LI-6262 CO2/H2O分析仪接气室法在草原群落蒸散量与CO2交换量测定中的应用

植物群落蒸散量和CO2交换量的测定方法多种多样.该文以水分、CO2动态的区域性整合为目标,开创了一种新的、同时测定群落蒸散量和CO2交换量的方法--LI-6262 CO2/H2O分析仪接气室法.借助这种方法测定了内蒙古锡林河流域典型草原区群落蒸散量和CO2交换量,取得了较好的结果.该方法将群落的重要生态过程:蒸散与光合、呼吸作用的测定联系起来,也因此得到一系列表征群落特性的有用指标;同时该方法具有精度高、简便易携带、适于野外操作等特点,经进一步改进后可广泛用于草原、沙地及湿地植物群落的气体通量测定.对于精确研究草原区各种植物群落类型的水分利用、光合和呼吸特性及草原区植被在全球气候变化中的地位和作用等有重要的实用价值.     

LI-6262CO2／H2O分析仪接气室法在草原群落蒸散量与CO2交换量测定中的应用

植物群落蒸散量和CO2交换量的测定方法多种多样。该文以水分、CO2动态的区域性整合为目标,开创了一种新的、同时测定群落蒸散量和CO2交换量的方法——LI—6262CO2／H2O分析仪接气窒法。借助这种方法测定了内蒙古锡林河流域典型草原区群落蒸散量和CO2交换量,取得了较好的结果。该方法将群落的重要生态过程2蒸散与光合、呼吸作用的测定联系起来,也因此得到一系列表征群落特性的有用指标;同时该方法具有精度高、简便易携带、适于野外操作等特点,经进一步改进后可广泛用于草原、沙地及湿地植物群落的气体通量测定。对于精确研究草原区各种植物群落类型的水分利用、光合和呼吸特性及草原区植被在全球气候变化中的地位和作用等有重要的实用价值。     

A Novel and Economical Synthesis of 2″-O-Alkyl-Uridines

Abstract

A highly efficient, two-step method to make 2′-O-methyluridine is described using only inexpensive reagents and no chromatography. The method is applicable for some other alkyls as well as some other pyrimidine derivatives.     

Predominance of prostaglandin D2 and I2 in the rat gastric mucosa--analysis by high-performance liquid chromatography

We have developed a method for measuring prostaglandins (PGs) in rat gastric mucosa by high-performance liquid chromatography (HPLC). The levels of PGD2 and 6-keto-PGF1 alpha, a degradation product of PGI2, were five times higher than those of PGE2 and PGF2 alpha. Oral administration of indomethacin (6 mg/kg body weight) completely abolished the synthesis of all detectable PGs uniformly. These results suggest that endogenous PGs, especially PGD2 and I2, play some roles in the function of the gastric mucosa.     

Comparison of chemical and enzymatic synthesis of 2-acetamido-2-deoxy-D-mannose 6-phosphate: a new approach

Chemical and enzymatic methods to synthesis of 2-acetamido-2-deoxy-D-mannose-6-phosphate (ManNAc-6-P) have been investigated. A new preparative method has been developed although some established procedures were tried. In this new method, a 6-O-acetyl or 4,6-di-O-acetyl group of the per-O-acetylated 2-acetamido-2-deoxy-D-mannose (ManNAc) were regioselectively removed with an esterase from the yellow yeast, Rhodosporidium toruloides, followed by phosphorylation and O-deacetylation under mild conditions. 1H and 13C NMR data spectra of ManNAc-6-P were recorded.     

新型冠状病毒基因组序列的网络平台与基因分型

新型冠状病毒(SARS-CoV-2)是引起2019新型冠状病毒肺炎(COVID-19)的病原体,目前COVID-19仍在世界范围内大规模流行。随着学者对SARS-CoV-2研究的不断深入,以及各大数据库的序列资源共享,一些学者开发了SARS-CoV-2相关序列分析网络在线平台,并发表了对SARS-CoV-2基因分型、命名的规则。"GISAID"是目前SARS-CoV-2基因组序列共享和储存最大的数据库,"Nextstrain"和"CoV-GLUE"是国际最常用的SARS-CoV-2序列分析平台。目前有四种比较通用的SARS-CoV-2的基因分型方法,在本文中分别简称为:"中国分型法"、"Pangolin分型法"、"GISAID分型法"和"Nextstrain分型法"。这四种分型方法的定义不尽相同,但又有相似之处。本综述对目前SARS-CoV-2在线分析网络平台和不同的基因分型方法进行了较为系统的介绍、对比和总结。     

Enumeration of free-living aerobic n(2)-fixing h(2)-oxidizing bacteria by using a heterotrophic semisolid medium and most-probable-number technique

A heterotrophic semisolid medium was used with two sensitive assay methods, C(2)H(2) reduction and O(2)-dependent tritium uptake, to determine nitrogenase and hydrogenase activities, respectively. Organisms known to be positive for both activities showed hydrogenase activity in both the presence and absence of 1% C(2)H(2), and thus, it was possible to test a single culture for both activities. Hydrogen uptake activity was detected for the first time in N(2)-fixing strains of Pseudomonas stutzeri. The method was then applied to the most-probable-number method of counting N(2)-fixing and H(2)-oxidizing bacteria in some natural systems. The numbers of H(2)-oxidizing diazotrophs were considerably higher in soil surrounding nodules of white beans than they were in the other systems tested. This observation is consistent with reports that the rhizosphere may be an important ecological niche for H(2) transformation.     

Polarization Force Fields for Peptides Implemented in ECEPP2 and MM2

Abstract

The empirical conformational energy program for peptides (ECEPP2) and molecular mechanics (MM2) have been used for the simulation of the For-Gly-NH₂ backbone. I propose two different methods for the calculation of the polarization energy term: the polarization procedure by non-interacting induced dipoles (NID) which assumes scalar isotropic point polarizabilities and the polarization scheme by interacting induced dipoles (ID) which calculates tensor effective anisotropic point polarizabilities (method of Applequist). I present a comparative study of ECEPP2 and MM2 + polarization. I discuss molecular mechanics results including the total energy differences, partitional analyses of the total steric energies and torsion dihedral angles. The γ global and the α, β and Δ local minima are stabilized by intramolecular hydrogen bonds. Although ECEPP2-based calculations rather under or over-estimate the relative energy of some local minima, the ID polarization energy term represents a significant correction to the total relative energy.     

The analysis of recombinant interleukin-2 by thermospray liquid chromatography-mass spectrometry

The complete sequence of recombinant human interleukin-2 expressed in Escherichia coli has been confirmed by thermospray liquid chromatography-mass spectrometry (TS-LC-MS) of a tryptic digest derived from 100 micrograms (7 nmol) of reduced carboxymethylated interleukin-2. The preparation was shown by this method to contain predominantly unprocessed N-terminal initiator Met, with some authentic N-terminal Ala; the rest of the protein was as predicted from the DNA sequence, though some deamidated material was noted. TS-LC-MS proved to be a rapid and efficient method for surveying the protein tryptic peptide products allowing all the data to be collected in one chromatographic run; all tryptic fragments were identified by their molecular ions including those for the larger peptides (Mr 1500-3500) which, due to the presence of doubly and triply charged molecular ions, were brought within the mass range of the instrument (1800 Da). It is proposed that TS-LC-MS is a good general method for analyzing recombinant protein digests with respect to sequence confirmation, processing, and post-translational modification, and since each chromatographic peak is identified allows for subsequent monitoring of the protein by LC using uv detection. The method suffers from the disadvantages that all the sample is consumed during the experiment and that no fragment (sequence) ions are generally observed.     

Relationship between chloroplastic H2O2 and the salicylic acid response

Reactive oxygen species (ROS) act as signaling molecules for regulating plant responses to abiotic and biotic stress and there exist source- and kind-specific pathways for ROS signaling. Recently, we created a novel system for producing H₂O₂ in Arabidopsis chloroplasts by chemical-dependent thylakoid membrane-bound ascorbate peroxidase (tAPX) silencing using an estrogen-inducible RNAi method. Microarray analysis revealed that the expression of a large set of genes was altered in response to tAPX silencing, some of which are known to be involved in pathogen response/resistance. Furthermore, we found that tAPX silencing enhances the levels of salicylic acid (SA) and the response to SA, a central regulator for biotic stress response. In this addendum, we describe the relationship between chloroplastic H₂O₂ and SA in stress response, and discuss the function of the kind- and source-specific ROS signaling in SA-mediated stress response.     

The rate of diffusion of Ca2+ and Ba2+ in a nerve cell body.

A spectrophotometric method was developed to directly measure the diffusion rate of Ca2+ and some other ions in nerve cell bodies, using pulsed ionophoretic injections and an optical microprobe to record locally absorbance changes of the dye arsenazo III. We report here that Ca2+ and Ba2+ diffuse at approximately the same rate in nerve soma cytoplasm, having effective diffusion coefficients in the range of 7-12 X 10(-7) cm2/s, while identical measurements conducted in an electrolytic solution yielded values of 5.2 X 10(-6) cm2/s for Ca and 5.4 X 10(-6) cm2/s for Ba. The results are discussed in relation to the mechanisms that regulate the intracellular concentration of free Ca.     

Purification of cytochrome c peroxidase for monitoring H2O2 production.

One of the most precise methods of determining hydrogen peroxide (H₂O₂) formation by biological systems is based on measuring the rate of enzyme-substrate complex formation between H₂O₂ and cytochrome c peroxidase (CCP). The main problem with this method is that CCP is not commercially available and has to be prepared in the laboratory. We have modified some currently available methods for purifying a highly active preparation of CCP in about 4 d. It includes a batch extraction of protein using DEAE-sepharose followed by concentration either by lyophilization or by passing the extract through a small DEAE-sepharose column instead of by ultrafiltration. The concentrated preparation is passed through a Sephadex G-75 column and the final CCP crystallized against water. The final preparations had a purity index (PI, ratio of absorbance at 408 nm/280 nm, equivalent to heme/protein ratio) above 1.2. These changes make the overall procedure very simple, preserving enzyme activity and spectral properties. In addition, we point out that special care has to be taken to eliminate cytochrome c from crude CCP extracts. Cytochrome c not only introduces an artifact when determining PI, but is also may act as a hydrogen donor for CCP when monitoring H₂O₂ formation, thus decreasing the sensitivity of this method.     

Analysis of Content of 2-Oxoacids in Rat Brain Extracts Using High-Performance Liquid Chromatography

Biochemistry (Moscow) - 2-Oxoacids are involved in a number of important metabolic processes and can be used as biomarkers in some human diseases. A new optimized method for quantification of...     

The synthesis and P388 cytotoxicity of mycalazol 11 and related 5-acyl-2-hydroxymethylpyrroles

We report a general method for the synthesis of mycalazol 11 and some related 5-acyl-2-hydroxymethylpyrroles using a Stille coupling of 5-(tri-n-butylstannyl)pyrrole-2-carboxaldehyde with an acid chloride as the key step. The newly prepared 5-acyl-2-hydroxymethylpyrroles 5-7, together with the 5-carboxamido-2-hydroxymethylpyrrole 10, have been assayed for in vitro cytotoxicity against the P388 murine leukemia cell line.     

Enumeration of Free-Living Aerobic N2-Fixing H2-Oxidizing Bacteria by Using a Heterotrophic Semisolid Medium and Most-Probable-Number Technique

A heterotrophic semisolid medium was used with two sensitive assay methods, C₂H₂ reduction and O₂-dependent tritium uptake, to determine nitrogenase and hydrogenase activities, respectively. Organisms known to be positive for both activities showed hydrogenase activity in both the presence and absence of 1% C₂H₂, and thus, it was possible to test a single culture for both activities. Hydrogen uptake activity was detected for the first time in N₂-fixing strains of Pseudomonas stutzeri. The method was then applied to the most-probable-number method of counting N₂-fixing and H₂-oxidizing bacteria in some natural systems. The numbers of H₂-oxidizing diazotrophs were considerably higher in soil surrounding nodules of white beans than they were in the other systems tested. This observation is consistent with reports that the rhizosphere may be an important ecological niche for H₂ transformation.     

NDRG2在人胚胎呼吸系统的表达特点

目的该实验通过对16-28周人胚胎呼吸系统NDRG2表达的研究,旨在阐明NDRG2在16-28周人胚胎呼吸系统中的表达规律,为进一步明确新的发育相关基因ndrg2的功能提供依据。方法搜集16-28周胎儿呼吸系统的肺和气管组织,制成石蜡切片,用抗NDRG2单克隆抗体,行免疫组化染色(ABC法),从蛋白质水平观察NDRG2表达情况。统计阳性细胞数,利用统计学方法,判断不同胎龄的肺和气管间NDRG2表达有无差别。结果免疫组化染色表明,NDRG2在16-28周胚胎呼吸系统中有广泛的表达,阳性产物主要位于上皮细胞的胞浆中,但是不同胎龄之间NDRG2的表达未见显著差别。结论NDRG2在16-28周胚胎呼吸系统中有广泛的表达,提示NDRG2在早期胚胎的呼吸系统上皮细胞的生长与发育过程中起一定作用。而阳性产物主要表达在上皮细胞的胞浆中,说明NDRG2可能是一种胞浆蛋白。     

一类神经传播方程的特征差分方法和最佳阶l^2误差估计

给出矩形域上一类神经传播方程的特征差分,利用沿特征线方向构造差分逼近格式的方法和技巧．对给定的模型进行离散数值逼近和数值分析．特别是在沿特征线方向构造离散差分格式的过程中,可能会出现离散点在定义域之外的问题．本文提供了一个新的有效的差分逼近的处理方法,得到了该方法的三。一模误差估计．     

橡胶树胶乳C-乳清双向电泳样品制备技术的建立及优化

在TCA/丙酮沉淀法的基础上,用乙醇和乙醚洗涤（称双乙法）沉淀获得橡胶树胶乳C-乳清蛋白样品,并在样品溶解时通过超声助溶进一步提高样品的溶解度。结果显示,利用改良后的样品制备方法（TCA/丙酮+双乙法+超声处理）所获得的C-乳清蛋白样品的溶解性大幅增加,蛋白得率高达8.47 mg/mL C-乳清,为传统TCA/丙酮法的1.6倍;同时降低了盐离子浓度,等电聚焦时升压顺利、聚焦完全,双向电泳的图谱质量明显改善,在银染2D胶上可获得1 206个蛋白点,为传统TCA/丙酮法的2.7倍。本文对胶乳C-乳清蛋白样品制备方法进行深入优化,获得了重现性较好的高质量双向电泳蛋白图谱,促进了橡胶树蛋白质组学研究。     

开放式空气CO2浓度增高条件下旱地土壤气体CO2浓度廓线测定

设计了一套适合于FACE(free airCO2 enrichment)平台的旱地土壤气体CO2 浓度廓线测定方法 ,并将其应用于田间实验 .在江苏省无锡市郊区具有太湖地区典型水稻土的稻麦轮作农田 ,对FACE和对照麦田以及裸土 0～ 30cm土层的土壤气体CO2 浓度廓线进行了观测研究 .结果表明 ,所采用的方法满足进行旱地农田土壤气体CO2 浓度廓线研究的要求 ;在 0～ 30cm土层中 ,上层土壤气体中的CO2 向上垂直扩散要比下层土壤快 ;在作物旺盛生长期 ,大气CO2 浓度升高 2 0 0± 4 0 μmol·mol-1使 0～ 30cm土层的土壤气体CO2 浓度显著提高 14 %± 5 % (t 检验P <0 .0 0 1) .