乙型脑炎病毒NS2A-C60A位点突变对其生物学特性影响研究*

目的:旨在探索Ⅰ型日本乙型脑炎病毒传代致弱后基因组突变NS2A-C60A对乙脑病毒生物学特性的影响。方法:首先通过对传代致弱及原始乙脑毒株基因组序列进行测序比对、结构预测分析并利用Western blotting(WB)确定了目标研究位点NS2A-C60A;然后使用反向遗传定点突变技术构建拯救了包含NS2A-C60A单点突变的病毒株;最后利用噬斑形态观察、生长曲线、双萤光素酶分析,WB以及炎性因子检测和动物实验研究了该单点突变对于乙脑病毒生物学特性的影响。结果:首次研究发现Ⅰ型乙脑病毒传代致弱会导致NS1'蛋白表达的显著下降以及可能的相关位点NS2A-C60A,并成功拯救获得了NS2A-C60A单点突变毒株rJEV-C60A,研究发现NS2A-C60A突变对乙脑病毒的生长特性及噬斑形成没有显著影响,但是能够显著降低乙脑病毒NS1'蛋白的表达,并且该位点突变能够轻微阻碍乙脑病毒对细胞炎性因子表达的抑制,动物实验结果显示NS2A-C60A点突变病毒与原毒株具有相似的神经毒力,说明该位点突变不是影响乙脑病毒毒力致弱的关键位点。结论:新发现的NS2A-C60A位点突变能够显著减少乙脑病毒NS1'蛋白的表达,但是对其增殖、诱导炎症及神经毒力等生物学特性没有显著影响。     

离散广义Logistic模型的稳定性和浑沌现象

文[1]提出了单种生长的连续性文广义Logistic dx/dt=γx({K-x}/(K+px))其中γ>ο为种群的内禀生长率,K>0为环境容纳量,ν>-1表示种群对环境(包括营     

几种生态因子对菹草光合作用的影响

本文研究了光照、pH、温度对菹草光合作用的影响。在一定温度条件下,菹草的净产氧量与一定范围的光照强度呈直线相关。菹草的光补偿点随温度的上升而上升。在菹草自然生活的环境中,温度低于30℃时,升温有利于菹草的光合作用。高pH(PH>10.0)下碳源缺乏对菹草的光合作用影响较大。高pH与强光照射的协同作用严重影响菹草的光合作用。水温与氮、磷营养盐不足并非夏季自然水体中菹草死亡的主要原因。而不良光照(水表层光抑制,中、下层光饥饿)和高pH下缺乏光合碳源的协同作用便可能导致菹草夏季死亡。     

羊红细胞超氧化物歧化酶的研究

自羊红细胞分离得到一种高等电点的铜.锌-超氧化物歧化酶(Cu.ZnSOD)。其沉降系数(S)为3.23,亚基分子量为16600,等电点为8.50,紫外最大吸收峰位于259nm,酶分子中含有铜和锌,氨基酸组成特点与其它动物来源的Cu.Zn-SOD相同。该酶的比活性为5500U/mg(黄嘌吟氧化酶—细胞色素还原法);对KCN的抑制作用敏感,最适pH值为6。     

Identification of N- and C-terminal corticotropin peptides in the Mr 80000 form of neurophysin

The 125I-labeled Mr 80000 form of neurophysin has been purified from bovine neurohypophysi. Tryptic digests of this species were analyzed, prior to or after treatment with carboxypeptidase B, by high-pressure liquid chromatography followed by isoelectric focusing and the fragments compared with those generated by a similar treatment of reference bovine 1-39 adrenocorticotropin. The ACTH peptides 22-39 and 1-8, as well as the 1-7 derivative of the latter were identified by those two independent criteria. This provides chemical evidence supporting the hypothesis [8] that high Mr neurophysin may contain the sequence of ACTH.     

A Simple Numerical Procedure for Estimating the Prior Probability in the Biomathematical Proof of Paternity

This note gives a simple procedure for finding the maximum likelihood estimate of the prior probabilities in paternity cases. The procedure is based on a fixed point principle.     

Microbial production and uptake of nitric oxide in soil

Abstract Fluxes of NO from three different soils have been studied by a flow-through system in the laboratory as a function of gas flow rate, of NO mixing ratio, and of incubation conditions. The dependence of net NO fluxes on gas flow rates and on NO mixing ratios could be described by a simple model of simultaneous NO production and NO uptake. By using this model, rates of gross NO production, rate constants of NO uptake, and NO compensation mixing ratios could be determined as function of the soil type and the incubation condition. Gross NO production rates were one to two orders of magnitude larger under anaerobic than under aerobic conditions. NO uptake rate constants, on the other hand, were only 5–8 times larger so that the compensation mixing ratios of NO were in a range of about 1600–2200 ppbv under anaerobic and of about 50–600 ppbv under aerobic conditions. The different soils exhibited similar NO uptake rate constants, but the gross NO production rate and compensation mixing ratio was significantly higher in an acidic (pH 4.7) sandy clay loam than in other less acidic soils. Experiments with autoclaved soil samples showed that both NO production and NO uptake was mainly due to microbial metabolism.     

Molecular dynamics of human alpha-fetoprotein fragment LDSYQCT and its analogs at different dielectric constants

A comparative study of the conformation dynamics of the human alpha-fetoprotein fragment LDSYQCT and heptapeptides derived from it by point substitutions has revealed a significant influence of electrostatic interactions on the set of preferred conformations and dynamics of amino acid residues when the peptides with blocked termini are examined at ? = 1. Peptide flexibility rises when the termini are left free (charged). At ? = 10 or 80, the set of probable conformations for all residues expands to much the same extent, i.e., at higher permittivity of the medium the dynamic effects of amino acid changes are leveled off.     

Linking behavioral states to landscape features for improved conservation management

1. A central theme for conservation is understanding how animals differentially use, and are affected by change in, the landscapes they inhabit. However, it has been challenging to develop conservation schemes for habitat‐specific behaviors.
2. Here we use behavioral change point analysis to identify behavioral states of golden eagles (Aquila chrysaetos) in the Sonoran and Mojave Deserts of the southwestern United States, and we identify, for each behavioral state, conservation‐relevant habitat associations.
3. We modeled behavior using 186,859 GPS points from 48 eagles and identified 2,851 distinct segments comprising four behavioral states. Altitude above ground level (AGL) best differentiated behavioral states, with two clusters of short‐distance movement behaviors characterized by low AGL (state 1 AGL = 14 m (median); state 2 AGL = 11 m) and two associated with longer‐distance movement behaviors and characterized by higher AGL (state 3 AGL = 108 m; state 4 AGL = 450 m).
4. Behaviors such as perching and low‐altitude hunting were associated with short‐distance movements in updraft‐poor environments, at higher elevations, and over steeper and more north‐facing terrain. In contrast, medium‐distance movements such as hunting and transiting were over gentle and south‐facing slopes. Long‐distance transiting occurred over the desert habitats that generate the best updraft.
5. This information can guide management of this species, and our approach provides a template for behavior‐specific habitat associations for other species of management concern.

     

Computational Modeling of Protein Stability: Quantitative Analysis Reveals Solutions to Pervasive Problems

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