高效液相色谱法测定桂花叶片中游离氨基酸浓度

建立了自动在线柱前衍生反相高效液相色谱法同时测定桂花叶片中21种游离氨基酸的方法。样品超纯水超声提取,经阳离子交换树脂柱纯化,有效降低了色素、糖类等杂质对定量的影响,同时减轻了样品对液相色谱柱的损害。以邻苯二甲醛(OPA)与9-芴甲基氯甲酸酯(FMOC)为衍生剂,Agilent Zorbax Eclipse-AAA色谱柱分离,梯度洗脱,荧光检测器检测,在19min内完成桂花叶片中21种氨基酸的分析,双内标法定量。结果 21种氨基酸线性关系、精密度、准确性、重现性良好。标准氨基酸的保留时间和峰面积平均相对标准偏差分别为0.14%和2.99%,加标回收率平均为91.09%。桂花叶片游离氨基酸中,含量最多的是谷氨酸,占总游离氨基酸的24%。本实验方法保证了氨基酸浓度定量的准确可靠性,可用于高等植物叶片中游离氨基酸浓度的测定。     

Microbial bioavailability of dissolved organic nitrogen (DON) in the sediments of Lake Shankou, Northeastern China

Dissolved organic nitrogen(DON)extracted from Lake Shankou sediments using KCl was isolated into hydrophobic and hydrophilic fractions.The bioavailabilities of the hydrophobic and hydrophilic fractions to three types of bacterial communities collected from sediments,activated sludge and compost products were examined.The DON recoveries obtained by DAX-8 and cation exchange resins treatment were 96.17% ± 1.58% and 98.14% ±0% for the samples obtained from N4 and N14 stations,respectively.After 25 days of incubation at 25°C,most DON(59% to 96%)was degraded.Hydrophilic DON exhibited a higher reduction rate than hydrophobic DON during the growth phase.Untreated wastewater from Changshuihe town was the main degradable DON source to station N4,and 93% of hydrophilic DON and 80% of hydrophobic DON were degraded.Station N14 received a large amount of refractory DON from forest soils and exhibited DON degradation rates of 82% and 71% for the hydrophilic and hydrophobic fractions,respectively.Amino acid contents and fluorescence intensities were also analyzed.Approximately 27% to 74% of amino acids were taken up by day 5,and their concentration gradually increased in the following days due to the decomposition of dissolved proteins.Parallel factor analysis resulted in identification of tryptophan-like proteins,tyrosine-like proteins and FA-like substances.During the growth phase,40%–51% of the tryptophan-like proteins were taken up by bacteria,and the accumulation of tyrosine-like proteins was attributed to the release of biotic substances.The concentration of the FA-like substances decreased due to microbial decomposition.     

A new process to improve short-chain fatty acids and bio-methane generation from waste activated sludge

As an important intermediate product, short-chain fatty acids(SCFAs) can be generated after hydrolysis and acidification from waste activated sludge, and then can be transformed to methane during anaerobic digestion process. In order to obtain more SCFA and methane,most studies in literatures were centered on enhancing the hydrolysis of sludge anaerobic digestion which was proved as un-efficient. Though the alkaline pretreatment in our previous study increased both the hydrolysis and acidification processes, it had a vast chemical cost which was considered uneconomical. In this paper, a low energy consumption pretreatment method, i.e. enhanced the whole three stages of the anaerobic fermentation processes at the same time, was reported, by which hydrolysis and acidification were both enhanced, and the SCFA and methane generation can be significantly improved with a small quantity of chemical input. Firstly, the effect of different pretreated temperatures and pretreatment time on sludge hydrolyzation was compared. It was found that sludge pretreated at 100°C for 60 min can achieve the maximal hydrolyzation. Further, effects of different initial p Hs on acidification of the thermal pretreated sludge were investigated and the highest SCFA was observed at initial p H 9.0with fermentation time of 6 d, the production of which was 348.63 mg COD/g VSS(6.8 times higher than the blank test) and the acetic acid was dominant acid. Then, the mechanisms for this new pretreatment significantly improving SCFA production were discussed. Finally,the effect of this low energy consumption pretreatment on methane generation was investigated.     

铜绿微囊藻培养过程中氨基酸的释放特征及其对水体有机质的贡献

为深入分析铜绿微囊藻水华暴发对水体有机质、氨基酸含量及组成的影响,进一步揭示蓝藻水华暴发对湖泊内源氨基酸和有机质的贡献及养分循环机制,采集太湖北部富营养化区域梅梁湾中的水样,用于在室内培养太湖蓝藻水华优势种——铜绿微囊藻(Microcystis aeruginosa),采用邻苯二甲醛(OPA)柱前衍生-反相高效液相色谱法(HPLC)分析铜绿微囊藻生长、衰亡过程中氨基酸的摩尔浓度及其组成特征的变化,探讨藻类产生的氨基酸和有机质对湖泊水体中有机质、TC(总碳)及DTN(溶解性总氮)的贡献. 结果表明:铜绿微囊藻在生长过程中产生的氨基酸对水体中TC、DTN、TOC(总有机碳)的贡献率分别为23%~37%、46%~93%和46%~83%;在衰亡期,水体中难降解氨基酸(如甘氨酸、丝氨酸、丙氨酸和赖氨酸)的摩尔浓度(c)为60.4 μmol/L,显著高于同时期易降解氨基酸(如酪氨酸、苯丙氨酸、谷氨酸和精氨酸)的摩尔浓度(40.9 μmol/L);c(D-氨基酸)/c(L-氨基酸)由初始的0.28降至0.09,表明在铜绿微囊藻对数生长至衰亡期间,水体中有机质的降解程度逐渐降低. 研究显示,在水体有机质降解程度降低的同时,氨基酸摩尔浓度逐步增加,因此大量未降解的氨基酸沉积下来成为水体有机质来源之一.      

Phospholipid fatty acid biomarkers in a freshwater periphyton community exposed to uranium: discovery by non-linear statistical learning

Phospholipid fatty acids (PLFA) have been widely used to characterize environmental microbial communities, generating community profiles that can distinguish phylogenetic or functional groups within the community. The poor specificity of organism groups with fatty acid biomarkers in the classic PLFA-microorganism associations is a confounding factor in many of the statistical classification/clustering approaches traditionally used to interpret PLFA profiles. In this paper we demonstrate that non-linear statistical learning methods, such as a support vector machine (SVM), can more accurately find patterns related to uranyl nitrate exposure in a freshwater periphyton community than linear methods, such as partial least squares discriminant analysis. In addition, probabilistic models of exposure can be derived from the identified lipid biomarkers to demonstrate the potential model-based approach that could be used in remediation. The SVM probability model separates dose groups at accuracies of ∼87.0%, ∼71.4%, ∼87.5%, and 100% for the four groups; Control (non-amended system), low dose (amended at 10 μg U L⁻¹), medium dose (amended at 100 μg U L⁻¹), and high dose (500 μg U L⁻¹). The SVM model achieved an overall cross-validated classification accuracy of ∼87% in contrast to ∼59% for the best linear classifier.     

镉、汞、铅在体内对氨基酸掺入微粒体的特异性抑制作用

本实验采用DL-(~3H)-亮氨酸作为蛋白质合成的原料,从亚细胞水平观察镉、汞、铅在动物体内对肝脏各亚细胞组分蛋白合成的影响。实验结果表明,给雄性大鼠腹腔一次注入2.4mg/kg醋酸镉后72h和一次注给2.0mg/kg氯化汞或100mg/kg醋酸铅后24h,均可不同程度地抑制DL-(~3H)-亮氨酸掺入微粒体蛋白,而对其它组分包括细胞核、线粒体、去微粒体后上清液蛋白中DL-(~3H)-亮氨酸的掺入无明显影响。     

桂西北明山金矿床表生带矿石中氨基酸的分布特征研究

在总结目前关于氨基酸溶金作用研究成果的基础上,对桂西北明山卡林型金矿床表生带的矿石样品进行了氨基酸的分离、定性和定量研究,结果表明,各种氨基酸的稳定性与所处的成岩成矿环境有关,因此不同环境中对成岩成矿发挥作用的氨基酸种类是不同的,所起的作用也有所差异;进行氨基酸溶金作用模拟实验时应该首先考虑氨基酸在不同成岩成矿环境中的稳定性。结合已有的氨基酸溶金作用模拟实验所得到的认识,对桂西北卡林型金矿成矿过程中氨基酸的作用进行了探讨。     

直链烷基苯磺酸盐促进剩余污泥产生短链脂肪酸的研究

采用批试试验的方法研究了十二烷基苯磺酸钠(C12-LAS)对剩余污泥在厌氧发酵过程中产生的短链脂肪酸(SCFAs)的影响.结果表明,C12-LAS的投加极大地提高了剩余污泥厌氧发酵过程中的SCFAs产量.当C12-LAS加入量低于0.1g·g-1时,SCFAs产量随着C12-LAS加入量的增加而增加,然而,当C12-LAS加入量高于0.1g·g-1时,SCFAs产量反而有所降低.从污泥产酸量以及经济成本考虑,C12-LAS的最佳投加量为0.02g·g-1,此时剩余污泥的SCFAs最大产量出现在第6天.进一步的研究表明,C12-LAS不仅促使大量的碳水化合物和蛋白质脱离污泥颗粒并溶解到液相中,而且抑制了产甲烷菌的活性.尽管剩余污泥经历着酸化过程,但由于其释放出大量的NH4 -N,污泥在整个厌氧发酵过程中的pH值逐渐升高.     

取代苯甲酸在天然河流中的生物降解及其定量结构--生物降解性相关研究

以天然河流水作为微生物源 ,采用碘量法测定了 2 0种苯甲酸类化合物的 5日生化需氧量 ,并以其占理论需氧量的百分数作为表征生物降解性的参数 ,得出各类取代苯甲酸类化合物的生物降解能力为 :羟基 >氨基 >羧基 >甲氧基 >氯基 >硝基 ;对于同一种取代基 ,对位取代基化合物生物降解能力最大 ,而邻位、间位取代基化合物生物降解能力大体相同。计算了苯甲酸类化合物的分子连接性指数 ,并以 5日生化需氧量占理论需氧量的百分数为参数建立了 QSBR模型。分析结果表明 ,分子连接性指数5Xvpc、5Xp- 5Xvp 能较好地反映取代苯甲酸的生物降解性     

A Global Overview of Atmospheric Acid Deposition Fluxes

This paper presents a summary of globalacid deposition flux data taken from a globalassessment report on acid deposition prepared forUNEP/WMO (Whelpdale and Kaiser, 1996). There is a largevariation in the spacial coverage and reliability ofmonitoring around the world. Many more stationsmeasure wet deposition than collect appropriate datafor estimating dry deposition. The widespread regionswith highest precipitation concentrations anddeposition fluxes of sulphate and nitrate coincideclosely with the regions of highest density ofSO₂ and NO_x precursor emissions occurringprimarily in the mid-latitude, northern hemispherebelt where a large fraction of the worlds fossilfuels is consumed. Organic acids in precipitation makea minor contribution to acidity (<20%) inindustrial regions, but in the rest of the world theyare of same order, or even exceed, inorganic acids.Less is known about dry deposition, but it appears topredominate near strong emission sources with wetdeposition predominating farther downwind. The molarratio of the N/S contribution to acidic deposition isclose to 1.0 over large areas of Europe and NorthAmerica, but is highly variable elsewhere, beinghighest in equatorial regions due to biomass burningand lowest near smelters and other large sources of SO₂.