变形链球菌UA159葡萄糖基转移酶B催化活性区的基因克隆及表达

为获得具有良好生物活性的可溶性葡萄糖基转移酶催化活性区(GTFB/CAT),根据NCBI上已发表的Streptococcus mutans UA159(血清型c)GTFB的DNA测序结果,按照GTFB/CAT两端的序列设计引物,利用PCR克隆技术钓取S.mutans UA159(血清型c)的GTFB/CAT基因,连入表达载体p ET-28b(+)中构成p ET-28b(+)-GTFB/CAT重组体,将重组载体转入大肠杆菌BL21(E.coil BL21)宿主菌中进行诱导表达,最佳诱导条件为37℃或30℃、4 h、诱导剂IPTG的浓度为1 mmol/L,产物经Ni2+-NAT树脂亲和层析纯化,得到了不可溶的GTFB/CAT包涵体,包涵体通过变性-复性最终得到可溶性蛋白,产物经SDS-PAGE分析表明,在44 ku处有一明显条带,与预期蛋白分子量一致,蛋白纯度约为80%,采用Somogyi法测得GTFB/CAT蛋白的比酶活为1.66 IU/mg。研究表明:成功克隆GTFB/CAT基因并通过在E.coil BL21原核体系中表达得到有生物活性的可溶性蛋白,为后续研究GTF的抗结剂及预防龋齿的效果及机理奠定了基础。     

薤白多糖体外抗氧化活性及其对小鼠急性肝损伤的保护作用研究

本文研究了薤白多糖清除各种自由基及其对小鼠急性肝损伤的保护作用。采用浸提、分步醇沉法提取了三种薤白多糖,利用红外光谱初步分析了其结构组成。结果表明：AMP40在清除羟基自由基（·OH）、超氧阴离子自由基（O2＋）等抗氧化评价体系中比AMP60及AMP80具有更强的清除自由基活性,在实验最大浓度时清除率可分别达到40．96％和49．840／0;在对小鼠急性化学性肝损伤的保护作用研究中,发现通过预先灌胃200、400和800mg／kgBW的薤白多糖AMP40,可以抑制肝损伤小鼠血清中谷丙转氨酶（ALT）和谷草转氨酶（AST）活性的升高,同时能使小鼠肝脏中SOD活性、CAT活性、GSH活性以及T-AOC水平显著增加,而MDA含量显著减少（P〈0．05或P〈0．01）,且这种变4e-AMP40呈现一定的剂量依赖关系,表明AMP40具有一定的肝保护作用。研究表明了薤白多糖的抗氧化活性与其分子量大小及糖醛酸含量密切相关。     

Inactivation of Escherichia coli O157:H7 in vitro and on the surface of spinach leaves by biobased antimicrobial surfactants

This study was conducted to evaluate the effect of biosurfactants on the populations of Escherichia coli O157:H7 in suspension and on spinach leaves. Eight surfactants including four soybean oil-based biosurfactants, sodium dodecyl sulfate (SDS), polyoxyethylene sorbitan monooleate (Tween 80), sophorolipid (SO) and thiamine dilauryl sulfate (TDS) at concentrations of 0.1%, 0.5% and 1.0% were tested in bacterial suspension, and the most effective biosurfactants were applied on spinach leaves. Results showed that the soybean oil-based biosurfactants, SDS or Tween 80 did not significantly affect E. coli O157:H7 populations. SO and TDS at concentrations of 1.0% were effective in reducing E. coli O157:H7 populations in bacterial suspension. E. coli O157:H7 with an initial population of 7.1 log CFU/mL was not detectable (detection limit: 1 log CFU/mL) after 1 min in 1.0% TDS or after 2 h in 1.0% SO. On spinach leaves, SO at 1% did not significantly affect E. coli when compared to a water wash during 7 days post-treatment storage at 4 °C. However, TDS (1.0%) wash was as effective as 200 ppm chlorine in reducing population of spot inoculated E. coli O157:H7, achieving 3.1 and 2.7 log CFU/per leaf at day 0, and 1.4 and 1.9 log CFU/leaf at day 7 when compared with a water wash. No apparent change in spinach visual quality was observed. None of treatments caused changes in visual quality of spinach. Electron micrographs suggested ultrastructural damage of bacterial cells such as separation of the outer membrane from the cytoplasmic membrane. Overall, our results showed that SO and TDS may be potential sanitizers in inactivating human pathogens such as E. coli O157:H7 in wash water and on fresh produce.     

薤白多糖体外抗氧化活性及其对小鼠急性肝损伤的保护作用研究

本文研究了薤白多糖清除各种自由基及其对小鼠急性肝损伤的保护作用。采用浸提、分步醇沉法提取了三种薤白多糖,利用红外光谱初步分析了其结构组成。结果表明：AMP40在清除羟基自由基（?OH）、超氧阴离子自由基（O2-?）等抗氧化评价体系中比AMP60及AMP80具有更强的清除自由基活性,在实验最大浓度时清除率可分别达到40.96%和49.84%;在对小鼠急性化学性肝损伤的保护作用研究中,发现通过预先灌胃200、400和800 mg/kg BW的薤白多糖AMP40,可以抑制肝损伤小鼠血清中谷丙转氨酶（ALT）和谷草转氨酶（AST）活性的升高,同时能使小鼠肝脏中SOD活性、CAT活性、GSH活性以及T-AOC水平显著增加,而MDA含量显著减少（P<0.05或P<0.01）,且这种变化对AMP40呈现一定的剂量依赖关系,表明AMP40具有一定的肝保护作用。研究表明了薤白多糖的抗氧化活性与其分子量大小及糖醛酸含量密切相关。     

豆渣不同菌种发酵后成分变化的研究

用根霉、毛霉、米曲霉菌分别对一定量的豆渣进行发酵,对发酵前后6个时期豆渣的营养成分、酶活力进行分析,结果表明,发酵后豆渣的品质明显提高。豆渣中氨基酸态氮的含量均升高;豆渣中的可溶性总糖含量也明显提高,脂肪含量有所降低。豆渣中蛋白酶活力及淀粉酶活力在发酵前期为最大值,随着时间的延长逐步降低,且毛霉产蛋白酶能力较强,最大值达到96.4 U/g,而根霉产淀粉酶能力较强,最大值达到13.2 U/g。     

碳纳米管吸附腐植酸的动力学、热力学及机理研究

针对天然水中腐植酸(HA)类溶解性有机物去除问题, 采用多壁碳纳米管为吸附剂, 在不同的pH值、吸附剂量、初始HA浓度下进行吸附动力学实验, 用准二级速率方程拟合了动力学数据, 其线性相关度在0.99以上, 拟合得到的平衡吸附量为27mg/g,与实验结果(25.5 mg/g)基本一致. 在25~50℃下进行了碳纳米管吸附腐植酸的等温吸附实验, 以Langmuir模型拟合的平衡吸附量为29.7mg/g, 与实验结果相近. 用Clapeyron-Clausius与Gibbs- Helmholtz方程计算的自由能(Δ G)、焓(Δ H)、熵(Δ S)皆为负值, 说明碳纳米管对腐植酸的吸附为放热熵减过程. 碳纳米管的表面、管间隙、管内腔及管束之间形成的束聚孔为其有效吸附点位, 腐植酸与碳纳米管间的π-π作用也是吸附的主要原因之一.     

Persistence,Engagement, and Migration in Engineering Programs

Records from the Multiple‐Institution Database for Investigating Engineering Longitudinal Development indicate that engineering students are typical of students in other majors with respect to: persistence in major; persistence by gender and ethnicity; racial/ethnic distribution; and grade distribution. Data from the National Survey of Student Engagement show that this similarity extends to engagement outcomes including course challenge, faculty interaction, satisfaction with institution, and overall satisfaction. Engineering differs from other majors most notably by a dearth of female students and a low rate of migration into the major. Noting the similarity of students of engineering and other majors with respect to persistence and engagement, we propose that engagement is a precursor to persistence. We explore this hypothesis using data from the Academic Pathways Study of the Center for the Advancement of Engineering Education. Further exploration reveals that although persistence and engagement do not vary as much as expected by discipline, there is significant institutional variation, and we assert a need to address persistence and engagement at the institutional level and throughout higher education. Finally, our findings highlight the potential of making the study of engineering more attractive to qualified students. Our findings suggest that a two‐pronged approach holds the greatest potential for increasing the number of students graduating with engineering degrees: identify programming that retains the students who come to college committed to an engineering major, and develop programming and policies that allow other students to migrate in. There is already considerable discourse on persistence, so our findings suggest that more research focus is needed on the pathways into engineering, including pathways from other majors.     

共轭亚油酸的生理活性及制备方法研究进展

旨在为进一步提高共轭亚油酸产量提供理论依据,总结概述了共轭亚油酸的生理活性与制备方法的研究进展。共轭亚油酸是一种天然存在于反刍动物体内的物质,具有降低胆固醇含量、抗癌、抗氧化、提高免疫力等重要生理功能,在减肥、癌症治疗、哮喘治疗等方面发挥了重要作用,在功能性膳食研发领域拥有巨大潜力。由于共轭亚油酸的天然含量与来源无法满足人们日常生活的需求,因此研究更高产率的共轭亚油酸的合成方法一直是热点内容。合成共轭亚油酸的方法主要有生物合成法和化学合成法,生物合成法中的微生物合成法和酶催化异构化合成法是近年来的研究热点。