FAB MS/MS for phosphatidylinostitol,-glycerol,-ethanolamine and other complex phospholipids

Fast atom bombardment (FAB) of phosphatidylinositol, phosphatidylethanolamine, cardiolipin, phosphatidic acid and phosphatidylglycerol produces a limited number of very informative negative ions. Especially significant is the formation of (M−H)⁻ ions and ions that correspond to the carboxylate portions of these molecules. FAB desorption in combination with collisional activation allows for characterization of fragmentation and determination of structural features. Collisional activation of the carboxylate anion from complex lipids is especially informative. Structural characterization of the fatty acids can be achieved as the released saturated carboxylate anions undergo highly specific charge remote fragmentations that are entirely consistent with the chemistry of carboxylate anions desorbed from free fatty acids. This permits both identification of the modification and assignment of its location on the acid chain. FAB-desorbed alkyl acetyl glycerophosphocholines (platelet-activating factor) do not produce (M−H)⁻ ions. However, significant high mass ions are formed, and these can be collisionally activated for structural characterization.     

Fast atom bombardment and tandem mass spectrometry for determing iso- and anteiso-fatty acids

Branched fatty acids can be distinguished from isomeric straight chain fatty acids by collisionally activating the (M-H)⁻ ions desorbed by using fast atom bombardment (FAB) mass spectrometry (MS). In particular, an acid with iso- fatty branching can be readily distinguished from one containing anteiso- branching; the latter undergoes loss of the elements of CH₄ and C₂H₆ but not C₃H₈. These decompositions are another example of remote charge site fragmentation. Mixtures of homologs and isomers can be investigated by using the combination of FAB and tandem mass spectrometry (MS-MS).     

Surface and aqueous properties of anionic gemini surfactants having dialkyl amide,carboxyl, and carboxylate groups

A systematic study of the equilibrium surface properties (in water and in the presence of 10⁻² M NaCl) of a novel series of anionic gemini surfactants, (CH₂)₂[N(COC_nH_2n+1)CH(COOH)CH₂COOH]·2NaOH (GA), where (n+1)=8, 10, 12, 14, and 16, was investigated. The responses of humans to closed patch tests with (CH₂)₂[N(COC₁₁H₂₃)CH(COOH)−CH₂COOH]₂·2NaOH (GA-12) were also investigated. Premicellar self-aggregation (both in water and 10⁻² M NaCl) occurred when the N-acyl group contained more than 14 carbon atoms, since the critical micelle concentration (CMC) values decreased and the pC₂₀ values increased as (n+1) increased for (n+1) ≤14; the CMC values increased and the pC ₂₀ values decreased as (n+1) increased for (n+1)>14, both in water and in 10⁻² M NaCl. The absence of a break in the specific conductance-surfactant molar concentration plots for the GA homologs indicates protonation of the carboxylate group and strong Na⁺ release during micellization. This is a structural characteristic of the anionic geminis having N-dialkylamide and carboxylate groups in a molecule. The skin irritation potential of GA-12 is lower than that of the corresponding “monomer”, C₁₁H₂₃CON(CH₃)CH(COOH)CH₂(COOH)·NaOH, and the analog, C₁₁H₂₃CON(CH₃)CH₂COONa·H₂O.     

Reactions of diazomethane with glycerolipids in the presence of serum or inorganic salts

Diazomethane is widely used for the selective methylation of nonesterified fatty acids in the presence of other lipids. However, when the reaction is carried out directly with plasma or serum, substantial methanolysis of phospholipid acyl groups occurs. Because of the importance of rigorous selectivity in the assay of unesterified fatty acids which are present only in trace amounts in cells and body fluids, we have investigated the diazomethane procedure in detail and reached the following conclusions: (i) When diazomethane reacts with lipid extracts in organic solvent, no ester hydrolysis occurs. (ii) In the presence of serum or plasma, diazomethane reacts with water and inorganic salts, causing the solution to become basic (CH₂N₂+NaCl+HOH→CH₃Cl+Na⁺+OH⁻+N₂); methoxide ions are formed from methanol (CH₃OH+OH⁻→CH₃O⁻+HOH) causing extensive methanolysis (CH₃O⁻+RO−CO−R′→CH₃O−CO−R′+RO⁻). An analogous reaction takes place with ethanol. All esters of glycerol are transesterified in aqueous salt solution by this mechanism. It is therefore essential to prepare a lipid extract prior to the assay of unesterified fatty acids when using the diazomethane procedure. We dedicate this paper to Dr. Hermann Schlenk on the occasion of his 80th birthday.     

Studies on the reactions of ω-carbethoxy fatty acid sodioesters with brominated compounds

Several ω-carbethoxy fatty acid sodioesters (C₂H₅-O₂ CCHNa(CH₂)_n−1-CO₂C₂H₅ and C₂H₅-O₂CCHNa(CH₂)_n−2-CHNaCO₂ C₂H₅ where n/6, 7, or 8) were condensed with ω-bromoaliphatic esters (Br(CH₂)_zCO₂C₂H₅ where z-5, 8 or 10), α,ω-dibromoalkanes (Br(CH₂)_n′-Br where n′=4, 6 or 8) and α,α′ m- or p-xylene. Tri- and tetraesters and several carbethoxy cycloheptanones which arose mainly from Dieckmann type condensations were isolated. The infrared spectra of the tri- and tetraesters were compared with those of their parent ω-carbethoxy fatty acid ester and additional peaks in the regions ofV _C=O andV _C-O-C were observed. Reactions involving the formation of both the α-sodio and α,α′ salts are also discussed.     

Exploring the effect of alkyl end group on poly(L-lactide) oligo-esters. Synthesis and characterization

Poly(L-lactide) (PLLA) oligo-esters with α-hydroxyl-ω-alkyl (alkyl = −CH₂−[CH₂−CH₂]_m−CH₃, where m = 1, 2, 4, 5, 6, 7, 8, 9, and 10) end groups were synthesized by ring-opening polymerization of L-lactide (L-LA) catalyzed by tin(II) 2-ethylhexanoate Sn(Oct)₂ in the presence of aliphatic alcohols as initiators (HO−CH₂−[CH₂−CH₂]_m−CH₃, where m = 1, 2, 4, 5, 6, 7, 8, 9, and 10). High yields (~ 62 to 71%) and M _n(NMR) in the range of 2120–2450 Da (PLLA) were obtained. Effects of alkyl end groups on thermal properties of the oligo-esters were analyzed by DSC, TGA and SAXS. Glass transition temperature (T _g) gradually decreases with increase in the percent of−CH₂−[CH₂−CH₂]_m−CH₃ end group, as results alkyl end group provides most flexibility to PLLA. An important effect of alkyl end group on a double cold crystallization (T _c1 and T _c2) was observed, and is directly related with the segregation phase between alkyl end group and PLLA. TGA analysis revealed that PLLA oligo-esters are more thermally stable with docosyl (−C₂₂H₄₅) respect to the butyl (−C₄H₉) end group, probably is due to steric hindrance of the end group (docosyl respect to butyl) toward intermolecular and intramolecular transesterification. SAXS analysis showed that alkyl end group as docosyl restricted the growth of lamellae thickness (D) due to steric hindrance. Characterization of hydroxyl and alkyl end groups in the PLLA oligo-esters was determined by MALDI-TOF, GPC, FT-IR and ¹ H and ¹³ C NMR.     

Studies on cobalt catalyst supported on silica with different pore size for Fischer–Tropsch synthesis

The adsorption and surface reactions of acetonitrile and acetonitrile-oxygen gas mixture were studied on TiO₂-supported Au catalysts at 300–673 K. FTIR spectra show different kinds of molecularly adsorbed CH₃CN:acetonitrile can be bonded to weak Lewis acid sites (2295 cm⁻¹), to strong Lewis acid sites (2337 cm⁻¹) of titania; it can be coordinated linearly through the lone electron pair of the N atom on Au sites and η² (C,N) CH₃CN species can be formed on Au particles. CH₃CN dissociates on Au sites, the resulting CN_(a) can be oxidized in small extent by lattice oxygen and in a greater extent by gaseous oxygen into NCO surface species. The formation of other products (CH₃NH₂, H₂, CO₂, CH₄, C₂H₄ and CO) was demonstrated and discussed.     

Identification of carrot inositol phospholipids by fats atom bombardment mass spectrometry

Inositol phospholipids from carrot cell membranes grown in suspension cultured were purified by thinlayer chromatography (TLC) or column chromatography and tentatively identified by co-migration on TLC with animal inositol phospholipid standards. For more rigorous chemical characterization, carrot inositol phospholipids were then analyzed by negative ion fast atom bombardment mass spectrometry (FABMS). One phosphatidylinositol (PI), two lysophosphatidylinositols (LPI), and one phosphatidylinositol monophosphate (PIP) were identified in the carrot samples by the observation of ions [M-H]⁻ and numerous fragment ions in the negative FAB mass spectra. MS/MS analysis were carried out to obtain further structural information of these phospholipids using a double-focusing mass spectrometer in which the magnetic sector (B) and the electrostatic analyzer (E) were scanned at a constant ratio (B/E). These B/E linked scans provided fragment ions of selected precursor ions while eliminating matrix and other contaminating ions. No molecular ions were detected for lysophosphatidylinositol monophosphate (LPIP) or phosphatidylinositol bisphosphate (PIP₂), but fragment ions corresponding to these structures were observed. The primary fatty acids present in the carrot inositol phospholipids were linoleic (18∶2) and palmitic (16∶0) acids, whereas animal lipids contained arachidonic (20∶4), stearic (18∶0), linoleic, and palmitic acids. The only phosphatidylinositol found in carrot cells was palmitoyl linoleoyl PI.     

Isolation and characterization of the monounsaturated long chain fatty acids ofMycobacterium tuberculosis

The positions of double bond in the monounsaturated C₁₅−C₃₂ fatty acids ofMycobacterium tuberculosis H37Ra were established by gas chromatography/mass spectrometry of the ozonized esters and their pyrrolidide derivatives. The monounsaturated C₁₅−C₂₁ fatty acids had the double bond primarily at the Δ⁹ position while the monounsaturated longer chain fatty acids (C₂₂−C₃₂) had the double bond in several positions. Many of the latter acids, especially the odd-numbered series, were very complex isomeric mixtures. Quantitation showed the most abundant even-numbered long chain fatty acid isomers to be as follow: C₂₂, Δ⁴; C₂₄, Δ⁵; C₂₆, Δ⁷ and Δ⁹; C₂₈, Δ⁹; C₃₀, Δ¹¹ and Δ¹³; C₃₂, Δ¹³ and Δ¹⁵.     

Fatty acid and cholesterol synthesis from specifically labeled leucine by isolated rat hepatocytes

Hepatocytes isolated from female rats meal-fed a high-glucose diet were incubated in Krebs-Henseleit bicarbonate medium containing 16.5 mM glucose,³H₂O, and¹⁴C-labeled amino acids (−)-Hydroxycitrate depressed the incorporation of³H₂O and [¹⁴C] alanine into fatty acids and cholesterol. Incorporation of [U-¹⁴C] leucine into lipids was not affected but incorporation of³H₂O into lipids was decreased significantly by (−)-hydroxycitrate. (−)-Hydroxycitrate depressed the incorporation of radioactivity from [2-¹⁴C]leucine into fatty acids and cholesterol by 61 and 38%, respectively, and stimulated the incorporation of radioactivity from [4,5-³H]leucine 35 and 28%. As [2-¹⁴C]leucine labels the acetyl-CoA pool and [4,5-³H]leucine labels the acetoacetate pool, it was concluded that mitochondrial 3-hydroxy-3-methylglutaryl-CoA is not incorporated intact into cholesterol, and that acetoacetate can be activated effectively in the liver cytosol for support of cholesterol and fatty acid synthesis.     

Mass spectrometric analysis of the fatty acids and nonsaponifiable lipids ofEimeria tenella oocysts

The fatty acids and nonsaponifiable lipids ofEimeria tenella oocysts were analyzed by gas liquid chromatography and combined gas liquid chromatographymass spectrometry. The fatty acids detected were identified as C_14∶0, C_16∶0, C_16∶1, C_18∶0, C_18∶1, and C_18∶2. Though the wt of the fatty acid fraction decreased during sporulation from 91 μg per 10⁶ oocysts to 47 μg per 10⁶ oocysts, the relative amounts of these fatty acids did not change appreciably. The nonsaponifiable lipids ofE. tenella consisted of cholesterol and unbranched primary alcohols of 22, 24, 26, 28, 30, and 32 carbons. Mass fragmentography demonstrated that each species of alcohol consisted of saturated and monounsaturated derivatives. Trimethylsilyl ethers of fatty alcohols were found to offer several important advantages over free alcohols for mass spectrometric characterization. Before sporulation, most fatty alcohols were in the oocyst wall. During sporulation, the wt of the nonsaponifiable lipids increased from 16 μg per 10⁶ oocysts of 44 μg per 10⁶ oocysts due largely to synthesis of C₂₄ and C₂₆ alcohols. The newly synthesized fatty alcohols were not deposited in the oocyst wall.     

Characterization of polypyrrole films incorporating various anions

The conductivity of polypyrrole films has been enhanced by electrochemical post-deposition doping with various anions. The change of conductivity was found to depend on the type and concentration of the anion. Results for the polypyrrole films doped with anions of H₂SO₄, (C₂H₅)₄N(O₃SC₆H₄CH₃), KI, CH₃C₆H₄SO₃H · H₂O (p-toluene sulphonic acid monohydrate), AlCl₃, KBrO₃ and HNO₃ showed that in the case of H₂SO₄, (C₂H₅)₄ N(O₃SC₆H₄CH₃) and CH₃C₆ H₄SO₃ H · H₂O the conductivity can be enhanced by up to a factor of two, from a value of 67 S cm^–1 up to 165, 102 and 95 S cm^–1, respectively. Doping with I^– had a negligible effect on the conductivity which was about 71 S cm^–1, while in the case of AlCl₃, KBrO₃ and HNO₃ the conductivity of the polypyrrole decreased significantly for certain anion concentrations.     

Application of the Bifunctional Switch-Type Cryptand Ion Chromatographic Stationary Phase for Ion Separation

ABSTRACT

Poly(styrene/divinylbenzene) resin with cryptand 22 as an anchoring group was synthesized and applied in ion chromatography as a packing material for separations of organic anions as well as cations. The cryptand can not only form strong complexes with metal cations, but it has also shown a remarkable complexing ability with organic anions after protonation at pH < 7. The protonated cryptand resin has been applied as an anion exchanger to successfully separate some organic carboxylate anions including HCOO^?, CH₃COO^?, CH₃CH₂COO^?, and some geometric isomers, e.g., fumarate and maleate ions, with water as the eluent. Alternatively, after deprotonated at pH > 7, the cryptand resin can be switched as a cation exchanger to separate inorganic cations. The effects of solvents, temperature, pH values, and flow rates of eluents on the separation of organic anions were also investigated.     

One-Dimensional Coordination Polymer Assembled by Tetraaza Macrocyclic Nickel(II) Complex and trans-1,4-Cyclohexanedicarboxylate ligand

The reaction of [Ni(L)]Cl₂·2H₂O (L = 3.14-dimethyl-2,6,13,17-tetraazatricyclo[14,4,0^1.18,0^7.12]docosane) with trans-1,4-cyclohexanedicarboxylic acid (H₂chdc) generates a 1D coordination and 2D hydrogen-bonded polymer {[Ni(L)(chdc)₂]·2H₂O}_n (1). The polymer complex was characterized by X-ray crystallography, spectroscopy and magnetic susceptibility. Each nickel(II) ion has a distorted octahedral coordination environment with the four secondary amines of the macrocycle in which two trans carboxylate anions of the chdc²⁻ ligand have assembled around each nickel center. The electronic spectrum of 1 in the solid state exhibits a high-spin octahedral environment. The magnetic behavior of 1 reveals a weak intramolecular antiferromagnetic interaction with J values of −1.15(2) cm⁻¹.     

Synthesis of highly ordered supermicroporous silica using short-chain cationic trimeric surfactant as structure-directing agent

Highly ordered supermicroporous silica was synthesized by short chains cationic trimeric surfactant [C₁₀H₂₁N⁺(CH₃)₂(CH₂)₂N⁺(CH₃)(C₁₀H₂₁) (CH₂)₂N⁺(CH₃)₂C₁₀H₂₁] · 3Br⁻ (denoted C_10-2-10-2-10) with a short spacer group (s = 2) as the structure-directing agent and tetraethyl orthosilicate as the precursor. The obtained samples were characterized by small-angle X-ray diffraction, high resolution transmission electron microscopy, and N₂ adsorption–desorption. The results showed that the pore structure of the resulting samples belonged to the two-dimensional hexagonal structure (space group 2D-p6mm) with a pore size from 1.92 to 2.16 nm, which was within the supermicroporous range. The high-quality supermicroporous silica was formed at a low molar ratio of C_10-2-10-2-10 to tetraethyl orthosilicate (0.08:1), which indicated that the self-assembly ability of C_10-2-10-2-10 was stronger than that of corresponding monovalent surfactants. We strictly compared the methods of calculating surface area and pore size of supermicroporous materials, and the surface area was found to be in the range of 910–1,135 m² g⁻¹ by the α_s plot method. With the increase of hydrothermal temperature, the ordering of the supermicroporous structure increased first then decreased, at the same time the pore size was enlarged.     

Experimental study of the limiting conditions for diffusion combustion of gases and vapors in various media

Extinction conditions for diffusion flames of gases and vapors in various media were studied experimentally. The limiting blowout velocities of a diffusion jet when heated H₂−N₂ and H₂−H₂O mixtures flow out into air were found. The minimum fire-extinguishing concentrations upon diffusion combustion of gases (CH₄ and C₃H₈) and liquids (A-76 gasoline) were measured. Translated fromFizika Goreniya i Vzryva, Vol. 34, No. 2, pp. 3–8, March–April, 1998.     

Soap-based detergent formulations: XVII. Synthesis and surface active properties of alkylbenzene derived amine oxides

Amine oxides C_nH_2n+1C₆H₄SO₂NH(CH₂)₃-NMe₂—O⁻ were prepared for testing as lime soap dispersing agents in phosphate free, soap-based, sodium silicate built laundry detergents. These amine oxides were synthesized via a three step route from a variety of pure 1-phenylalkanes and also from a commerical detergent alkylate mixture. The process included (a) the sulfonation of the phenylalkane with chlorosulfonic acid, (b) reaction of the resulting alkarylsulfonyl chloride with H₂N(CH₂)₃NMe₂ or with H₂N(CH₂)₃N(CH₂CH₂OH)₂ under anhydrous conditions, and (c) oxidation with aqueous H₂O₂. The amine oxides were water soluble and in some instances isolable as crystalline hydrates. They were found to be thermally stable below 125 C and highly surface active. Optimum detergency and lime soap dispersability were achieved by the model compound of alkyl chain length n=8. This was in contrast to the behavior of the related amphoteric sulfobetaine series C_nH_2n+1C₆H₄SO₂NH(CH₂)₃NMe₂(CH₂)₃-SO₃ ⁻, whose optimum detergency and lime soap dispersability previously had been observed to reach a maximum at chain length n=12. Detergency screening tests showed that soap-based detergents formulated with the sulfobetaines outperformed the ones formulated with the amine oxides. Presented at the AOCS Meeting, Dallas, April 1975.     

Gemini surfactant controlled preparation of well-ordered lamellar mesoporous molybdenum oxide

A series of well-ordered lamellar mesoporous molybdenum oxides were prepared using gemini surfactant [C _n H_2n+1N⁺(CH₃)₂–(CH₂)₂–N⁺(CH₃)₂C _n H_2n+1] · 2Br⁻(denoted as C _n-2-n , n = 12, 14 and 16) as the structure-directing agent and ammonium heptamolybdate tetrahydrate (NH₄)₆Mo₇O₂₄ · 4H₂O as the precursor. The obtained samples were characterized by X-ray powder diffraction, thermal analysis, transmission electron microscopy and nitrogen adsorption–desorption. Results showed that contrary to complete structure collapse after removing tetradecyltrimethylammonium bromide (TTAB) from molybdenum oxide/TTAB composite, the lamellar mesostructure was retained after removal of C _n-2-n from corresponding composite. The effects of alkyl chain length and concentration of gemini surfactants on the structure of the mesoporous molybdenum oxide were also investigated. The specific surface area of extracted sample was as high as 116 m² g⁻¹. The maintenance of the lamellar mesostruture was due to the strong self-assembly ability of gemini surfactants and the strong electrical interaction between gemini surfactants and molybdenum oxide.     

Fatty acid metabolism in marine fish: Low activity of fatty acyl Δ5 desaturation in gilthead sea bream (Sparus aurata) cells

Marine fish have an absolute dietary requirement for C₂₀ and C₂₂ highly unsaturated fatty acids. Previous studies using cultured cell lines indicated that underlying this requirement in marine fish was either a deficiency in fatty acyl Δ5 desaturase or C_18–20 elongase activity. Recent research in turbot cells found low C_18–20 elongase but high Δ5 desaturase activity. In the present study, the fatty acid desaturase/elongase pathway was investigated in a cell line (SAF-1) from another carnivorous marine fish, sea bream. The metabolic conversions of a range of radiolabeled polyunsaturated fatty acids that comprised the direct substrates for Δ6 desaturase ([1-¹⁴C]18∶2n−6 and [1-¹⁴C]18∶3n−3), C_18–20 elongase ([U-¹⁴C]18∶4n−3), Δ5 desaturase ([1-¹⁴C]20∶3n−6 and [1-¹⁴C]20∶5n−3), and C_20–22 elongase ([1-¹⁴C]20∶4n−6 and [1-¹⁴C]20∶5n−3) were utilized. The results showed that fatty acyl Δ6 desaturase in SAF-1 cells was highly active and that C_18–20 elongase and C_20–22 elongase activities were substantial. A deficiency in the desaturation/elongation pathway was clearly identified at the level of the fatty acyl Δ5 desaturase, which was very low, particularly with 20∶4n−3 as substrate. In comparison, the apparent activities of Δ6 desaturase, C_18–20 elongase, and C_20–22 elongase were approximately 94-, 27-, and 16-fold greater than that for Δ5 desaturase toward their respective n−3 polyunsaturated fatty acid substrates. The evidence obtained in the SAF-1 cell line is consistent with the dietary requirement for C₂₀ and C₂₂ highly unsaturated fatty acids in the marine fish the sea bream, being primarily due to a deficiency in fatty acid Δ5 desaturase activity.     

Effects of phenyl-based pendent groups on helical conformation of poly(<Emphasis Type="Italic">N</Emphasis>-propargylamides)

Five achiral N-propargylamide monomers with various phenyl-based substitutents, [HC ≡ CCH₂NHCOR, R for M1: C₆H₄CH₃; M2: C₆H₄CH₂CH₃; M3: C₆H₄(CH₂)₂CH₃; M4: C₆H₄(CH₂)₃CH₃; M5: C₆H₄C(CH₃)₃], were synthesized and polymerized with a rhodium catalyst, (nbd)Rh⁺B^-(C₆H₅)₄ (nbd = 2,5-norbornadiene). The corresponding five homopolymers were obtained in high yields of 90–95% and with moderate molecular weights (M _n ≥ 10 000). All the polymers possessed high cis contents (≥95%). Poly(1)–poly(3) exhibited UV-vis absorption peaks at approx. 350 nm, which indicates that the three polymers formed helical conformations, while no UV-vis absorption peaks could be observed in poly(4) and poly(5) in the wavelength range of 320–500 nm, demonstrating that these two polymers could not adopt helical structures under the examined conditions. To confirm the helical structures formed in poly(1)–poly(3), a chiral monomer, M6, was utilized to copolymerize with M2, which was used as the representative for M1−M3. M6 was utilized since its polymer could form stable helices under suited conditions. The resulting copolymers exhibited remarkable CD effects, however, the maximum wavelength in the copolymers varied remarkably, mainly depending on the composition of the copolymers. It is concluded that in the formation of ordered helical conformations, the substitutents of varied bulk led to different steric repulsion and varied synergic effects among the neighboring pendent groups.