Thin-layer Chromatography-flame Ionization Detection Research Articles

Characterization of Petroleum Heavy Oil Fractions Prepared by Preparatory Liquid Chromatography with Thin-Layer Chromatography, High-Resolution Mass Spectrometry, and Gas Chromatography with an Atomic Emission Detector

In this study, a preparatory-scale fractionation method was developed. To verify the effectiveness of this method, an oil sample was fractionated into five fractions, referred to as saturate, aro1, aro2, polar1, and polar2; these fractions were completely characterized by thin-layer chromatography–flame ionization detection (TLC–FID), field desorption (FD) and (+) atmospheric pressure photoionization (APPI) high-resolution mass spectrometry (HR-MS), and gas chromatography with an atomic emission detector (GC–AED). TLC–FID analysis was used to compare the results obtained by the fractionation method to those obtained from the conventional saturates, aromatics, resins, and asphaltenes (SARA) method. FD–MS was employed to characterize the hydrocarbon class compounds in the saturate and aro1 fractions. As observed from the FD–MS spectra, non-aromatic hydrocarbon compounds were abundant in saturates, while mono- and diaromatic compounds were abundant in the aro1 fraction. This result is in good agreement with ...

Characterization of pitch derived from pyrolyzed fuel oil using TLC-FID and MALDI-TOF

In this work, pitch was synthesized by a thermal reaction of pyrolyzed fuel oil (PFO), and its thermal properties were characterized using thermogravimetric and softening-point analyses. Thin-layer chromatography-flame ionization detection (TLC-FID) was performed to identify the saturated, aromatic, resin, and asphaltene (SARA) fractions to better understand the characteristics of the pitch produced during the high-temperature reaction of PFO. In addition, MALDI-TOF analysis was adapted to confirm the molecular weight segment. During the reaction, the thermal properties of the prepared pitch were determined as a function of the reaction time and temperature. The asphaltene fraction was generated as the aromatic fraction of the material decreased. The pitch properties were observed to be a function of the changes in the molecular weight distribution due to processes such as distillation, condensation, and cracking.

Application Evaluation of Asphalt mixtures using SDAR (Solvent DeAsphaltene Residue)

PURPOSES : The objective of this study is to evaluate the SDAR (solvent deasphaltene residue), which is obtained from the solvent deasphalting (SDA) process, as a pavement material. METHODS : The physical properties of the SDAR were evaluated based on its chemical composition, and asphalt mixtures with the SDAR were fabricated and used for the evaluation of mechanical properties. Firstly, the chemical composition of SARA (saturate, aromatic, resin and asphaltene) was analyzed using the TLC-FID (thin-layer chromatography-flame ionization detector). Moreover, the basic material properties of the asphalt binder with the SDAR were evaluated by the penetration test, softening point test, ductility test, and PG (performance grade) grade test. The rheological properties of the asphalt binder with the SDAR were evaluated by the dynamic shear modulus () obtained using the time-temperature superposition (TTS) principle. Secondly, the mechanical properties of the asphalt mixtures with the SDAR were evaluated. The compactibility was evaluated using the gyratory compacter. Moreover, the tensile strength ratio (TSR) was used for evaluating the moisture susceptibility of the asphalt mixtures (i.e., susceptibility to pothole damage). The dynamic modulus , which is a fundamental property of the asphalt mixture, obtained at different temperatures and loading cycles, was used to evaluate the mechanical properties of the asphalt mixtures. RESULTS AND CONCLUSION : The SDAR shows stiffer and more brittle behavior than the conventional asphalt binder. As the application of the SDAR directly in the field may cause early failures, such as cracks on pavements, it should be applied with modifiers that can favorably modify the brittleness property of the SDAR. Therefore, if appropriate additives are applied on the SDAR, it can be used as a pavement material because of its low cost and strong resistance to rutting.

Improved separation and analysis of glycolipids by Iatroscan thin-layer chromatography–flame ionization detection

We demonstrate improved power of Iatroscan thin layer chromatography/flame ionization detection (TLC–FID) technique for analysis of complex marine lipid mixture by developing protocol for the separation and analysis of glycolipids including sulfoquinovosyldiacylglycerols (SQDG), monogalactosyldiacylglycerols (MGDG) and digalactosyldiacylglycerols (DGDG). We have modified the common protocol used so far for the analysis of lipid classes by replacing the elution step which uses pure acetone for the elution of acetone mobile polar lipids, with the elution step containing chloroform–acetone (72:28, v:v) for separation of MGDG and DGDG. To separate SQDG from the complex lipid matrix we introduced solvent mixture acetone–chloroform–methanol–formic acid (33:33:33:0.6, v:v:v:v). Quantification of glycolipid classes was performed after calibration with glycolipid standards for the masses between 0.2 and 2.7–5.0μg. With this new protocol we have successfully separated three glycolipids from the complex particulate lipid mixture of the seawater samples. Such an approach extends the power of existing protocol for the analysis of lipids which altogether ensure detection and quantification of 18 lipid classes what was demonstrated on seawater samples. This enables to gain a very broad system overview of the particularly complex environments as are seas, oceans and freshwaters.

Investigation on recycling of SBS modified asphalt binders containing fresh asphalt and rejuvenating agents

The use of polymer modified asphalt binder in asphalt concrete pavements for over 20years, large numbers of waste modified asphalt mixture have been produced. In this study, regeneration of waste SBS modified asphalt binder was investigated by adding fresh SBS modified asphalt binder and rejuvenating agents. Effects of content of rejuvenating agent and ratio of recovery asphalt to fresh asphalt on physical properties of regenerated SBS modified asphalt binder were researched. The rheological behavior and short-term aging of regenerated SBS modified asphalt binder was investigated and chemical compound was analyzed using Thin-layer chromatography/flame ionization detection (TLC/FID) and Fourier Transform Infrared (FTIR) Spectroscopy. The results indicated that regenerated SBS modified asphalt binder with both good physical properties and pavement performances was obtained by blending recovered SBS modified asphalt with fresh SBS modified asphalt and rejuvenating agent, and the optimum physical and rheological properties occurred when the ratio of recovery asphalt to fresh asphalt was 35:65 and the content of rejuvenating agent was 5∼10 wt%. The result of RTFOT indicated that the regenerated SBS modified asphalt binder have good aging resistance, especially rejuvenating agent II was used to reclaimed SBS modified asphalt binder.

Measurement and analysis of small pelagic fish condition: A suitable method for rapid evaluation in the field

As condition is a key variable in population dynamics (especially for survival, growth and reproduction), the use of well-defined and accurate fish condition indices is capital. In particular, condition indices (morphometric, bioenergetic and biochemical) have never been compared and validated for the European anchovy Engraulis encrasicolus, the European pilchard Sardina pilchardus and the European sprat Sprattus sprattus. The accuracy of two indirect methods, the morphometric relative condition index Kn and the bioenergetics index determined with the Distell Fish Fatmeter was investigated by comparing with a direct measure of relative lipid content carried out with a thin layer chromatography-flame ionization detector. Estimations from the fatmeter correlated quite well with the relative lipid contents of all species, regardless of the reproductive period (R2=0.69 for anchovy, R2=0.75 for sprat and R2=0.48 for sardine). Kn correlated more poorly with relative lipid content (R2=0.22 for anchovy and R2=0.41 for sardine, ns for sprat), especially during the reproductive period, pointing out the difficulty for such an index to precisely reflect changes in fat allocation. During the reproductive period, changes in Kn could reflect other processes, such as changes in protein content. Therefore, these different types of commonly used indices do not reflect exactly the same type of energy stores. The high repeatability of the fatmeter was brought to light, so that only one measurement on each fish side may be necessary to evaluate the relative lipid content of a small pelagic fish. Finally, fatmeter measurements were not affected by freezing storage up to one month for anchovy (R2=0.66) and sardine (R2=0.90), making it possible to use frozen samples of both commercial and scientific survey. In contrast, the freezing storage for sprat should be avoided. Based on this study, the Fatmeter appears to be a suitable indirect method to assess condition and fat content of sardine and anchovy on a large number of individuals.

Chemical Characterization of Gilsonite Bitumen

This research provides new insights into the chemical composition of the Gilsonite in order to ascertain its properties which can assist in the refining and processing paths of the natural resource. Gilsonite, naturally occurring asphaltite bitumen, consists of a complex mixture of organic compounds. It was collected in the Uinta Basin near the town of Bonanza, Utah. The aim of this work is to obtain a more complete picture of molecular structure of Gilsonite, very important in fuel processing industry, matching and interpreting the results from different techniques. The Gilsonite was characterized by elemental analysis (EA) to determine the concentrations of C, H, N, S, and O, by Fourier transform infrared spectroscopy (FTIR) for comparative analysis of the chemical structures, by Nuclear magnetic resonance spectroscopy of hydrogen (1H NMR) to ascertain the aliphatic and aromatic hydrogen fractions, and by Thin layer chromatography-flame ionization detection (Iatroscan TLC-FID) to quantify saturated and aromatic hydrocarbons, and resin/asphaltene fractions. The results were evaluated in combination with the available geological data and with some bitumens to evaluate, chemically, possible mechanisms of Gilsonite formation. Low hydrogen to carbon atomic ratio (1.44), low sulfur (0.27 wt.%) and high nitrogen (3.25 wt.%) contents were the main characteristics of the Gilsonite from Uinta Basin. FTIR revealed the presence of alkane, aromatic rings, phenyl rings, alcohols, carbonyl groups, organic sulfoxides, and sulfate salts, confirming the fact that Gilsonite is composed of high molecular weight polycyclic constituents comprising of nitrogen, sulfur and oxygen heteroatoms. Likewise, FTIR proved that Gilsonite includes fingerprint of clay minerals. Iatroscan data showed interestingly that Gilsonite contains considerable amount of asphaltenes (79.7 wt.%) and nil amount of aromatics (0 wt.%). While, the yields of saturates and resins account only for 1.6 wt.% and 18.7 wt.%, respectively. Furthermore, SARA method estimated that Gilsonite is extremely instable (Colloidal instability index, CII = 4.34). Proton NMR measurements indicated that the aliphatic hydrogen portion is approximately 95.38% and the aromatic hydrogen fraction is about 4.62%.

A Simple Method for Determining the Flaxseed or Fish Oil Content with <i>N</i>,<i>N</i>-dimethylformamide in Microcapsules Prepared by Spray Drying

A simple method was developed for determination of the oil content in spray-dried microcapsules by dissolving the microcapsules in N,N-dimethylformamide (DMF). Powders containing flaxseed or fish oils were prepared by homogenization and subsequent spray drying to form coarse and fine emulsions. Sodium caseinate (SC) and maltodextrin (MD) were used as an emulsifier and wall material, respectively. The oil contents in the powders were quantified using a thin-layer chromatography-flame ionization detector after hexane extraction; the results agreed well with the initial oil contents on a dry basis in the feed emulsion, regardless of the oil-droplet size in the powders. The fatty acid compositions of the flaxseed and fish oils in the powders were obtained without an extraction process, using the proposed method. After dissolving the microcapsules in DMF, the peroxide value (POV) of the encapsulated oil was determined using the acetic acid- chloroform method. Although SC, MD, and DMF slightly increased the POV, the effect of the increase on the POV was not significant. The proposed method therefore enables easy and rapid estimation of the oil content, fatty acid composition, and POV of an encapsulated oil.

Detection of intracellular neutral lipid content in the marine microalgae Prorocentrum micans and Phaeodactylum tricornutum using Nile red and BODIPY 505/515

Diatoms and dinoflagellates not only have extensive distribution and a huge biomass in marine ecosystems, but also have high lipid accumulation in nature or after physiological and genetic modification, which indicates that these organisms may be optimal candidate algal strains for biodiesel production. In this study, we determined the content of intracellular neutral lipids (triacylglycerol [TAG]) in the dinoflagellate Prorocentrum micans and in the diatom Phaeodactylum tricornutum using NR and BODIPY 505/515 staining. The freshwater green alga Scenedesmus obliquus was used as a control. Optimum concentrations of 1.000 and 1.500 μg mL−1 were determined for neutral lipid Nile red (NR) staining in P. micans and P. tricornutum. Unlike NR staining, the optimal concentrations of BODIPY 505/515 staining in P. micans and P. tricornutum were lower, at 0.100 and 0.075 μg mL−1, respectively. High correlation coefficients of R2 = 0.990 and R2 = 0.989 were obtained for P. micans and P. tricornutum intracellular neutral lipid content and the relative fluorescence intensity with NR staining, while the reference alga, S. obliquus, had a relatively low correlation coefficient of R2 = 0.908 when stained with NR. The neutral lipid content determined by thin-layer chromatography-flame ionization detector matched the analytical data from fluorescence measurements. These results indicated that NR and BODIPY 505/515 staining can be used as an excellent high-throughput approach to screen marine diatoms and dinoflagellates.

The Use of a Nano-nickel Catalyst for Upgrading Extra-heavy Oil by an Aquathermolysis Treatment Under Steam Injection Conditions

Nano-nickel catalyst was prepared in microemulsion system, and used in the viscosity reduction process of extra-heavy oil by aquathermolysis. The results showed that the nano-nickel had a good catalytic performance in the aquathermolysis, and the viscosity of extra-heavy oil San56-13-19 was reduced by 90.36% at 200°C. The structure and group composition of the heavy oil were tested and analyzed by thin-layer chromatography-flame ionization detection, Fourier transform infrared spectroscopy, elemental analysis, vapor phase osmometer, and hydrogen-1 nuclear magnetic resonance before and after the aquathermolysis. It was found that the pyrolysis of asphaltene played a key role in viscosity reduction, and the O-containing products such as alcohol, carboxylate, and fatty acid can reduce the viscosity of heavy oil during the catalytic aquathermolysis.

Efficient and Quick Method for Saturates, Aromatics, Resins, and Asphaltenes Analysis of Whole Crude Oil by Thin-Layer Chromatography–Flame Ionization Detector

Saturates, aromatics, resins, and asphaltenes (SARA) analysis by thin-layer chromatography–flame ionization detector (TLC–FID) is a fast and efficient technique for group-type analysis of hydrocarbon residues. The present paper attempts to provide a new method for measurement of SARA fractions of whole crude oils using TLC–FID while addressing the issues related to FID calibration and loss of lighter hydrocarbon components during analysis. The experimental results obtained by the new method are compared to the traditional methods.

Keratins and lipids in ethnic hair

Human hair has an important and undeniable relevance in society due to its important role in visual appearance and social communication. Hair is mainly composed of structural proteins, mainly keratin and keratin associated proteins and lipids. Herein, we report a comprehensive study of the content and distribution of the lipids among ethnic hair, African, Asian and Caucasian hair. More interestingly, we also report the study of the interaction between those two main components of hair, specifically, the influence of the hair internal lipids in the structure of the hair keratin. This was achieved by the use of a complete set of analytical tools, such as thin layer chromatography-flame ionization detector, X-ray analysis, molecular dynamics simulation and confocal microscopy. The experimental results indicated different amounts of lipids on ethnic hair compositions and higher percentage of hair internal lipids in African hair. In this type of hair, the axial diffraction of keratin was not observed in X-ray analysis, but after hair lipids removal, the keratin returned to its typical packing arrangement. In molecular dynamic simulation, lipids were shown to intercalate dimers of keratin, changing its structure. From those results, we assume that keratin structure may be influenced by higher concentration of lipids in African hair.

Formation of semi-crystalline fraction, in which all diethylene glycol (DEG) is contained, during its extraction from human tissues: the probable cause of false negative results in fatal DEG poisoning cases

Dear Editor, Diethylene glycol (DEG) can be found in commercial products such as antifreeze, brake fluid, and lubricants. In addition, DEG has been found as a contaminant of raw materials in the production of pharmaceuticals. At least ten mass DEG poisoning events have occurred over the past 70 years. The first and largest outbreak, which resulted in 105 deaths, occurred in the United States in 1937 [1]. In 1967, a mass poisoning occurred in South Africa in which 7 children died [2]. In 1992 in Argentina, 29 people died after consuming propolis syrups that contained high DEG concentrations; the drug was widely commercialized in Argentina to treat mild upper respiratory tract infections [3]. Thereafter, pediatric medicinal syrups contaminated with DEG caused the deaths of 33 children in India in 1998 [4], and 85 children in Haiti in 1995–1996 [5]. The most recent outbreak took place in Panama in 2006, in which more than 100 people died due to DEG poisoning [1]. In spite of these repeated mass DEG poisonings, only a few analytical methods for DEG analysis, by gas chromatography (GC) [3] and GC–mass spectrometry (MS) [6–8], have been reported. There is a pressing need to establish and improve the methods for analysis of DEG, especially for postmortem human samples. As a result of our extensive experience in analysis of DEG in postmortem samples, we hereby report an important characteristic of DEG that we observed during sample extraction. Common chemicals, including ethylene glycol, DEG, fatty acids, phospholipids, and cholesterols, were of the highest chromatographic purity commercially available. GC was performed on a Shimadzu GC-14 A equipped with a Shimadzu CR 4A integrator (Shimadzu, Kyoto, Japan). A J&W DB-Wax column (30 m 9 0.53 mm i.d., 1.5 lm film thickness, Agilent, Santa Clara, CA, USA) was used. The injector temperature was set at 250 C and the flameionization detector (FID) was set at 250 C. An initial oven temperature of 110 C was held for 2 min before a temperature ramp of 8 C/min was used to reach the final temperature of 210 C. The carrier gas was nitrogen (12 cm/min). For thin-layer chromatography (TLC) analysis of lipid components, an Iatroscan TLC–FID apparatus (Mitsubishi Kagaku, Iatron, Tokyo, Japan) was used . Tissue samples (whole blood, liver, and kidney) were obtained from 15 victims of massive intoxication who ingested propolis syrups contaminated with DEG. Ten millilitres of blood was obtained by puncturing the femoral vein and was analyzed after 24 h. Fifty grams each of liver and kidney was taken from the victims and stored frozen at -20 C until analysis (3 days after collection). We isolated DEG from tissues by continuous Soxhlet extraction with methanol for 12 h. The extract obtained from each sample was purified using a charcoal column and evaporated to 1 ml. Then 10 ll of the concentrated extract was used for analysis of DEG by GC–FID. When the methanol extract was stored in a refrigerator at 2–4 C for several hours, a semi-crystalline substance appeared, adhering to the glass wall of the test tube. When subjected to GC analysis, the supernatant fraction of the This article is for the special issue TIAFT2012 edited by Osamu Suzuki.

Kinetics of methyl ester production from mixed crude palm oil by using acid-alkali catalyst

The production of biodiesel from high free fatty acid mixed crude palm oil using a two-stage process was investigated. The kinetics of the reactions was determined in a batch reactor at various reaction temperatures. It was found that the optimum conditions for reducing high free fatty acid (FFA) in MCPO (8–12 wt.%/wt oil) using esterification was a 10:1 molar ratio of methanol to FFA and using 10 wt.%/wt of sulfuric acid (based on FFA) as catalyst. The subsequent transesterification reaction to convert triglycerides to the methyl ester was found to be optimal using 6:1 molar ratio of methanol to the triglyceride (TG) in MCPO and using 0.6 wt.%/vol TG sodium hydroxide as catalyst. Both reactions were carried out in a stirred batch reactor over a period of 20 min at 55, 60 and 65 °C. The concentration of compounds in each sample was analyzed by Thin Layer Chromatography/Flame Ionization Detector (TLC/FID), Karl Fischer, and titration techniques. The results were used for calculating the rate coefficients by using the curve-fitting tool of MATLAB. Optimal reaction rate coefficients for the forward and reverse esterification reactions of FFA were 1.340 and 0.682 l mol −1 min −1, respectively. The corresponding optimal transesterification, rate coefficients for the forward reactions of TG, diglyceride (DG), and monoglyceride (MG) of transesterification were 2.600, 1.186, and 2.303 l mol −1 min −1, and for the reverse reactions were 0.248, 0.227, and 0.022 l mol −1 min −1, respectively.

Analysis of biodiesel conversion using thin layer chromatography and nonlinear calibration curves

Biodiesel (BD) is a fuel produced by the (trans)esterification reaction between the components of vegetable oil (or animal fat) and an alcohol. The presence of several substrates complicates analytical separation of the mixture, yet understanding of the complex reaction kinetics requires acquisition of a large body of data. The two well-established methods of gas chromatography (GC) and HPLC are time consuming and expensive when analyzing multiple samples. Additionally, it is not always possible to record all the reactants on one elution profile. We examined applicability of thin layer chromatography (TLC) for this purpose, where the detection was based on either flame ionization detector (FID) or a modified staining procedure. The suggested staining method gave no background and appeared well suited for quantitative analysis. The relevant calibrations are presented, and the general principles of analysis of nonlinear responses are discussed. Several experimental samples were produced by enzymatic conversion of rapeseed oil to BD. One reaction step resulted in 85–95% conversion (6 h). The second step (after removal of glycerol and water) increased the yield to 97–98%. All components of the mixtures were separated and quantified. Relation of the BD contents measured by TLC and GC gave the values of 1.03 ± 0.07 (TLC-staining) and 0.95 ± 0.04 (TLC–FID), indicating applicability of the TLC-methods.

Use of TLC‐FID and GC‐MS/FID to examine the effects of migratory state, diet and captivity on preen wax composition in White‐throated Sparrows Zonotrichia albicollis

Preen wax is important for plumage maintenance and other functions. Its chemical composition is complex, and separating and quantifying its components, commonly by gas chromatography (GC), can be challenging. We present a simple analytical system consisting of thin‐layer chromatography/flame ionization detection (TLC‐FID) using a solvent system of 100% toluene to analyse the complex compound classes present in preen wax. We used GC and TLC‐FID to investigate the effects of migratory status, diet and captivity on the preen wax composition of White‐throated Sparrows Zonotrichia albicollis, and to measure the quantity of preen wax on the head, primary and tail feathers. White‐throated Sparrows produced preen wax containing only monoesters regardless of migratory state. The monoesters contained several isomers consisting of homologous series of fatty alcohols (C10–C20) and fatty acids (C13–C19) esterified together in different combinations to form monoesters with total carbon numbers ranging from C23 to C38. Weighted average monoester carbon number was greater in captive birds than in wild birds and was greater in captives fed a formulated diet enriched with sesame oil than in birds fed the same diet enriched with fish oil. Captivity and migratory state also affected the complexity of the mixture of monoesters. There was significantly more preen wax on head feathers compared with primary and tail feathers. We suggest that among its many functions, preen wax may play a role in drag reduction by affecting the physical properties of feathers, and/or the fluid flow at their surfaces.

Mechanism of Catalytic Aquathermolysis: Influences on Heavy Oil by Two Types of Efficient Catalytic Ions: Fe3+ and Mo6+

In this paper, we have used thin-layer chromatography−flame ionization detection (TLC-FID), elemental (EL) analysis, 1H nuclear magnetic resonance (1H NMR), and gas chromatography/mass spectroscopy (GC/MS) to analyze the changes in heavy oil, reaction water, and pyrolytic gas during catalytic aquathermolysis comprehensively, and then describe the same and different influences on heavy oil during the aquathermolysis catalyzed by two types of typical efficient catalytic ions: Fe3+ and Mo6+. The results showed that, using these two ions, seven types of actions were observed during the reaction: pyrolysis; depolymerization; hydrogenation; isomerization; ring opening; oxygenation, alcoholization, and esterification; and reconstruction. It was also found that the former caused more changes in the resin, saturated hydrocarbon, and oxygen-containing groups, whereas the latter led to more changes in the asphaltene, aromatic hydrocarbon, and sulfur-containing groups.

LIPID CLASS, CAROTENOID, AND TOXIN DYNAMICS OF KARENIA BREVIS (DINOPHYCEAE) DURING DIEL VERTICAL MIGRATION1

The internal lipid, carotenoid, and toxin concentrations of Karenia brevis (C. C. Davis) Gert Hansen and Moestrup are influenced by its ability to use ambient light and nutrients for growth and reproduction. This study investigated changes in K. brevis toxicity, lipid class, and carotenoid concentrations in low-light, nitrate-replete (250 μmol quanta · m(-2) · s(-1) , 80 μM NO3 ); high-light, nitrate-replete (960 μmol quanta · m(-2) · s(-1) , 80 μM NO3 ); and high-light, nitrate-reduced (960 μmol quanta · m(-2) · s(-1) , <5 μM NO3 ) mesocosms. Reverse-phase HPLC quantified the epoxidation state (EPS) of the xanthophyll-cycle pigments diadinoxanthin and diatoxanthin, and a Chromarod Iatroscan thin layer chromatography/flame ionization detection (TLC/FID) system quantified changes in lipid class concentrations. EPS did not exceed 0.20 in the low-light mesocosm, but increased to 0.65 in the high-light mesocosms. Triacylglycerol and monogalactosyldiacylglycerol (MGDG) were the largest lipid classes consisting of 9.3% to 48.7% and 37.3% to 69.7% of total lipid, respectively. Both lipid classes also experienced the greatest concentration changes in high-light experiments. K. brevis increased EPS and toxin concentrations while decreasing its lipid concentrations under high light. K. brevis may mobilize its toxins into the surrounding environment by reducing lipid concentrations, such as sterols, limiting competition, or toxins are released because lipids are decreased in high light, reducing any protective mechanism against their own toxins.

Membrane remodeling and glucose in Drosophila melanogaster: A test of rapid cold-hardening and chilling tolerance hypotheses

Insect cold tolerance varies at both the population and species levels. Carbohydrate cryoprotectants and membrane remodeling are two main mechanisms hypothesised to increase chilling tolerance in Drosophila melanogaster, as part of both long-term (i.e., evolutionary) change and rapid cold-hardening (RCH). We used cold-selected lines of D. melanogaster with and without a pre-exposure that induces RCH to test three hypotheses: (1) that increased cold tolerance would be associated with increased free glucose; (2) that increased cold tolerance would be associated with desaturation of membrane phospholipid fatty acids; and (3) that increased cold tolerance would be associated with a change in phospholipid head group composition. We used colourimetric assays to measure free glucose and a combination of thin layer chromatography-flame ionization detection and gas chromatography to measure membrane composition. We observed a consistent decrease in free glucose with RCH, and no relationship between free glucose and basal cold tolerance. Also, phospholipid head group ratios and fatty acid composition showed no change following an RCH treatment. Thus, we conclude that changes in free glucose and membrane composition are unlikely to be significant determinants of variation in cold tolerance of D. melanogaster.

Inhibitory Effect of Aged Petroleum Hydrocarbons on the Survival of Inoculated Microorganism in a Crude-Oil-Contaminated Site

We studied the effects of aged total petroleum hydrocarbons (aged TPH) on the survival of allochthonous diesel-degrading Rhodococcus sp. strain YS-7 in both laboratory and field investigations. The aged TPH extracted from a crude oil-contaminated site were fractionized by thin-layer chromatography/flame ionization detection (TLC/FID). The three fractions identified were saturated aliphatic (SA), aromatic hydrocarbon (AH), and asphaltene-resin (AR). The ratio and composition of the separated fractions in the aged TPH were quite different from the crude-oil fractions. In the aged TPH, the SA and AH fractions were reduced and the AR fraction was dramatically increased compared to crude oil. The SA and AH fractions (2 mg/L each) of the aged TPH inhibited the growth of strain YS-7. Unexpectedly, the AR fraction had no effect on the survival of strain YS-7. However, crude oil (1,000 mg/L) did not inhibit the growth of strain YS-7. When strain YS-7 was inoculated into an aged crude oil-contaminated field and its presence was monitored by fluorescent in situ hybridization (FISH), we discovered that it had disappeared on 36 days after the inoculation. For the first time, this study has demonstrated that the SA and AH fractions in aged TPH are more toxic to an allochthonous diesel-degrading strain than the AR fraction.