Unsaturated Alkyl Chains Research Articles

Phospho- and phosphonolipids of the aegean pelagic scyphomedusa Pelagia noctiluca

The total lipid content found in Pelagia noctiluca (0.19% of the whole-body weight) is comparable to that reported for other stinging jellyfish species. Its polar lipid components were found to represent 26.2% of the total lipids and to contain 75.7% glycerophospholipids and 24.3% sphingophosphonolipids. The individual lipid classes obtained by column Chromatographic fractionation were purified by preparative TLC, and their structure was confirmed by a combination of Chromatographic and analytical determinations before and after mild alkaline hydrolysis or dry acid methanolysis, and by IR analysis. The overall composition of the polar lipids was: cardiolipin, 9.1%; phosphatidylethanolamine, 24.8% (of which 55% was glyceryl ether analog); phosphatidylcholine, 36.3% (of which 62% was glyceryl ether analog); lysophosphatidylethanolamine and lysophosphatidylcholine, 5.0%; ceramide aminoethylphosphonate, 21.0% plus 3.3% (another two minor species). Unsaturated fatty acyl groups represented about 52 and 33%, respectively, in phosphatidylethanolamine and phosphatidylcholine, while their glyceryl ether analogs were found to contain about 41 and 91% unsaturated fatty alkyl chains, respectively (total unsaturation 49 and 51%, respectively). In contrast, saturated fatty acyl groups with 14–16 carbon atoms were almost exclusive components (about 96%) of the major ceramide aminoethylphosphonate species.

The effects of cholesterol on lateral diffusion and vertical fluctuations in lipid bilayers. An electron-electron double resonance (ELDOR) study

Electron-electron double resonance (ELDOR) and saturation-recovery spectroscopy employing 14N:15N stearic acid spin-label pairs have been used to study the effects of cholesterol on lateral diffusion and vertical fluctuations in lipid bilayers. The 14N:15N continuous wave electron-electron double resonance (CW ELDOR) theory has been developed using rate equations based on the relaxation model. The collision frequency between 14N-16 doxyl stearate and 15N-16 doxyl stearate, WHex (16:16), is indicative of lateral diffusion of the spin probes, while the collision frequency between 14N-16 doxyl stearate and 15N-5 doxyl stearate, WHex (16:5), provides information on vertical fluctuations of the 14N-16 doxyl stearate spin probe toward the membrane surface. Our results show that: (a) cholesterol decreases the electron spin-lattice relaxation time Tle of 14N-16 doxyl stearate spin label in dimyristoylphosphatidylcholine (DMPC) and egg yolk phosphatidylcholine (egg PC). (b) Cholesterol increases the biomolecular collision frequency WHex (16:16) and decreases WHex (16:5), suggesting that incorporation of cholesterol significantly orders the part of the bilayer that it occupies and disorders the interior region of the bilayer. (c) Alkyl chain unsaturation of the host lipid moderates the effect of cholesterol on both vertical fluctuations and lateral diffusion of 14N-16 doxyl stearate. And (d), there are marked differences in the effects of cholesterol on lateral diffusion and vertical fluctuations between 0-30 mol% and 30-50 mol% of cholesterol that suggest an inhomogeneous distribution of cholesterol in the membrane.

Syntheèse et étude structurale de complexes aminocarbéniques contenant un ligand 1,4 bidenté

The synthesis of aminocarbene complexes of tungsten, containing either a free or a coordinated double bond is described. The crystal structure of complex (CO)5W[(NCH3)(CH2(CHCH2)][Ph], in which the geometry of the double bond does not permit coordination and of complex (CO)4WC(NCH2CHCH2)(η2-CH2CHCH2) in which the unsaturated alkyl chain is coordinated to the metal, is outlined.

Dynamic fluorescence quenching studies on lipid mobilities in phosphatidylcholine-cholesterol membranes

Bimolecular collision rate of 8-anilinonaphthalene-1-sulfonic acid (ANS) and the nitroxide doxyl group attached to various carbons on stearic acid spin labels ( n-SASL) in phosphatidylcholine-cholesterol membranes in the fluid phase was studied by observing dynamic quenching of ANS fluorescence by n-SASL's. The excited-state lifetime of ANS and its reduction by the n-SASL doxyl group were directly measured by the time-correlated single photon counting technique to observe only dynamic quenching separately from static quenching and were analyzed by using Stern-Volmer relations. The collision rate of ANS with the n-SASL doxyl group ranges between 1 · 10 7 and 6 · 10 7, and the extent of dynamic quenching by n-SASL is in the order of 5- ⪢ 6- > 7- < 9- < 10- < 12- < 16-SASL (< 5-SASL) in dimyristoylphosphatidylcholine (DMPC) membranes. Collision rate of 16-SASL is only 10% less than that of 5-SASL. Since the naphthalene ring of ANS is located in the near-surface region of the membrane, these results indicate that the methyl terminal of SASL appears in the near surface area frequently, probably due to extensive gauche-trans isomerism of the methylene chain. The presence of 30 mol% cholesterol decreases the collision rate of ANS with 12- and 16-SASL doxyl groups but not with the 5-SASL doxyl group in DMPC membranes. On the other hand, in egg-yolk phosphatidylcholine membranes, inclusion of 30 mol% cholesterol does not affect the collision of ANS with either 5-SASL or 16-SASL doxyl groups, in agreement with our previous observation that alkyl chain unsaturation moderates cholesterol effects on lipid motion in the membrane (Kusumi et al., Biochim. Biophys. Acta 854, 307–317). It is suggested that dynamic quenching of ANS fluorescence by lipid-type spin labels is a useful new monitor of membrane fluidity that reports on various lipid mobilities in the membrane; a class of motion can be preferentially observed over others by selecting a proper spin label, i.e., rotational diffusion of lipid about its long axis and translational diffusion by using 5-SASL, wobbling motion of the lipid long axis by using 7-SASL or androstane spin label, and gauche-trans isomerism by using 16-SASL.

New polyacetylenes from the sponge [formula omitted

Six new compounds, characterized by a long unsaturated alkyl chain (nC 22), were isolated from a marine sponge. All compounds except for one, possess an enyne terminus on one side of the molecule and either a terminal acetylene (in four) or a propargyl alcohol on the other end. Four of the compounds were unequivocally identified mainly by spectroscopic methods. Acetylenic compounds are well-known constituents of plants: only few, however, are known from marine organisms and to our knowledge only one group of compounds contains more than a single triple bond. Among the acetylene containing marine natural products are: A group of halogenated ethers, characterized by a straight-chain C-15 carbon skeleton and a terminal enyne function which has been isolated from algae 1 and a sea hare 2, carotenoids 3, two steroids 4, a sesquiterpene 5 and polyketids 6,7. A diacetylene was found in a group of several n C-22 straight-chain compounds isolated from a marine sponge 8. One of the compounds found in the latter sponge contains, again, the enyne terminus - an end group which turns out to be quite abundant in the above and the herewith discussed compounds. In our continuing search for bioactive compounds from marine organisms we have isolated from the sponge Siphonochalina sp . 9 collected at several places in the southern part of the Gulf of Eilat (the Red Sea) six n C-22 straight-chain acetylenic compounds. Extraction of the freeze-dryed sponge (petrol ether, 4% dry weight) and subsequent repeated chromatographies (LH-20 and Silica gel) 10,11 gave six closely related new compounds, named in order of polarity, Δ 15-docos-1-yne ( 1 ; RF 12a=0.65; 0.2% based on the dry weight of the animal), octahydrosiphonochalyne ( 2 ; Rf 12a=0.55; 0.4%), dihydrosiphonochalyne ( 4 ; Rf 12a=0.44; 0.1%) siphonochalyne ( 3 ; Rf 12b=0.34; 0.2%), dehydrosiphonochalynol ( 6 ; Rf 12b=0.55; 0.1%) and siphonochalynol ( 5 ; Rf 12b=0.43; 0.3%).

Ionic transport through model membranes. II. Function of cholesterol and steroid hormones

1. 1. The kinetics of transfer of a water-soluble azo dye, Orange IV, from an aqueous into phospholipid micelles in an adjacent organic phase have been investigated as a method of evaluating the possible effects of various hydrocarbons on the structure of the lipid micelles and interfacial films. The transport of this dyestuff probe apparently requires the presence of unsaturated alkyl chains in the lipid, provided by egg phosphatidylcholine or by synthetic lecithin (1-oleyl-2-hexadecyl ether). 2. 2. The kinetics had previously been shown to be retarded by those n- alkanes that are promoters of carcinogenesis. On the basis of this correlation it had been predicted n- C 18H 38 and n- C 20H 42 should be the most active biologically of the n- alkanes . This has been confirmed in detail by biological tests for promoting activity. 3. 3. Inclusion of cholesterol and various steroid metabolites, including androgens and progestogens, had profound effects on the rate of dye transport by egg phosphatidylcholine (very little transfer to the bulk organic phase was achieved by the steroids without the phospholipid). Cholesterol had the maximum retarding effect, but increased somewhat the ultimate equilibrium transfer of dye to the micelles in the organic phase. 4. 4. The C 19 steroids, dihydrotestosterone, testosterone, androsterone, and epiandrosterone enhanced the rate of transport by lecithin-cholesterol micelles in different critical ranges of concentration. The four steroids were thus ranked in the same order of effective concentration in the model transport system as they are in assays of their biological activities as androgens. The metabolic intermediate, pregnenolone, affected the transport kinetics similarly to testosterone. In contrast, the C 21 hormone, progesterone, and the estrogen analog, diethylstilbestrol, retarded ionic transport in this model.

Fibrosing properties, in the rat, of compounds related to dicetyl (di- n-hexadecyl) phosphate —I

In this preliminary survey, twenty-six compounds, related in one way or another to dicetyl(di- n-hexadecyl)phosphate, were compared with this substance as to tissue fibrosing activity by subcutaneous injections in the rat. Only dialkylphosphates (and the single alkylborate used) with a chain length of sixteen or eighteen carbon atoms were active. The only substance with unsaturated alkyl chains, dioleyl(C 18)phosphate, was inactive. Dicholesteryl-phosphate and phosphite were not active. None of the phosphites (di- or tri-) was active. Dicetylborate produced less flbrosis than the phosphate and this was accompanied by marked eosinophilia and subsequent encapsulated necrosis. Dioctadecyl phosphate was indistinguishable in these experiments from dicetyl phosphate.