Crystal structures and thermal analyses of alkyl 2-deoxy-α-d-arabino-hexopyranosides

The crystal structures of alkyl 2-deoxy-α-d-arabino-hexopyranosides, with the alkyl chain lengths from C₈ to C₁₈, are established by the single crystal X-ray structural determination. The even-alkyl chain length derivatives crystallized orthorhombic, with space group P2₁2₁2₁, whereas the odd-alkyl chain length derivatives crystallized monoclinic, with space group P2₁. The sugar moieties retained a ⁴C₁ chair conformation and the conformation of the alkyl chains was all-trans. The molecules formed a bilayer structure, in which alkyl chains were interdigitated. The hydrogen bonds, originating from the sugar moieties, were observed in adjacent layers and also within the same layer, resulting in the formation of infinite chains. The alkyl chains arranged parallel to each other and formed planar structures. The thermal properties of the alkyl 2-deoxy glucosides were analyzed further. It was observed that none of the derivatives exhibited mesomorphism. This study establishes that the absence of the hydroxyl group at C-2 of the sugar moiety results in a non-mesogenic nature of the alkyl 2-deoxy-α-d-glycosides, as opposed to the profound mesogenic nature of the normal alkyl glycosides.     

Effects of alkyl chain length of gallates on their antifungal property and potency as an environmentally benign preservative against wood-decay fungi

This study investigated effects of alkyl chain length of eight aliphatic gallates from C₁ to C₁₈ on their antifungal activity and free radical scavenging activity, which are two important indicators in developing wood preservatives. Results from the agar plate test showed that the antifungal activity against wood-rot fungi of gallates was related to alkyl chain length. It increased with increasing alkyl chain length, reaching a maximum at octyl gallate (C₈), and then decreased as chain length increased. Octyl gallate also exhibited potential antifungal activity against soft-rot Chaetomium globosum and copper-tolerant fungi Wolfiporia extensa and Poria placenta, which are difficult to combat with current copper-based wood preservatives. Octyl gallate is a potent antifungal agent with excellent antifungal activity over a broad antifungal spectrum. All of the gallates tested, regardless of their alkyl chain length, showed strong scavenging activity on the DPPH radical with EC₅₀ values around 1–5 μg ml^?1, indicating that the alkyl chain length was not directly related to this activity. Results from the soil block test showed that excellent antioxidants such as propyl gallate (C₃) and octyl gallate impart wood with good resistance against wood-decay fungi. This suggests that antioxidants have potential as environmentally benign wood preservatives.     

Role of hydroxyl group on the mesomorphism of alkyl glycosides: synthesis and thermal behavior of alkyl 6-deoxy-β-d-glucopyranosides

A homologous series of alkyl 6-deoxy-β-d-glucopyranoside amphiphiles was prepared, in an effort to identify the role of hydroxyl group in the mesomorphic behavior of alkyl glycosides. Synthesis was performed by a chlorination of the sugar moiety in alkyl β-d-glucopyranosides with methylsulfonyl chloride in DMF, followed by a metal mediated dehalogenation to secure alkyl 6-deoxy-β-d-glucopyranosides, wherein the alkyl chain length varied from C₉ to C₁₆. The mesomorphic behavior of these 6-deoxy alkyl glycosides was assessed using polarizing optical microscopy, differential scanning calorimetry and X-ray diffraction method. Whereas the lower homologues exhibited a monotropic SmA phase till sub-ambient temperatures, the higher homologues formed a plastic phase. A partial interdigitized bilayer structure of SmA phase is inferred from experimental d-spacing and computationally derived lengths of the molecules. The results were compared with those of normal alkyl glucopyranosides, retained with hydroxyl groups at C-2–C-6 carbons, and alkyl 2-deoxy-glucopyranosides, devoid of a hydroxyl group at C-2 and the comparison showed important differences in the mesomorphic behavior.     

Synthesis,antimicrobial evaluation and molecular modeling of 5-hydroxyisoquinolinium salt series; the effect of the hydroxyl moiety

In the present paper, we describe the synthesis of a new group of 5-hydroxyisoquinolinium salts with different lengths of alkyl side-chain (C₁₀–C₁₈), and their chromatographic analysis and biological assay for in vitro activity against bacterial and fungal strains. We compare the lipophilicity and efficacy of hydroxylated isoquinolinium salts with the previously published (non-hydroxylated) isoquinolinium salts from the point of view of antibacterial and antifungal versatility and cytotoxic safety. Compound 11 (C₁₈) had to be excluded from the testing due to its low solubility. Compounds 9 and 10 (C₁₄, C₁₆) showed only moderate efficacy against G+ bacteria, notably with excellent potency against Staphyloccocus aureus, but no effect against G− bacteria. In contrast, non-hydroxylated isoquinolinium salts showed excellent antimicrobial efficacy within the whole series, particularly 14 (C₁₄) against G+ strains and 15 (C₁₆) against fungi. The electronic properties and desolvation energies of 5-hydroxyisoquinolinium and isoquinolinium salts were studied by quantum-chemistry calculations employing B3LYP/6-311++G(d,p) method and an implicit water-solvent simulation model (SCRF). Despite the positive mesomeric effect of the hydroxyl moiety reducing the electron density of the quaternary nitrogen, it is probably the higher lipophilicity and lower desolvation energy of isoquinolinium salts, which is responsible for enhanced antimicrobial versatility and efficacy.     

Inhibitory effect of amines on polar filament extrusion byPlistophora anguillarum spores

In in vitro tests, amines were screened for the inhibition of polar filament extrusion by spores ofPlistophora anguillarum, a microsporidian parasite of the eel. Primary amines having C₈ ⁻ C₁₈ alkyl chains were effective, irrespective of the anions bound. Secondary amines having a branched C₈ chain and tertiary amines having C₁₄−C₁₈ chains were also effective. Asymmetry in side chains seemed to be required for inhibitory action. Quaternary ammonium salts having C₁₂−C₁₆ alkyl chains and some germicides or disinfectants such as cetyl pyridinium chloride and benzethonium chloride were also effective. Diamines and amides were ineffective regardless of the length of their alkyl chins. In in vivo tests, eel larvae-fed for 4 days with a commercial feed supplemented with 5×10⁸ cells of spores and 4g of laurylamine aspartate/100 g feed, and thereafter with the usual commercial feed for 26 days—were not infected.     

Asymmetric binuclear titanocenes linked by alkyl benzyl ethers: Synthesis, characterization and use as catalysts for ethylene polymerization

A series of novel asymmetric binuclear titanocenes linked with alkyl benzyl ethers p-[(C₅H₅TiCl₂)C₅H₄CH₂]C₆H₄O(CH₂)_n[C₅H₄(TiCl₂C₅H₅)] (n = 2-5) (13-16) have been synthesized by treating p-(LiC₅H₄CH₂)C₆H₄O(CH₂)_n(C₅H₄Li) (n = 2-5) (9-12) with C₅H₅TiCl₃. The new complexes have been characterized by elemental analysis and NMR spectra. Their catalytic activity for ethylene polymerization was investigated in the presence of aluminoxane (MAO). The results show that 13-16 are efficient catalysts for producing polyethylene (PE) with a broad molecular weight distribution (MWD). Their catalytic activity is highly dependent on the length of the alkyl chain and the polymerization conditions. A longer alkyl chain increases the catalytic activity, whereas the molecular weight of the produced polyethylene decreases.     

Dielectric properties of yeast cells: Effect of some ionic detergents on the plasma membranes

Summary Dielectric measurements were made on suspensions of yeast cells treated with two homologous series of sodium alkyl (C₈, C₁₀, C₁₂, C₁₄) sulfonates and alkyl (C₈, C₁₀, C₁₂, C₁₄, C₁₆, C₁₈) benzyl dimethyl ammonium chlorides over a frequency range of 10 kHz to 100 MHz. Dielectric dispersions observed for the suspensions of intact yeast cells are found to be reduced by treatment with these detergents, the reduction being accompanied by a decrease in packed volume of the cells and by a leakage of intracellular compounds. The reduction of dielectric dispersions is considered to be caused by a decrease in volume of the cells in suspensions and an increase in conductivity of the cell membranes. An effect of the alkyl chain length of the detergents on the reduction of dielectric dispersions is also examined for these ionic detergents. The reducing effect shows the maximum at the alkyl chain, C₁₄ for sodium alkyl sulfonates and at C₁₆ for alkyl benzyl dimethyl ammonium chlorides. These results are consistent with hemolysis and bactericidal activity.     

Effects of cationic surfactants on settling properties of sewage activated sludge

Various alkyltrimethylammonium bromides ATABs, R = C₁ to C₆ were added to a mixed liquor of sewage activated sludge and the effects on settling properties were investigated. The 30-min settled sludge volume decreased from 28% to 24, 20, 17, and 15% on addition of 1 mM C₁₀, C₁₂, C₁₄, and C₁₆ compounds to mixed liquor (sludge concentration, 1.28 g/l), respectively. With increasing alkyl chain length, the amounts of ATABs adsorbed by the sludge, and metal ions released from the sludge, increased. However, a quantitative correlation was not observed between the two. In addition, the adsorption of ATABs resulted in a small decrease in sludge wet weight. However, such a change was not observed on addition of ATABs bearing short alkyl chains. A good correlation was observed between the amounts of ATABs adsorbed and their organic solvent/water partition coefficients. These results indicated that the effectiveness of ATABs as sludge conditioners depends on their hydrophobicity.     

Use of sodium dodecyl sulphate for stimulation of biodegradation of n-alkanes without residual contamination by the surfactant

The capacity of a range of aliphatic alkanes (C₆–C₁₆), intermediates of n-decane oxidation and sodium dodecyl sulphate (SDS) to induce decane-mineralization activity in the cells of Pseudomonas C12B was compared with that for n-decane. The comparison on quantitative basis had two serious limitations: low solubility of tested inducers in aqueous solutions and their toxicity to bacterial cells. Carbon chain length and the presence of hydroxyl group were the important factors for induction activity. However, presence of hydroxyl groups at both ends of alkyl chain prevented the induction of decane-mineralization activity. Good induction activity by SDS was caused either by the presence of free end of alkyl chain, or by bacterial hydrolysis of sulphate group to yield alcohol, which in turn served as true inducer. The presence of SDS in the culture medium with n-decane as main source of carbon and energy accelerated the growth of Pseudomonas C12B. SDS disappeared from the culture medium in early stages of cultivation suggesting preferential degradation by the bacterium, while the consumption of n-decane was accelerated. This may be associated with the capacity of SDS to induce decane-mineralization system in Pseudomonas C12B and/or with the ability of SDS to stimulate the surface attachment of competent bacteria resulting in the close proximity of the cells with alkane droplets, and thus, enhanced breakdown of the hydrocarbon pollutant.     

Primary biodegradation of a series of alkyl sulfosuccinates by mixed bacterial culture

A mixed bacterial culture capable of primary biodegradation of sodium alkyl sulfosuccinates R¹-OOC−CH(SO₃Na)−CH₂−COO−R² was obtained from soil microorganisms by enrichment cultivation and adaptation in the presence of mono-n-dodecyl sulfosuccinate. Gram-negative psychrophilic bacteria with proteolytic, lipolytic and ammonifying activities were prevalent in the culture. The process of primary biodegradation of alkyl sulfosuccinates can be described by firstorder reaction kinetics. The rate constants for linear esters were ascending in the order C₄<C₅<C₆ (45 μmol/min per g cell protein) and further descending with increasing length of the carbon chain C₆>C₈>=C₁₃. Substitution of cyclohexyl for n-hexyl group resulted in fourfold decrease in biodegradation rate. Terminal branching of alkyl chain does not affect the rate of primary biodegradation.     

The Toxoplasma gondii type-II NADH dehydrogenase TgNDH2-I is inhibited by 1-hydroxy-2-alkyl-4(1H)quinolones

The apicomplexan parasite Toxoplasma gondii does not possess complex I of the mitochondrial respiratory chain, but has two genes encoding rotenone-insensitive, non-proton pumping type-II NADH dehydrogenases (NDH2s). The absence of such “alternative” NADH dehydrogenases in the human host defines these enzymes as potential drug targets. TgNDH2-I and TgNDH2-II are constitutively expressed in tachyzoites and bradyzoites and are localized to the mitochondrion as shown by epitope tagging. Functional expression of TgNDH2-I in the yeast Yarrowia lipolytica as an internal enzyme, with the active site facing the mitochondrial matrix, permitted growth in the presence of the complex I inhibitor DQA. Bisubstrate kinetics of TgNDH2-I measured within Y. lipolytica mitochondrial membrane preparations were in accordance with a ping-pong mechanism. Using inhibition kinetics we demonstrate here that 1-hydroxy-2-alkyl-4(1)quinolones with long alkyl chains of C₁₂ (HDQ) and C₁₄ are high affinity inhibitors for TgNDH2-I, while compounds with shorter side chains (C₅ and C₆) displayed significantly higher IC₅₀ values. The efficiency of the various quinolone derivatives to inhibit TgNDH2-I enzyme activity mirrors their inhibitory potency in vivo, suggesting that a long acyl site chain is critical for the inhibitory potential of these compounds.     

Bile salts of vertebrates: structural variation and possible evolutionary significance

Biliary bile salt composition of 677 vertebrate species (103 fish, 130 reptiles, 271 birds, 173 mammals) was determined. Bile salts were of three types: C₂₇ bile alcohols, C₂₇ bile acids, or C₂₄ bile acids, with default hydroxylation at C-3 and C-7. C₂₇ bile alcohols dominated in early evolving fish and amphibians; C₂₇ bile acids, in reptiles and early evolving birds. C₂₄ bile acids were present in all vertebrate classes, often with C₂₇ alcohols or with C₂₇ acids, indicating two evolutionary pathways from C₂₇ bile alcohols to C₂₄ bile acids: a) a ‘direct’ pathway and b) an ‘indirect’ pathway with C₂₇ bile acids as intermediates. Hydroxylation at C-12 occurred in all orders and at C-16 in snakes and birds. Minor hydroxylation sites were C-1, C-2, C-5, C-6, and C-15. Side chain hydroxylation in C₂₇ bile salts occurred at C-22, C-24, C-25, and C-26, and in C₂₄ bile acids, at C-23 (snakes, birds, and pinnipeds). Unexpected was the presence of C₂₇ bile alcohols in four early evolving mammals. Bile salt composition showed significant variation between orders but not between families, genera, or species. Bile salt composition is a biochemical trait providing clues to evolutionary relationships, complementing anatomical and genetic analyses.     

Insights into the Alkyl Peroxide Reduction Pathway of Xanthomonas campestris Bacterioferritin Comigratory Protein from the Trapped Intermediate-Ligand Complex Structures

Considerable insights into the oxidoreduction activity of the Xanthomonas campestris bacterioferritin comigratory protein (XcBCP) have been obtained from trapped intermediate/ligand complex structures determined by X-ray crystallography. Multiple sequence alignment and enzyme assay indicate that XcBCP belongs to a subfamily of atypical 2-Cys peroxiredoxins (Prxs), containing a strictly conserved peroxidatic cysteine (C_P48) and an unconserved resolving cysteine (C_R84). Crystals at different states, i.e. Free_SH state, Intra_SS state, and Inter_SS state, were obtained by screening the XcBCP proteins from a double C48S/C84S mutant, a wild type, and a C48A mutant, respectively. A formate or an alkyl analog with two water molecules that mimic an alkyl peroxide substrate was found close to the active site of the Free_SH or Inter_SS state, respectively. Their global structures were found to contain a novel substrate-binding pocket capable of accommodating an alkyl chain of no less than 16 carbons. In addition, in the Intra_SS or Inter_SS state, substantial local unfolding or complete unfolding of the C_R-helix was detected, with the C_P-helix remaining essentially unchanged. This is in contrast to the earlier observation that the C_P-helix exhibits local unfolding during disulfide bond formation in typical 2-Cys Prxs. These rich experimental data have enabled us to propose a pathway by which XcBCP carries out its oxidoreduction activity through the alternate opening and closing of the substrate entry channel and the disulfide-bond pocket.     

Alkyl esters from pinus radiata foliage epicuticular wax

Wax esters from the epicuticular wax of juvenile and mature-tree Pinus radiata foliage have been shown by capillary column GC-MS to consist mainly of short chain (C₆–C₁₂)alkanols esterified with long chain acids (C₂₄–C₃₂) and long chain alkanols (C₂₄–C₃₂) esterified with short chain acids (C₆-C₁₄) in a non-random manner. Mature-tree foliage wax esters also contained nonacosan-10-ol esterified with dodecanoic and tetradecanoic acids.     

Enzymatic synthesis of poly(ε-caprolactone) in monocationic and dicationic ionic liquids

Enzymatic polymerization can offer metal-free routes to polymer materials that could be used in biomedical applications. To take advantage of the unique properties of ionic liquids (ILs) for enzyme stability, monocationic ionic liquid (MIL) and dicationic ionic liquid (DIL) were used to promote the ring-opening polymerization of ε-caprolactone (ε-CL) using Candida antarctica lipase B as catalyst. Considering the molecular weight (M _n ) and reaction yield of the resulting polymer (PCL), high density and viscosity of ILs would be good, especially in the case of DIL. With the same total alkyl chain length, the density and viscosity of [C₄(C₆Im)₂][PF₆]₂ were higher than that of [C₁₂MIm][PF₆]. Using a lipase/CL/ILs ratio of 1:20:20 (by wt) for 48 h at 90 °C, the highest M _n and reaction yield of PCL were 26,200 g/mol and 62 % with [C₄(C₆Im)₂][PF₆]₂, while the M _n and reaction yield of PCL obtained in [C₁₂MIm][PF₆] were 11,700 g/mol and 37 %.     

Nonallergenic urushiol derivatives inhibit the oxidation of unilamellar vesicles and of rat plasma induced by various radical generators

Urushiols consist of an o-dihydroxybenzene (catechol) structure and an alkyl chain of 15 or 17 carbons in the 3-position of a benzene ring and are allergens found in the family Anacardiaceae. We synthesized various veratrole (1,2-dimethoxybenzene)-type and catechol-type urushiol derivatives that contained alkyl chains of various carbon atom lengths, including –H, –C₁H₃, –C₅H₁₁, –C₁₀H₂₁, –C₁₅H₃₁, and –C₂₀H₄₁, and investigated their contact hypersensitivities and antioxidative activities. 3-Decylcatechol and 3-pentadecylcatechol displayed contact hypersensitivity, but the other compounds did not induce an allergic reaction, when the ears of rats were sensitized by treatment with the compounds every day for 20 days. Catechol-type urushiol derivatives (CTUDs) exerted very high radical-scavenging activity on the 1,1-diphenyl-2-picrylhydrazyl radical and inhibited lipid peroxidation in a methyl linoleate solution induced by 2,2′-azobis(2,4-dimethylvaleronitrile) (AMVN). However, veratrole-type urushiol derivatives did not scavenge or inhibit lipid peroxidation. CTUDs also acted as effective inhibitors of lipid peroxidation of the egg yolk phosphatidylcholine large unilamellar vesicle (PC LUV) liposome system induced by various radical generators such as AMVN, 2,2′-azobis(2-amidino-propane) dihydrochloride, and copper ions, although their efficiencies differed slightly. In addition, CTUDs suppressed formation of cholesteryl ester hydroperoxides in rat blood plasma induced with copper ions. CTUDs containing more than five carbon atoms in the alkyl chain showed excellent lipophilicity in a n-octanol/water partition experiment. These compounds also exhibited high affinities to the liposome membrane using the ultrafiltration method of the PC LUV liposome system. Therefore, CTUDs seem to act as efficient antioxidative compounds against membranous lipid peroxidation owing to their localization in the phospholipid bilayer. These results suggest that nonallergenic CTUDs act as antioxidants to protect against oxidative damage of cellular and subcellular membranes.     

Complete degradation of xenobiotic surfactants by consortia of aerobic microorganisms

Linear alkylbenzene sulphonates are primarily attacked via a hydroxylation of the alkyl chain from the methyl group followed by β-oxidation. The alkyl chain is metabolized by pure cultures to give sulphophenyl carboxylates which accumulate in the medium. In mixed culture, other microorganisms are capable of degrading sulphophenyl carboxylates. Formation of ethylene glycol monosulphates as major products of alkyl ethoxy sulphates demonstrates that the ether bonds are cleaved. The bacteria involved in growing on the alkyl chain are unable to utilize the hydrophilic moiety. This hydrophilic moiety, in turn, is degraded by other microorganisms. The degradation of alkylphenol ethoxylates and highly branched alcohol ethoxylates proceeds by shortening the polyoxyethylene chain leaving the hydrophobic part of the molecule. The biodegradation of linear alcohol ethoxylates and ethoxylated fatty amines is initiated by a central cleavage or ω-oxidation. Subsequent oxidation of the alkyl chains results in the production of polyethylene glycols and secondary ethoxylated amines. Both polar moieties are metabolized by other microorganisms. Degradation of alkyltrimethylammonium salts and alkylamines is initiated by a cleavage of the C _alkyl -N bond. The central fission leads to the formation of alkanals which are readily converted by β-oxidation. The alkyl chain-utilizing bacteria are not able to degrade the methylamines. The methylamines, in turn, are subject to biodegradation by methylotrophs. The limited metabolic capacities of pure cultures of microorganisms utilizing surfactants point to the requirement of consortia to degrade surfactants completely. Complete degradation of surfactants is accomplished by mixed cultures of microorganisms constructed on the basis of synergistic and commensalistic relationships. However, degradation of a surfactant by one member of a commensalistic consortium may lead to the production of toxic or non-toxic metabolites. Waste water treatment without the build up of such metabolites can be achieved in plants operated with sludge retention times that are suitable for maintaining all microorganisms of the consortium. In contrast, in natural ecosystems the introduction of a surfactant may result in a transient formation of a metabolite.     

A comparison of the effects of prenatal exposure of CD‐1 mice to three imidazolium‐based ionic liquids

BACKGROUND: Ionic liquids (ILs; salts with melting points below 100°C) exhibit wide liquid ranges, non‐flammability, and thermal stability among other properties. These unique salts are best known as “green” alternatives to traditional volatile organic solvents, which are utilized in both academia and industry. Our current study compares the developmental toxicity potential of three representative ionic liquids, with various chain lengths: 1‐ethyl‐3‐methylimidazolium chloride ([C₂mim]Cl), 1‐butyl‐3‐methylimidazolium chloride ([C₄mim]Cl), and 1‐decyl‐3methylimidazolium chloride ([C₁₀mim]Cl). METHODS: From gestation days (GD) 6‐16, mated CD‐1 mice were orally dosed with one of the following: 1,000, 2,000, or 3,000 mg/kg/day [C₂mim]Cl; 113, 169, or 225 mg/kg/day [C₄mim]Cl; 50, 75, or 100 mg/kg/day [C₁₀mim]Cl; or the vehicle only. Dams were sacrificed on GD 17, and their litters were examined for adverse effects. RESULTS: Fetal weight was significantly decreased in the two highest dosage groups exposed to [C₄mim]Cl and [C₁₀mim]Cl in comparison with their controls, but the [C₂mim]Cl treated groups were not affected. An apparent teratogenic effect was associated with both [C₄mim]Cl and [C₁₀mim]Cl, as the offspring exhibited certain uncommon morphological defects. However, the incidences of malformations were low and no correlation between incidence and dosage could be made. No morphological defects were observed in any of the [C₂mim]Cl‐treated groups, despite maternal morbidity at the highest dosage level. CONCLUSIONS: This study indicates that [C₄mim]Cl and [C₁₀mim]Cl may have adverse effects on development at high maternal exposures and strongly supports the supposition that the toxicity of imidazolium‐based ILs is influenced by alkyl chain length. Birth Defects Res (Part B) 89:233–238, 2010. © 2010 Wiley‐Liss, Inc.     

Rigidized 1-aryl sulfonyl tryptamines: synthesis and pharmacological evaluation as 5-HT6 receptor ligands

A series of N₁-arylsulfonyl-3-(pyrrolidin-3-yl)-1H-indole and N₁-arylsulfonyl-3-(4-chloro-2,5-dihydro-1H-pyrrol-3-yl)-1H-indole derivatives (tryptamine derivatives with rigidized side chain) have been prepared and tested for their binding affinity to 5-HT₆ receptor. Several compounds displayed potent binding affinity for the 5-HT₆ receptor when tested in in vitro binding assay. The primary SAR indicates that rigidification of dimethylamino alkyl chain at C₃ of indole carbon maintains the binding affinity to 5-HT₆R. The lead compound N₁-benzenesulfonyl-3-(4-chloro-1-methyl-2,5-dihydro-1H-pyrrol-3-yl)-1H-indole, 10a (K_b = 0.1 nM) has shown excellent in vitro affinity and was active in animal models of cognition like NORT and water maze.     

Formation of complex ether lipids from 1-O-alkylglycerols in cell suspension cultures of rape

Photomixotrophic cell suspension cultures of rape, Brassica napus, were incubated with rac-1-O-[1′-¹⁴C]hexadecylglycerol. Radioactivity was incorporated predominantly into choline glycerophospholipids. Prolonged incubation led also to considerable proportions of labeled ethanolamine glycerophospholipids. In addition to these ionic lipids,isomeric hexadecylacylglycerols as well as hexadecyldiacylglycerols were formed. About a third of the hexadecylglycerol supplied as substrate was cleaved within 48 h incubation. The palmitic acid formed by oxidative cleavage of the substrate was incorporated predominantly into choline glycerophospholipids, ethanolamine glycerophospholipids, and triacylglycerols. Incubation of an equimolar mixture of homologous saturated rac-1-O-[1′¹⁴C]alkylglycerols (C₁₄, C₁₆, C₁₈, C₂₀) with rape cells showed that alkylglycerols with alkyl moieties having 16 and 18 carbon atoms were incorporated preferentially. Incubation of labeled hexadecyglycerol with a homogenate of rape cells led also predominantly to choline glycerophospholipids; highest yields were obtained at pH 7. Neither the 1-O-alkyl moieties in choline glycerophospholipis nor those in ethanolamine glycerophospholipids were desaturated to 1-O-alk-1′-enylmoieties. The results of these experiments led to the following conclusions: (1) The acylation of 1-O-alkylglycerols to isomeric alkylacylglycerols is catalyzed by two acyltransferases differing in their specificity with regard to the chain length of the alkyl moiety in the substrate. (2) CDP-Choline: diacylglycerol cholinephosphotransferase and CDP-ethanolamine: diacylglycerol ethanolaminephosphotransferase are two enzymes differing in various respects. Cholinephosphotransferase exhibits a much higher affinity for 1-O-alkyl-2-O-acylglycerols than ethanolaminephosphotransferase. The two enzymes show marked differences with regard to their specificity for 1-O-alkyl-2-O-acylglycerols differing in the chain lengths of their alkyl moieties.