Comparative analysis of the methods for measurement of membrane surface potential of planar lipid bilayers

Different methods for the measurement of the membrane surface potential Φ_m, or changes therein (ΔΦ_m), are described and compared with respect to their sensitivity, generality of application and ease of use. Examples of the measurement of ΔΦ_m for the determination of the surface charge density of planar lipid bilayers are presented.     

Formal analysis of effective core potential methods

Effective core potentials are analyzed from the standpoint of the underlying frozen core approximation. The content of the pseudoorbital, the content of the potential, and the properties of both are elaborated, showing the points at which they differ from the frozen core approximation and where possible deficiencies might lie.     

MALDI imaging of neutral cuticular lipids in insects and plants

The spatial distribution of neutral lipids and hydrocarbons has been imaged using MALDI-TOF mass spectrometry on intact plant and insect surfaces, namely wings and legs of the gray flesh fly (Neobellieria bullata), wings of common fruit fly (Drosophila melanogaster), leaves of thale cress (Arabidopsis thaliana), and leaves of date palm tree (Phoenix sp.). The distribution of wax esters (WEs) and saturated and unsaturated hydrocarbons (HCs) was visualized. The samples were attached on a target and multiply sprayed with lithium or sodium 2,5-dihydroxybenzoate. The deposits were homogenous, consisting of small islands (50–150 µm) of matrix crystals separated by small areas (10 µm) of uncovered cuticle. Samples of N. bullata wings were found to contain HCs and WEs distributed close to their basal parts. The distribution of sodium and potassium ions was visualized on samples prepared by sublimation of 2,5-dihydroxybenzoic acid. Pheromonal dienes were detected on D. melanogaster female wings. A homogenous distribution of saturated WEs was observed on A. thaliana and Phoenix sp. leaf samples. The optimum number of laser shots per pixel was found to be higher than for polar compounds imaging.     

古菌脂质的前处理方法比较及超高效液相色谱-高分辨质谱分析

古菌是一类兼具真菌及细菌细胞特征、大多生活在极端环境下的单细胞微生物。由于膜结构及代谢通路的特殊性,研究古菌脂质对深入探究极端环境下生命的正常活动具有重要意义。前处理方法在组学分析中会极大影响最终结果的准确度及可靠性。该文基于超高效液相色谱-高分辨质谱联用(ultra-performance liquid chromatography-high resolution mass spectrometry, UPLC-HRMS)技术,以嗜热嗜压古菌Pyrococcus yayanosii为模式生物,采用Bligh-Dyer加酸法、Folch法、甲基叔丁基醚(methyl tert-butyl ether, MTBE)法及固相萃取(SPE)法提取脂质成分,从提取效率、重复性、歧视性等角度进行方法评价,并最终确定SPE法和MTBE法的提取重复性和提取效率最好,适合高通量古菌全脂质提取。利用SPE提取、高分辨质谱分析对P.yayanosii的常规脂质进行了全面分析,共鉴定到了1 402种脂质。本研究旨在为古菌和其他极端微生物的非靶向脂质组学分析和脂质代谢研究提供方法参考。     

Antioxidant potential and phytochemical composition of extracts obtained from Phyllanthus phillyreifolius by different extraction methods

Abstract

Phyllanthus phillyreifolius (Euphorbiaceae), poorly studied plant species, was fractionated using conventional and high pressure extraction techniques such as supercritical fluid and pressurized liquid extractions. Lipophilic substances were extracted with n-hexane and supercritical CO₂ with or without co-solvent ethanol, meanwhile higher polarity fractions were recovered with acetone and 70% ethanol. Antioxidant potential was assessed by various chemical assays, which revealed that 70% ethanol was the most effective solvent for recovery of antioxidants. UPLC-MS phytochemical analysis of hydrophilic extracts confirmed geraniin as the main constituent of P. phillyreifolius. Other quantitatively important compounds were phyllanthusiin D and elaeocarpusin. Three isomers of tocopherol (α, β and γ) were quantified by HPLC in lipofhilic extracts. Generally, the results from this study revealed high antioxidant potential of P. phillyreifolius; consequently the plant may be considered as a promising source of antioxidants for functional foods, nutraceuticals and pharmaceutical formulations.     

Spreading and segregation of lipids in air-stable lipid microarrays

As a result of heterogeneous spreading of distinct lipids within the same microspots of air-stable lipid microarrays, ganglioside GM1 tends to segregate and thus enrich within the center area of microspots where being predetermined by the quill pin used for array fabrication, as indicated by the binding pattern of fluorescein-cholera toxin subunit B.     

Elemental composition of wood as a potential marker to evaluate heat treatment intensity

Microanalyses of pine and beech blocks treated under nitrogen at 240 °C for different times have been investigated to evaluate correlation between mass loss due to treatment and elemental composition. Oxygen content decreases with treatment intensity and is directly proportional to treatment time. In the same time, carbon content increases significantly indicating formation of carbonaceous materials within the wood structure. Acetylation has been investigated to evaluate the effect of heat treatment on the quantity of free hydroxyl groups present in the wood. The results indicate a significant decrease of reactivity of heat-treated samples compared to untreated ones. Although this decrease depends on the treatment intensity, no obvious correlation was observed between weight gain due to acetylation and mass loss due to treatment. All these results suggest that elemental composition of heat-treated wood could be a valuable marker to evaluate mass losses due to thermal degradation and consequently treatment intensity.     

Electrochemical analysis of nucleic acids as potential cancer biomarkers

In recent years, a huge progress has been made regarding the development of electrochemical (EC) assays for detection of nucleic acids — DNA or RNA — as potential cancer biomarkers. Various ingenious strategies for determination of DNA methylation of gene promoters, circulating tumor DNAs, viral nucleic acids, or short noncoding microRNAs were presented, many of them showing remarkable sensitivities. However, a majority of these assays were not applied into clinical samples from patients, which is crucial should the electrochemistry compete with conventional, routinely used techniques. In this review, we critically evaluate strengths and weaknesses of EC assays that recognized this necessity and successfully determined endogenous DNA or RNA in patient samples with various forms of tumors.     

Influence of the method of isolating lipids on their composition

Institute of the Chemistry of Plant Substances, Academy of Sciences of the Republic of Uzbekistan, Tashkent, fax (3712) 89 14 75. Translated from Khimiya Prirodnykh Soedinenii, No. 4, pp. 623–624, July–August, 1995. Original article submitted November 7, 1994.     

Oxidation of lipids and membranes I: in vitro formation of peroxidative lipid polymers.

Fluorescent polymers were obtained by oxidizing partly emulsified linolenic acid with different oxidants. The speed of formation of polymers differed for the various oxidants, and the difference was not a simple function of the oxidation potential. The speed of polymerization also depended on the nature of the emulsion. The presence of egg albumen in the emulsion enhanced polymer formation with all oxidants. When the oxidants used are arranged in the order of decreasing speed of polymer formation, the order is different in the presence of albumen from what it is in the absence of albumen. With different oxidation catalysts most antioxidants and amino acids tested enhanced polymerization. In oxidation with ferric ions, with K-dichromate, and without added oxidants the only antioxidants which delayed polymerization were "inhibitors." "Retarders" enhanced polymerization. With KMnO4 slight delay was caused by some retarders. The findings indicate that not only oxidation catalysts, but also proteins, amino acids, and antioxidants enhance polymerization. The possibility is suggested that in animal cells lipid pigment formation might represent a mechanism for neutralizing free radicals.     

Fatty acid composition of neutral lipid: Classes of Citrus seed oil

The constituents of total lipids and neutral lipid classes, i.e., hydrocarbons, wax esters, sterol esters, triacylglycerols, free fatty acids, 1,3-diacylglycerols, 1,2-diacylglycerols, free sterols, alcohols, and monoacylglycerols of three species of Citrus namely Citrus sinensis, Citrus paradisi, Citrus aurantium were investigated by thin layer and gas chromatography. Palmitic, oleic and linoleic acids were the major components in all the lipids and lipid classes studied.     

Educational Web site: Radioisotopic methods of determining body composition

We have designed a Web site intended to inform the general public aboutexisting nuclear technologies based on the measurement of radioisotopes inthe human body. The presentation is focused on the concept of radioisotopemeasurements for determination of body composition (bone, muscle, water, fat),and the risks, benefits, and clinical applications of these techniques. Procedurescovered are ⁴⁰K whole body counting, delayed-gamma neutron activation,prompt-gamma neutron activation, and dual-energy X-ray absorptiometry. Theinformation presented is tailored for the nonscientific public, in order topromote familiarity with and understanding of the basic concepts of radioisotopemeasurements in the human body. Further development of the site will includegreater scientific detail, suitable for student instruction or for continuingeducation requirements of various certification programs.     

The protein composition of ferret parotid saliva as revealed by high-resolution electrophoretic methods.

Ferret parotid saliva has been analysed using sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and two-dimensional electrophoresis (2-DE) to determine, for the first time, its protein composition. SDS-PAGE, in combination with Coomassie Brilliant Blue (CBB) staining, revealed up to 20 bands and the patterns were characterised by major protein constituents of Mr 105000, 51000, 47000, 33000, 22000 and 16 400 common to all samples from all animals. Sequential samples collected from the same animal during prolonged stimulation of the parasympathetic nerve (40 min at 40 Hz) showed subtle but reproducible protein changes. Saliva collected from different animals varied widely in the amount of a protein Mr 66000. 2-DE, in combination with silver staining, revealed up to 300 spots and the patterns were characterised by major protein constituents of Mr 105000 (pI 6.3-7.2), Mr 66000 (pI 4.7-5.3), Mr 51000 (pI 5.0-5.7), Mr 47000 (pI 6.0-7.5), and Mr 33000 (pI 4.7-6.0). Many of the polypeptide spot clusters consisted of one or more horizontal strings of spots suggesting extensive microheterogeneity. Both SDS-PAGE and 2-DE indicated that the protein patterns of ferret parotid saliva evoked by electrical stimulation of the parasympathetic nerve in the absence or presence of atropine are similar, i.e., the protein composition of the atropine-resistant nonadrenergic, noncholinergic (NANC) secretion is similar to that of saliva evoked in the absence of muscarinic receptor blockade.     

Application of capillary electrophoretic methods for the analysis of plant phloem and xylem saps composition: A review

Plant vascular tissue is essential for the exchange of water, nutrients, metabolic products, and signals among distant organs in cormophytes. The compositions of phloem and xylem saps are highly dependent on many internal and external factors, and thus their analysis provides a valuable insight into plant physiology, growth, and development as well as nutrition status or presence of biotic or abiotic stresses. Capillary electrophoresis characterized by highly efficient separations and minuscule sample requirements represents a suitable analytical technique for this purpose because the sap constitutes a complex mixture with generally minimal availability. This review aims at providing a comprehensive overview of published capillary electrophoretic methods for the analysis of primary components present in the phloem and xylem saps of higher plants.     

The lipid composition of the Western Mediterranean aerosol

Summary Marine remote aerosol samples collected in a fixed station situated at 1100 m above sea level in Mallorca Island (Western Mediterranean) have been analyzed for lipids, both neutral and acidic, by capillary gas chromatography (GC) and GC coupled to mass spectrometry. Higher plant and algal compounds are predominant. The former encompass distributions of even numbered C22–C32 n-alkan-1-ols (8–21 ng/m³) and n-aldehydes, C25–C32 odd numbered n-alkanes (3–6 ng/m³), and n-nonacosan-10-ol, -sitosterol (0–0.09 ng/m³), dehydroabietic acid and triterpenols. The latter are constituted by even numbered C14–C18 fatty acids (0.6–30 ng/m³) and cholest-5-en-3-ol (0–0.86 ng/m³). Pyrolytic polycyclic aromatic hydrocarbons are also found (86–410 pg/m³) whereas direct petrogenic inputs are not significant.