植物组织中糖与糖醇乙酰化及毛细管气相色谱分析

介绍了一种用1-甲基咪唑为溶剂和催化剂、盐酸羟胺和乙酸酐为肟化和乙酰化试剂,对植物样品中糖与糖醇进行乙酰化衍生化后的气相色谱分离和质谱鉴定的分析方法.并对糖与糖醇乙酰化影响较大的反应温度、反应时间、反应物组成和反应物浓度等条件进行了比较研究,确定了糖与糖醇乙酰化各步反应的最佳反应温度和反应时间,分析了各组分间相互作用及其用量对衍生化效率的影响.对多种糖与糖醇乙酰化产物进行毛细管气相色谱分离、FID检测及GC-MS结构鉴定.研究证明,在合适条件下应用此方法对糖与糖醇进行乙酰化,反应完全,产物单一,能得到理想的分离、检测和定量分析效果.适用于微量植物组织中多种单糖、双糖及其糖醇的定量分析.     

Microbial Community Structure Associated with Biogeochemical Processes in the Sulfate–Methane Transition Zone (SMTZ) of Gas-hydrate-bearing Sediment of the Ulleung Basin,East Sea

We investigated the biogeochemical constituents, microbial communities and functional genes (mcr and dsr) associated with anaerobic methane oxidation and sulfate reduction, and metabolic activities by sulfate reduction in the sulfate–methane transition zone (SMTZ) of gas-hydrate-bearing sediment of the Ulleung Basin in the East Sea. Maxima in the sulfate reduction rate (12.6 nmol cm^?3 d^?1), CO concentration (83 μM), and gene abundances of dsrA (9.1 × 10⁶ copies cm^?3) and mcrA (11.6 × 10⁶ copies cm^?3) occurred in the SMTZ. The peaks of CO consistently found in the SMTZ suggested that CO is an intermediate metabolic product related to methane oxidation. Candidate division JS1, the predominant bacterial group that comprised 59.0–63.7% of the 16S rRNA gene sequences, was recognized as an important organic carbon oxidizer. Both Marine Benthic Group D (MBGD) and Marine Benthic Group B (MBGB), which constituted 40.8–52.9 and 10.3–43.9% of the 16S rRNA gene sequences, respectively, were the dominant archaeal groups. Analysis of functional gene diversity revealed that anaerobic methanotroph-1-related phylotypes appeared to be the major CH₄ oxidizer, whereas Firmicutes-like group was a predominant sulfate reducer in the 0.8 mbsf in SMTZ with low SO₄^2? concentration. Overall results indicated that JS1 and two archaeal groups (MBGB and MBGD) seem to play a significant role in carbon and elements cycles in the gas-hydrate-bearing subsurface sediment of the Ulleung Basin.     

Psidium guajava Paluma responses to environmental conditions and ozone concentrations in the urban forest of São Paulo,SE-Brazil

Tropospheric ozone concentrations (O₃) are continuously increasing with harmful effects on vegetation. Ozone uptake triggers oxidative stress that may promote adverse changes in various plant physiological processes. The aim of this study was to evaluate the relationship between meteorological conditions and O₃ exposure in foliar injuries, gas exchanges and antioxidant enzyme activity in Psidium guajava Paluma. Saplings of Paluma were exposed in a site contaminated by O_3. Foliar injuries, gas exchanges, and the activity of superoxide dismutase (SOD), ascorbate peroxidase (APX) and glutathione reductase (GR) were evaluated weekly. Results were analyzed by multivariate analysis. The O₃ exposure reduced carbon assimilation and induced the onset of foliar injuries. The enzymatic activities were more related to meteorological conditions than to O₃ exposure, indicating that these enzymes are not this species’ first line of defense. However, our finding indicates that Paluma may be considered a response indicator, given its presentation of foliar injuries even at low O₃ concentrations.     

Chemical Composition,Enantiomeric Analysis,AEDA Sensorial Evaluation and Antifungal Activity of the Essential Oil from the Ecuadorian Plant Lepechinia mutica Benth (Lamiaceae)

This study describes the GC‐FID, GC/MS, GC‐O, and enantioselective GC analysis of the essential oil hydrodistilled from leaves of Lepechinica mutica (Lamiaceae), collected in Ecuador. GC‐FID and GC/MS analyses allowed the characterization and quantification of 79 components, representing 97.3% of the total sample. Sesquiterpene hydrocarbons (38.50%) and monoterpene hydrocarbons (30.59%) were found to be the most abundant volatiles, while oxygenated sesquiterpenes (16.20%) and oxygenated monoterpenes (2.10%) were the minor components. In order to better characterize the oil aroma, the most important odorants, from the sensorial point of view, were identified by Aroma Extract Dilution Analysis (AEDA) GC‐O. They were α‐Pinene, β‐Phellandrene, and Dauca‐5,8‐diene, exhibiting the characteristic woody, herbaceus, and earthy odors, respectively. Enantioselective GC analysis of L. mutica essential oil revealed the presence of twelve couples and two enantiomerically pure chiral monoterpenoids. Their enantiomeric excesses were from a few percent units to 100%. Moreover, the essential oil exhibited moderate in vitro activity against five fungal strains, being especially effective against M. canis, which is a severe zoophilic dermatophyte causal agent of pet and human infections.     

Mentha suaveolens Ehrh. Chemotypes in Eastern Iberian Peninsula: Essential Oil Variation and Relation with Ecological Factors

Essential oil (EO) extracts coming from two representative populations of Mentha suaveolens Ehrh . subesp. suaveolens in Eastern Iberian Peninsula were analyzed by gas chromatography coupled with mass spectrometry and flame ion detector. Plant sampling was carried out in the morning and evening in order to study diurnal variation in EO profiles. Likewise, leaves and inflorescences were analyzed separately. Two chemotypes corresponding to each one of the populations were identified, with piperitenone oxide (35.2 – 74.3%) and piperitone oxide (83.9 – 91.3%), respectively, as major compounds. Once different chemotypes were identified, canonical correspondence analysis was employed to evaluate the effect of the bioclimatic and edaphic factors recorded in each location on the observed differences. Statistical analysis suggested that these chemotypes were closely related to specific environmental factors, mainly the bioclimatic ones. Concretely, piperitenone oxide chemotype can be associated to supramediterranean bioclimatic conditions and soils with major salinity and water field capacity. On the other hand, the most volatile fraction (hydrocarbon monoterpenes) reached its higher level in the morning; specifically, a noticeable amount of limonene was found in morning samples of flowers (4.8 – 10.6%). This fact can be related to ecological role of volatile compounds in order to attract pollinator insects.     

On Dioxygen and Substrate Access to Soluble Methane Monooxygenases: An all‐Atom Molecular Dynamics Investigation in Water Solution

In a preliminary exploration of the dummy model for diiron proteins, random‐acceleration molecular dynamics (RAMD) revealed that a pure four‐helix bundle structure, like hemerythrin, constitutes an efficient cage for dioxygen (O₂), which can only leave from defined, albeit very broad, gates. However, this well ordered structure does not constitute an archetype on which to compare O₂ permeation of other diiron proteins, like the complex of soluble methane monooxygenase hydroxylase with the regulatory protein (sMMOH‐MMOB). The reason is that with this complex, unlike hemerythrin, the four helices of the four‐helix bundle are heavily bent, and RAMD showed that most traps for O₂ lie outside them. It was also observed that, in spite of a nearly identical van der Waals radius for O₂ and the natural substrate CH₄, the latter behaves under RAMD as a bulkier molecule than O₂, requiring a higher external force to be brought out of sMMOH‐MMOB along trajectories of viable length. All that determined with sMMOH‐MMOB multiple gates and multiple pathways to each of them through several binding pockets, for both O₂ and CH₄. Of the two equally preferred pathways for O₂, at right angle with one another, one proved to be in accordance with the Xe‐atom mapping for sMMOH. In contrast, none of the pathways identified for CH₄ proved to be in accordance with such mapping, CH₄ looking for more open avenues instead.     

一种水华蓝藻气囊的分离纯化及气囊结构蛋白的鉴定

【目的】从水华蓝藻铜绿微囊藻(Microcystis aeruginosa PCC 7806)的细胞中分离纯化出高纯度且完整的气囊,并对气囊的结构组成蛋白进行鉴定。【方法】采用渗透冲击与溶菌酶处理相结合的方法,进行多次低速离心提纯气囊,纯化所得气囊用负染色透射电镜观察气囊的纯度、完整度和形态。将纯化得到的气囊溶解后进行SDS-PAGE电泳,电泳后的蛋白条带运用LC-MS质谱法完成鉴定。【结果】从气囊的电镜照片可以看出提纯后的气囊纯度高,完整性好。气囊是两端呈锥状的圆柱体状,各气囊的直径大小一致,约120 nm,但长度不同,从约500 nm到1 500 nm不等。SDS-PAGE电泳和质谱法鉴定出气囊的两种主要结构组成蛋白Gvp A和Gvp C。【结论】这些研究对后续揭示气囊的精细结构和深入研究水华蓝藻浮力调节机制具有重要的意义。     

Metabolomic analysis identifies altered metabolic pathways in Multiple Sclerosis

Multiple sclerosis (MS) is a chronic, demyelinating disease that affects the central nervous system and is characterized by a complex pathogenesis and difficult management. The identification of new biomarkers would be clinically useful for more accurate diagnoses and disease monitoring. Metabolomics, the identification of small endogenous molecules, offers an instantaneous molecular snapshot of the MS phenotype. Here the metabolomic profiles (utilizing plasma from patients with MS) were characterized with a Gas cromatography-mass spectrometry-based platform followed by a multivariate statistical analysis and comparison with a healthy control (HC) population. The obtained partial least square discriminant analysis (PLS-DA) model identified and validated significant metabolic differences between individuals with MS and HC (R2X = 0.223, R2Y = 0.82, Q2 = 0.562; p < 0.001). Among discriminant metabolites phosphate, fructose, myo-inositol, pyroglutamate, threonate, l-leucine, l-asparagine, l-ornithine, l-glutamine, and l-glutamate were correctly identified, and some resulted as unknown. A receiver operating characteristic (ROC) curve with AUC 0.84 (p = 0.01; CI: 0.75–1) generated with the concentrations of the discriminant metabolites, supported the strength of the model. Pathway analysis indicated asparagine and citrulline biosynthesis as the main canonical pathways involved in MS. Changes in the citrulline biosynthesis pathway suggests the involvement of oxidative stress during neuronal damage. The results confirmed metabolomics as a useful approach to better understand the pathogenesis of MS and to provide new biomarkers for the disease to be used together with clinical data.     

HS-SPME-GC / MS 在大熊猫尿液化学成分检测中的应用

尿液在大熊猫化学通讯过程中具有重要作用。对大熊猫尿液中化学成分的检测是揭示大熊猫尿液中化学物质组成及其功能的关键。本实验通过使用顶空固相微萃取技术(Headspace-solid phase microextraction,HSSPME)对大熊猫尿液样品进行前期处理,继而利用气相色谱- 质谱联用技术(Gas chromatography-mass spectrometry,GC / MS)对大熊猫尿液中化学成分进行检测。共检测到56 个峰,通过在NIST (National Institute of Standards
and Technology)质谱库中进行检索,初步推定出其中的38 种物质。除此之外,还对HS - SPME 萃取头的净化方法进行了探索和改进。结果表明,顶空固相微萃取技术结合气相色谱- 质谱联用技术能够应用于大熊猫尿液中挥发性与半挥发性化合物的检测,并且能够得到较好的实验结果,为揭示大熊猫化学通讯机理提供基础。     

农林生态系统的大气调节功能及价值核算方法

农林生态系统的生态服务功能之一是对大气环境的调节作用。归纳了农林生态系统吸收和释放气体的途径、测定方法及相关因素,以及农业管理方式和大气环境变化对农林生态系统的影响方式。从固C释O、吸收或排放CH₄和N₂O、净化SO₂等3部分提出了农林生态系统调节大气生态功能的核算公式,并列举了有关参数。根据核算,佛山市农林生态系统调节大气生态功能总价值18.18亿元。