Saturated Alkyl Chains Research Articles

Electron attachment and intramolecular electron transfer in unsaturated chloroderivatives

The electron transmission (ET) and dissociative electron attachment (DEA) spectra of chloroalkyl ethene and ethyne derivatives are reported. B3LYP/6-31G* calculations are employed to evaluate the virtual orbital energies for the optimised geometries of the neutral states of these molecules and other related π-systems. The calculated π* MO energies correlate linearly with the energies of electron attachment to the π* LUMO measured in the ET spectra with a correlation coefficient of 0.993. The vertical attachment energies supplied by B3LYP/6-311+G** calculations, where the basis set includes diffuse functions, are often in significant disagreement with experiment, describing the singly occupied MO of the lowest-lying anion state as a diffuse σ* MO rather than a valence π* MO. The relative Cl− anion currents measured in the DEA spectra of the present molecular systems are compared to those previously found in benzene analogues. The Cl− yield reflects the efficiency of intramolecular electron transfer from the π-system (where the extra electron is first trapped) to the remote chlorine atom. Replacement of a carbon atom with a silicon atom in the intermediate saturated alkyl chain causes a notable increase of the Cl− current, ascribed to the lower energy of the empty σ*Si–C MOs and consequent greater ability to promote through-bond coupling between the π* and σ*C–Cl MOs. Comparison between the corresponding benzene, ethene and ethyne derivatives reveals that the Cl− current is also significantly influenced by the nature of the π-functional group, in agreement with the inverse dependence on energy of the lifetime of the temporary π* anion state.

Self-assembling structures of long-chain phenyl glucoside influenced by the introduction of double bonds.

Four long-chain phenyl glucoside amphiphiles possessing a saturated or unsaturated long alkyl chain group as the self-assembling unit of a highly organized molecular architecture were synthesized. Their self-assembling properties were investigated by EF-TEM, SEM, CD, FT-IR, and XRD. Compound 2 possessing one double bond in the lipophilic portion showed twisted helical fibers, which formed a bilayered structure with a 3.59 nm period, while compound 3 showed the helical ribbons and left-handed nanotubular structures with 150-200 nm inner diameters and ca. 20 nm of wall. Very interestingly, compound 4 possessing three double bonds showed a nanotubular structure with ca. 70 nm of inner diameter through a helical ribbon, which formed a loose bilayered structure with 4.62 nm. These results indicate that self-assembling properties strongly depend on the number of cis double bonds.

Alkylglycosides with an Isoprenoid-Type Hydrophobic Chain Can Afford Greater Control of Aqueous Phase Structures at Low Temperatures

We have proposed novel alkylglycosides, AGs, that consist of an isoprenoid-type hydrophobic chain, the 3,7,11,15-tetramethylhexadecyl (phytanyl) group. One notable feature of the proposed AGs lies in the fact that their Krafft eutectic temperatures, TK, are well below room temperature although the total number of carbon atoms in the hydrophobic chain is as large as 20. As compared to the conventional AGs with straight and saturated alkyl chains, their low TK values significantly expand our freedom to control their aqueous phase structures at low temperatures. The aqueous phase structures are controlled by modification of the headgroup: an HII phase for the glycerol headgroup, a cubic phase with crystallographic space group Pn3m/Pn3 at low temperatures and an HII phase at higher temperatures for a xylose headgroup, and an Lα phase for a glucose and a maltose headgroup.

Photoionization Studies of Chromophore-Labeled Amino Acids and Peptides

The photoionization characteristics of a naphthol chromophore covalently tethered to a few different amino acids and small peptides are investigated. To isolate the chromophore from the biological molecules the linkage between them is constructed from saturated alkyl chains of up to 12 carbons in length. Experimental results are compared with those of previous studies that explored the photoionization of macromolecules.

Acyl and alkyl chain length of GPI-anchors is critical for raft association in vitro

We determined the acyl and alkyl chain composition of GPI-anchors isolated from MDCK and Fischer rat thyroid (FRT) cells. Both cell lines synthesize GPI-anchors containing C16/C18 or C18/C18 saturated acyl and alkyl chains. The GPI-anchored placental alkaline phosphatase (PLAP) expressed in both cells is raft-associated and PLAP purified from FRT cells is raft-associated in vitro when reconstituted into liposomes containing raft lipids. In contrast, the GPI-anchored variant surface glycoprotein from Trypanosoma brucei which contains C14 acyl and alkyl chains shows no significant raft association after reconstitution in vitro. These data indicate that the acyl and alkyl chain composition of GPI-anchors determines raft association.

Temperature Dependence of the Outer-Sphere Reorganization Energy

The temperature dependence of the intervalence charge transfer transition (IT) has been studied for a mixed-valence dinuclear iron complex. The two “halves” of this complex consist of trisbipyridineiron moieties that are triply linked with saturated alkyl chains. Because the complex is symmetric, the energy of the IT band is a direct measure of the reorganization energy for electron transfer between the two irons. Moreover, for the specific complex under investigation here, the inner-sphere reorganization energy is essentially zero because of an exact cancellation of sigma- and pi-bonding changes upon changing the oxidation state of each iron. As a consequence, the energy of the IT transition is a direct measure of the outer-sphere (solvent) reorganization energy. The energy of the IT band has been investigated over the temperature range −28 °C to 30 °C. The derivative of the outer-sphere reorganization energy with respect to temperature found from this study was −3.2 ± 0.4 cm-1K-1. Theoretical calculations based on the Marcus two spheres in a dielectric continuum model and a molecular based model developed by Matyushov were also carried out for comparison with the experimental results. The continuum model predicts a positive slope for the derivative while the Matyushov model gives a negative slope that differs from that of the experimental data by a factor of ∼2 in magnitude.

2-Alkylcyclobutanones as markers for irradiated foodstuffs—I. Synthesis of saturated and unsaturated standards

The reaction scheme suggested for the synthesis of 2-alkylcyclobutanone standards, the key step being a Wittig reaction between a protected ketoaldehyde and phosphoranes with alkyl chains of variable length, has made it possible to prepare different 2-alkylcyclobutanones with saturated alkyl chains (C6 to C14) (in yields varying from 27 to 36%) as well as 2-alkylcyclobutanones with monounsaturated chains (C12 and C14) (in yields of 23 and 17%). In addition, the 2-alkylcyclobutanones synthesized with an odd number of carbon atoms in the saturated alkyl chain, especially 2-undecylcyclobutanone (C11), might be utilized as internal standards when assaying these chemical compounds by GC/MS.

Atypical Behavior of a New Dialkyl Macrocycloureide in Langmuir−Blodgett Film Formation

This work deals with the behavior studied through the Langmuir-Blodgett technique of a synthetic fluorescent macrocycloureide substituted with two C 18 -saturated alkyl chains, the distearylmacrocycloureide (DSM). The DSM monolayer exhibited a peculiar behavior when compressed, and a well-defined monolayer to bilayer transition was observed on the π-A isotherms.

Molecular switching in phospholipid-azobenzene mixed monolayers by photoisomerization

Molecular switching in phospholipid and azobenzene mixed monolayers on a water surface was examined by Maxwell displacement current (MDC) measurements coupled with surface–pressure measurements. MDC and thermally stimulated current (TSC) measuring techniques also examined molecular switching in these monolayers on a solid substrate. It was found that the molecular aggregation of pure azobenzene monolayers in both Langmuir (L) and Langmuir–Blodgett (LB) films is reduced by the introduction of phospholipids possessing unsaturated long alkyl chains (DOLPC) or saturated long alkyl chains (DPPC), and that the cis–trans photoisomerization in a mixed monolayer is accelerated. However the contribution of the two kinds of lipids in mixed monolayers was found to be different. The temperature dependence of charge induced across these mixed LB films, due to photoisomerization, corresponded well with that of 4-octyl-4′-(5-carboxyl-pentamethyleneoxy)-azobenzene (8A5H) LB films. Finally it was concluded that the cis-state 8A5H molecules, in monolayers, return to the trans-state during heating.

Molecular Switching in Phospholipid and Azobenzene Mixed Monolayers Using Maxwell-Displacement-Current-Measuring Technique

Molecular switching in phospholipid and azobenzene mixed monolayers was examined by Maxwell-displacement-current (MDC) measurement in combination with the surface pressure measurement. It was found that the molecular aggregation of pure azobenzene monolayers was reduced by the introduction of phospholipids possessing unsaturated long alkyl chains (DOLPC) or saturated long alkyl chains (D-DPPC). The surface pressure change was detected from mixed monolayers over the entire range of molecular area with alternating irradiation of ultraviolet and visible light. On the one hand, MDC was generated from DOLPC-azobenzene mixed monolayers over the entire range of the molecular area, whereas the generation of MDC from D-DPPC-azobenzene mixed monolayers was limited in the molecular area. We discussed the generation of MDC from phospholipids-azobenzene mixed monolayers in combination with the surface pressure change measurement.

Glycolipid Enzyme Model. XII. Effect of Reaction Fields on Hydrolyses of Amino Acid Esters.

In hydrolyses of amino acid esters using a glycolipid hydrolase model, the effects of phospholipids added were examined as reaction field. Phospholipids with saturated hydrophobic alkyl chains (phase transition temperature, 60.0∼86.9°C), with moderately unsaturated alkyl chains(-4.5∼5.8°C), and with highly unsaturated alkyl chains(-24.2∼25.2°C) were used in this study. The hydrolysing activity of a glycolipid depended on the kind of phospholipids. The activity was suppressed by saturated phospholipids in a gel state, but was increased by unsaturated phospholipids in a liquid crystal state, particularly when present at more than 60 mol%. The increase in uptake velocity of a substrate in the liquid crystal state in the reason for this. The unsaturated phospholipids also enhanced the capacity of amino acid recognition by a glycolipid. In the hydrolase model system, high hydrolysing velocity and substrate recognition are thus achieved by unsaturated phospholipids as reaction fields.

Structural Analysis of Normal Chain Groups Loaded on Solid Surfaces.

The surface microstructure is one of the important factors to determine functions and properties of materials. It is necessary to characterize the surface microstructure for the purpose of controlling and designing. This review deals with mobilities and structures of functional groups adsorbed on the surfaces of inorganic solids after chemical modification. I focus on the measurements and simulations on the microstructures of normal saturated alkyl chains, since these chains have few complicated interaction between inter- and/or inter-molecules, such as hydrogen bonding.

Ester- and ether bond cleavage in immature kerogens

Quaternary ammonium salt Aliquat 336 and 18-Crown-6 enhance hydrolysis of Timahdit-M kerogen when used as a phase transfer catalyst. The yield of hydrolysis products was higher with Aliquat than with 18-Crown-6, but the identified products were found in lower concentration, the difference being soluble heavy parts from kerogen which cannot be analyzed directly. Both reactions afforded series of aliphatic mono- and dicarboxylic acids, alkylsuccinic acids and alkanols, but differences in distributions were observed. The range of monocarboxylic acids was shorter with Aliquat than with 18-C-6, C 14C 18 compared to C 12C 32, but palmitic and stearic acids were dominant in the two cases. C 10 and C 12 alkyl succinic acids were identified in Aliquat products. Aromatic acids were the major hydrolysis products (59%) with crown ether; only one aromatic acid was found with Aliquat. Hydrocarbons and tertiary amines were obtained from both reactions, they were obviously present in the kerogen as trapped molecules. Many tertiary amines arising from the decomposition of the reagent were obtained with Aliquat. The results give evidence of an important reticulation involving ester groups in the Timahdit-M kerogen. Series of n-, iso- and anteisoalkanes were obtained through HI/LAD treatment of Irati and Aleksinac kerogens, originating probably from glycerol-ether lipids. C 27C 34 α,β-hopanes were also found to be linked to kerogen (Irati) by ether bonds. Reaction with CF 3CO 2H (Irati) afforded seven series of branched alkenes, indicating that branched saturated alkyl chains were bound to aromatic moieties of kerogen by ether groups. Acetates of cholesterol and 24-ethylcholesterol were identified in the BF 3-Et 2O/Ac 2O products. Esters of fatty acids (max C 16, C 18) were also identified. Only alkanes were produced on AII 3 reaction. Each reaction afforded the same series of n-alkanes. This would reflect modifications in the kerogen matrix during these various treatments, resulting in the release of tightly trapped molecules.

Lamellar-non-lamellar phase transitions in synthetic glycoglycerolipids studied by time-resolved X-ray diffraction

Abstract The phase sequences of eight fully hydrated synthetic, stereochemically pure glycoglycerolipids with saturated alkyl chains 12–18 carbon atoms long and a glucose, galactose or mannose head group are followed in real time during heating and cooling scans using synchrotron X-ray diffraction. One of them, 1,2-di-O-hexadecyl-3-O-β-D-glucosyl-sn-glycerol, has been characterized by X-ray diffraction for the first time. A summary of the lamellar-non-lamellar transition sequences and reversibility for all eight glycoglycerolipids studied is provided. It includes also observations of intermediate phases, previously not detected. Lattice parameters of the various phases have been determined as functions of chain length in monoglucosides. While the repeat periods of the lamellar phases increase linearly with chain length, an anomalously high lattice spacing of the inverted hexagonal phase is observed at a chain length of 14 carbon atoms. This maximum coincides with the disappearance of the cubic phases from...

Isolation of 5-(8′Z-heptadecenyl)-resorcinol from etiolated rice seedlings as an antifungal agent

A new antifungal substance against rice blast fungus ( Pyricularia oryzae), 5-(8′Z-heptadecenyl)resorcinol, was isolated from etiolated rice seedlings together with a mixture of its homologues with C 13, C 15, and C 17 saturated alkyl chains. Its structure was determined by 1NMR, 13C-NMR, and MS spectra. Its ED 50 was ca 40μg/ml. These 5-alkylresorcinols were newly produced after germination and the concentration reached 50 μg g −1 fresh weight on day 6.

Glucose oxidase mediation by soluble and immobilized electroactive detergents

A series of novel, surface-active, inorganometallic complexes of osmium were synthesized and then characterized (using electrochemical techniques) as electron transfer mediators for glucose oxidase (EC 1.1.3.4, GOD) from Aspergillus niger. The mediators contain a dipyridylamine ligand bearing (on the amine nitrogen) a saturated alkyl chain (typically C 5 to C 12), ω-terminated with either a methyl group or a functional group such as carboxyl or hydroxyl. Such compounds displayed subtle differences in their interactions with GOD. The presence of a ω-functional group tended to diminish a mediator's micelle-forming activity, but also concomitantly decreased the denaturing action of the mediator towards the protein structure of GOD. However, the presence of an ionised carboxyl group slowed GOD mediation relative to that of similar mediator bearing a methyl-terminated long alkyl chain, probably because of the additional negative charge. The ω-carboxyl functionality allowed covalent coupling of mediators to NH 2-bearing graphite electrodes. GOD was co-immobilized and the resulting, reagentless, glucose-sensitive electrodes were characterized. Immobilization of the mediator did not appear to affect unduly the ability to mediate GOD. Additionally, complexes were directly coupled to lysine groups of GOD to give a self-mediating enzyme.

Substrate selectivity in esterification of less common fatty acids catalysed by lipases from different sources

Lipases from microorganisms (Candida cylindracea, Rhizopus arrhizus and Rhizomucor miehei), animal tissue (porcine pancreas) and a higher plant (rape, Brassica napus) have been evaluated as biocatalysts in the esterifications with n-butanol with regard to their substrate specificity towards fatty acids having a cis-4 unsaturation, e.g. docosahexaenoic (n-3 22:6), cis-6 unsaturation, e.g. petroselinic (n-12-18:1), γ-linolenic (n-6 18:3) and stearidonic (n-3 18:4), as well as cis-8 unsaturation, e.g. dihomo-γ-linolenic (n-6 20:3) acid, and fatty acids having unusual structures, e.g.cyclopentenyl (hydnocarpic and chaulmoogric), hydroxy (ricinoleic and 12-hydroxystearic) and epoxy (cis- and trans-9,10-epoxystearic) acids. A common feature of all the lipases tested is their ability to discriminate strongly against unsaturated fatty acids having a cis-4, cis-6 or a cis-8 unsaturation as substrates for esterification, whereas cyclopentenyl, hydrocy and epoxy acids are very well accepted as substrates. Esterification of the fatty acids of Hydnocarpus wightiana seed oil with n-butanol, catalysed by each of the above lipases, revealed that, as compared to the cyclopentenyl fatty acids having saturated alkyl chains, gorlic acid — a cyclopentenyl acid having a cis-6 unsaturation — is also strongly discriminated against as a substrate for esterification.

Pressure−Area Isotherms for Double-Chain Amphiphiles Bearing Two Hydroxyl Groups Derived from Diepoxides

The pressure−area (π−A) isotherms for a series of double-chain amphiphiles bearing two hydroxyl groups were measured by the conventional film-balance technique. These double-chain compounds were prepared by reaction of epichlorohydrin with various dihydroxy compounds which become the connecting moiety, followed by reaction of the resultant diepoxides with fatty alcohols. They are synthetic precursors of double-chain surfactants bearing two anionic head groups which have been developed as high-performance “gemini surfactants” by the authors' group. The effect of the following factors on the π−A isotherms for these compounds was examined: the length of the saturated hydrophobic alkyl chains, the difference between saturated and unsaturated aliphatic chains, temperature, the structure of the connecting group between the two hydrophobic chains, and the difference in configuration of the chiral molecules. Some relationships between the structures of these double-chain amphiphiles and their adsorptive behavior...

O/W Lipid Emulsions for Parenteral Drug Delivery. II. Effect of Composition on Pharmacokinetics of Incorporated Drug

The potential usefulness of O/W lipid emulsions as injectable drug delivery systems for lipophilic drugs was examined using a model lipophilic drug, sudan II (clogP = 5.4) in the normal rats. The standard lipid emulsion composed of soybean oil and egg yolk phosphatides increased the blood concentration of sudan II after i.v. injection when compared with its solubilized solution by plasma. However, it was still lower than that of the oil particles, and the distribution of sudan II to liver, lungs, adipose tissue, heart, and muscle was not altered, and only that to brain and kidneys was decreased. Herein, the effect of extensive alterations in the lipid emulsion composition on the blood concentration and organ distribution of sudan II was examined in comparison with the standard formulation. Addition of cholesterol, use of pure egg yolk phosphatidylcholine, use of phospholipids with saturated alkyl chain, use of saturated long chain triglycerides, and use of saturated medium chain triglycerides were tested. The oil particles of all tested lipid emulsions were still located in plasma space, and use of saturated medium chain triglycerides was the most effective way to increase blood concentration of sudan II, resulting in higher distribution to liver, lungs, spleen, and brain. This was caused by the increase of the steady-state partition of sudan II to the oil particles, and not by alteration of their organ distribution clearance.

Pseudo-acylceramide with linoleic acid produces selective recovery of diminished cutaneous barrier function in essential fatty acid-deficient rats and has an inhibitory effect on epidermal hyperplasia.

Pseudo-acylceramides with different acyl properties were investigated for their capacity to restore diminished barrier function in essential fatty acid-deficient rats. Daily topical applications of synthetic pseudo-acylceramides containing ester-linked linoleic acid caused a dose-dependent, significant reduction of transepidermal water loss (TEWL). Both other pseudo-acylceramides with ester-linked oleic acid or saturated alkyl chains and ordinary ceramides exhibited a poor effect on recovery of TEWL. Furthermore, pseudoceramide containing ether-linked linoleic acid, which is biologically inactive in terms of degradation by hydrolytic enzymes, also induced a significant and similar increase in the barrier function. This restoration of barrier function by pseudo-acylceramides with linoleic acid was accompanied by suppressed DNA synthesis in the EFAD rat epidermis. In UVB-irradiated guinea pig skin, topical applications of the pseudo-acylceramides with linoleic acid immediately after the exposure significantly reduced epidermal hyperplasia, secondary to markedly diminished barrier disruption, whereas linoleic acid itself did not. A comparison of both the anti-hyperplasia and the barrier recovery effects in the series of pseudo-ceramide derivatives examined revealed that the suppressive effect on the induced epidermal hyperplasia was paralleled by the recovery of the barrier defect in EFAD rats. These findings directly suggest that acylceramide with an ester-linked linoleic acid has an essential role in the epidermal permeability barrier.