Examination of the distribution of nicosulfuron in sunflower plants by matrix‐assisted laser desorption/ionisation mass spectrometry imaging

Matrix‐assisted laser desorption/ionisation mass spectrometry imaging (MALDI‐MSI) has been used to image the distribution of the pesticide nicosulfuron (2‐[[(4,6‐dimethoxypyrimidin‐2‐yl)aminocarbonyl]aminosulfonyl]‐N,N‐dimethyl‐3‐pyridinecarboxamide) in plant tissue using direct tissue imaging following root and foliar uptake. Sunflower plants inoculated with nicosulfuron were horizontally sectioned at varying distances along the stem in order to asses the extent of translocation; uptake via the leaves following foliar application to the leaves and uptake via the roots from a hydroponics system were compared. An improved sample preparation methodology, encasing samples in ice, allowed sections from along the whole of the plant stem from the root bundle to the growing tip to be taken. Images of fragment ions and alkali metal adducts have been generated that show the distribution of the parent compound and a phase 1 metabolite in the plant. Positive and negative controls have been included in the images to confirm ion origin and prevent false‐positive results which could originate from endogenous compounds present within the plant tissue. Copyright © 2009 John Wiley & Sons, Ltd.     

Characterization of barley leaf tissue using direct and indirect desorption electrospray ionization imaging mass spectrometry

Chemical profiling of barley (Hordeum vulgare) leaves was demonstrated using direct and indirect desorption electrospray ionization (DESI) imaging mass spectrometry. Direct DESI analysis of the untreated leaves was not possible despite a significant content of hydroxynitrile glucosides known to reside in the epidermis of the leaves. Instead, the epidermis was stripped off the leaves, thus allowing direct DESI imaging to be performed on the back of the epidermis. Furthermore, indirect DESI imaging was performed by making imprints in porous Teflon of the intact leaves as well as of the stripped epidermis. The DESI images reveal accumulation of hydroxynitrile glucosides in the leaf epidermis, homogeneously distributed throughout the surface. The indirect DESI approach enables relative quantitation, confirming variations of hydroxynitrile glucosides content in primary leaves of three different cultivars of barley seedlings. The study presents an example of how to overcome the morphological barriers from the plant surface and perform rapid and repeatable DESI imaging. In addition, a comparison is made of direct and indirect DESI imaging, contributing to the characterization of the recently developed method of indirect DESI imaging of plant material via porous Teflon imprints.     

Determination of pharmaceutical compounds in skin by imaging matrix-assisted laser desorption/ionisation mass spectrometry

Matrix-assisted laser desorption/ionisation (MALDI) quadrupole time-of-flight mass spectrometry (Q-TOFMS) has been used to detect and image the distribution of a xenobiotic substance in skin. Porcine epidermal tissue was treated with 'Nizoral', a medicated shampoo containing ketoconazole (+/-)-1-acetyl-4-[p-[[(2R,4S)-2-(2,4-dichlorophenyl)-2-(imidazol-1-ylmethyl)-1,3-dioxolan-4-yl]methoxy]phenyl]piperazine) as active ingredient. Following incubation for 1 h at 37 degrees C all excess formulation was washed from the surface. A cross-section of the drug-treated tissue was then blotted onto a cellulose membrane, precoated in matrix (alpha-cyano-4-hydroxycinnamic acid (CHCA)), by airspray deposition. In separate experiments the tissue surface was treated with Nizoral within a triangular former, and subsequently blotted onto a matrix-coated membrane. Sample membranes were then mounted into the recess of specialised MALDI targets with adhesive tape. All samples were analysed by MALDI-TOFMS using an Applied Biosystem 'Q-star Pulsar i' hybrid Q-TOF mass spectrometer fitted with an orthagonal MALDI ion source and imaging software. Detection of the protonated molecule was readily achievable by this technique. Treatment of the tissue within a template gave rise to images depicting the expected distribution of the drug, demonstrating that this technique is capable of producing spatially useful data. Ion images demonstrating the permeation of the applied compound into the skin were achieved by imaging a cross-sectional imprint of treated tissue. A calibration graph for the determination of ketoconazole was prepared using the sodium adduct of the matrix ion as an internal standard. This enabled construction of a quantitative profile of drug in skin. Conventional haematoxylin and eosin staining and microscopy methods were employed to obtain a histological image of the porcine epidermal tissue. Superimposing the mass spectrometric and histological images appeared to indicate drug permeation into the dermal tissue layer.     

Rapid analysis of intact phospholipids from whole bacterial cells by matrix-assisted laser desorption/ionization mass spectrometry combined with on-probe sample pretreatment

Matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOFMS), utilizing an on-probe sample pretreatment, was applied to the rapid and direct detection of intact phospholipids from whole bacterial cells. The sample preparation procedure involved depositing growing bacterial colonies from culture dishes directly onto the MALDI probe followed by treatment of the sample spot with a 3 micro L aliquot of an aqueous 0.05 M solution of sodium iodide prior to the addition of a 2,5-dihydroxybenzoic acid (DHB) matrix solution (ca. 8 mg dissolved in 70% acetonitrile/30% H(2)O containing 0.1% of trifluoroacetic acid). The MALDI spectra obtained from whole bacteria cells showed a series of ions generated from bacterial phospholipids, such as phosphatidylethanol-amines (PEs) and phosphatidylglycerols (PGs), which were clearly observed as well-resolved peaks. The ranges of the observed total carbon numbers in two acyl groups for PEs and PGs (30-36 and 33-36, respectively) were in good agreement with those reported previously. Furthermore, the distinct discrimination of four species of the Enterobacteriaceae family cultured identically was achieved by using principal components analysis (PCA) conducted on the relative peak intensities of phospholipids observed from the MALDI spectra.     

A novel analytical approach for investigation of anthracene adsorption onto mangrove leaves

A solid surface fluorimetry approach was established for direct determination of anthracene (An) adsorbed onto fresh mangrove leaves. The experimental results showed that the linear dynamic ranges for determination of An adsorbed onto Avicennia marina (Am), Bruguiera gymnorrhiza (Bg), Kandelia candel (Kc) and Rhizophors stylosa (Rs) leaves varied from 0.92 to 8.71, 0.089 to 0.70, 0.063 to 5.61 and 0.11 to 1.82 microgg(-1), with detection limits of 5.77, 1.79, 4.29 and 1.42 ngg(-1), respectively, and with a relative standard deviation less than 10% (n=5). The experimental recovery results for adsorbed An on Am, Bg, Kc and Rs leaves were among 79.2-85.9, 75.1-102.3, 70.2-93.8 and 73.1-110.8%, respectively. Using the established method, we investigated the effects of exposure time of An and the different quantity of leaf-wax among the four species of mangrove on the amount of An adsorbed. Under the same experimental conditions, the adsorption of An on the upper and lower sides of the same mangrove leaf, and at different regions on the upper side of the same mangrove leaf were also studied. The results demonstrated that the leaves of different mangrove species contained different quantities of leaf-wax, and with the same exposure conditions to An, the quantity of leaf-wax among the four species showed a significant positive correlation with the amount of An adsorbed onto the leaves.     

Silica nanoparticles pre-spotted onto target plate for laser desorption/ionization mass spectrometry analyses of peptides

We report on the simple deposition of Stöber silica nanoparticles (SiO₂ NPs) on conventional MALDI target plate for high throughput laser desorption/ionization mass spectrometry (LDI-MS) analyses of peptide mixtures with sensitivity in the femtomolar range. This low-cost easily prepared material allowed straightforward LDI experiments by deposition of the studied samples directly onto a pre-spotted MALDI plate. This analytical strategy can be performed in any laboratory equipped with a MALDI-TOF instrument. All key benefits of organic matrix-free technologies were satisfied while maintaining a high level of detection performances (sensitivity and reproducibility/repeatability). In particular, sample preparation was simple and detection in the low mass range was not hampered by matrix ions. Imaging studies were undertaken to query sample dispersion into the inert SiO₂ NPs and to help into the search of the best experimental conditions producing homogeneous analyte distribution within the deposit. In contrast to commercial disposable LDI targets designed for single use and requiring an adaptor such as NALDI™, the proposed SiO₂ NPs pre-spotting on a MALDI target plate allowed very easily switching between MALDI and LDI experiments. They can be conducted either simultaneously (positions with an organic matrix or SiO₂ NPs) or in the row (support prepared in advance, stored and washed after use). The overall cost and versatility of the methodology made it very attractive to MALDI users in many domains (peptidomics, proteomics, metabolomics).     

Local distribution of radioactivity in tree leaves contaminated by fallout of the radionuclides emitted from the Fukushima Daiichi Nuclear Power Plant

We analyzed fresh and dead leaves collected in forests in Fukushima after the Fukushima Daiichi Nuclear Power Plant (FDNPP) accident, using autoradiography. Both fresh and dead leaves of Cryptomeria japonica were contaminated by radionuclides (¹³⁴Cs and ¹³⁷Cs). Contamination of the fresh leaves was possibly attributed to interception of radionuclides by tree canopies, whereas the dead leaves indicated the direct deposition of radionuclides by fallout and/or washout of radionuclides intercepted by tree canopies. Translocation of radiocesium from a contaminated branch to new leaves growing after the FDNPP accident was not clearly observed, although transfer of radiocesium from leaf parts to male flowers occurred. Fallen leaves of Quercus serrata, which started growing after the FDNPP accident, did not show radioactivity, indicating that significant amounts of translocation from other parts to new leaves did not occur. Fallen leaves of Q. serrata collected from a litter showed hot spots originating from direct fallout. Needles of Pinus densiflora were also contaminated by fallout. Leaching with pure water removed soluble fractions of radiocesium and hot particles from the surface of the contaminated leaves, but significant amounts of radioactivity remained. This means that foliar absorption occurred in both fresh and dead leaves. Further leaching experiments using surfactant and acetone could not remove the remaining radiocesium from the leaves. The leaching experiments indicate that radiocesium in the contaminated leaves is strongly fixed in leaf tissues and is not readily released unless leaf tissues are decomposed.     

Method validation for the analysis of 169 pesticides in soya grain, without clean up, by liquid chromatography-tandem mass spectrometry using positive and negative electrospray ionization

Part of a comprehensive study on the comparison of different extraction methods, GC-MS(/MS) and LC-MS/MS detection methods and modes, for the analysis of soya samples is described in this paper. The validation of an acetone-based extraction method for analysis of 169 pesticides in soya, using LC-MS/MS positive and negative electrospray ionisation (ESI) mode, is reported. Samples (5 g) were soaked with 10 g water and subsequently extracted with 100 mL of a mixture of acetone, dichloromethane and light petroleum (1:1:1), in the presence of 15 g anhydrous sodium sulphate. After centrifugation, aliquots of the extract were evaporated and reconstituted in 1.0 mL of methanol, before direct injection of the final extract (corresponding with 0.05 g soya mL(-1)) into the LC-MS/MS system. Linearity, r(2) of calibration curves, instrument limit of detection/quantitation (LOD/LOQ) and matrix effect were evaluated, based on seven concentrations measured in 6-fold. Good linearity (at least r(2)> or =0.99) of the calibration curves was obtained over the range from 0.1 or 0.25 to 10.0 ng mL(-1), corresponding with pesticide concentrations in soya bean extract of 2 or 5-200 microg kg(-1). Instrument LOD values generally were 0.1 or 0.25 ng mL(-1). Matrix effects were negligible for approximately 90% of the pesticides. The accuracy, precision and method LOQ were determined via recovery experiments, spiking soya at 10, 50, 100 microg kg(-1), six replicates per level. In both ESI modes, method LOQ values were mostly 10 or 50 microg kg(-1) and more than 70% of pesticides analysed by each mode met the acceptability criteria of recovery (70-120%) and RSD (< or =20%), at one or more of the three levels studied. A fast, easy and efficient method with acceptable performance was achieved for a difficult matrix as soya, without cleanup.     

Application of phenylboronic acid modified hydrogel affinity chips for high-throughput mass spectrometric analysis of glycated proteins

The complexity of the human plasma proteome is greatly increased by post-translational modifications. Besides physiological modifications, pathological conditions such as diabetes are responsible for adding to this complexity by producing advanced glycation endproducts (AGEs). When searching for specific biomarkers it is a prerequisite to reduce this complexity prior to analysis. To do this, agarose hydrogel was used to create a high-capacity affinity layer on the modified aluminum surface of MALDI (matrix-assisted laser desorption/ionization) targets. 3-Aminophenylboronic acid was immobilized via cyanogen bromide activation as a ligand for affinity sorption of glycated proteins, followed by their direct detection by MALDI. High protein capacity of prepared MALDI chips, efficient separation and low non-specific protein binding were demonstrated. The results show that phenylboronic acid modified hydrogels are very suitable for creating affinity surfaces for the high-throughput analysis of AGEs.     

光纤荧光法对吸附于红树叶片表面上荧蒽的测定

利用光纤荧光法实现了吸附于白骨壤(Am)、海漆(Ea)、秋茄(Kc)、桐花树(Ac)和老鼠簕(Ai)叶片表面上荧蒽(Fla)的定量测定.所建方法测定吸附于Am、Ea、Kc、Ac和Ai叶片表面上Fla的线性范围分别为2.5 ～500、2.0 ～600、4.5 ～1 100、15 ～600、3.5 ～450 ng/spot,相应的检出限分别为0.91、0.63、1.12、3.52、1.40 ng/spot,方法的相对标准偏差小于7.8%(n=15),加标回收率分别为97% ～108%、78% ～95%、77% ～90%、84% ～108%和78% ～102%.利用所建方法考察了5种红树叶片正反面吸附不同量Fla的信号强度随时间的变化情况.结果表明:在200 min内,叶片正反面上Fla的信号均发生不同程度的衰减,且反面的信号衰减率大于正面;5种红树叶片正反面对Fla的吸附特性均不同;吸附于叶片正面的Fla多残留在叶片表面,而吸附于叶片反面的Fla易向叶片内部迁移.     

A systematic study on extraction of total arsenic from down-scaled sample sizes of plant tissues and implications for arsenic species analysis

An easily feasible, species-conserving and inexpensive protocol for the extraction of total arsenic and arsenic species from terrestrial plants was designed and applied to the investigation of accumulation and metabolization of arsenite (As(III)), arsenate (As(V)), monomethylarsonate (MMA(V)), and dimethylarsinate (DMA(V)) by the model plant Tropaeolum majus. In contrast to existing extraction methods hazardous additives and elaborate procedures to enhance the extraction yields were omitted. The proposed protocol is suited to down-scale the sample sizes used for the extractions and to promote a compartmentally resolved analysis of the arsenic distribution within individual leaves, leaf stalks, and stems instead of the conventional extraction of pooled samples. In a two-step extraction, the high extraction efficiencies (85-92%) for arsenic achieved by phosphate buffer from larger amounts (200mg) of homogenized leaf material in a one-step extraction, could be enhanced to 94-100% in a second extraction step. A strong dependence of the arsenic extractability on the type of arsenic species accumulated in the tissue as well as on the type of the tissue (leaf, leaf stalk, stem) was found. For the extraction of 5mm long segments cut from individual leaves without previous homogenization of the plant parts yields between 75 and 93% depending on arsenic species prevailing in the cells were obtained using 1 or 10mM phosphate buffer. The total extraction and analysis protocol was validated using a standard reference material as well as by spiking experiments. The arsenic species analysis by IC/ICPMS revealed a number of nine unidentified metabolites in the plant extracts in addition to the species MMA(V), DMA(V), As(III), and As(V) that were provided to the plants during their growth phase.     

On particle ionization/enrichment of multifunctional nanoprobes: washing/separation-free, acceleration and enrichment of microwave-assisted tryptic digestion of proteins via bare TiO2 nanoparticles in ESI-MS and comparing to MALDI-MS

A simple, rapid, straightforward and washing/separation free of in-solution digestion method for microwave-assisted tryptic digestion of proteins (cytochrome c, lysozyme and myoglobin) using bare TiO(2) nanoparticles (NPs) prepared in aqueous solution to serve as multifunctional nanoprobes in electrospray ionization mass spectrometry (ESI-MS) was demonstrated. The current approach is termed as 'on particle ionization/enrichment (OPIE)' and it can be applied in ESI-MS, atmospheric pressure-matrix-assisted laser desorption/ionization mass spectrometry (AP-MALDI-MS) and matrix-assisted laser desorption/ionization time-of-flight mass spectrometry (MALDI-TOF-MS). The bare TiO(2) NPs can assist, accelerate and effectively enhance the digestion efficiency, sequence coverage and detection sensitivity of peptides for the microwave-assisted tryptic digestion of proteins in ESI-MS. The reason is attributed to the fact that proteins or partially digested proteins are easily attracted or concentrated onto the surface of TiO(2) NPs, resulting in higher efficiency of digestion reactions in the microwave experiments. Besides, the TiO(2) NPs could act as a microwave absorber to accelerate and enrich the protein fragments in a short period of time (40-60 s) from the microwave experiments in ESI-MS. Furthermore, the bare TiO(2) NPs prepared in aqueous solution exhibit high adsorption capability toward the protein fragments (peptides); thus, the OPIE approach for detecting the digested protein fragments via ESI and MALDI ionization could be achieved. The current technique is also a washing and separation-free technique for accelerating and enriching microwave-assisted tryptic digestion of proteins in the ESI-MS and MALDI-MS. It exhibits potential to be widely applied to biotechnology and proteome research in the near future.     

PSMA@Ag复合微球的制备及其在MALDI-MS分析小分子化合物中的应用研究

基质辅助激光解吸电离质谱(MALDI-MS)作为一种有力的分析手段,在生物分子分析中有着广泛的应用,但很难应用于分子量小于500的待测物的分析。该文利用聚多巴胺修饰还原法制备了核壳结构的聚苯乙烯-马来酸酐共聚物@银纳米壳层(PSMA@Ag)复合微球。采用傅立叶红外光谱法验证了聚多巴胺(PDA)的成功修饰。结合扫描电子显微镜(SEM)和紫外-可见光谱(UV-Vis)分析结果,发现Ag纳米壳层成功地包覆在PSMA微球的表面。将制备的PSMA@Ag复合微球作为辅助基质直接应用于MALDI-MS,成功地从0.5μL待测物样品中检测到2 pmol脯氨酸(M_w=115)和1 pmol丝氨酸(M_w=105)。研究结果证明PSMA@Ag微球对MALDI的离子化过程有促进作用,为解决MALDI-MS在分析小分子待测物时背景噪声过大,信号无法分辨的问题提供了一个有效途径。     

Matrix-assisted laser desorption/ionization imaging mass spectrometry for direct measurement of clozapine in rat brain tissue

Matrix-assisted laser desorption/ionization hyphenated with quadrupole time-of-flight (QTOF) mass spectrometry (MS) has been used to directly determine the distribution of pharmaceuticals in rat brain tissue slices which might unravel their disposition for new drug development. Clozapine, an antipsychotic drug, and norclozapine were used as model compounds to investigate fundamental parameters such as matrix and solvent effects and irradiance dependence on MALDI intensity but also to address the issues with direct tissue imaging MS technique such as (1) uniform coating by the matrix, (2) linearity of MALDI signals, and (3) redistribution of surface analytes. The tissue sections were coated with various matrices on MALDI plates by airspray deposition prior to MS detection. MALDI signals of analytes were detected by monitoring the dissociation of the individual protonated molecules to their predominant MS/MS product ions. The matrices were chosen for tissue applications based on their ability to form a homogeneous coating of dense crystals and to yield greater sensitivity. Images revealing the spatial localization in tissue sections using MALDI-QTOF following a direct infusion of (3)H-clozapine into rat brain were found to be in good correlation with those using a radioautographic approach. The density of clozapine and its major metabolites from whole brain homogenates was further confirmed using fast high-performance liquid chromatography/tandem mass spectrometry (HPLC-MS/MS) procedures.     

Direct observation of bulk and surface chemical morphologies of Ginkgo biloba leaves by Fourier transform mid- and near-infrared microspectroscopic imaging

Fourier transform infrared microspectroscopy is a powerful tool to obtain knowledge about the spatial and/or temporal distributions of the chemical compositions of plants for better understanding of their biological properties. However, the chemical morphologies of plant leaves in the plane of the blade are barely studied, because sections in this plane for mid-infrared transmission measurements are difficult to obtain. Besides, native compositions may be changed by chemical reagents used when plant samples are microtomed. To improve methods for direct infrared microspectroscopic imaging of plant leaves in the plane of the blade, the bulk and surface chemical morphologies of nonmicrotomed Ginkgo biloba leaves were characterized by near-infrared transmission and mid-infrared attenuated total reflection microspectroscopic imaging. A new self-modeling curve resolution procedure was proposed to extract the spectral and concentration information of pure compounds. Primary and secondary metabolites of secretory cavities, veins, and mesophylls of Ginkgo biloba leaf blades were analyzed, and the distributions of cuticle, protein, calcium oxalate, cellulose, and ginkgolic acids on the adaxial surface were determined. By the integration of multiple infrared microspectroscopic imaging and chemometrics methods, it is possible to analyze nonmicrotomed leaves and other plant samples directly to understand their native chemical morphologies in detail.

Simultaneous detection of phosphatidylcholines and glycerolipids using matrix‐enhanced surface‐assisted laser desorption/ionization‐mass spectrometry with sputter‐deposited platinum film

Matrix‐assisted laser desorption/ionisation (MALDI) imaging mass spectrometry (IMS) allows for the simultaneous detection and imaging of several molecules in brain tissue. However, the detection of glycerolipids such as diacylglycerol (DAG) and triacylglycerol (TAG) in brain tissues is hindered in MALDI‐IMS because of the ion suppression effect from excessive ion yields of phosphatidylcholine (PC). In this study, we describe an approach that employs a homogeneously deposited metal nanoparticle layer (or film) for the detection of glycerolipids in rat brain tissue sections using IMS. Surface‐assisted laser desorption/ionisation IMS with sputter‐deposited Pt film (Pt‐SALDI‐IMS) for lipid analysis was performed as a solvent‐free and organic matrix‐free method. Pt‐SALDI produced a homogenous layer of nanoparticles over the surface of the rat brain tissue section. Highly selective detection of lipids was possible by MALDI‐IMS and Pt‐SALDI‐IMS; MALDI‐IMS detected the dominant ion peak of PC in the tissue section, and there were no ion peaks representing glycerolipids such as DAG and TAG. In contrast, Pt‐SALDI‐IMS allowed the detection of these glycerolipids, but not PC. Therefore, using a hybrid method combining MALDI and Pt‐SALDI (i.e., matrix‐enhanced [ME]‐Pt‐SALDI‐IMS), we achieved the simultaneous detection of PC, PE and DAG in rat brain tissue sections, and the sensitivity for the detection of these molecules was better than that of MALDI‐IMS or Pt‐SALDI alone. The present simple ME‐Pt‐SALDI approach for the simultaneous detection of PC and DAG using two matrices (sputter‐deposited Pt film and DHB matrix) would be useful in imaging analyses of biological tissue sections. Copyright © 2015 John Wiley & Sons, Ltd.     

激光诱导纳秒时间分辨荧光法原位测定吸附于红树叶片表面的菲

实现吸附于植物叶片表面多环芳烃(Polycyclic aromatic hydrocarbons,PAHs)的现场原位测定,是该研究领域的发展方向之一。本实验利用激光诱导纳秒时间分辨荧光(Laser-induced nanosecond time-resolved fluorescence,LITRF)系统,建立了原位测定吸附于秋茄(Kandelia obovata,Ko)、木榄(Bruguiera gymnorhiza,Bg)和桐花树(Aegiceras corniculatum,Ac)3种红树叶片表面菲(Phenanthrene,Phe)的新方法。本方法测定吸附于Ko、Bg和Ac叶片表面Phe的线性范围分别为2~1400 ng/spot,1~1000 ng/spot和4~2000 ng/spot,检测限分别为0.20,0.14和0.42 ng/spot,加标回收率为89.6%~108.1%,78.2%~92.4%和93.2%~112.9%,且方法的相对标准偏差小于6.0%(n=9)。将方法用于实验室暴露样品的原位测定,并与光纤荧光法对比,其灵敏度、线性范围改善显著,更有利于实现植物叶片上PAHs的现场原位测定。     

Mass Spectrometry Detection of Nitrobenzoic Acids and Their Salts on the Surface of Construction Materials

The application of mass spectrometry to the detection of m-nitrobenzoic and 3,5-dinitrobenzoic acids and their salts on the surface of construction materials used in rocketry is described. Analytes are washed with acetonitrile from the studied surface and then analyzed by HPLC?MS with electrospray ionization or the matrix assisted laser desorption/ionization (MALDI). For electrospray ionization, the limit of detection is 6 μg/L and for MALDI ionization, 2 μg/L. The MALDI technique also ensures the direct investigation of samples without washing out; in this case, mass spectra can be visualized by constructing 2D diagrams of the distribution of nitrobenzoic acids over the surface.     

MALDIMSI在脂质组学研究中的应用

脂质组学概念自2003年被提出以来,其已成为研究生物体、组织或细胞中脂质的结构、功能及代谢途径的一门学科。脂质的种类众多,同时结构非常复杂,脂质的分析充满了困难和挑战。基质辅助激光解吸电离质谱成像(MALDI MSI)分析技术不仅可以进行物质鉴定,而且可对被分析物进行空间分布成像,近年来,该技术广泛地应用于脂质组学的研究。该文介绍了MALDI MSI在脂质组学研究中的样品处理、基质喷涂及应用方面的研究进展,并就目前存在的问题及解决方案进行了探讨,以期扩展MALDI MSI的应用范围。     

Surface contamination effects on leaf chemical composition in the Atlantic Forest

Summary The exogenous material that adheres to the leaf surface affects the elemental composition of the plant itself, thereby constituting one of the major error sources in plant analysis. The present work investigated the surface contamination of leaves from the Atlantic Forest. Instrumental neutron activation analysis (INAA) was applied to assess the efficiency of leaf EDTA-washing. Chemical element concentrations were corrected using Sc (soil tracer) since resuspended soil is the main source of contamination in leaves. As a result, EDTA-washing should be used mainly for the evaluation of terrigenous elements, while the Sc-corrected concentrations are considered satisfactory for the other elements.