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71.
β-木糖苷酶(β-xylosidase,酶编号EC 3.2.1.37)是木聚糖降解酶系中的重要组成部分。本研究以毕赤酵母Pichia pastoris GS115为宿主菌尝试表达反刍兽月形单胞菌Selenomonas ruminantium中的β-木糖苷酶基因Sxa。根据毕赤酵母对密码子的偏爱性、mRNA二级结构、GC含量和稀有密码子,对Sxa基因进行优化;通过基因合成技术获得了全长基因mSxa并构建重组酵母表达载体pPIC9K-mSxa;以BglⅡ酶切重组载体pPIC9K-mSxa,电击转化将m Sxa基因导入毕赤酵母GS115中,获得的转化子经过表型和遗传霉素G418抗性筛选、PCR鉴定,得到表达β-木糖苷酶基因的工程菌GS115-pPIC9K-mSxa;通过活性测定获得高效表达β-木糖苷酶的重组酵母,并对重组β-木糖苷酶的酶学性质进行了初步研究。结果表明,重组β-木糖苷酶的分子量约为66 kDa。在发酵罐水平表达的酶活性达到了287.61 IU/mL。对酶学性质研究显示,该酶在温度为40-60℃,pH为5.0-7.0时较稳定,其最适反应温度和pH分别为55℃和6.0,专一性地作用于β-木糖苷键。Mn~(2+)和Ca~(2+)对该酶具有激活作用,而Fe~(3+)、Cu~(2+)、Co~(2+)、Mg~(2+)、EDTA及SDS抑制其酶活性。本研究首次将反刍兽月形单胞菌的β-木糖苷酶基因转化到毕赤酵母中获得表达,并具有较高活性,为进一步工业化应用奠定了基础。 相似文献
72.
73.
真光层深度的遥感反演及其在富营养化评价中的应用 总被引:2,自引:0,他引:2
真光层深度直接影响水体中浮游植物的分布和初级生产力以及水体生态环境,是水生态研究的一个重要参数.利用2006年10月24日~11月2日太湖水下实测光谱数据和光合有效辐射(PAR)数据,通过数据的处理和分析,尝试建立真光层深度与水面以下遥感反射率的关系模型,并利用真光层深度与透明度的关系,建立水体富营养化真光层深度评价模型.研究结果表明:真光层深度与归一化遥感反射率具有很好的相关性;选用特定波段的归一化反射率作为变量,建立两者的关系模型能较好的反演真光层深度,所建立的模型算法中,指数模型拟合方程的综合效果好于其他模型,波段比值算法反演精度要好于单波段算法;利用利用真光层深度进行富营养化评价具有一定的应用价值,利用该模型对太湖水体进行富营养化评价,得出太湖西部湖区大部分已富营养化,东部湖区处于中营养化和轻度富营养化状态. 相似文献
74.
紫蓬山区三种鹭繁殖生物学研究 总被引:27,自引:1,他引:27
作者报道了1996年4~7月紫蓬山区的池鹭,白鹭和夜鹭的繁殖行为和雏鸟的食性及生长,结果表明:巢前期三种鹭取食地点远离巢区;求偶方式主要有婚飞,显示饰羽,求偶喂食和象征性营巢行为;获得巢材的方式不同,异步产卵,异步孵化;雏出孵前,白鹭和夜鹭的迅速加固和扩大巢的行为,育雏期,取食大小随雏鸟日龄增大而增大,取食距离随雏期延长而缩短,三者雏鸟重增长的数学模型分别为:w=205.1e^-(0.065e)^ 相似文献
75.
Exploring Health Literacy in Medical University Students of Chongqing,China: A Cross-Sectional Study
Yan Zhang Fan Zhang Ping Hu Wenjie Huang Lu Lu Ruixue Bai Manoj Sharma Yong Zhao 《PloS one》2016,11(4)
Health literacy is important in public health and healthcare, particularly in effective communication between patients and health professionals. Although most medical students will eventually work as health professionals after graduation, research on health literacy of medical students is scarce. This study aimed to assess the health literacy level of medical students in Chongqing, China, and its influencing factors. A cross-sectional study was conducted and 1,275 participants (250 males and 1,022 females) who majored in five different disciplines were involved. The Health Literacy Questionnaire was used as the survey tool. The junior students obtained the highest scores, whereas the freshman students had the lowest scores on each scale. The average score of males was higher than that of females except in “feeling understood and supported by healthcare providers,” and the average score of students who reside in urban areas was higher than that of students in rural areas. Moreover, the average score of engineering students was higher than that of medical or health sciences students. Multiple linear regression models (Radj2 = 0.435, P = 0.000) showed that the grade, socioeconomic status, and parent’s highest level of education were positively correlated with health literacy. In conclusion, the health literacy levels of the medical students are insufficient and need improvement. 相似文献
76.
Idiopathic dilated cardiomyopathy (IDC) has been hypothesized as a multifactorial disorder initiated by an environment trigger
in individuals with predisposing human leukocyte antigen (HLA) alleles. Published data on the association between HLA-DR polymorphism
and IDC risk are inconclusive. To derive a more precise estimation of the relationship, a meta-analysis was performed. A total
of 19 case–control studies including 1,378 cases and 10,383 controls provided data on the association between HLA-DR polymorphism
and genetic susceptibility to IDC. Overall, statistically elevated frequencies of HLA-DR4 (OR 1.58; 95% CI 1.21–2.07; P = 0.0009) and HLA-DR5 (OR 1.35; 95% CI 1.05–1.73; P = 0.02) alleles were found in patients with IDC compared with controls. Individuals with HLA-DR3 antigen have a protective
effect against IDC (OR 0.72; 95% CI 0.58–0.90; P = 0.004). In summary, this meta-analysis indicated that certain HLA-DR alleles may be genetic markers for susceptibility
and resistance to IDC. 相似文献
77.
Enzymatic Recovery of Elemental Palladium by Using Sulfate-Reducing Bacteria 总被引:9,自引:2,他引:9 下载免费PDF全文
Worldwide usage of platinum group metals is increasing, prompting new recovery technologies. Resting cells of Desulfovibrio desulfuricans reduced soluble Pd2+ to elemental, cell-bound Pd0 supported by pyruvate, formate, or H2 as the electron donor without biochemical cofactors. Pd reduction was O2 insensitive, opening the way for recycling and recovery of Pd under oxic conditions. 相似文献
78.
哈萨克族学生体质发育状况的10年比较分析 总被引:1,自引:0,他引:1
报道新疆阿勒泰地区1995年2589名城镇7—18岁哈萨克族(哈族)中小学生身高、体重、胸围、坐高、肩宽、骨盆宽6项体质发育指标的调查结果。男女生体质发育指标随年龄增加而增长,各项指标的年均增长值皆为男生大于女生。与1985年比较,哈族学生的身高、体重、胸围皆有不同程度增长。哈族男女生的身高突增年龄仍分别为14岁和10岁,但是其身高增长却不伴有相应比例的坐高增长,女生部分年龄组的肩宽和男女生各年龄组的骨盆宽呈现负增长,提示哈族学生的体型与10年前相比已经开始有所改变。 相似文献
79.
Xiaohui Zhan Fengjuan Zhang Ziyang Zhong Ruhao Chen Yong Wang Ling Chang Ralph Bock Bihua Nie Jiang Zhang 《Plant biotechnology journal》2019,17(9):1814-1822
CRISPR/Cas systems provide bacteria and archaea with molecular immunity against invading phages and foreign plasmids. The class 2 type VI CRISPR/Cas effector Cas13a is an RNA‐targeting CRISPR effector that provides protection against RNA phages. Here we report the repurposing of CRISPR/Cas13a to protect potato plants from a eukaryotic virus, Potato virus Y (PVY). Transgenic potato lines expressing Cas13a/sgRNA (small guide RNA) constructs showed suppressed PVY accumulation and disease symptoms. The levels of viral resistance correlated with the expression levels of the Cas13a/sgRNA construct in the plants. Our data further demonstrate that appropriately designed sgRNAs can specifically interfere with multiple PVY strains, while having no effect on unrelated viruses such as PVA or Potato virus S. Our findings provide a novel and highly efficient strategy for engineering crops with resistances to viral diseases. 相似文献
80.
Singhal NS Patel RT Qi Y Lee YS Ahima RS 《American journal of physiology. Endocrinology and metabolism》2008,295(2):E331-E338
Resistin has been linked to components of the metabolic syndrome, including obesity, insulin resistance, and hyperlipidemia. We hypothesized that resistin deficiency would reverse hyperlipidemia in genetic obesity. C57Bl/6J mice lacking resistin [resistin knockout (RKO)] had similar body weight and fat as wild-type mice when fed standard rodent chow or a high-fat diet. Nonetheless, hepatic steatosis, serum cholesterol, and very low-density lipoprotein (VLDL) secretion were decreased in diet-induced obese RKO mice. Resistin deficiency exacerbated obesity in ob/ob mice, but hepatic steatosis was drastically attenuated. Moreover, the levels of triglycerides, cholesterol, insulin, and glucose were reduced in ob/ob-RKO mice. The antisteatotic effect of resistin deficiency was related to reductions in the expression of genes involved in hepatic lipogenesis and VLDL export. Together, these results demonstrate a crucial role of resistin in promoting hepatic steatosis and hyperlipidemia in obese mice. 相似文献