Fast classification and compositional analysis of cornstover fractions using Fourier transform near-infrared techniques

The objectives of this research were to determine the variation of chemical composition across botanical fractions of cornstover, and to probe the potential of Fourier transform near-infrared (FT-NIR) techniques in qualitatively classifying separated cornstover fractions and in quantitatively analyzing chemical compositions of cornstover by developing calibration models to predict chemical compositions of cornstover based on FT-NIR spectra. Large variations of cornstover chemical composition for wide calibration ranges, which is required by a reliable calibration model, were achieved by manually separating the cornstover samples into six botanical fractions, and their chemical compositions were determined by conventional wet chemical analyses, which proved that chemical composition varies significantly among different botanical fractions of cornstover. Different botanic fractions, having total saccharide content in descending order, are husk, sheath, pith, rind, leaf, and node. Based on FT-NIR spectra acquired on the biomass, classification by Soft Independent Modeling of Class Analogy (SIMCA) was employed to conduct qualitative classification of cornstover fractions, and partial least square (PLS) regression was used for quantitative chemical composition analysis. SIMCA was successfully demonstrated in classifying botanical fractions of cornstover. The developed PLS model yielded root mean square error of prediction (RMSEP %w/w) of 0.92, 1.03, 0.17, 0.27, 0.21, 1.12, and 0.57 for glucan, xylan, galactan, arabinan, mannan, lignin, and ash, respectively. The results showed the potential of FT-NIR techniques in combination with multivariate analysis to be utilized by biomass feedstock suppliers, bioethanol manufacturers, and bio-power producers in order to better manage bioenergy feedstocks and enhance bioconversion.     

植物萜类代谢工程

植物萜类化合物不仅在植物生命活动中起重要作用,而且具有重要商业价值。随着近年来萜类代谢途径和调控机理研究的深入,代谢工程已成为提高萜类产量最有潜力的途径之一。对萜类代谢工程领域具代表性的研究结果进行了全面回顾,然后讨论了萜类代谢工程的研究方法和策略,其中重点探讨了功能基因组学方法在萜类代谢途径及调控机理研究方面的应用。     

海洋氮循环中细菌的厌氧氨氧化

细菌厌氧氨氧化过程是在一类特殊细菌的厌氧氨氧化体内完成的以氨作为电子供体硝酸盐作为电子受体的一种新型脱氮反应.厌氧氨氧化菌的发现,改变人们对传统氮的生物地球化学循环的认识:反硝化细菌并不是大气中氮气产生的唯一生物类群.而且越来越多的证据表明,细菌厌氧氨氧化与全球的氮物质循环密切相关,估计海洋细菌的厌氧氨氧化过程占到全球海洋氮气产生的一半左右.由于氮与碳的循环密切相关,因此可以推测,细菌的厌氧氨氧化会影响大气中的二氧化碳浓度,从而对全球气候变化产生重要影响.另外,由于细菌厌氧氨氧化菌实现了氨氮的短程转化,缩短了氮素的转化过程,因此为开发更节约能源、更符合可持续发展要求的废水脱氮新技术提供了生物学基础.     

Linking seasonal inorganic nitrogen shift to the dynamics of microbial communities in the Chesapeake Bay

Seasonal shifts of dissolved inorganic nitrogen (DIN) and the dynamics of microbial communities for nitrogen transformation were investigated in the water column of Chesapeake Bay. The relative abundance of nitrogen over phosphorus (N*) showed a strong seasonal and spatial pattern: gradually decreased from upstream to downstream; high in winter and low in summer. Because the phosphorus concentration remained relatively stable, the spatiotemporal pattern of N* implied that a substantial fraction of DIN was removed in the bay, especially in summer. Correlation analyses indicated the functional microbial communities and environmental variables, such as temperature, dissolved oxygen, salinity, played important roles for connecting the seasonal variation of N*. Among them, temperature was the trigger factor. High temperature in the summer induced the growth of functional microbes, which subsequently consumed a large portion of DIN inputted from the tributaries and reduced the N*. The current study provided the relative importance of microbial communities and environmental variables in driving the DIN loss in the bay.     

植物激素对草莓叶片不定芽形成的影响

用试管内生长的草莓幼嫩叶片作外植体,培养在MS基本培养基上附加1.5—2.5毫克/升6—BA和0.1毫克/升NAA,可直接诱导成不定芽,诱导率可达20%。如果不定芽继代培养在同样浓度的培养基上,继而可形成大量的丛生芽。能使叶外植体形成不定芽的植物激素组合而不能使其愈伤组织分化成芽。IAA与6—BA的不同浓度组合对不定芽形成效果不明显。     

鸡传染性喉气管炎病毒gB基因的克隆及其在耻垢分枝杆菌中的表达

以ILTV基因组为模板 ,利用PCR特异扩增出gB基因 ,定向克隆到中间质粒载体pY_α ,构建了中间质粒pY_α_gB。然后以中间质粒pY_α_gB为模板 ,扩增出含有人结核分枝杆菌启动子hsp70基因和堪萨斯分枝杆菌α信号肽基因的hsp_α_gB片段 ,回收补平后与穿梭表达载体pRR3平端连接 ,从而构建大肠杆菌_分枝杆菌穿梭表达质粒pR_α_gB。再将其电转化至耻垢分枝杆菌M .smegmatismc2 15 5 ,ELISA检测表明重组菌株M .smegmatismc2 15 5 (pR_α_gB)的表达产物具有很好的反应原性。Westernblot检测说明gB基因在分枝杆菌中获得了表达并具有良好的免疫原性。鸡胚中和试验结果表明该重组菌株可以中和 1个剂量EID50 的ILTV强毒 ,能够保护SPF鸡胚抵抗强毒攻击     

NADH荧光法快速检测细菌总数

基于细菌胞内NADH的荧光特性及其在胞内含量稳定的特性, 建立一种快速检测细菌总数的新方法。该荧光法的NADH检测限为1 nmol/L, NADH含量在10 nmol/L~0.2 mmol/L间与荧光强度呈良好线性关系(R2 =0.9905)。经离心获得菌体细胞, 热Tris-HCl法提取胞内NADH, 以 342 nm为激发波长, 461 nm为发射波长测定提取液荧光强度, 1 h内可检测到样品1×104 CFU/mL菌数。结果表明该方法快速、灵敏、简便、重复性好, 可适用于食品卫生与安全、环境检测等领域活细菌数量的定量检测。     

Mechanisms of the acute ischemia-induced arrhythmogenesis--a simulation study

The underlying ionic mechanisms of ischemic-induced arrhythmia were studied by the computer simulation method. To approximate the real situation, ischemic cells were simulated by considering the three major component conditions of acute ischemia (elevated extracellular K(+) concentration, acidosis and anoxia) at the level of ionic currents and ionic concentrations, and a round ischemic zone was introduced into a homogeneous healthy sheet to avoid sharp angle of the ischemic tissue. The constructed models were solved using the operator splitting and adaptive time step methods, and the perturbation finite difference (PFD) scheme was first used to integrate the partial differential equations (PDEs) in the model. The numerical experiments showed that the action potential durations (APDs) of ischemic cells did not exhibited rate adaptation characteristic, resulting in flattening of the APD restitution curve. With reduction of sodium channel availability and long recovery of excitability, refractory period of the ischemic tissue was significantly prolonged, and could no longer be considered as same as APD. Slope of the conduction velocity (CV) restitution curve increased both in normal and ischemic region when pacing cycle length (PCL) was short, and refractory period dispersion increased with shortening of PCL as well. Therefore, dynamic changes of CV and dispersion of refractory period rather than APD were suggested to be the fundamental mechanisms of arrhythmia in regional ischemic myocardium.     

多基因SNP位点及多种危险因素与老年汉族冠心病的关联分析

目的:探索老年冠心病多基因遗传易感性基础及相关的危险因素。方法:采用病例-对照研究方法,共入选老年汉族冠心病患者246例,非冠心病患者185例,纳入性别、年龄、吸烟,饮酒,高血压史、糖尿病史、高脂血症史、同型半胱氨酸、氨基末端脑钠肽前体、超敏C反应蛋白、抗凝血酶III、胆固醇、甘油三酯、高密度脂蛋白、低密度脂蛋白共15种危险因素与冠心病的关联性进行logistic回归分析。同时使用美国Sequenom高通量基因多态性分型技术研究了10种基因11个单核苷酸基因多态性(SNP)位点与冠心病的关联性。结果:15种危险因素中,发现增龄、高血压、抗凝血酶III(ATIII)下降是冠心病主要的危险因素,P<0.05。11个SNPs中3个SNP,血小板糖蛋白GP1BA rs2243093(-5T/C),血管紧张素转化酶ACE rs4332(547C/T)与ATIII rs2227589(893C/T)与老年汉族患者冠心病相关联。rs2243093(-5T/C)突变基因型CC与TT+AT比较,P=0.029(OR=3.41,CI:1.19-9.75);rs4332(547C/T)杂合型TC与CC+TT相比,P=0.003(OR=0.56,CI:0.38-0.82);rs2227589(893C/T),CT+CT与野生基因型CC相比较,P=0.003(OR=1.79,CI:1.22-2.63)。结论:增龄、抗凝血酶III下降、高血压是影响老年冠心病的主要危险因素,血小板、抗凝血系统、肾素-血管紧张素系统三种机制参与了老年冠心病的发生与发展。