Use of online educational resources before and during the COVID-19 era in oral and maxillofacial surgery

Restrictions to traditional face-to-face meetings were mandated by many government authorities during the COVID-19 pandemic, impacting the delivery of educational training sessions for maxillofacial surgery trainees in the traditional group manner. An online survey was designed to review what effect the pandemic had on the use and uptake of online educational sources amongst a representative cohort of maxillofacial surgery trainees in higher specialist training. Their attitudes and satisfaction with online resources were considered. The use of live sources such as webinars and pre-recorded materials (e.g. YouTube videos) was investigated. Engagement with online sources was considered prior to, and then during the pandemic. Alterations in the behaviour of trainees were demonstrated, with increasing online resource use seen once the COVID-19 pandemic took hold. Online pre-recorded resource use increased by 26% during the pandemic, with the median number of hours watched per month increasing from 1-5 h to 5-10 h (p < 0.001). Engagement with live online sources (webinars) increased by 52% and median time watched increased from 15 h per month to 10-20 h per month (p < 0.001). Trainees expressed satisfaction with the quality and flexibility of the resources. There was a firmly positive response to live webinars with regard to teaching quality, audio and video quality, ease of access and relevance to training needs. Pre-recorded and live online resources may prove a useful alternative or adjunct to face-to-face teaching when regulations limit or restrict social interactions.

A Chromosomal Hybrid Zone in the Australian Huntsman Spider, Delena Cancerides (Araneae, Sparassidae) - Evidence for a Hybrid Zone Near Canberra, Australia

Data are presented that indicate the presence of a hybrid zone between two chromosomal races of the endemic Australian spider Delena cancerides. Electrophoretic data verify the hybridising taxa as members of the Victorian telocentric race and a chain-carrying race. Evidence is presented that indicates the hybrid zone is of natural origin, as opposed to being the result of human introductions.

Interaction of cholesterol with conformationally restricted phospholipids in vesicles

The interaction of cholesterol with conformationally restricted analogs of dipalmitoylphosphatidylcholine (DPPC) and dipalmitoylphosphatidylglycerol (DPPG) in the liquid-crystalline phase has been studied in vesicles. These analogs contain one of three cyclopentane triols in place of the glycerol moiety found in natural phospholipids and make possible an analysis of whether a limitation of the conformational mobility in the glycerol backbone region affects the interaction with cholesterol. When cholesterol was incorporated into vesicles from cyclopentanoid phospholipids in which the acyl group vicinal to the head group is trans, the first-order rate constant for Cl- efflux is decreased similarly to that in vesicles from 'natural' DPPC or DPPG (about 50%). However, when the head group is in the unnatural 2 position, cholesterol has a much smaller effect on the rate of Cl- efflux (a decrease of about 20%). Cholesterol decreased the rate constants for valinomycin-mediated 86Rb+ efflux from vesicles of the cyclopentanoid PC analogs and of DPPC to a similar extent. The half-time values for spontaneous intervesicle cholesterol exchange were not markedly different using vesicles prepared with the natural glycerophospholipids and with the cyclopentano-phospholipids, suggesting that the geometrical orientation of the acyl chains or the head group has little influence on cholesterol desorption from the lipid/water interface.

Cyclopentanoid analogs of dipalmitoyl phosphatidic acid: effect of backbone geometry on thermotropic properties

Seven geometrical or positional isomers of dipalmitoyl cyclopentanophosphoric acid (DPCPA) have been synthesized and studied: 1,3/2-1P (I); 1,2/3-1P (II); 1,2/3-3P (III), 1,2,3/0-1P (IV); 1,2,3/0-2P (V); 1,3/2-2P (VI); 1,2/3-2P (VII). When dispersed in 0.1 M Tris-HCl at pH 7.4, I-VII gave thermal transitions (Tc) of 60.0 degrees, 59.0 degrees, 56.8 degrees, 55.3 degrees, 38.3 degrees, 36.8 degrees and 34.0 degrees C, respectively, as measured by differential scanning calorimetry (DSC). When the lipids were dispersed at pH 9.5 in 0.1 M borate, Tc of I-IV decreased, whereas Tc of V-VII increased. In contrast, at pH 1.5 in 0.1 M HCl/KCl, Tc of I-IV decreased slightly, but Tc of V-VII rose markedly. To determine the effect of head group geometry and substitution pattern on acyl chain motion, EPR spectra of 1-palmitoyl, 2-[16-doxylstearoyl]-glycero-3-phosphoric acid in bilayers of DPCPA isomers were acquired. Abrupt spectral changes occurred at temperatures closely correlating with transition temperatures observed by DSC. These results have led to the conclusions that: (i) isomers I-IV containing vicinal acyl chains form bilayers that exhibit structural transitions at temperatures higher than those at which transitions are exhibited by isomers V-VII which have a polar phosphate group interposed between the two chains; (ii) the effects of differences in backbone structure are transmitted down the entire length of the acyl chains; (iii) the orientation of the cyclopentane ring in the isomers I-IV is significantly different from that in isomers V-VII at pH values where the phosphate group is doubly negatively charged.

Cyclopentanoid analogs of phosphatidylcholine: susceptibility to phospholipase A2

Six isomers of dipalmitoylcyclopentanetriol phosphocholine (cyclopentano-lecithin) were tested as potential substrates for phospholipase A2. Since each of these analogs possesses a configuration that mimics a narrow range of conformations of a glycerophospholipid molecule, the analogs were used to assess the enzyme's conformational requirements. Studies showed that all of the analogs containing the phosphocholine at the C-1 (or C-3) position could be hydrolyzed, while only one of the three analogs that contains the polar head group at the C-2 position was susceptible. Kinetic studies, however, revealed that only the all-trans-(1,3/2-1P)-cyclopentano-lecithin gave initial rates of hydrolysis that were measurable by pH-stat. Acyl group specificity of the enzyme towards the all-trans isomer was determined with an analog was acyl groups were distinguishable. The synthesis of this mixed-acid-cyclopentano-PC is described herein. When this analog was enzymatically assayed, results unequivocally showed the enzyme to be specific for C-2 acyl hydrolysis. This specificity, and data showing that the all-trans analog is stereospecifically hydrolyzed, indicate that it is acted on in an analogous manner to dipalmitoylphosphatidylcholine. These studies indicate that although the configuration of the analog is not necessarily a prerequisite for hydrolysis, there does appear to be an optimal spatial orientation for enzymatic activity. The analogy between the susceptibilities of all-trans-(1,3/2-1P)-cyclopentano-lecithin and glycero-lecithin suggests that the conformation of the glycero-lecithin during phospholipase A2-mediated hydrolysis may be best simulated by the all-trans orientation of C-O bonds in the artificial substrate.

Synthesis and some properties of constrained short-chain phosphatidylcholine analogues: (+)- and (-)-(1,3/2)-1-O-(phosphocholine)2,3-O- dihexanoylcyclopentane-1,2,3-triol

Reported herein is the synthesis of (+)- and (-)-(1,3/2)-1-O-(phosphocholine)-2,3-O-dihexanoylcyclopentane-1,2, 3-triol. These are the enantiomers of a contrained analogue of dihexanoylphosphatidylcholine in which the glycerol backbone is replaced by all-trans cyclopentane-1,2,3-triol. Evidence is presented to demonstrate that the (-)-enantiomer is a substrate for phospholipase A2 (PLA2) (Crotalus atrox) while the (+)-enantiomer is not. This strict enantiomeric (and positional) specificity was exploited in conjunction with a novel application of DEAE-cellulose column chromatography, to achieve racemic resolution with an excellent yield. The constrained backbone geometry, and the experimentally accessible critical micellar concentration (CMC) of these analogues should render them useful probes for assessing the contribution of substrate conformation and flexibility to the catalytic efficiency of PLA2.

Phase transition properties of aqueous dispersions of homologues of all-trans 2,3-dipalmitoylcyclopentano-1-phosphocholine

In a previous publication, (Singer, M.A., Jain, M.K., Sable, H.Z., Pownall, H.H., Mantulin, W.W., Lister, M.D. and Hancock, A.J. (1983) Biochim. Biophys. Acta, 731, 373-377), we reported the properties of aqueous dispersions of the six diastereo-isomers of cyclopentanoid analogues of dipalmitoylphosphatidylcholine. Two of these isomers displayed unusually high enthalpies of transition, about double that of dipalmitoylphosphatidylcholine. One of the high enthalpy isomers whose configuration is all-trans has now been modified by the insertion of extra methylene residues (n = 3 through 9) between the nitrogen and phosphorus atoms of the headgroup. Vesicles were formed from these lipids and studied by 22Na permeability measurements, differential scanning calorimetry, fluorescence polarization, 31P-NMR, and freeze-fracture electron microscopy. Vesicles composed of lipids with n = 2 or 3 exhibit a sharp transition at 46 degrees C or 49 degrees C, respectively, and a high enthalpy with no detectable sub- or pretransitions. Lipids with n greater than 3 exhibit a main transition between 38 and 43 degrees C with enthalpies less than 10 kcal/mol and after prolonged coding (more than 3 days at 4 degrees C) a broad endotherm at about 20 +/- 3 degrees C with enthalpies greater than 4 kcal/mol. These same dispersions display a permeability peak at 20-25 degrees C and a second increase in 22Na efflux in the temperature range 30-40 degrees C. The results of 31P-NMR measurements suggest that the acyl chains in 2,3-dipalmitoylcyclopentano-1-phosphocholine (n = 2) bilayers have restricted rotation below the main phase transition temperature.

Synthesis of polar head group homologs of all-trans-cyclopentano-phosphatidylcholine, phosphatidyl-N,N-dimethylethanolamine, and phosphatidylethanolamine

The polar head group region of a conformationally restricted analog of phosphatidic acid (diacylglycero-phosphate) has been systematically modified to give analogs of phosphatidylcholine, phosphatidylethanolamine, and phosphatidyl-N,N-dimethylethanolamine. These analogs differ from their natural counterpart in both the backbone region and in the polar head region, respectively, as follows: the diacylglyceryl moiety has been replaced by an all-trans diacylcyclopentane-1,2,3-triol moiety and the phosphorus-nitrogen separation has been increased incrementally from two to nine methylene units. The synthesis of these homologous series involved phosphorylation of (1,3/2)-2,3-dipalmitoylcyclopentane-1,2,3-triol with each of a series of homologous bromoalkylphosphoric acid dichlorides, which were themselves obtained by phosphorus oxychloride treatment of the homologous bromoalkanols. The resulting bromoalkyl esters of 2,3-dipalmitoylcyclopentane-1,2,3-triol-1-phosphoric acid were reacted with trimethylamine, dimethylamine, or ammonia to give the cyclopentano-phosphatidylcholines, cyclopentano-N,N-dimethylethanolamines, and cyclopentano-phosphatidylethanolamine, respectively. All the compounds were obtained as stable microcrystalline solids. The yields of cyclopentano-phosphatidylethanolamines and of cyclopentano-N,N-dimethylethanolamines were reduced by the formation of compounds which analyzed as monoacyl (lyso) derivatives.

Synthesis of cyclopentano-N-methylphosphatidylethanolamines: aminolysis during the use of methylamine

Monomethylamine and N-benzyl-N-methylamine were used as nucleophiles in the amination of the bromoethylester of cyclopentano-phosphatidic acid. The former reagent led to extensive aminolysis and the quantitative formation of N-methylpalmitamide, rather than the desired cyclopentano-phosphatidyl-N-methylethanolamine. However, the method of Shapiro and Rabinsohn (1964. Biochemistry. 3:603-605), in which N-benzyl-N-methylamine was used as a nucleophile, was adapted for a successful synthesis.

Epitaxial crystallization of alkane chain lipids for electron diffraction analysis

Thin microcrystals of a wide variety of polymethylene chain materials, including n-alkanes, linear waxes, glycerides, a detergent, phospholipids and phospholipid analogs based on cyclopentane-1,2,3-triol, are epitaxially grown on naphthalene to give an orientation with long chain axes parallel to the best developed crystal face. These crystals, which represent a different orientation than those grown from solution, facilitate ab initio quantitative crystal structure analysis from electron diffraction intensity data from the projection yielding the most crystallographic information.

The properties of membranes formed from cyclopentanoid analogues of phosphatidylcholine

We have examined the thermal characteristics and barrier properties of vesicles formed from six analogues of 1,2-dipalmitoyl-sn-glycero-3-phosphocholine (DPPC). These analogues differ from DPPC in that the glycerol backbone has been replaced by each of the diastereoisomeric cyclopentane-1,2,3-triols. All of these compounds have main gel to liquid-crystal phase transition temperatures within 5 Kelvin of DPPC and four possess comparable enthalpies and entropies of transition. For two of the analogous, however, the values of the enthalpy and entropy of transition are more than double that of DPPC. The permeability characteristics and organization (as measured by diphenylhexatriene fluorescence depolarization) of vesicles formed from these two compounds suggest that their large transition enthalpy and entropy result from either a reorganization of the polar head group region during the transition or interdigitation of the acyl chains of opposing monolayers.

Synthesis of conformationally restricted acidic lipids. I. Cyclopentanoid analogs of phosphatidylserine

A series of six analogs of phosphatidylserine (PS) was synthesized in which the conformational mobility of the backbone was limited. Each analog was a derivative of one of the three diastereoisomeric cyclopentane-1,2,3-triols, so that the glycerol moiety of the PS was, in effect, replaced by each cyclopentane-1,2,3-triol. Four of the members of the series were vicinal dipalmitates [1,2/3-(1P); 1,2/3-(3P); 1,2,3/0-(1P); 1,3/2-(1P)] while the other two members were "unnatural" in that they contained a 2-phosphate group. The two 2-phosphate derivatives were meso-forms and each of the other four derivatives was a DL-pair. Each PS analog was obtained as a stable microcrystalline precipitate analyzing for the monohydrate of a mixture of mono- and di-sodium salts. The infrared spectra, melting behavior, and chromatographic mobility of each sodium salt mixture resembled those obtained for bovine (glycero-)-phosphatidyl-L-serine; the stereochemical differences in the ring caused only marginal variation in these properties. The optical rotation values of the compounds varied with the stereochemistry of the ring. The all-trans-2-phosphate isomer 8d exhibited a negative rotation value, in contrast to each of the other isomers. The all-trans isomer [1,3/2-(1P)] was shown to undergo diazometholysis with diazomethane to give the dimethyl ester of cyclopentano-phosphatidic acid.

DPN-linked sn-glycerol-3-phosphate dehydrogenase. Cyclopentanoid analogues mimic the active rotameric state of the natural substrate

Five diastereoisomeric cyclopentane-1,2,3-triol monophosphate analogues of sn-glycerol 3-phosphate have been studied as substrates and inhibitors of sn-glycerol-3-phosphate dehydrogenase (EC 1.1.18) of rabbit skeletal muscle. Of the five analogues, only two were substrates, DL-1,2,3/0-1P (analogue I) and DL-1,2/3-1P (analogue II). The rest were weak competitive inhibitors of the enzyme. Initial rate kinetic studies of the substrate-active analogues analyzed by a rapid equilibrium random-order mechanism showed that Ks (I) = 4.6 +/- 2.6 mM; Ks (II) = 2.2 +/- 0.6 mM compared with Ks (DL-glycerol-3-P) = 2.4 +/- 0.9 mM. Correlation of the structures of the five analogues with their activities indicates that the enzyme requires a syn orientation of the carbon-oxygen bonds about C-2 and C-3 for activity, which is optimized by an anti relationship between the hydroxyl groups at C-1 and C-2 of the cyclopentanetriol monophosphates. These results are used to deduce the conformation of sn-glycerol-3-P as it is bound in the active site of the enzyme.

Analogs of natural lipids. VII. Synthesis of cyclopentanoid analogs of phosphatidylcholine

A series of six analogs of phosphatidylcholine (lecithin) has been synthesized, in which the conformational mobility of the backbone is restricted. The analogs are derivatives of the three diastereoisomeric cyclopentane-1,2,3-triols and were obtained by triisopropylbenzenesulfonyl chloride-mediated condensation of isomers of dipalmitoylcyclopentanetriol phosphate (cyclopentano-phosphatidic acid) with choline tosylate. The cyclopentano-lecithins obtained include the following: 1,2,3/0-(1P); 1,2,3/0-(2P); 1,2/3-(1P); 1,2/3-(3P); 1,3/2-(1P); 1,3/2-(2P). The two -2P derivatives are mesoforms while the other four derivatives are DL-pairs. Each lecithin analog has been obtained as a stable microcrystalline solid. Elemental analysis indicates that the compounds are hydrated; the data were consistent with the presence of either one, or in two instances, of one-half molecule of water of hydration. The infrared spectra, melting behavior, and chromatographic mobility of each of the analogs resembled those obtained for dipalmitoyllecithin, but the influence upon physical properties of stereochemical differences among the analogs was observed throughout the series.

Synthesis of all-cis-1,3-diacylcyclopentane-1,2,3-triol-2-phosphate via acyl group migration in a cyclic diglyceride analog

The acid-catalyzed isomerization of the diglyceride analog (1,2,3/0)-1,2-dipalmitoylcyclopentane-1,2,3-triol has been used to generate syn-syn-1,3-diacyl-cyclopentane-1,2,3-triol, a required intermediate in the synthesis of a symmetrical all-cis-1,2,3/0-2P cyclopentanoid phosphatidic acid analog. The all-cis cyclo-phosphatidic acid analog has therefore been obtained in the free acid form and as the diphenyl ester, dimethyl ester, and dipotassium salt derivatives. The compounds have been characterized by microanalysis and spectroscopic methods. The 1,2,3/0-2P analog is now available for comparative studies with the corresponding all-trans cyclophosphatidic acid (1,3/2-2P).

Glycerol conformation and the crystal structure of lipids. I. An electron diffraction study of tripalmitin and conformationally fixed analogs

Transmission electron diffraction is used as a qualitative analytical probe of polymethylene chain packing in three conformationally-restricted analogs of tripalmitin derived from configurational isomers of cyclopentane-1,2,3-triol. The analysis demonstrates that the all trans "tuning-fork" conformation seen in X-ray crystal structure analyses on homologous compounds is also found in microcrystals, in contrast to a proposal by Fringeli et al. (Z. Naturforsch. 27b, 780 [1972]) that an all cis conformation of the triglyceride exists in solvent-grown microcrystals and in multilayers. The presence of mixed polymorphs is also shown for bulk samples previously examined by X-ray powder diffraction techniques by other workers.

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.

Analogs of natural lipids. II. Polymorphic behavior of the tris-homoacyl derivatives of cyclopentane-1,2,3-triols

The polymorphic behavior of three series of tris-homoacyl (C14:0, C16:0 and C18:0) cyclopentane-1,2,3-triol analogs of the natural saturated triglycerides has been studied using differential thermal analysis, Fourier transform infrared spectroscopy, and X-ray diffraction. It was found that the triglyceride analogs derived from the 1,2,3/0 and 1,2/3 cyclopentanetriols exhibit different polymorphic behavior than that of the natural triglycerides. The analogs derived from 1,3/2 cyclopentanetriol, however, were found to parallel the polymorphic behavior of the natural triglycerides quite closely. This polymorphic behavior is discussed in terms of the different configurations which the chains assume in each of the triglyceride analogs.

Analogs of natural lipids. IV. Synthesis and properties of cyclopentanoid analogs of phosphatidic acid

A new series of phosphatidic acid analogs has been synthesized in which the glycerol moiety of diacylglycerophosphoric acid is replaced by each of the three isomeric cyclopentane-1,2,3-triols (1,3/2, DL-1,2/3, and 1,2,3/0). Of the seven possible configurational and positional phosphatidic acid analogs of this series, five isomers have been obtained and characterized by spectroscopic methods and microanalysis. Four of the five isomers are 1-(or 3-)phosphoryl derivatives, while the fifth is a 2-phosphate. The analogs were prepared in configurationally pure form by unequivocal synthetic procedures involving selectively blocked intermediates: acyl migration was avoided by the use of mild deblocking procedures. The anhydrous lipid products, all of which are dipalmitoyl esters, are solids indefinitely stable at room temperature in the free acid or potassium salt form; they have chromographic mobility and melting points similar to dipalmitoyl glycerophosphoric acid the dipotassium salts bind water of hydration tenaciously, remaining hydrated after drying in vacuo at 100 degrees C. NMR spectra of dimethyl esters of some of the analogs show nonequivalence of the two methyl groups, consistent with the diastereotopic nature of those groups. In addition to their intrinsic interest as conformationally restricted acidic lipids, the analogs are now available as starting materials for the synthesis of the more complex acidic and amphoteric lipids required for our exploitation of these cyclopentanoid analogs as unique probes for the study of lipid-lipid and protein-lipid interactions.

Analogs of natural lipids. III. Nonequivalence of methyl groups in methylated phospholipids

The dimethyl esters of a series of diastereoisomeric cyclopentanoid analogs of phosphatidic acid (A.J. Hancock, M.H. Stokes, and H.Z. Sable. 1977. J. Lipid Res. 18: 81-92.) have been studied by proton NMR spectroscopy at 60, 100, and 300 MHz. The signals of the P-O-CH3 protons near delta 3.80 show the expected doubling due to the 31P-1H coupling. In addition, the spectra of three of the isomers show additional multiplicity the line separation (in Hz) being proportional to the frequency of the spectrometer. This multiplicity is due to the nonequivalence of the two methoxyl groups on phosphorus, predictable from their diastereotopic nature. The same explanation is proposed for similar observations on other compounds made by other authors. The practical utility of symmetry considerations in lipid chemistry is discussed briefly.

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.

Analogs of natural lipids. I. Synthesis and properties of tris-homoacyl derivatives of cyclopentane- 1,2,3-triols

A new series of analogs of triglycerides has been synthesized, in which the glycerol moiety is replaced by each of the three isomeric cyclopentanetriols. For each of the isomeric cyclopentane-1,2,3-triols (1,2,3/0; DL-1,2/3; and 1,3/2), the tris-homoacyl derivatives of octanoic, decanoic, lauric, myristic, palmitic, stearic, and dihydrosterculic acids were prepared by treatment of the respective triols with the appropriate acyl chloride in pyridine. The dihydrosterculates were prepared by fusing the triols with a mixture of the acyl anhydride and the corresponding potassium salt. It is proposed that because of restricted rotation of the carbon-carbon bonds the cyclopentanoid compounds are analogs of specific rotamers of triglycerides. Infrared spectra (KBr discs) obtained at room temperature show differences in crystal structure from series to series. A band near 720 cm-minus 1 (CH2 rock) is doubled in the 1,2,3/0 and 1,2/3 series and is single in the 1,3/2 series and the triglycerides. In each spectrum with a doublet at 720 cm-minus 1, a band near 1470 cm-minus 1 (CH2 bend) is doubled also. A strong band at 890 cm-minus 1 present in the triglyceride spectra is weak or missing from the spectra of the analogs. A band at 1418 cm-minus 1 (bending of CH2 adjacent to C equal to 0) present in the triglyceride spectra is demonstrable only in the 1,2,3/0 derivatives in comparison with the other three series. In all series the dihydrosterculates show a decrease in apparent polarity, relative to the stearates, significantly greater than expected from the introduction of an additional carbon atom. The potential utility of the analogs as probes of the effects of conformation on the physical properties and enzymatic susceptibility of glycerides is discussed.

Synthesis of sulfate esters of phosphatidylglycerol (diphytanyl ether analog)

Synthesis of 1-sn-phosphatidyl-3'-sn-glycero-1'-sulfate (phosphatidylglycero-1-sulfate) was achieved by monosulfation of 1-sn-phosphatidyl-3'-sn-glycerol (diphytanyl ether analog) with an equimolar amount of SO(3)-pyridine complex at room temperature; with excess sulfation reagent at 60 degrees C, the 1',2'-disulfate ester was obtained. The phosphatidyl-glycero-2-sulfate isomer was synthesized by an unambiguous route starting from the bacterial 2,3-di-O-phytanyl-sn-glycerol. The synthetic phosphatidylglycerosulfates were characterized by analytical, chromatographic, optical rotatory, and spectral (infrared and NMR) data and compared with the phosphatidylglycerosulfate isolated from Halobacterium cutirubrum.