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Biomedical subjects

M Kates

Publications and source records attributed to M Kates.

At least 55 records · Page 3Linked to original sources
PubMed1982

Phosphatidylsulfocholine bilayers. An infrared spectroscopic characterization of the polymorphic phase behavior.

The thermal response of aqueous dispersions of phosphatidylsulfocholines (dimyristoyl-, dipalmitoyl- and distearoyl-) was studied by Fourier transform infrared spectroscopy. Comparison with that of the corresponding phosphatidylcholines showed several close resemblances, including the observation in the gel phase of a "pretransition" and of a "subtransition". The similarity in the thermotropic phase behavior of these two lipid classes is consistent with the total replacement of phosphatidylcholine by phosphatidylsulfocholine in certain marine diatoms.

Lipid Bilayers↗
PubMed1982

Studies on fluorescence polarization of 1-acyl-2-cis- or trans-parinaroyl sn-3-glycerophosphorylcholines in model systems and microsomal membranes.

Fluorescent lecithin probes containing cis- or trans-parinaric acid (PnA) at the 2-position cis-parinaroylphosphatidylcholine (cis-PnPC) and trans-parinaroyl phosphatidylcholine (trans-PnPC)) showed similar behavior to that of the free cis- or trans-parinaric acids (cis-PnA or trans-PnA) in bilayer vesicles of synthetic saturated lecithins. Transition temperatures detected by cis-PnPC were about 1 degree C than those observed with trans-PnPC. In mixed lecithin vesicles, the trans-PnPC probe monitored a higher temperature melting component than did the cis-probe. Both probes were readily incorporated into microsomal membranes and into sonicated vesicles prepared from the microsomal phospholipids. With either cis- or trans-PnPC no change in polarization ratio was observed for microsomal membranes between 40 degrees C and 0 degrees C but this ratio increased with decreasing temperature between 0 degrees C and -5 degrees C. However, vesicles of extracted phospholipids showed a continuous increase in polarization ratio with decreasing temperature between 20 degrees C and -15 degrees C with trans-PnPC and between 5 degrees C and -15 degrees C with cis-PnPC. These results suggest that the two lecithin probes monitor different environments in the membranes and phospholipid vesicles prepared from them.

Animals↗
PubMed1982

Polar lipids in phototrophic bacteria of the Rhodospirillaceae and Chromatiaceae families.

The polar lipids of photosynthetic purple bacteria of the genera Chromatium, Thiocapsa, Thiocystis, Ectothiorhodospira, Rhodopseudomonas, Rhodospirillum, and Rhodomicrobium were analyzed. Characteristic compositions of the polar lipids were found for most of the Rhodospirillaceae and Chromatiaceae species. Phosphatidylethanolamine, phosphatidylglycerol, and cardiolipin were the major phospholipids in most species. Phosphatidylcholine was present as a major component in all species of the genus Ectothiorhodospira, but was not detected in the remaining Chromatiaceae. It was also present in most of the Rhodospirillaceae species. No glycolipids were found in any of the Ectothiorhodospira species. In the Rhodospirillaceae, the glycolipids mono- and digalactosyl diglycerides were generally absent. Sulfoquinovosyl diglyceride was present in significant amounts in at least three species of the Rhodospirillaceae and may have been present in most of them, but only in traces. All of the Chromatiaceae species contained several glycolipids, one of which was similar to monogalactosyl diglyceride. Ornithine lipids were found in large amounts in most Rhodospirillaceae, but were absent in Ectothiorhodospira and in the other Chromatiaceae. The species examined could be divided into three groups on the basis of their lipid composition: (i) the genus Ectothiorhodospira; (ii) the remaining Chromatiaceae; and (iii) the Rhodospirillaceae. The data presented are compared with those available in the literature, and differences from other phototrophic organisms are discussed.

Chromatiaceae↗
PubMed1981

Novel polar lipids from the methanogen Methanospirillum hungatei GP1.

The methanogenic bacterium Methanospirillum hungatei GP1 has been shown to contain two unusual phosphoglycolipids (phosphoglycolipid I and phosphoglycolipid II) that account for 64% (by wt.) of the total cellular lipids. These lipids are derivatives of the dibiphytanyldiglycerol tetraether. One of the free hydroxyls of this tetraether is esterified with glycerophosphoric acid and the other is linked glycosidically to a disaccharide with structure alpha-Glcp-(1 leads to 2)-beta Gal phi in phosphoglycolipid I and beta-Gal phi-(1 leads to 6)-beta Gal phi in phosphoglycolipid II. Smaller amounts of the sn-2,3-diphytanylglycerol analog of phosphatidylglycerol and diglycosyldiphytanylglycerol ethers (DGD-I and DGD-II) containing the same disaccharide residues as in phosphoglycolipid I and phosphoglycolipid II, respectively, were identified, together with very small amounts of diglycosyldibiphytanyldiglycerol tetraethers (DGT-I and DGT-II) containing the same disaccharide residues as in phosphoglycolipid I and phosphoglycolipid II, respectively. A biosynthetic pathway involving head-to-head condensation of phosphatidylglycerol with DGD-I or DGD-II to form phosphoglycolipid I or phosphoglycolipid II, respectively, is proposed.

Carbohydrate Conformation↗
PubMed1981

Novel complex polar lipids from the methanogenic archaebacterium Methanospirillum hungatei.

The methanogenic archaebacterium Methanospirillum hungatei contains two unusual phosphoglycolipids that account for 64 percent of the total cellular lipids. These lipids are derivatives of the dibiphytanyl diglycerol tetraether, previously identified in methanogens. One of the free hydroxyls of this tetraether is esterified with glycerophosphoric acid, and the other is linked glycosidically to a disaccharide. The two phosphoglycolipids may function as covalently bonded lipid bilayers to impart stability and rigidity to methanogen membranes.

Cell Membrane↗
PubMed1981

[Can phosphatidyl sulfocholine, the sulfonium analog of lecithin, efficiently replace lecithin in natural membranes?].

Lecithin does not exist in the marine diatom, Nitzschia alba, being completely replaced by phosphatidylsulfocholine (PSC), the sulfonium analogue of phosphatidylcholine (PC). Thus, the question arises: how can PSC effectively replace lecithin in a natural membrane? We have compared the physical properties of a homologous series of synthetic PSC's (di - 14:0, di- 16:0, di- 18:0, di 18:1) in aqueous dispersion with those of a similar series of PC's. The PSC's formed liposomes having similar properties to those of the PC's. However, the saturated PSC homologues showed main transition temperatures 2-4 degrees C above those of the corresponding PC's as measured by differential scanning calorimetry, fluorescence polarization or electron paramagnetic resonance. Furthermore, there was no significant difference between the two types of membranes with respect to their permeability to urea or 6-carboxyfluorescein either in the presence or absence of cholesterol. We have also shown that yeast cells can grow and survive in spite of a complete replacement of PC by PSC in their membranes. The sulfonium analogue of lecithin would appear to be able to replace PC in natural membranes because of the similarity in their physical properties.

Choline↗
PubMed1980

The lipids of Halobacterium marismortui, an extremely halophilic bacterium in the Dead Sea.

The lipids of an extremely halophilic bacterium, Halobacterium marismortui, isolated from the Dead Sea, were found to contain 86% polar lipids and 14% non-polar lipids. Four major polar lipids were detected, all derivatives of 2,3-di-O-phytanyl-sn-glycerol: (1) a novel glycolipid, 2,3-di-O-phytanyl-1-O-[beta-D-glucopyranosyl-(1'-6')-O-alpha-D-mannopyranosyl-( 1'-2')-O-alpha-D-glucopyranosyl]-sn-glycerol (11 mol%); (2) phosphatidylglycerol (11 mol%); (3) phosphatidylglycerophosphate (62 mol%); (4) phosphatidylglycerosulfate (17 mol%). In addition, a minor glycolipid (less than 1 mol%) was detected and partially characterized. Trace levels of two other unidentified glycolipids and of two unidentified phospholipids were also detected. In contrast to Halobacterium cutirubrum and H. halobium, H. marismortui did not contain any detectable sulfated glycolipid but appeared to compensate for this deficit in sulfate by having a high content of phosphatidylglycerosulfate compared to that in H. cutirubrum. The number of negative changes per mol ionic lipid appeared to be about the same for both halophiles. The non-polar lipids in H. marismortui consisted mostly of squalenes, vitamin MK-8 and bacterioruberins with traces of beta-carotene, lycopene and retinal, as in H. cutirubrum.

Chromatography, Gas↗
PubMed1980

Exclusive formation of all-trans-phytoene by a colorless mutant of Halobacterium halobium.

A spontaneously occurring Halobacterium halobium mutant (strain W5002-1) was isolated which accumulated phytoene as the only C40 polyene. Its configuration was established as all-trans (7,8,11,12,7',8',11',12',-octahydro-psi,psi-carotene) by its chromatographic and spectral properties. Neither bacterioruberins (C50) nor retinal (C20) could be detected in this mutant strain. The biosynthetic pattern of isoprenoid compounds in this mutant strain confirms for the first time our conjecture that spontaneously arising H. halobium mutants can be isolated with defects in the carotenoid pathway and lends further support to our previous hypothesis suggesting all-trans-phytoene to be the precursor for more unsaturated carotenoids in halobacteria.

Carotenoids↗
PubMed1980

Fluorescence polarization studies of rat liver microsomes with altered phospholipid desaturase activities.

Phospholipid desaturase activity of rat liver microsomes can be varied by dietary manipulation: rats starved and refed a "fat-free" diet have two to three times the activity of normal controls whereas starved rats have no detectable activity. These changes were accompanied by changes in fatty acid composition of the microsomal phospholipids, resulting in a double bond: saturated fatty acid mole ratio (moles double bonds per mole saturated fatty acid) of 5.7 in control and starved rats and 4.7 in starved-refed rats. Fluorescence polarization ratio P (I parallel/I perpendicular to x instrument correction factor) of cis- and trans-parinaric acid (PnA) showed no significant differences in physical state of the three microsomal preparations. However, the isolated microsomal phospholipids with trans-PnA as probe showed differences in the temperature at which onset of a change in polarization ratio occurred (starved-refed greater than normal greater than starved rats). With the cis-PnA as probe, the polarization ratio showed no change in the range 10-40 degrees C but was significantly higher (1.8) in starved-refed rats than in normal and starved rats (1.6 in both cases). These data indicate that the microsomal phospholipids of starved-refed animals were in a less fluid state than those from control and starved rats and that this decrease in fluidity was correlated with an increase in phospholipid desaturase activity.

Animals↗
PubMed1979

Studies on the biosynthesis of sulfolipids in the Diatom Nitzschia alba.

Labeling of sulfolipids in Nitzschia alba was studied after growth of the cells in media containing L-[35S]cystine, L-[35S], L-[35S]cysteine, L-[35S]-methionine or a mixture of L-[Me-3H]methionine and L-[35S]methionine, [35S]Cysteine or [35S]cystine labeled the deoxyceramide sulfonate and the sulfonium analog, phosphatidylsulfocholine (and its lyso derivative) but not the sterol sulfate nor the sulfoquinovosyl diglyceride; [35S]methionine labeled only the phosphatidylsulfocholine and its lyso derivative. With the [35S]- and [Me-3H]methionine mixture (3H/35S ratio 1.0) the phosphatidylsulfocholine had a 3H/35 S ratio of 1.5 indicating that both sulfonium methyl groups were derived from methionine. Probable biosynthetic pathways for these novel sulfolipids are discussed.

Amino Acids, Sulfur↗
PubMed1979

Membrane-bound phospholipid desaturases.

This review covers studies on membrane-bound phospholipid desaturases in yeast and rat liver carried out in this laboratory. In yeast the desaturase system was shown to effect the direct desaturation of dioleoyl-lecithin to dilinoleoyl-lecithin. In rat liver the desaturase was capable of converting 2-eicosatrienoyl-lecithin to 2-arachidonoyl-lecithin. Both systems required reduced pyridine nucleotides, O2 and cytochrome b5. Eicosatrienoyl-lecithin desaturase along with eicosatrienoyl-CoA desaturase of rat liver microsomes was solubilized with detergents and purified 7-8-fold from the microsomal pellets. Both activities were reconstituted in the presence of deoxycholate on addition of the other components of the cytochrome b5-electron transport chain (cytochrome b5 and NADH-cytochrome b5 reductase) to the solubilized desaturase; addition of lecithin further stimulated the activities. The demonstration of desaturation of eicosatrienoyl-lecithin by a solubilized and partially purified desaturase provides strong evidence for the direct desaturation of the lecithin substrate without prior conversion to the acyl-CoA thiolester.

Acyl Coenzyme A↗
PubMed1979

Effect of glycerol on carotenogenesis in the extreme halophile, Halobacterium cutirubrum.

Growth of cells of Halobacterium cutirubrum in complex medium in the presence of 0.1 to 0.5% glycerol was slightly stimulated (about 10%), but the content of the major red pigment, bacterioruberin, was reduced fourfold and that of the minor red pigments, mono- and bisanhydrobacterioruberins, was also reduced but to a lesser extent. The content of the C40 carotenes, beta-carotene and lycopene, however, was greatly increased in 0.1 to 0.5% glycerol but was then reduced to negligible amounts at higher glycerol concentrations (1 to 5%). Similar effects of glycerol on carotenogenesis were observed when cells were grown in a chemically defined medium (BSMK), but growth of cells was considerably slower.

Carotenoids↗
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↗