Sequence relationship of glycosylated and unglycosylated gag polyproteins of Moloney murine leukemia virus.

Both glycosylated and unglycosylated polyproteins coded by the gag gene are produced in cells infected with Moloney murine leukemia virus. GpP80gag is a glycosylated precursor of a larger gag glycoprotein exported to the cell surface, whereas Pr65gag is an unglycosylated precursor of the virion internal structural proteins. GpP80gag contains not only carbohydrate, but also additional polypeptide sequences not found in Pr65gag. In the experiment reported here, we localized the differences between GpP80gag and Pr65gag with respect to the domains of the individual gag proteins. This was done by comparison of partial proteolytic cleavage fragments from Pr65gag, from GpP80gag, and from the unglycosylated form of GpP80gag (P75gag) which had been immunoprecipitated by antisera specific for gag proteins p30, p15, and p10. We conclude that the additional polypeptide sequences in GpP80gag are located at or very near the amino terminus of the polyprotein. The carbohydrate in GpP80gag is attached to polypeptide sequences held in common between GpP80gag and Pr65gag.     

Bubble flow in the downflow section of an airlift tower

Characterization of the two-phase flow in the downflow section of the airlift tower is necessary for accurate modeling of the airlift tower. A Split-cylinder airlift tower was investigated for superficial gas velocities ranging from 0.0683 to 0.3315 m/sec for an air–water system. Statistical cross-covariance techniques were used to yield velocities, void fractions, and flow rates corresponding to upward and downward components of bubble flow in the downflow section of the airlift tower. From these results the fraction of incoming air entrained in the downflow section was determined as a function of superficial gas velocity and position.     

Nodule infection by bean yellow mosaic virus in Phaseolus vulgaris.

Infection of root nodules of beans, Phaseolus vulgaris L., by bean yellow mosaic virus (BYMV) and the effect of the disease on the specific activity of the nodule are reported. Infectivity and serological microprecipitin assays with two sources of BYMV antiserum demonstrated that nodules from bean plants whose leaves had been inoculated with BYMV contain BYMV antigen. The disease reduced the fresh weights of tops, roots, and root nodules and induced premature nodule decay and/or nodule drop. The disease also reduced leghemoglobin content, on a plant weight basis, and N2 fixation rate, on an individual plant basis, as measured by the acetylene reduction assay. The increased leghemoglobin content per gram-nodule in BYMV-infected nodules relative to healthy nodules might be associated with multiplication of the virus in the nodule and/or unknown cellular effects derived from the BYMV-Rhizobium interaction.     

Effects of temperature on diphosphopyridine nucleotide-linked isocitrate dehydrogenase from bovine heart. Aspects of the kinetics, stability, and quarternary structure of the enzyme.

A temperature-dependent conformational change of the active DPN-linked isocitrate dehydrogenase was observed. When initial reaction kinetic data were examined between 35 and 5 degrees, the Hill number (n) varied from 2 at higher to n approaching unity at lower temperatures, with an inflection point at 17 degrees. The presence of manganous isocitrate in the incubation media shifted the transition temperature for enzyme inactivation by 5,5'-dithiobis(2-nitrobenzoate) from 8-16 degrees. These temperature-dependent transitions were paralleled by progressive changes in sedimentation velocities from s20, w of 10.4 at 25 degrees to 7.3 at 10 degrees as measured by active band centrifugation. The linear Arrhenius plot for apparent V max and the constancy of S0.5 for the substrate manganous isocitrate between 35 and 5 degrees suggest that this temperature-dependent conformational change may not be solely related to manganous isocitrate. Further indications of equilibria between different species of enzyme in solution and effects of substrates and cofactors on conformation came from studies of specific activity of enzyme diluted into buffers at 3 and 25 degrees. Dilution to concentrations between 10 and 25 mum enzyme resulted in relatively rapid protein concentration-dependent inactivation which could be prevented and fully reversed by manganous isocitrate. No further substantial inactivation was found subsequent to this phase at 25 degrees. Lowering the temperature of the dilution buffer to 3 degrees favored formation of enzyme species exhibiting a further time and pH-dependent loss of activity which became independent of protein concentration below 7 mum enzyme. The rate of cold inactivation was reduced by raising the ionic strength of the buffer and its progress could be arrested by manganous isocitrate; however, the substrate did not restore the original activity.     

中国虫草一新记录种

【目的】对一个寄生鳞翅目幼虫的虫草标本Dxhir140901进行分类鉴定。【方法】采用形态学比较和基于ITS1-5.8S-ITS2rDNA的系统发育与进化网络分析进行鉴定。【结果】形态学观察：标本的分离菌株形态显示其为典型的被毛孢属真菌,具有两型产孢结构：A型产孢细胞柱状,(1.8?6.3) μm×1.8 μm;B型产孢细胞锥形,基部柱状,向上逐渐变细无明显颈部,基部宽3?3.8 μm,长21?63 μm,颈部宽1.8?2.0 μm,菌丝末端可直接形成产孢细胞;孢子橘瓣形或卵形,(8.1?10.8) μm×(2.7?5.4) μm,具粘液,黏液层厚1.8?2.7 μm。系统发育分析结果显示该菌株与巨针线形虫草Ophiocordyceps macroacicularis聚为一支,支持率为98%,进化网络分析也支持上述结果。【结论】通过与O. macroacicularis的形态比较和分子系统学分析结果,Dxhir140901及其分离株Gzuifr-hir140901为巨针线形虫草Ophiocordyceps macroacicularis S. Ban, T. Sakane & Nakagiri的无性阶段,该种为中国新记录种。     

城乡建设用地关联对生态系统服务的影响——以洞庭湖地区为例

城乡建设用地数量及相互联系的变化是空间要素及结构演化的重要方面,深刻影响着生态环境质量和生态系统服务水平,研究城乡建设用地关联对生态系统服务的影响对国土空间高质量发展具有重要意义。以洞庭湖地区为研究对象,从土地利用关联视角出发,运用引力模型、InVEST模型、面板数据模型等方法,定量研究了城乡建设用地关联对生态系统服务的影响。结果表明：（1）洞庭湖地区城镇建设用地规模呈现上升趋势,农村居民点用地规模呈现下降趋势;（2）城乡建设用地关联强度呈不断增强趋势,且强关联网格以建成区为核心向周边扩展,低关联网格分布于远离建成区的地方;（3）生境质量和碳储量呈现下降趋势,食物供给则呈现上升趋势,各项生态系统服务价值具有显著的空间异质性;（4）城乡建设用地关联强度对生态系统服务具有负向影响,人口密度、GDP密度、夜间灯光、道路网络对生态系统服务也呈现负向影响,归一化差异植被指数与生态系统服务之间则存在显著的正相关。研究结果有助于了解关联视角下城乡建设用地对生态系统服务的影响机制,可以为制定合理的城乡空间发展战略提供科学依据。     

Single-cell transcriptomic atlas of primate cardiopulmonary aging

Aging is a major risk factor for many diseases,especially in highly prevalent cardiopulmonary comorbidities and infectious diseases including Coronavirus Diseas...     

Microbial adaptive evolution

Bacterial species can adapt to significant changes in their environment by mutation followed by selection, a phenomenon known as “adaptive evolution.” With the development of bioinformatics and genetic engineering, research on adaptive evolution has progressed rapidly, as have applications of the process. In this review, we summarize various mechanisms of bacterial adaptive evolution, the technologies used for studying it, and successful applications of the method in research and industry. We particularly highlight the contributions of Dr. L. O. Ingram. Microbial adaptive evolution has significant impact on our society not only from its industrial applications, but also in the evolution, emergence, and control of various pathogens.