides did not show the high amounts of polyunsaturated acids (18 : 2, 18 : 3) normally found in photosynthesizing organisms. All polar lipids were found to be associated with various cell membrane fractions in N. alba.

Cell Membrane↗
PubMed1978

Identification of the sulfolipids in the non-photosynthetic diatom Nitzschia alba.

The four major sulfolipids in the non-photosynthetic marine diatom, Nitzschia alba, were isolated in pure form and their structures were established spectrometrically and by identification of their hydrolysis products as (a) 24-methylene cholesterol sulfate, (b) 1-deoxyceramide-1-sulfonate, (c) phosphatidyl sulfocholine (a sulfonium analogue of phosphatidylcholine) and (d) sulfoquinovosyl diglyceride. The major characteristic fatty acids of the sulfolipids were: for the deoxyceramide sulfonate, 16 : 0 (26%) and 16 : 1-delta3-trans (64%); for the sulfonium analogue, 14 : 0 (30%), 18 : 1 (12%), 18 : 2 (8%), 20 : 5 (27%) and 22 : 6 (4%); and for the sulfoquinovosyl diglyceride (two species, respectively), 14 : 0 (9%, 22%), 16 : 0 (16%, 28%), 18 : 1 (8%, 22%), 20 : 5 (42%, 23%) and 22 : 6 (14%, 2%). Traces of lyso-derivatives of sulfoquinovosyl diglyceride and phosphatidyl sulfocholine were also detected. The deoxyceramide sulfonate and the phosphatidyl sulfocholine represent novel membrane lipid components not previously detected in other organisms. They may however have a widespread distribution in marine diatoms and perhaps in marine organisms generally.

Ceramides↗
PubMed1978

Studies on trimethylsilyl derivatives of 1,2-dialkylglycerols by gas-liquid chromatography mass spectrometry.

Trimethylsilyl derivatives of 1,2-dihexadecyl- and 1,2-dioctadecyl-glycerols were subjected to analysis by a gas chromatograph mass spectrometer system. The mass chromatographic identification of four kinds of glycerophospholipids, 1,2-dihexadecyl, 1-hexadec-1-enyl-2-hexadecanoyl, 1-hexadecyl-2-hexadecanoyl- and 1,2-dihexadecanoyl-glycerol is also described.

Chromatography, Gas↗
PubMed1978

A new double-labelling procedure for determination of amino acid composition: application to bacteriorhodopsin.

A new double-labelling procedure for amino acid analysis which requires only routine chromatographic equipment is described. When 1-fluoro-2,4-dinitro[3H]benzene is reacted with a mixture of 14C-labelled amino acids followed by reaction with the same 14C-labelled amino acid mixture diluted with an unlabelled sample of amino acids, the 3H:14C ratio in the resulting 2,4-dinitrophenyl (DNP) amino acid derivatives of the diluted sample will be increased in proportion to the quantity of unlabelled amino acid in the diluted sample. This procedure gave reliable results when applied to the known proteins insulin and lysozyme. The procedure is most advantageous when applied to amino acids which are unstable during acid hydrolysis or present in low molar fractions. When applied to the analysis of the bacteriorhodopsin in Halobacterium cutirubrum, this procedure showed the presence of one histidine residue and four tryptophan residues per mole protein but no cystine or cysteine; in general, the analyses obtained were consistent with those originally reported by Oesterhelt, D. and Stoeckenius, W. (1971) (Nature (London) New Biol. 233, 149-152) for bacteriorhodopsin of H. halobium.

Amino Acids↗
PubMed1977

Application of open-tubular gas-liquid chromatography in an investigation of the stability of pristanic and phytanic acids towards alkaline treatment of their methyl or [-] menthyl esters.

Comparison between GLC separation of the (--) menthyl and methyl esters of two diastereoisomeric isoprenoid acids of geological interest showed that a 46 m x 0.25 mm ID butanediol succinate column gives effective separation of 2S,6R,10R- and 2R,LR,10R-isomers of (--) menthyl pristanate (2,6,10,14-tetramethylpentadecanoate), but inferior separation of the corresponding methyl ester mixture. With the latter, a small proportion (2%) of 2S,6R,10R-isomer is well resolved from the major 2R,6R,10R-component on a 92 m column. Use of the methyl esters in such analyses thus avoids the cumbersome preparation of the menthyl esters. No epimerization at the 2-methyl carbon of pristanic acid and its methyl or (--) menthyl esters was detected after treatment in 1N aqueous or methanolic NaOH under reflux for 1 hr or at 120 degrees (sealed tube) for 24 hr. Similarly no 3-methyl carbon epimerization was observed inphytanic (3R,7R,11R,15-tetramethylhexadecanoic) acid and its methyl ester after the same treatments.

Alkalies↗
PubMed1977

Direct desaturation of eicosatrienoyl lecithin to arachidonoyl lecithin by rat liver microsomes.

A microsomal enzyme system from rat liver was shown to catalyze desaturation, in presence of reduced pyridine nucleotides and oxygen, of 1-acyl-2-[14C]eicosatrienoyl-sn-glycero-3-phosphorylcholine to 1-acyl-2-[14C]arachidonoyl-sn-glycerophosphorylcholine. This desaturation was linear with time and proportional to microsomal protein concentration, and proceeded with no significant breakdown of the lecithin substrate. The microsomal enzyme system will also desaturate 1,2-di-[14C]eicosatrienoyl-sn-glycero-3-phosphorylcholine and [14C]eicosatrienoyl-CoA, but not free [1-14C]eicosatrienoic acid in the absence of ATP, Mg2+, and CoA. Desaturation of 1-acyl-2-[14C]eicosatrienoyl-glycerophosphorylcholine as well as [14C]eicosatrienoyl-CoA was dependent on oxygen and either NADH or NADPH, and was inhibited by cyanide but not by carbon monoxide, indicating the involvement of cytochrome b5 and not P450. The activity of both eicosatrienoyl-glycerophosphorylcholine desaturase and the eicosatrienoyl-CoA desaturase was increased in rats that had been starved for 48 h and refed a fat-free diet. These data indicate the existence of a new route to synthesis of arachidonate, namely, by desaturation of eicosatrienoyl lecithin to arachidonoyl lecithin.

8,11,14-Eicosatrienoic Acid↗
PubMed1977

Characterization of the alkyl ether species of phosphatidylcholine in bovine heart.

The molecular types of lecithin in beef heart lipids were investigated by a combination of mild hydrolytic procedures and silicic acid chromatography. The major species of sn-glycero-3-phosphorylcholine (GPC) were found to be: diacyl-GPC (57%), alk-l-enyl, acyl-GPC (39%), alkyl acyl-GPC (3%), and dialkyl-GPC ( less than 1%). No di-alk-l-enyl-GPC or alk-l-enyl alkyl-GPC were detected. The derived monoalkyl-and dialkyl-glycerols were characterized by their infrared spectra and alkyl chain compositions.

Animals↗
PubMed1976

Comparison of purple membrane from Halobacterium cutirubrum and Halobacterium halabium.

Direct comparison of purple membrane preparations from Halobacterium cutirubrum and Halobacterium halobium was carried out. Both preparations were found to be essentially identical with respect to their molecular weight, retinal content, lipid composition, fingerprinting of peptides from peptide digestion, electron micrographs and X-ray diffraction patterns, and behaviour as a light-activated proton pump. Thus, there would appear to be no species differences in the purple membranes from these two bacteria.

Bacteriorhodopsins↗
PubMed1976

Lipid composition of Neurospora crassa.

The lipids of Neurospora crassa, isolated in pure form from freeze-dried mycelium, were found to contain squalene, sterol esters, triglycerides, free fatty acids, geranylgeraniol, free sterols, carotenoids, cardiolipin, phosphatidyl ethanolamine, phosphatidyl choline, phosphatidyl serine, and phosphatidic acid. The above compounds were isolated in pure form by column and thin layer chromatography and were characterized by infrared spectroscopy and chromatographic mobilities. Fatty acid moieties were characterized by gas liquid chromatographic retention times of their methyl esters relative to those of authentic standards. The fatty acid composition of the triglycerides was found to be similar to that of phosphatidic acid, cardiolipin, and lecithin.

Carotenoids↗
PubMed1976

Synthesis of monophytanyl ether analogues of lysophosphatidic and lysophosphatidyl glycerol.

The chemical synthesis of 3-O-phytanyl-sn-glycero-1-phosphoric acid (monophytanyl ether analogue of lysophosphatidic acid) was effected by condensation of 1-iodo-2-O-benzyl-3-O-phytanyl-sn-glycerol with silver di-p-nitrobenzyl phosphate in anhydrous toluene followed by catalytic hydrogenolysis of the resulting phosphotriester to remove the benzyl and p-nitrobenzyl groups. Synthesis of 3-O-phytanyl-sn-glycero-1-phosphoryl-1'-sn-glycerol (monophytanyl ether analogue of lysophosphatidyl glycerol) was carried out by conversion of the above phosphotriester to the monosilver salt of the suitably blocked lysophosphatidic acid which was condensed with 1-iodo-2-O-t-butyl-3-O-benzyl-sn-glycerol. Removal of the protecting aromatic and t-butyl groups from the resulting blocked triester intermediate gave the desired phytanyl ether analogue of lysophosphatidyl glycerol. Both lyso analogues were isolated as analytically and chromatographically pure potassium salts. Their physical properties and behavior towards acid hydrolysis are described.

Magnetic Resonance Spectroscopy↗
PubMed1976

Nonpolar lipids of a halotolerant species of Staphylococcus epidermidis.

The nonpolar lipids of a halotolerant Staphylococcus epidermidis, isolated in pure culture from a growth medium for extreme halophiles containing 25% sodium chloride, were found to contain squalene, menaquinone-7, free fatty acids (mainly anteiso-15:0 and anteiso-17:0), undecaprenol, nonaprenol with predominately cis-isoprene residues, heptaprenol, with predominately trans-isoprene residues, and 1,2- and 1,3-diglycerides containing anteiso- 15:0 and anteiso-17:0 branched chain fatty acid residues. The above compounds were isolated in pure form by column and thin-layer chromatography and were characterized by ultraviolet, proton magnetic resonance, and mass spectra. Fatty acid moieities were characterized by gas-liquid chromatographic retention times of their methyl esters.

Chromatography, Thin Layer↗
PubMed1976

Enzymatic synthesis of C40 carotenes by cell-free preparation from Halobacterium cutirubrum.

[14C]Mevalonate or (14C)isopentenyl pyrophosphate was found to be converted to transphytoene, trans-phytofluene, lycopene, and beta-carotene by a cell-free 270 000 X g supernatant fraction prepared from Halobacterium cutirubrum cells that were broken by manual grinding with glass beads. Incubations were done under N2 in the dark at 37 degrees C in 4 M NaCl in presence of FAD, NADP, and MgCl2; ATP was also added when mevalonate was the substrate. This system was also capable of converting trans-(14C)phytoene to beta-carotene via the intermediates trans-phytofluene, zeta-carotene, neurosporene, lycopene, and gamma-carotene. Each of these labelled intermediates on incubation separately with the same enzyme system was shown to be converted to the intermediates farther down the pathway. The results of this study show that the biosynthetic pathway for the formation of C40 carotenes in H. cutirubrum proceeds as follows: isopentenyl pyrophosphate leads to trans-phytoene leads to trans-phytofluene leads to zeta-carotene leads to neurosporene leads to lycopene leads to gamma-carotene leads to beta-carotene. This pathway differs from that in higher plants in that the cis isomers of phytoene and phytofluene are not on the main pathway of carotene biosynthesis, as they are in higher plants. Furthermore, trans-phytoene, which has not been reported to have any role in higher plants, appears to be the main intermediate in carotene biosynthesis in H. cutirubrum.

Carotenoids↗