Functional secretion of a type 1 antifreeze protein analogue by optimization of promoter, signal peptide, prosequence, and terminator in Lactococcus lactis

Lactococcus lactis is a food-grade microorganism of major commercial importance. Antifreeze protein is a potent cryogenic protection agent for the cryopreservation of food and pharmaceutical materials. In this study, extracellular expression of a novel recombinant type I antifreeze protein analogue (rAFP) in L. lactis was optimized. An efficient SlpA promoter (P SlpA) was fused to various signal peptides (SPs) and propeptide sequences to examine the extracellular expression levels of rAFP. An efficient signal peptide, SP sacB, fused to prosequence AE, enabled higher extracellular rAFP production; use of the SlpA terminator (Ter SlpA) was a further improvement. The extracellularly expressed rAFP successfully inhibited ice recrystallization and is thus potentially applicable for cryogenic preservation.     

Synthesis and insecticidal activities of novel N-sulfenyl-N'-tert-butyl-N,N'-diacylhydrazines. 2. N-substituted phenoxysulfenate derivatives

A series of novel N-substituted phenoxysulfenyl- N'- tert-butyl- N, N'-diacylhydrazines were designed and synthesized as insect growth regulators via the key intermediates N-chlorosulfenyl- N'- tert-butyl- N, N'-diacylhydrazines. Compared to the parent compounds, these N-substituted phenoxysulfenyl derivatives displayed better solubility and improved hydrophobicities. The insecticidal activities of the new compounds were evaluated. The results of bioassays showed that the title compounds possessed a combination of strong stomach as well as contact poison property higher than the corresponding parent compounds. In particular, N-(4-chlorophenoxy)sulfenyl -N'- tert-butyl- N-4-ethylbenzoyl- N'-3,5-dimethylbenzoylhydrazide ( IIIi) as a field testing candidate has higher stomach toxicities against oriental armyworm and tobacco cutworm than the corresponding parent compound RH-5992. Furthermore, the compound IIIi exhibits higher contact activities against Asian corn borer, tobacco cutworm, and cotton bollworm than RH-5992.     

Input–Output Budgets for Inorganic Nitrogen Under Acid Rain in a Subtropical Evergreen Mixed Forest in Central-South China

Inorganic nitrogen deposition and leaching in stream water were monitored from January, 2001 to December, 2004 in a subtropical evergreen mixed forest in central-south China. The seasonal concentration and flux of inorganic nitrogen in bulk precipitation and stream water, seasonal mean net retention of nitrogen and net flux of H⁺ transformed by nitrogen were estimated and quantified in Shaoshan forest. The research results show that the correlation coefficient of fluxes between bulk precipitation and stream water is significant, with a coefficient 0.916 at the 0.01 level. Mean fluxes of inorganic nitrogen input are 2.62 g m^?2 a^?1 and 0.516 g m^?2 a^?1 in form of bulk precipitation and dry deposition respectively, and output in stream water is around 0.22 g m^?2 a^?1, which indicates that most of nitrogen input is reserved in the forest. Net retention of nitrogen reaches 2.916 g m^?2 a^?1, just higher than other study plots over the world. Along with the translating of nitrogen ( ${\text{NH}}_4^ + - {\text{N}}$ and ${\text{NO}}_3^ - - {\text{N}}$ ), H⁺ is imported to the forest ecosystem at the same time. At our study plots, net flux of H⁺ transformed by nitrogen is about 73.57 mmol m^?2 a^?1. The positive value suggests that Shaoshan forest is still a finer buffering system to nitrogen deposition and it is far from nitrogen saturation in spite of the high nitrogen deposition.     

Interactive effects of Cd and PAHs on contaminants removal from co-contaminated soil planted with hyperaccumulator plant <Emphasis Type="Italic">Sedum alfredii</Emphasis>

Purpose  

Soil contamination by multiple organic and inorganic contaminants is common but its remediation by hyperaccumulator plants is rarely reported. The growth of a cadmium (Cd) hyperaccumulator Sedum alfredii and removal of contaminants from Cd and polycyclic aromatic hydrocarbons (PAHs) co-contaminated soil were reported in this study.     

法兰类锻件挤镦过程的有限元分析

采用有限元法对法兰类锻件的挤镦成形过程进行了有限元分析计算,与试验结果对比表明,无论是等效应变ε分布曲线,还是压力载荷位移曲线都趋于一致,从而为应用塑性有限元法指导法兰类锻件的工艺设计提供了依据。     

黑河中游绿洲不同质地土壤水分的入渗与再分布

该文利用双环入渗仪,通过定水头法研究了黑河中游绿洲地区玉米地和防护林地土壤水分的入渗过程,并利用Hydrus-1D模型和Trime-IPH手持式TDR分别对土壤水分的入渗和再分布过程进行了动态模拟和测定。结果表明:不同质地土壤水分入渗和再分布差异明显。土壤下部粘土夹层不仅对水分入渗起到显著的阻碍作用,而且具有较强的持水保水能力。统计分析表明,试验期间模拟土壤含水量的均方根误差和相对误差分别在0.02cm3/cm3和0.68%以下,模拟剖面储水量的均方根误差和相对误差分别在0.908 cm和0.9%以下,因此Hydrus-1D模型对绿洲地区土壤水分在垂直方向的运移模拟具有较高的精确度,这为该区域水分管理和可持续发展提供理论依据。     

竹材草酸预水解过程木质素的溶出规律

为了探索用草酸预处理竹材制备溶解浆,该文用不同用量的草酸对竹材进行预水解,测定预水解过程竹材木质素含量的变化,用场发射扫描电镜(field emission scanning electron microscope,FE-SEM)观察水解后假木质素在竹纤维表面的分布状况,用核磁共振技术(cross polarisation/magic angle spinning carbon-13 nuclear magnetic resonance,CP/MAS 13C-NMR)分析木质素的结构变化。研究结果表明,在竹片草酸预水解过程中,竹片预水解得率将随着预水解时间的延长而下降,并且,草酸用量越大,得率下降越多。基于水解后竹材基质的木质素含量会随着预水解时间的延长而逐渐升高,并且,草酸用量越大,木质素含量升高越多;而基于竹材原料的木质素含量则随着预水解时间的延长先下降再增加,并且,草酸用量越大,增加的速率也越大。竹材木质素由于芳基醚键(β-O-4)断裂,酚型木质素含量提高。纤维素和半纤维素降解产物在预水解过程形成的假木质素类物质会以微球的形式附着在竹片表面。该研究可为探索竹材快速高选择性去除半纤维素的预水解方法提供参考。     

Comparison of the chemical composition and physicochemical properties of different fibers prepared from the peel of Citrus sinensis L. Cv. Liucheng

Fiber-rich fractions (FRFs) including soluble and insoluble dietary fibers (SDF and IDF), alcohol-insoluble solid (AIS), and water-insoluble solid (WIS) were isolated from the peel of Citrus sinensis L. cv. Liucheng for analysis and tests. The peel was rich in insoluble FRFs (IDF, AIS, and WIS; 476-515 g kg(-1) of peel), which were mainly composed of pectic substances and cellulose, and also contained pectic polysaccharide-rich SDF (94.1 g kg(-1) of peel). These insoluble FRFs had water-holding capacities (15.5-16.7 mL g(-1)), oil-holding capacities (2.35-5.09 g g(-1)), cation-exchange capacities (454-997 mequiv kg(-1)), and swelling properties (14.6-21.1 mL g(-1)) much higher than those of cellulose. These results recommended the consumption of these peel insoluble FRFs of desired physicochemical properties as sources of food fibers or low-calorie bulk ingredients in food applications requiring oil and moisture retention. Further investigations on the physiological functions of these peel FRFs using animal-feeding experiments are underway.     

Antiproliferative and chemopreventive effects of adlay seed on lung cancer in vitro and in vivo

This study examined the effects of different extracts of adlay seed on the growth of human lung cancer cells in vitro and in vivo. The data showed that a methanolic extract, but not a water extract, of adlay seed exerted an antiproliferative effect on A549 lung cancer cells by inducing cell cycle arrest and apoptosis. It was also found that tumor growth in vivo was inhibited by the methanolic extract in a dose-dependent manner. The chemopreventive effect of adlay seed on the tobacco-specific carcinogen 4-(methylnitrosamino)-1-(3-pyridyl)-1-butanone (NNK)-induced lung tumorigenesis in A/J mice was also investigated. Groups of mice were pre-fed with different diets, followed by feeding with NNK-containing drinking water for 8 months. The results indicated that feeding with diet containing 30% of powdered adlay seed reduced the number of surface lung tumors by approximately 50%. Taken together, these results indicate that the components of adlay seed exert an anticancer effect in vitro and in vivo and may be useful for the prevention of lung tumorigenesis.     

广西贺州地区温室内空气湿度时空变化研究

以温室为研究对象,探讨研究了晴天、阴天、雨天3种不同类型天气条件下温室内空气相对湿度与绝对湿度的日周期时空变化规律以及整个冬季空气相对湿度与绝对湿度的时空变化规律。为合理调控温室内空气湿度以控制作物病虫害、提高产量和改善品质提供科学依据。