Long-chain Compounds Research Articles

Geopolymer formation and its unique properties

The characteristic property of naturally-occurring geopolymers is a high content of humic materials that are recognized by the nitrogen function. Through a simulated geopolymerization, biopolymers with non-nitrogen function, such as xanthan gum, were found to have the characteristics of humic acid by means of UV–Vis spectrometry. This fact ascertains that any kind of biopolymer may naturally transform to a geopolymer. A geopolymer is a type of crosslinked long-chain compound, built in three-dimensional structures whose property is immune to microbial degradation. A crosslinked biopolymer was shown to have the same characterization as a geopolymer that has a long life due to its crosslinking capacity and anti-microbial properties. In this study, the formation of petroleum-based geopolymers (e.g., kerogen) was introduced. This study may elucidate the structure of geomacromolecules and the mechanism of their formation, closely related with crosslink reaction between inorganic and organic molecules. This will further change the conventional definition of geopolymer that involves only the inorganic geopolymer.

Raman studies on the coverage integrity of monolayers formed on silver from various ω-functionalised alkanethiols

Silver substrates were modified with monolayers formed from: 2-aminoethanethiol (cysteamine, CYS), sodium 2-mercaptoethanesulfonate (MES), 3-mercaptopropionic acid (MPA), 11-mercaptoundecanoic acid (MUA) and 16-mercaptohexadecanoic acid (MHA). Then, such modified silver substrates were kept in the aqueous solutions of laccase (LAC) from Trametes versicolor and bovine serum albumin (BSA). The composition and structure of formed organic adlayers have been determined from their surface-enhanced Raman scattering (SERS) spectra. The analysis of measured spectra was based on the assumption that, for studied systems, SERS spectrum is dominated by the contribution from molecules directly interacting with the metal surface. In situ SERS measurements showed that the modification of the silver surface with a linkage monolayer formed from CYS, MES or MPA practically prevents the direct interaction of BSA molecules with the metal substrate. However, such monolayers do not prevent the direct interaction of LAC with the silver surface. Thus, the coverage integrity of the linkage monolayer can be destroyed by the adsorption of one peptide (in this case LAC), whereas, during the adsorption of the other peptide (in this case BSA) the coverage integrity is not destroyed. It means that the coverage integrity of a linkage monolayer should be independently determined in the solution of individual peptide. The modification of silver surfaces with monolayers formed from long-chain compounds (MUA and MHA) prevents the direct interaction of both LAC and BSA with the metal surface.

Composição do óleo essencial de Sinningia aggregata

The essential oil isolated by hydrodistillation from the aerial parts of Sinningia aggregata (Ker. Gawl.) Wiehler (Gesneriaceae) was analyzed by capillary GC and GC/MS. Seventeen components were identified, representing 91,8% of the total oil. The oil was characterized by a high content of long-chain aliphatic compounds (49,8%) and oxygenated sesquiterpenes (40,2%). The two major components were methyl linoleate (28,4%) and 1-octadecanol (16,9%). Among the sesquiterpenes, (Z)-nerolidol acetate (8,8%), spathulenol (7,8%) and (E)-nerolidol (6,7%) are present in appreciable amounts. Monoterpenes and phenylpropanoids were not found in the oil.

Classical nucleation theory applied to molecular orientations in vapor-deposited organic thin films

Molecular orientational mechanism during physical vapor deposition of various linear long-chain compounds has been interpreted on the basis of a classical nucleation theory modified for the anisotropic nucleus formation. In this model, the anisotropy of the surface energy is considered, and initial small nuclei with two fundamental orientations (normal and lateral) are assumed to be formed and dissociated repeatedly by the thermal energy. The critical energy of nucleus formation for each orientation is calculated as a function of the chemical-potential change of the system. The calculated results are similar to those observed for actual orientational phenomena of long-chain molecules at various chemical-potential changes; i.e., a higher substrate temperature and/or a lower deposition rate result/s in a higher degree of normal orientation.

Host sphingolipid biosynthesis as a target for hepatitis C virus therapy

An estimated 170 million individuals worldwide are infected with hepatitis C virus (HCV), a serious cause of chronic liver disease. Current interferon-based therapy for treating HCV infection has an unsatisfactory cure rate, and the development of more efficient drugs is needed. During the early stages of HCV infections, various host genes are differentially regulated, and it is possible that inhibition of host proteins affords a therapeutic strategy for treatment of HCV infection. Using an HCV subgenomic replicon cell culture system, here we have identified, from a secondary fungal metabolite, a lipophilic long-chain base compound, NA255 (1), a previously unknown small-molecule HCV replication inhibitor. NA255 prevents the de novo synthesis of sphingolipids, major lipid raft components, thereby inhibiting serine palmitoyltransferase, and it disrupts the association among HCV nonstructural (NS) viral proteins on the lipid rafts. Furthermore, we found that NS5B protein has a sphingolipid-binding motif in its molecular structure and that the domain was able to directly interact with sphingomyelin. Thus, NA255 is a new anti-HCV replication inhibitor that targets host lipid rafts, suggesting that inhibition of sphingolipid metabolism may provide a new therapeutic strategy for treatment of HCV infection.

Properties of Monolayers of Long-Chained Aliphatic Compounds Adsorbed at an Amalgamated Platinum Electrode

Electrochemical impedance spectra are obtained in a wide potential range for electrodes covered by monolayers of cetyl alcohol and stearic acid. The conditions for the determination of true values of the monolayer’s capacitance and ohmic resistance are found. It is shown that the restructuring of the stearic acid monolayer in alkaline solutions slightly increases its true resistance and consequently does not involve an increase in its dielectric constant. This validates the assumption on the thinning of the monolayer, which follows from the increase of its capacitance. The short-term adsorption of the above aliphatic compounds results in the formation of a monolayer whose chains are orientated parallel to the electrode surface while during the long-term adsorption, the chains are normal to the surface.

Validation of a screening method based on liquid chromatography coupled to high-resolution mass spectrometry for analysis of perfluoroalkylated substances in biota

A screening method for analysis of perfluoroalkylated substances (PFAS) in biota samples has been developed and validated using liver samples from polar cod ( Boreogadus saida) and glaucous gull ( Larus hyperboreus). The method was based on extraction of target compounds from homogenised samples into the solvent mixture used as mobile phase in high-performance liquid chromatography (HPLC), i.e. methanol/water (50:50; 2 mM ammonium acetate). The extract was filtered and directly injected into a HPLC/time-of-flight mass spectrometry (TOF-MS) system. Quantification was performed using 7 H-perfluoroheptanoic acid as internal standard and a calibration standard solution dissolved in sample extract for each matrix type (matrix-matched calibration standard). The method is very time and cost efficient. Except for long-chain compounds and perfluorooctane sulfonamide (which cannot be covered by this method), recoveries were between 60% and 115% and method detection limits were in the range 0.04–1.3 ng/g wet weight. Blank values could be neglected with the exception of perfluorooctane sulfonate (PFOS), perfluorohexanoic acid (PFHxA) and perfluorooctanoic acid (PFOA). One of the major challenges in PFAS analysis is ionisation disturbance by co-eluting matrix in the ion source of the mass spectrometer. Both matrix and analyte specific signal enhancement and suppression was observed and quantified. Repeated extractions ( n = 3) gave relative standard deviations (RSD) <35% for all PFAS. Accuracy was examined by comparing the screening method to the generally applied ion pair extraction (IPE) method. PFAS concentration values of a glaucous gull liver sample deviated by less than 30% for the two methods, provided that matrix-matched calibration standards were employed in both methods.

IR Spectra, Conformational Lability, and Intermolecular Interactions in Long‐Chain Aliphatic Compounds

AbstractFor Abstract see ChemInform Abstract in Full Text.

Quantitative determination of alkylated quaternary amines and their n‐hydroxylated metabolites in an enzyme incubation matrix by liquid chromatography electrospray ionization mass spectrometry

A simple, rapid and sensitive reversed-phase liquid chromatography method coupled to electrospray ionization mass spectrometry has been developed for studying the in vitro metabolism of the long-chain quaternary ammonium compounds dodecyltrimethylamine, tetradecyltrimethylamine and hexadecyltrimethylamine. Samples were prepared from the biological matrix by a simple protein precipitation stage. The separation was performed using a BDS Hypersil C8 3 microm particle size (100 x 3 mm i.d.) column with a fast gradient separation (60% B to 100% B) using a mobile phase of 10 mm aqueous ammonium acetate (pH 4.0, with 0.06% triethylamine; (A)-acetonitrile (B) at 0.7 mL min(-1). To minimize contamination of the MS source a switching value was used to divert the solvent front to waste. Decylammonium bromide was used as the internal standard and analytes were identified and quantified by positive ion electrospray selected ion monitoring of their intact molecular cations. The assay had a limit of quantitation of 0.25 microm (6.25 pmol on column) and was linear over the range 0.25--100 microm assay concentration for this series of long-chain quaternary amines. The precision of intra- and inter-day assays was better than 19% and the accuracy was between 93 and 109%. The method was used to assess the in vitro metabolism of the quaternary amines by wild-type cytochrome P450 enzyme CYP 4 A 1 and mutants in an artifical membrane system.

Synthesis and mesomorphic properties of glycosyl dialkyl- and diacyl-glycerols bearing saturated, unsaturated and methyl branched fatty acid and fatty alcohol chains: Part I. Synthesis

Glycosyl dialkyl- and diacyl-glycerols bearing saturated, unsaturated or chiral methyl branched chains in the tail and disaccharide and trisaccharide carbohydrate headgroups were synthesised. Standard procedures were used for the preparation of the educts and the glyco lipids: trichloracetimidate procedure for the preparation of long-chained compounds, glycosylation using the β-peracetate and boron trifluoride etherate was successful for the preparation of lipids with a medium-alkyl chain length. Preparation of the ester was afforded in a multi-step synthesis according to published procedures. Thus, several lipids were synthesised in a few synthetic steps in good yields. The introduction of unsaturated or methyl branched chains lead to liquid crystallinity at ambient temperature, because these compounds will be used as model compounds for biological systems. The biophysical properties of these compounds will be reported in a following paper.

Comparison of the Supramolecular Structures of Two Glyco Lipids with Chiral and Nonchiral Methyl-Branched Alkyl Chains from Natural Sources

Two alkyl glycosides with the same type of disaccharide headgroups (melibiose) and different methyl-branched alkyl chains, short chiral [(2R,4R,6R,8R)-2,4,6,8-tetramethyldecyl, extracted from an animal source] and long nonchiral (3,7,11,15-tetramethylhexadecyl, from a plant source), were synthesized. The supramolecular aggregate structure formed in dilute solutions was investigated by small-angle neutron scattering and surface tension measurements. The lyotropic phase diagram was studied by differential scanning calorimetry and water penetration scans. The thermotropic phase behavior was investigated by polarizing microscopy. The compounds showed unusual phase behavior: (i) The liquid-crystalline polymorphism is reduced to only form smectic A phases in the pure state; the formation of lyotropic phases such as hexagonal or lamellar phases was not observed. (ii) The compound with the longer nonchiral alkyl chain is more soluble in water than the one with the shorter chiral chain, most likely because of the different flexibilities of the chains. (iii) For the long-chain compound, the formation of micelles is observed, whereas the short-chain compound forms large disklike/bilayer aggregates. The method of methylation of the chain controls the self-assembly and can explain different biological functions for either plants (variable temperature) or animals (constant temperature).

Inelastic neutron scattering study on the polytypism of even-numbered [formula omitted]-alkanes

The thermodynamic properties of the two polytypes of n -hexatriacontane ( n - C 36 H 74 ), single-layered structure Mon and double-layered structure Orth II, have been studied with incoherent inelastic neutron scattering and solubility measurements. The solubility measurements show that Orth II is more stable than Mon, because of its larger entropy. The neutron scattering measurements reveal that the vibrational modes of Orth II shift to the lower frequencies compared with those of Mon in the frequency region below 120 cm - 1 . The vibrational modes in this region make a dominant contribution to the vibrational entropy of a system, and the advantage of Orth II in vibrational entropy due to the low-frequency shifts is estimated to be 7.8 J K - 1 mol - 1 at 288 K under the harmonic approximation, which is in good agreement with the entropy difference between Mon and Orth II determined by solubility measurements. These results suggest that the relative stability of polytypic structures of long-chain compounds is mainly determined by the vibrational entropy of the low-frequency modes.

Study of thermodynamic stabilities of polytypes of n-C36H74 by solubility measurements and incoherent inelastic neutron scattering

The thermodynamic properties of the two polytypes of n-hexatriacontane (n-C36H74), single-layered structure Mon and double-layered structure Orth II have been investigated by means of solubility measurements and incoherent inelastic neutron scattering. The solubility measurements reveal that Orth II is more stable than Mon by 1.2 kJ/mol because of the advantage of larger entropy. The neutron scattering measurements show that the vibrational modes of Orth II shift to the lower frequencies compared with those of Mon in the frequency region below 120 cm(-1). The advantage of Orth II in vibrational entropy due to the low-frequency shifts is estimated to be 9.6 J K(-1)/mol at 288 K under the harmonic approximation, which nearly agrees with the entropy difference of 6.8 J K(-1)/mol between Mon and Orth II determined by solubility measurements. These results suggest that the difference in vibrational entropy due to low-frequency modes mainly contributes to the relative thermodynamic stabilities of polytypic structures of long-chain compounds. From the frequency of methyl torsional mode, it is suggested that the cohesive force at the lamellar interface is stronger in Mon than in Orth II.

Distinct critical fluctuations and molecular motions manifest in a model biomembrane

Lattice dynamics in bis-( n-C 16H 37NH 3) 2SnCl 6, where the hydrocarbon part is analogous to lipid membrane, was investigated by means of 200 MHz 1H nuclear magnetic resonance. As a result, critical fluctuations and molecular dynamics associated with the phase transitions, an order–disorder and a conformational phase transition, were distinguished in a wide temperature range. The dynamical origin of the critical fluctuations, observed in the long-chain compounds but not in the short-chain compounds, by the laboratory frame spin–lattice relaxation measurements, is revealed and discussed in this work.

Implications of long-chain anteiso compounds in acidic freshwater lake environments: Inawashiro-ko in Fukushima Prefecture, Japan

A series of long-chain (⩾C 23) monomethyl-branched alkanes, alk-1-enes, alkanoic acids and alkanols were identified in settling particles and surface sediments from some acidic freshwater lakes in Japan by Fukushima et al. [Verh. Int. Verein. Limnol. 25 (1993) 835; Geochem. J. 30 (1996) 111]. Mass spectra of those branched compounds showed that the methyl side-chain is present at the C-3 position of alkanes, and at the ω-2 position in the functionalized compounds, i.e., the anteiso position. The present work was undertaken to evaluate the source of the anteiso compounds and to assess their utility as molecular markers of lake water acidity. The lake system examined is Inawashiro-ko, the third largest freshwater lake in Japan, where the pH is 5.0–5.5. The anteiso compounds are present in the sediments, as well as in suspended material in the lake water. In the water column, the majority of the anteiso compounds occur in the fine particulate matter (0.6 ≪ 40 μm). Analysis of the suspended materials in the inflowing river waters proves that the anteiso compounds are not transported from outside of the lake via any rivers, including the Nagase-gawa that acidifies the lake water. The results indicate that the anteiso compounds are produced within the lake by planktonic microbes and might be useful molecular markers for lake acidity.

Cuticular hydrocarbon dynamics in young adult Polistes dominulus (Hymenoptera: Vespidae) and the role of linear hydrocarbons in nestmate recognition systems

In social insects, cuticular hydrocarbons (CHCs) play an important role in nestmate discrimination processes, but young individuals are usually not discriminated. We studied CHC changes in young workers of the social wasp Polistes dominulus. A quantitative estimation demonstrated that total quantities of CHCs increased after emergence, with branched alkanes increasing drastically when compared with other classes of hydrocarbons. The relative quantity of longer-chain compounds increased with respect to shorter ones; unsaturated compounds decreased. These changes might reduce the capacity of the cuticle to acquire compounds of environmental origin. We then tested whether individuals acquire hydrocarbons from the environment, and whether this capability equally characterises newly emerged and mature wasps. We exposed wasps of two age classes (adults younger or older than 24h) to four linear hydrocarbons in turn, and observed how nestmates reacted to their re-introduction into the natal colony. Exposed young wasps elicited significantly more aggressive responses than control sisters; but treated wasps older than 24h were generally accepted by nestmates. Chemical assays showed that exposed young wasps readily absorbed hydrocarbons; older ones did not incorporate hydrocarbons, suggesting that the chemical profiles of mature wasps are less prone to chemical shifts than those of newly emerged wasps.

Wax and suberin development of native and wound periderm of potato (Solanum tuberosum L.) and its relation to peridermal transpiration.

Native and wound periderm was isolated enzymatically from potato (Solanum tuberosum L. cv. Desirée) tubers at different time intervals between 0 days up to 4 weeks after harvesting. Wound periderm formation was induced by carefully removing native periderm from freshly harvested tubers before storage. The chemical composition of lipids (waxes) obtained by chloroform extraction, as well as the monomeric composition of native and wound suberin polymer after transesterification by boron trifluoride/methanol, was analyzed using gas chromatography and mass spectrometry. Both types of periderm contained up to 20% extractable lipids. Besides linear long-chain aliphatic wax compounds, alkyl ferulates were detected as significant constituents. In wound periderm they amounted to more than 60% of the total extracts. Within 1 month of storage, suberin amounts in the polymer increased 2-fold in native periderm (180 microg cm(-2)), whereas in wound periderm about 75.0 microg cm(-2) suberin polymer was newly synthesized. Native potato tuber periderm developed a very efficient transport barrier for water with permeances decreasing from 6.4 x 10(-10) m s(-1) to 5.5 x 10(-11) m s(-1) within 1 month of storage. However, the water permeability of wound periderm was on average 100 times higher with permeances decreasing from 4.7 x 10(-8) m s(-1) after 3 days to only 5.4 x 10(-9) m s(-1) after 1 month of storage, although suberin and wax amounts in wound periderm amounted to about 60% of native periderm. From this result it must be concluded that the occurrence of suberin with wax depositions in cell walls does not necessarily allow us to conclude that these cell walls must be nearly perfect barriers to water transport. In addition to the occurrence of the lipophilic biopolymer suberin and associated waxes, the still unknown molecular arrangement and precisely localized deposition of suberin within the cell wall must contribute to the efficiency of suberin as a barrier to water transport.

04/01719 Identification of chemical structures in barkinite, vitrinite and fusinite using pyrolysis gas spectrometry: Sun, X. et al. Dizhi Xuebao, 2003, 77, (1), 135–143. (In Chinese)

The Permian Lepingian coal is known for its high content of , which is a unique liptinite macer-al located only in the Late Permian coals, South China. In this paper, Rock-Eval pyrolysis and pyrolysis gas chromatographic analyses were used to investigate the pyrolysate composition and the chemical structure of barkinite. At the same time, paralleled studies were also carried out on vitrinite and fusinite. The results show that at low temperatures, the pyrolyzates of and vitrinite are dominated by heteroatomic compounds, followed by aliphatic compounds, lower molecular (one- and two-ring) aromatic compounds (such as benzene and naphthalene), and alkyl aromatics (toluene and xylenes). However, the pyrolysis products of fusinite are mostly composed of aliphatic compounds. With increasing temperature, the proportion of aliphatic compounds from the three macerals increases, whereas the aromatic compounds and the heteroatomic compounds from barkinite and vitrinite decrease. At high temperatures, the pyrolysis products from these macerals sre dominated by low-chain aliphatic compounds. On the basis of these results, we can deduce that the chemical structures of these macerals are mainly composed of four kinds of function groups: (1) aliphatic compounds; (2) lower molecular (one- and two-ring) aromatic compounds, and alkyl aromatics; (3) heteroatomic function groups,- (4) multi-ring aromatics. The outlayers of the chemical structures of these coal macerals are mostly composed of heteroatomic compounds, lower molecular aromatic compounds and alkyl aromatics. The nucleus of the chemical structures of these coal macerals are dominated by multi-ring aromatic compounds. Between the outlayer and the nucleus, the chemical structures of these macerals are mainly composed of aliphatic compounds. The ways of hydrocarbon generation from coal macerals are based on the values of band energy. The smaller the bond energy function groups, the earlier they break off from coal macerals. Because heteroatomic compounds, benzene, naphthalene, toluene, xylenes, and long-chain aliphatic compounds have relatively low band energy, they were broken off from coal macerals first, then the higher-bond energy short-chain aliphatic compounds, and the remaining function groups in coal macerals are the multi-ring aromatic compounds of the highest bond energy.

Determination of long-chain fatty acid acyl-coenzyme A compounds using liquid chromatography–electrospray ionization tandem mass spectrometry

Acyl-CoAs have important role in fat and glucose metabolism of the cells. In this study we have developed an on-line HPLC–ESI-MS/MS method for determination of long-chain acyl-CoA compounds in rat liver samples. Six long-chain acyl-CoAs (C16:0, C16:1, C18:0, C18:1, C20:0 and C20:4) were separated with a C 4 reversed-phase column using triethylamine acetate and acetonitrile gradient. Negative electrospray ionization is very suitable for acyl-CoA compounds and excellent MS/MS spectra for long-chain acyl-CoAs can be obtained. MS/MS method with an ion trap mass spectrometer makes it possible to identify and quantitate individual acyl-CoAs simultaneously. The method proved to be sensitive enough for determination of all compounds of interest using 0.4–0.7 g of tissue and was validated in the range of 0.1–15.0 pmol/μl.

Amino acid-based surfactants

There is a pressing need for developing efficiently surfactants that are biodegradable and biocompatible. Surfactant molecules from renewable raw materials that mimic natural lipoamino acids are one of the preferred choices for food, pharmaceutical and cosmetic applications. Given their natural and simple structure they show low toxicity and quick biodegradation. The value of amino acids and vegetable oil derivatives as raw materials for the preparation of surfactants was recognized as soon as they were discovered early in the last century. The combination of polar amino acids/peptides (hydrophilic moiety) and non-polar long-chain compounds (hydrophobic moiety) for building up the amphiphilic structure has produced molecules with high surface activity. Our group has a wide experience in synthesis (chemical, enzymatic or, usually, by a combination of both methodologies) of amino acid-based surfactants obtained from the combination of natural saturated fatty acids, alcohols and amines with different amino acid head groups through ester and amide linkages. Thus, saturated single-chain, double-chain, and gemini surfactants of different ionic character have been found to be in all cases highly biodegradable, with low toxicity, ecotoxicity and irritation effects. Water solubility and self-aggregation properties were directly associated with the chemical structure of the molecule and only cationic lipoamino acids possessed antimicrobial activity. To cite this article: M.R. Infante et al., C. R. Chimie 7 (2004) .