小RNA病毒和小DNA病毒的三维结构模型

本文综述了小RNA病毒和小DNA病毒的主要结构特征,绘制出了它们的三维结构模型,从中找出了两者间的共同点和差异,为进一步研究两种病毒提供了依据。     

Thecate stem medusozoans (Cnidaria) from the early Cambrian Chengjiang biota

Cnidarians are phylogenetically located near the base of the ‘tree of animals’, and their early evolution had a profound impact on the rise of bilaterians. However, the early diversity and phylogeny of this ‘lowly’ metazoan clade has hitherto been enigmatic. Fortunately, cnidarian fossils from the early Cambrian could provide key insights into their evolutionary history. Here, based on a scrutiny of the purported hyolith Burithes yunnanensis Hou et al. from the early Cambrian Chengjiang biota in South China, we reveal that this species shows characters distinct from those typical of hyoliths, not least a funnel-shaped gastrovascular system with a single opening, a whorl of tentacles surrounding the mouth, and the lack of an operculum. These characters suggest a great deviation from the original definition of the genus Burithes, and a closer affinity with cnidarians. We therefore reassign the material to a new genus: Palaeoconotuba. Bayesian inference of phylogeny based on new anatomical traits identifies a new clade, including Palaeoconotuba and Cambrorhytium, as a stem group of sessile medusozoan cnidarians that are united by the synapomorphies of developing an organic conical theca and a funnel-like gastrovascular system. This study unveils a stem lineage of medusozoans that evolved a lifelong conical theca in the early Cambrian.     

海水酸化及升温对刺参生长及能量收支的影响

以东亚浅海生态系统中的关键种——刺参(Apostichopus japonicus)为实验对象,研究了CO₂驱动的海水酸化及升温对其生长及能量收支的影响。实验设置对照组(大连近海水温, pCO₂ 400μatm)、升温组(大连近海水温+3℃, pCO₂ 400μatm)、酸化组(大连近海水温, pCO₂ 1100μatm)和酸化升温组(大连近海水温+3℃,pCO₂ 1100μatm)。结果表明:与对照组相比,温度升高3℃对刺参的生长无显著影响;酸化组刺参的特定生长率最低,较对照组降低0.19%/d,个体体重的变异系数最大;酸化升温组刺参的终末体重和特定生长率与对照组相较无显著差异,但其摄食率和排粪率均显著高于对照组。升温组和酸化组的刺参能量的分配模式与对照组相比未发生明显改变,但酸化升温组刺参的能量分配模式发生显著变化,其粪便能所占摄食能的比例显著升高。研究表明,海水酸化抑制了刺参的生长但未改变其能量的分配,生长的降低主要取决于摄食减少;而海水酸化与温度升高的共同作用可能会通过...     

沙面结皮形成与微环境变化

研究结果表明沙坡头地区的大气年降尘(d相似文献   

固相萃取与气相色谱⁃质谱法联用测定食用植物油和含脂肪食品中氯丙醇酯的方法验证研究

氯丙醇酯是国际上广泛关注的食品加工过程污染物,其水解产物氯丙醇对人体（特别是婴幼儿）危害风险较大。采用固相萃取与气相色谱-质谱（gas chromatography-mass spectrometry,GC-MS）联用技术,对食用植物油和含脂食品中的氯丙醇酯[3-氯-1,2-丙二醇脂肪酸酯（简称3-MCPD酯）和2-氯-1,3-丙二醇脂肪酸酯（简称2-MCPD酯）]进行检测。该方法准确度高（3-MCPD酯和2-MCPD酯的平均回收率分别为98.9%和96.5%)、灵敏度高(3-MCPD酯和2-MCPD酯的检出限分别为0.042 mg·kg^-1和0.058 mg·kg^-1)、重现性好(相对标准偏差均低于5%)。76批次监测样品中,3-MCPD酯和2-MCPD酯的含量分别为0.042~4.865 mg·kg^-1(平均值为0.773 mg·kg^-1)和0.058~2.592 mg·kg^-1(平均值为0.469 mg·kg^-1)。经机构间的协同验证和英国FAPAS样的能力验证,2种氯丙醇酯在0.200~3.000 mg·kg^-1范围内线性良好,为进一步研究奠定了基础,同时也为食品加工企业严格控制生产过程建立了一种可行的检测方法。     

Nature of 2n gamete formation and mode of inheritance in interspecific hybrids of diploid Vaccinium darrowi and tetraploid V. corymbosum

RAPD markers were used to determine the level of heterozygosity transmitted via 2n gametes from V. darrowi selection Florida 4B (Fla 4B) to inter-specific hybrids with tetraploid V. corymbosum cv Bluecrop. The tetraploid hybrid US 75 was found to contain about 70% of Fla 4B's heterozygosity, a value attributed to a first-division restitution (FDR) mode of 2n gamete production. Crossovers during 2n gamete formation were evidenced by the absence of 16 dominant alleles of Fla 4B in US 75, and direct tests of segregation in a diploid population involving Fla 4B. RAPD markers that were present in both Fla 4B and US 75 were used to determine the mode of inheritance in a segregating population of US 75xV. corymbosum cv Bluetta. Thirty-one duplex loci were identified which segregated in a 51 ratio, indicating that US 75 undergoes tetrasomic inheritance.     

Regulation of cellulase synthesis in mycelial fungi: Participation of ATP and cyclic AMP

Summary ATP and cAMP in 4 strains of mycelial fungi were determined by luciferin-luciferase system and HPLC respectively. Cellulase synthesis was subject to the dual control of ATP and cAMP. No matter what carbon sourse was used, cellulase synthesis was repressed if intracellular ATP concentration was over 10^-7mg/ml. Exogenous cAMP could increase cellulase synthesis under depression conditions.