Effect of sterol structure on ordered membrane domain (raft) stability in symmetric and asymmetric vesicles

Sterol structure influences liquid ordered domains in membranes, and the dependence of biological functions on sterol structure can help identify processes dependent on ordered domains. In this study we compared the effect of sterol structure on ordered domain formation in symmetric vesicles composed of mixtures of sphingomyelin, 1, 2-dioleoyl-sn-glycero-3-phosphocholine (DOPC) and cholesterol, and in asymmetric vesicles in which sphingomyelin was introduced into the outer leaflet of vesicles composed of DOPC and cholesterol. In most cases, sterol behavior was similar in symmetric and asymmetric vesicles, with ordered domains most strongly stabilized by 7-dehydrocholesterol (7DHC) and cholesterol, stabilized to a moderate degree by lanosterol, epicholesterol and desmosterol, and very little if at all by 4-cholesten-3-one. However, in asymmetric vesicles desmosterol stabilized ordered domain almost as well as cholesterol, and to a much greater degree than epicholesterol, so that the ability to support ordered domains decreased in the order 7-DHC > cholesterol > desmosterol > lanosterol > epicholesterol > 4-cholesten-3-one. This contrasts with values for intermediate stabilizing sterols in symmetric vesicles in which the ranking was cholesterol > lanosterol ~ desmosterol ~ epicholesterol or prior studies in which the ranking was cholesterol ~ epicholesterol > lanosterol ~ desmosterol. The reasons for these differences are discussed. Based on these results, we re-evaluated our prior studies in cells and conclude that endocytosis levels and bacterial uptake are even more closely correlated with the ability of sterols to form ordered domains than previously thought, and do not necessarily require that a sterol have a 3β-OH group.     

种植体周围炎生物膜的微生物群落多样性研究进展

种植体周围炎是发生在骨性结合种植体周围组织的炎症,是由微生物引发的感染性疾病,可引起种植体周围支持组织丧失而导致种植失败。阐明种植体周围炎生物膜的微生物学基础,可为制定相应防治策略提供理论依据。随着测序技术的发展,基于16S rRNA基因的测序分析技术逐渐应用于与口腔种植体相关的微生物学研究,使人们对种植体周围炎生物膜的微生物群落多样性有了更全面的了解,也进一步认识到种植体周围炎和牙周炎菌斑生物膜的微生物结构存在显著差别。本文根据基于16S rRN基因A序列分析技术的最新研究成果,对种植体周围炎菌斑生物膜的微生物学研究进展作一综述。     

Advances in thermochemical conversion of woody biomass to energy,fuels and chemicals

Biomass has been recognised as a promising resource for future energy and fuels. The biomass, originated from plants, is renewable and application of its derived energy and fuels is close to carbon-neutral by considering that the growing plants absorb CO₂ for photosynthesis. However, the complex physical structure and chemical composition of the biomass significantly hinder its conversion to gaseous and liquid fuels.This paper reviews recent advances in biomass thermochemical conversion technologies for energy, liquid fuels and chemicals. Combustion process produces heat or heat and power from the biomass through oxidation reactions; however, this is a mature technology and has been successfully applied in industry. Therefore, this review will focus on the remaining three thermochemical processes, namely biomass pyrolysis, biomass thermal liquefaction and biomass gasification. For biomass pyrolysis, biomass pretreatment and application of catalysts can simplify the bio-oil composition and retain high yield. In biomass liquefaction, application of appropriate solvents and catalysts improves the liquid product quality and yield. Gaseous product from biomass gasification is relatively simple and can be further processed for useful products. Dual fluidised bed (DFB) gasification technology using steam as gasification agent provides an opportunity for achieving high hydrogen content and CO₂ capture with application of appropriate catalytic bed materials. In addition, multi-staged gasification technology, and integrated biomass pyrolysis and gasification as well as gasification for poly-generation have attracted increasing attention.     

Screening of free 17-alkyl-substituted anabolic steroids in human urine by liquid chromatography-electrospray ionization tandem mass spectrometry

A qualitative liquid chromatography-electrospray ionization tandem mass spectrometry method was developed for screening of the abuse of 4-chlorodehydromethyltestosterone, danazol, fluoxymesterone, formebolone, metandienone, oxandrolone, and stanozolol. The introduced method measures simultaneously nine different 17-alkyl-substituted anabolic androgenic steroids or their unconjugated metabolites in human urine, using methyltestosterone as an internal standard. Sample preparation involved one-step liquid extraction. Liquid chromatographic separation was achieved on a reversed-phase column with methanol-water gradient containing 5 mmol/l ammonium acetate and 0.01% (v/v) acetic acid. Compounds were ionized in the positive mode and detected by multiple reaction monitoring. All steroids within the study could be selectively detected in urine with detection limits of 0.1-2.0 ng/ml. The method showed good linearity up to 250 ng/ml with correlation coefficients higher than 0.9947. With simple and fast sample preparation, low limits of detection, and high selectivity and precision, the developed method provides advantages over the present testing methods and has the potential for routine qualitative screening method of unconjugated 17-alkyl-substituted anabolic steroids in human urine.     

Peptide separation by Hydrophilic-Interaction Chromatography: a review

Recent developments in the separation of peptides by high-performance liquid chromatography (HPLC) using polar sorbents with less polar eluents are summarized in this review. This separation mode is now commonly referred to as Hydrophilic-Interaction Chromatography (HILIC). The retention mechanism and chromatographic behavior of polar solutes under HILIC conditions are studied on TSKgel Amide-80 columns, which consist of carbamoyl groups bonded to a silica gel matrix, using a mixture of acetonitrile (MeCN)–water containing 0.1% trifluoroacetic acid (TFA). Some applications are given in peptide field using Hydrophilic-Interaction Chromatography.     

Plasma appearance and tissue accumulation of non-esterified, free astaxanthin in C57BL/6 mice after oral dosing of a disodium disuccinate diester of astaxanthin (Heptax)

Oral bioavailability of natural and synthetic carotenoids is generally poor in rodents, and this has limited the ability to test these antioxidant compounds in well-defined rodent models of human disease. Various strategies have been employed, with variable success, to increase the percentage of the total oral dose absorbed by the rodent GI tract. In the current study, a novel carotenoid derivative (the disodium disuccinate diester of astaxanthin; Heptax) was administered by oral gavage in a lipophilic emulsion to C57BL/6 mice. Plasma appearance and tissue accumulation of non-esterified, free astaxanthin was studied by HPLC over 72 h after single- and multiple-dose regimens. One-time dosing of Heptax in emulsion at 500 mg/kg resulted in significant appearance of free astaxanthin in plasma (Cmax=0.2 mg/l; 381 nM) and accumulation in solid organs (e.g. liver Cmax=0.9 mg/l; 1735 nM), levels not previously reported after single carotenoid doses in rodents. At each point in the concentration/time curve (AUC), free astaxanthin levels in liver were greater than the corresponding concentration in plasma, suggesting concentrative uptake by the liver. As the ED50 as an antioxidant for non-esterified, free astaxanthin in model systems is approximately 200 nM, the current results suggest that hepatoprotection against oxidative insults may be achieved after a single dose of Heptax in these animals. In humans, where the bioavailability of oral carotenoids ranges from 40 to 60% of the total dose when given in lipophilic vehicle, much smaller oral doses may be utilized for therapeutic benefit in a particular clinical application.     

Extrusion/spheronization of pectin-based formulations. II. Effect of additive concentration in the granulation liquid

Purpose. The aim of this study was to improve the formation of spherical pectin pellets by investigating the effect of additive concentration in the granulation liquid on the shape and size of the products as well as by identifying an optimal additive concentration.Methods. High-methoxylated, low-methoxylated, and amidated low-methoxylated pectin types were evaluated in combination with different concentrations of methanol, ethanol, citric acid, lactic acid, and calcium chloride. Pellets were prepared in a power-consumption-controlled twin-screw extruder, then spheronized and dried. The moisture content of the extrudate was determined, and the final products were characterized by image analysis and sieving analysis. A cloud point test was employed for the identification of an optimal additive concentration.Results. The concentration of additive in the granulation liquid affected the moisture content of the extrudate and the shape, size, and mechanical stability of the pectin pellets. Improvements in the pellet characteristics are dependent on the pectin type employed. The 2 low-methoxylated pectins were more sensitive to concentration changes than was the high-methoxylated type. Above a certain threshold concentration, the quality of the pellets are improved. This additive concentration differs according to type of pectin and type of additive.Conclusion. It was demonstrated that there is a concentration-dependent interaction between pectin and substances added to the granulation liquid that can be utilized to improve the formation of spherical pectin pellets.     

Real-time background suppression during frequency domain lifetime measurements

We describe real time background suppression of autofluorescence from biological samples during frequency domain or phase modulation measurements of intensity decays. For these measurements the samples were excited with a train of light pulses with widths below 1 ps. The detector was gated off for a short time period of 10 to 40 ns during and shortly after the excitation pulse. The reference signal needed for the frequency domain measurement was provided by a long-lifetime reference fluorophore which continues to emit following the off-gating pulse. Both the sample and the reference were measured under identical optical and electronic conditions avoiding the need for correction of the photomultiplier tube signal for the gating sequence. We demonstrate frequency domain background suppression using a mixture of short- and long-lifetime probes and for a long-lifetime probe in human plasma with significant autofluorescence.     

A plant growth retardant related to chlamydocin and its proposed mechanism of action

A comparison of the plant growth retardant activity of the chlamydocin analogues, compound 1, six derivatives from 1 and 2, and two synthetic analogues revealed that there are two types of retardant in chlamydocin analogues. One, for example in compound 1, requires an oxygen atom at C-8 of the 2-aminodecanoic acid moiety to show retardant activity. The other, for example in compound 8, requires no oxygen atom at C-8 but requires a specific alkyl group chain length for activity. To determine the differences in mode of action of both types of retardant, rice seedlings were separately treated with compounds 1 and 8, and after appearance of dwarfism, their endogenous ABA and GA(1) levels were determined and compared to those of the control. Treatment with 1 (10 nmol/plant) increased ABA levels 4 times higher than that of the control and decreased GA(1) levels to 20% of that of the control. Treatment with 8 (30 nmol/plant) did not affect the ABA level but decreased GA(1) content to 5% of that of the control.