Mixture Of Homologues Research Articles

SUCCESSFUL SEPARATION AND DETERMINATION OF BIOLOGICALLY ACTIVE OF ES-SILANATES FOR ISOTACHOPHORESIS

Hypercoordinated compounds, which belong to the group of ES-silanates, show biological activity. In the course of our work, an optimization of conditions for the determination of individual derivatives and separation of a mixture of homologs of ES-silanates by means of capillary isotachophoresis (ITP) was carried out. The investigations considered: 1-[(N,N-dimethyl)aminiomethyl]spirobi(1-sila-2,5-dioxacyclopentan-3-on)at and 1-[(N,N-dimethyl)aminiomethyl]spirobi(1-sila-2,5-dioxa-4-methylcyclopentan-3-on)at. A new terminating electrolyte was proposed: 4,4′-bis[1-{(N,N-dimethyl)aminiomethyl]spirobi(1-sila-2,5-dioxacyclopentan-3-on)at}. Optimum time of analysis did not exceed 7 min. Elaborated method of separation and determination of ES-silanates widens the possibility of research of biological activity of this group of compounds and its applications.

Crossover temperature (T CO) and the temperature gradient of refractive indices of a homologous mixture of 4O.6 and 6O.4

Temperature gradient of refractive indices, dn e /dT and dn o /dT, of the isotropic mixtures of the liquid crystals of nO.m compounds, namely N-(p-n-butyloxybenzylidene)-p-n-hexyl aniline, 4O.6, and N-(p-n-hexyloxybenzylidene)-p-n-butyl aniline, 6O.4, are estimated using the refractive index data. The former one exhibits a second-order nematic-to-smectic-A (N-SmA) phase transition, while the later compound shows a first-order (N-SmA) phase transition. These two compounds exhibit high clearing temperatures, i.e. well above the room temperature. It is found that the two materials and the mixtures exhibiting second-order N-SmA transition show the crossover temperatures (T CO’s) well below the room temperature while the mixtures showing first-order transition exhibiting T CO’s well above the room temperature.

Biodegradation of Alcohol Ethoxylates by Bacterial Consortium from Industrial Wastewater

AbstractIndustrial waste water, can contain pollutions such as inorganic water-insoluble substances (in particular sewage from electroplating). In nature, the microorganisms play a special role in maintaining life on earth. The decomposition of organic compounds into simple minerals is the main link in the circulation of biogenic elements, especially carbon, nitrogen, phosphorus, sulfur and other. The aim of the study was to evaluate the biodegradability of a model nonionic surfactant and identification of metabolites generated in the process of biodegradation using microbial consortium originating from electroplating wastewater. Tested model nonionic surfactant C12E10 is a mixture of polydisperse homologues of C12Ex, C14Ex and C16Ex series. Alcohol ethoxylates were isolated by liquid-liquid extraction (LLE) using chloroform. Aliquot of the extract was evaporated and reconstituted in the mobile phase for further LC-MS analysis.

Reminiscences of research on the chemistry and biology of natural sterols in insects, plants and humans.

Natural sterols often occur as a heterogeneous mixture of homologs, which had disturbed the progress of steroid research. Development and application of GC methodology overcame this difficulty and enabled us to obtain detailed sterol profiles. Together, fine synthesis of stereo-defined isomers and homologs of steroids having oxygenated side chains allowed us to compare them with natural samples as well as to investigate structure-activity relationship. Advance of HPLC technology also facilitated the determination of the stereochemical structure of naturally occurring steroidal compounds, which were obtained only in minute amounts. This review highlights three topics out of our steroid research that have been performed mainly at Tokyo Institute of Technology around 1970–1990. These are sterol metabolism in insects focusing on the mechanism of the conversion of plant sterols to cholesterol and ecdysone biosynthesis, the synthesis and biochemical research of active forms of vitamin D3 derivatives, and the synthesis and microanalysis of plant hormone brassinosteroids.

Optimising Immunogenicity with Viral Vectors: Mixing MVA and HAdV-5 Expressing the Mycobacterial Antigen Ag85A in a Single Injection

The Bacillus Calmette - Guerin (BCG) vaccine provides a critical but limited defense against Mycobacterium tuberculosis (M.tb). More than 60 years after the widespread introduction of BCG, there is an urgent need for a better vaccine. A large body of pre-clinical research continues to support ongoing clinical trials to assess whether viral vectors expressing M.tb antigens that are shared by BCG and M.tb, can be used alongside BCG to enhance protection. A major focus involves using multiple unique viral vectors to limit anti-vector immunity and thereby enhance responses to the insert antigen delivered. The successful introduction of viral vector vaccines to target M.tb and other pathogens will be reliant on reducing the costs when using multiple vectors and inhibiting the development of unwanted anti-vector responses that interfere with the response to insert antigen. This study examines methods to reduce the logistical costs of vaccination by mixing different viral vectors that share the same insert antigen in one vaccine; and whether combining different viral vectors reduces anti-vector immunity to improve immunogenicity to the insert antigen. Here we show that a homologous prime-boost regimen with a mixture of MVA (Modified Vaccinia virus Ankara) and Ad5 (human adenovirus type 5) vectors both expressing Ag85A in a single vaccine preparation is able to reduce anti-vector immunity, compared with a homologous prime-boost regimen with either vector alone. However, the level of immunogenicity induced by the homologous mixture remained comparable to that induced with single viral vectors and was less immunogenic than a heterologous Ad5 prime-MVA-boost regimen. These findings advance the understanding of how anti-vector immunity maybe reduced in viral vector vaccination regimens. Furthermore, an insight is provided to the impact on vaccine immunogenicity from altering vaccination methods to reduce the logistical demands of using separate vaccine preparations in the field.

Thermal analysis of hydrogen bonded benzoic acid liquid crystals

Novel homologous series of supramolecular hydrogen bonded liquid crystals have been investigated. Hydrogen bonds are formed between p-n octyloxy benzoic acid and various p-n alkyloxy benzoic acids whose carbon chain length varied from pentyl to dodecyl. These complexes are characterized by Fourier transform infrared spectroscopy, polarizing optical microscopy (POM), and differential scanning calorimetry (DSC). Phase diagram is constructed from POM and DSC data. The order of the phase transitions is determined by Navard and Cox ratio (NR). Characteristic phases like nematic, smectic C, and smectic F are identified. A new smectic ordering observed in this series is investigated by constructing phase diagram obtained from two binary mixtures of the present homologs. Inter-digitation of lamellar layers is observed to be one of the reasons for the occurrence of new smectic ordering. Optical tilt angle in smectic C phase is fitted to a power law. The magnitude of exponent of the power law is found to concur with the Mean Field theory predicted value.

Increase in flotation activity of salts of higher aliphatic amines, potassium chloride collectors

For increasing the flotation activity of potassium chloride collector, salts of higher aliphatic amines, effects of a temperature of collector solutions, mixtures of homologues of different chain length, a solubilization of organic oleophilic compounds in the colloidal solutions of amine salts were examined on their micellar structure and ion-molecular composition.

Revisiting the enniatins: a review of their isolation, biosynthesis, structure determination and biological activities.

Enniatins are cyclohexadepsipeptides isolated largely from Fusarium species of fungi, although they have been isolated from other genera, such as Verticillium and Halosarpheia. They were first described over 60 years ago, and their range of biological activities, including antiinsectan, antifungal, antibiotic and cytotoxic, drives contemporary interest. To date, 29 enniatins have been isolated and characterized, either as a single compound or mixtures of inseparable homologs. Structurally, these depsipeptides are biosynthesized by a multifunctional enzyme, termed enniatin synthetase, and are composed of six residues that alternate between N-methyl amino acids and hydroxy acids. Their structure elucidation can be challenging, particularly for enniatins isolated as inseparable homologs; however, several strategies and tools have been utilized to solve these problems. Currently, there is one drug that has been developed from a mixture of enniatins, fusafungine, which is used as a topical treatment of upper respiratory tract infections by oral and/or nasal inhalation. Given the range of biological activities observed for this class of compounds, research on enniatins will likely continue. This review strives to digest the past studies, as well as, describe tools and techniques that can be utilized to overcome the challenges associated with the structure elucidation of mixtures of enniatin homologs.

Alkyl Poly Glucosides (APGs) Surfactants and Their Properties: A Review

AbstractAlkyl polyglucosides are non-ionic surfactants consisting of a hydrophilic saccharide moiety and a hydrophobic fatty alkyl chain. They are synthesized from renewable raw materials and have excellent ecotoxicological profiles and are readily biodegradable. The alkyl polyglucosides are mixtures of homologues, anomers and isomers. The alkyl polyglucosides with a longer alkyl chain biodegrade faster than those with a shorter one. The short to medium alkyl chain containing alkyl polyglucosides are water soluble. They exhibit favorable wetting and surface tension reduction, electrolyte and hard water tolerance, great stability in wide pH range, synergism with other surfactants and act as hydrotropes and dispersants. The dermatological, toxicological, mildness and high compatibility to skin make alkyl polyglucosides superior to all other existing surfactants. They show good functionality in various applications like detergents, food emulsifiers, cosmetic surfactants, industrial emulsifiers and pharmaceutical granulating agents.

Individual and mixed adsorption of alkylcarboxylbetaines and fatty amide ethoxylates at Daqing sandstone/water interface

The individual adsorption of a series of alkylcarboxylbetaines, including single long-alkyl dimethylcarboxylbetaine (C12B, C14B, C16B, and C18B) and didodecylmethyl-carboxylbetaine (diC12B), as well as fatty amide ethoxylates (C12MEA-EO1 and CMEA-EO2), at negatively charged Daqing sandstone/water interface at 45°C were studied and compared with that of typical anionic and cationic surfactants. The results show that the saturated adsorption of surfactants at solid/water interface can be well characterized by a layer number, n, defined as the ratio of the saturated adsorption at solid/water interface to that at air/water interface, and in general the saturated adsorption of different species follows an order of anionic (n<0.5)<nonionic (0.5<n<1)<zwitterionic (n>1)<cationic surfactants (n>2). The adsorption of the alkylcarboxylbetaines is initially driven by the electrostatic interaction between the positive charges in surfactant molecules and negative charges on surface followed by the chain–chain interaction which inducing admicelle formation on the solid surface. The single long-alkyl carboxylbetaines have similar saturated adsorption, i.e. with n between 1.49 and 1.71, but the double long-alkyl carboxylbetaine, diC12B, gives a relatively lower n value (1.07) although it has a comparative saturated adsorption at solid/water interface due to its high adsorption at air/water interface. Lacking of the electrostatic interaction, the saturated adsorption of the fatty amide ethoxylates is in general low, as indicated by their low n values (0.595 and 0.526).For mixed adsorption systems nearly ideal mixing and middle synergism are observed for diC12B/C12B (homologous mixture), and diC12B/C12MEA-EO1/(zwitterionic/nonionic) mixtures, but strong synergisms are observed for SDS/C12B and SDS/C16B (anionic/zwitterionic) mixtures. Thus for surfactant–polymer flooding the achievement of low adsorption retention depends strongly on the species selected if mixed surfactants are necessary.

Quantitative analysis of enzymatic fractionation of multiple substrate mixtures

The enzymatic conversion of mixtures of multiple substrates was studied quantitatively, based on established methodology used for the enzymatic kinetic resolution of racemic mixtures, involving the use of competitive factors: ratios of specificity constants (k(cat)/K(M)) of substrate pairs. The competitive factors of the substrates were defined in relation to a reference substrate. These competitive factors were used to predict the composition of the reaction mixture as a function of the degree of conversion of the reaction. The methodology was evaluated using three different lipases to hydrolyze a model mixture of four fatty acid methyl esters and for the esterification of a mixture of the same fatty acids in free form with ethanol. In most cases, the competitive factors determined from the initial phase of the reactions predicted the product composition during the rest of the reaction very well. The slowest reacting fatty acid was erucic acid (both in free form and as methyl ester), which was thus enriched in the remaining substrate fraction, while the other fatty acids: lauric acid, palmitic acid and oleic acid were converted faster. Simulations of the compositions of reaction mixtures with different values of the competitive factors were carried out to provide an overview of what could be achieved using enzymatic enrichment. Possible applications include reactions involving homologous substrates and mixtures of multiple isomers. The analysis presented provides guidelines that can be useful in the screening and development of enzymes for enzymatic enrichment applications.

Separation of α-Tocopherol with a Two-Feed Simulated Moving Bed

A two-feed simulated moving bed (SMB) was proposed to utilize the stationary phase more effectively. Zone I is disconnected with zone II and zone III is disconnected with zone IV. Two feeds are added to zones I and III, while two desorbents are added to zones II and IV separately. The investigation on the movement of concentration bands indicated that the tail of the strong retained solute and the front of the weak retained solute were eluted from zones I and III orderly, so the streams from zones I and III could be cut into different fractions to give the products with high purity. The two-feed SMB was used to separate α-tocopherol from its homologue mixture successfully, and could double the productivity if both feeds were identical to the feed in the conventional four-zone SMB. The solvent consumption could be reduced by reusing the middle fraction without solutes.

Cyclic lipopeptide profile of the plant-beneficial endophytic bacterium Bacillus subtilis HC8

In a previous study (Malfanova et al. in Microbial Biotech 4:523–532, 2011), we described the isolation and partial characterization of the biocontrol endophytic bacterium B. subtilis HC8. Using thin-layer chromatography, we have detected several bioactive antifungal compounds in the methanolic extract from the acid-precipitated supernatant of HC8. In the present study, we have further analyzed this methanolic extract using liquid chromatography-mass spectrometry. Based on the comparison of retention times and molecular masses with those of known antifungal compounds, we identified three families of lipopeptide antibiotics. These include four iturins A having fatty acyl chain lengths of C14 to C17, eight fengycins A (from C14 to C18 and from C15 to C17 containing a double bond in the acyl chain), four fengycins B (C15 to C18), and five surfactins (C12 to C16). Evaluation of the antifungal activity of the isolated lipopeptides showed that fengycins are the most active ones. To our knowledge, this is the first report of an endophytic Bacillus subtilis producing all three major families of lipopeptide antibiotics containing a very heterogeneous mixture of homologues. The questions remain open which of these lipopeptides (1) are being produced during interaction with the plant and (2) are contributing to the biocontrol activity of HC8.

Development of a liquid chromatography tandem mass spectrometry method for trace analysis of trisiloxane surfactants in the aqueous environment: An alternative strategy for quantification of ethoxylated surfactants

Trisiloxane surfactants, often referred to as superspreaders or superwetters, are added to pesticides to enhance the activity and the rainfastness of the active substance by promoting rapid spreading over hydrophobic surfaces. To fill the lack of data on the environmental occurrence of these compounds, we have developed and validated a method for their trace analysis in the aqueous environment. The method is based on liquid–liquid extraction followed by liquid chromatography and tandem mass spectrometry. The oligomeric distribution of trisiloxane surfactant in a reference solution was determined by a theoretical calculation and by experimental measurements. Based on these results, the quantification was performed by comparison with a calibration made with a single homologue instead of a mixture of homologues. This approach avoids a time-consuming synthesis of pure homologues and reduces the risk of wrong estimation of the concentration because of different response factors of the sample and the standard. Such an approach could be applied to the quantification of other ethoxylated surfactants following a similar distribution. The validation was performed from 2 to 250ng/L (total surfactant concentration) in deionized water, tap water, and river water (Rhine water). Knowing the oligomeric distribution of the polymer in the reference solution, the corresponding calibration ranges were estimated for individual homologues. Limits of quantification were found to be between 0.37ng/L and 15ng/L. The total recovery of sample preparation was between 77% and 116%. Matrix effects were lower than 10% with river water and the relative standard deviation evaluated over ten identical samples of spiked river water was below 12%.

Modified normal-phase ion-pair chromatographic methods for the facile separation and purification of imidazolium-based ionic compounds

Imidazolium- and oligo(imidazolium)-based ionic organic compounds are important in the design of room-temperature ionic liquid materials; however, the chromatographic analysis and separation of such compounds are often difficult. A convenient and inexpensive method for effective thin-layer chromatography (TLC) analysis and column chromatography separation of imidazolium-based ionic compounds is presented. Normal-phase ion-pair TLC is used to effectively analyze homologous mixtures of these ionic compounds. Subsequent separation of the mixtures is performed using ion-pair flash chromatography on normal-phase silica gel, yielding high levels of recovery. This method also results in a complete exchange of the counter anion on the imidazolium compounds to the anion of the ion-pair reagent.

Interfacing Multistage Mass Spectrometry with Liquid Chromatography or Ion Mobility Separation for Synthetic Polymer Analysis

Synthetic polymers are naturally mixtures of homologs, even in pure form. More complexity is introduced by the presence of different comonomers, end groups and/or macromolecular architectures. The analysis of such systems is substantially facilitated by interfacing mass spectrometry (MS), which disperses based on mass, with an additional level of separation involving either interactive liquid chromatography (LC) or ion mobility (IM) spectrometry, both of which are readily coupled online with electrospray ionization and MS detection. IM-MS separates in the gas phase, post-ionization and, therefore, is ideally suitable for labile and reactive polymers. Its usefulness is illustrated with the characterization of non-covalent siloxane-saccharide complexes, metallosupramolecular assemblies and an air- and moisture-sensitive inorganic polymer, poly(dichlorophosphazene). Conversely, LC-MS which separates in solution phase, before ionization, is most effective for the analysis of polymeric mixtures whose components differ in polarity. Interactive LC conditions can be optimized to disperse by the content of hydrophobic units, as is demonstrated for amphiphilic polyether copolymers and sugar-based nonionic surfactant blends. Both LC-MS and IM-MS can be extended into a third dimension by tandem mass spectrometry (MS(2)) studies on select oligomers, in order to obtain insight into individual end groups and isomeric architectures, comonomer sequences and degree of substitution, for example, by hydrophobic functionalities.

Binary mixtures of liquid crystalline compounds with a reentrant smectic-A*phase

Binary mixtures of chiral liquid crystalline homologs have been studied. One compound designated 9ZBL exhibited reentrancy of a paraelectric smectic-A* phase, SmA*(RE), below the ferroelectric SmC* phase in the SmA*-SmC*-SmA*RE phase sequence. Stabilization of the SmA(RE) phase is established from studying binary mixtures of 9ZBL with its neighboring homologs 8ZBL and 10ZBL. Compound 8ZBL exhibits only SmA* phase in a wide temperature range and for 10ZBL the SmA*-SmC* phase sequence is observed on cooling. X-ray studies, dielectric spectroscopy, polarization, and tilt angle measurements have been carried out to characterize studied materials. For binary mixtures 9ZBL-10ZBL the reentrant SmA_(RE*) phase is observed for all studied concentrations. For binary mixtures 9ZBL-8ZBL a very small amount of 8ZBL (up to 0.5 mole %) causes disappearance of the SmC* phase. Nevertheless, a small anomaly in the temperature dependencies of the layer spacing, d(T), accompanied by a significant decrease in diffracted x-ray intensity occurs within the SmA* phase for mixtures containing up to 20 mole % of 8ZBL. This anomaly is evidence of the existence of a boundary between the SmA* and SmA(RE*) phases, thus proving their different nature.

A chemical investigation of the Antarctic sponge Lyssodendoryx flabellata

From the Antarctic sponge Lyssodendoryx flabellata, a new polycyclic compound, which we named flabellone, related to the oestrogenic hormone oestrone, has been elucidated by spectrometric and spectroscopic means. Along with flabellone, a glycosphingolipid (GSL) mixture featuring an unusual α-fucofuranosyl-3-β-glucopyranoside unit structurally identical to the previously reported terpioside has been isolated and identified. The mixture of GSL homologues exhibited inhibitory effects in mixed lymphocyte reactions on human cells.

Chemical Characterization and Physical and Biological Activities of Rhamnolipids Produced by Pseudomonas aeruginosa BN10

Pseudomonas aeruginosa BN10 isolated from hydrocarbon-polluted soil was found to produce rhamnolipids when cultivated on 2% glycerol, glucose, n-hexadecane, and n-alkanes. The rhamnolipids were partially purified on silica gel columns and their chemical structures elucidated by combination of one- and two-dimensional 1H and 13C NMR techniques and ESI-MS analysis. Eight structural rhamnolipid homologues were identified: Rha-C10-C8, Rha-C10-C10, Rha-C10-C12:1, Rha-C10-C12, Rha2-C10-C8, Rha2-C10-C10, Rha2-C10-C12:1, and Rha2-C10-C12. The chemical composition of the rhamnolipid mixtures produced on different carbon sources did not vary with the type of carbon source used. The rhamnolipid mixture produced by Pseudomonas aeruginosa BN10 on glycerol reduced the surface tension of pure water from 72 to 29 mN m(-1) at a critical micellar concentration of 40 mg 1(-1), and the interfacial tension was 0.9 mN m(-1). The new surfactant product formed stable emulsions with hydrocarbons and showed high antimicrobial activity against Gram-positive bacteria. The present study shows that the new strain Pseudomonas aeruginosa BN10 demonstrates enhanced production of the di-rhamnolipid Rha2-C10-C10 on all carbon sources used. Due to its excellent surface and good antimicrobial activities the rhamnolipid homologue mixture from Pseudomonas aeruginosa BN10 can be exploited for use in bioremediation, petroleum and pharmaceutical industries.

Determination of the homologue composition of some alkyltrimethyl quaternary ammonium antibacterial agents by gas chromatography

Abstract RECENT work has shown that the micellar properties of quaternary ammonium surface-active agents may be linked with their antibacterial action (Weiner, Hart &amp; Zografi, 1965). Micelle formation and antibacterial activity both depend markedly on the chain length of the hydrocarbon groups attached to the quaternary nitrogen, and other biological properties may also depend on this aspect of their structure (Hart &amp; Nissim, 1966). Commercially produced materials are mixtures of homologues and a method is described below for measuring the homologue composition.