The p53 isoforms are differentially modified by Mdm2

The discovery that the single p53 gene encodes several different p53 protein isoforms has initiated a flurry of research into the function and regulation of these novel p53 proteins. Full-length p53 protein level is primarily regulated by the E3-ligase Mdm2, which promotes p53 ubiquitination and degradation. Here, we report that all of the novel p53 isoforms are ubiquitinated and degraded to varying degrees in an Mdm2-dependent and -independent manner, and that high-risk human papillomavirus can degrade some but not all of the novel isoforms, demonstrating that full-length p53 and the p53 isoforms are differentially regulated. In addition, we provide the first evidence that Mdm2 promotes the NEDDylation of p53β. Altogether, our data indicates that Mdm2 can distinguish between the p53 isoforms and modify them differently.     

Alkaloids of Dyera costulata

Six bisindole alkaloids have been isolated from the leaves of Dyera costulata (Apocynaceae). One is the known ochrolifuanine A and the others are the novel ochrolifuanines E and F, and the 18-dehydroochrolifuanines A, E and F.     

Differential scanning calorimetric study of the thermal unfolding of beta-lactamase I from Bacillus cereus.

The irreversible thermal unfolding of the class A beta-lactamase I from Bacillus cereus has been investigated at pH 7.0, using differential scanning calorimetry (DSC) and inactivation kinetic techniques. DSC transitions showed a single peak with a denaturation enthalpy of 646 kJ.mol-1 and were moderately scan rate dependent, suggesting that the process was partially kinetically controlled. The inactivation kinetics at constant temperature showed that the irreversible denaturation of the enzyme occurs as the sum of two exponential terms whose amplitudes are strongly temperature dependent within the transition range so that, at the lowest temperatures within this interval, irreversible inactivation would proceed mainly through the slow phase. The fraction of irreversibly denatured enzyme (D) as a function of temperature for a given scanning rate was calculated by numerical integration of the kinetic equation with temperature, using previously determined kinetic parameters. This D form was the most populated of the unfolded states only at temperatures well above the maximum in the calorimetric transition. Combination of the results of kinetic and DSC experiments has allowed us to separate the contribution of the final D state to the excess enthalpy change from the contribution arising from the reversibly denatured forms of the enzyme (I(i), i = 1,..., n), with the resulting conclusion that the scan rate dependence of the calorimetric traces was the result of two different dynamic effects, viz., the irreversible step and a slow relaxation process during formation of the reversibly denatured intermediate states. Finally, the problems of using results obtained at a single scan rate to validate the two-state kinetic model are commented on.     

小麦赤霉病的药剂防治指标模型

经过推导,得出小麦赤霉病的两类药剂防治指标模型．在保证品质、收支有余的条件下,第一类模型附加产投比较佳、净收益最佳原则,第二类模型附加产投比最佳原则．灵敏度分析和合理性分析证明了模型的正确性．模型可做为小麦赤霉病药剂防治的决策工具．同时,给出了两类模型的BASIC计算程序．     

Extracellular targeting of the vacuolar tobacco proteins AP24, chitinase and β-1,3-glucanase in transgenic plants

The Nicotiana tabacum ap24 gene encoding a protein with antifungal activity toward Phytophthora infestans has been characterized. Analysis of cDNA clones revealed that at least three ap24-like genes are induced in tobacco upon infection with tobacco mosaic virus. Amino acid sequencing of the purified protein showed that AP24 is synthesized as a preproprotein from which an amino-terminal signal peptide and a carboxyl-terminal propeptide (CTPP) are cleaved off during post-translational processing. The functional role of the CTPP was investigated by expressing chimeric genes encoding either wild-type AP24 or a mutant protein lacking the CTPP. Plants expressing the wild-type construct resulted in proteins properly sorted to the vacuole. In contrast, the proteins produced in plants expressing the mutant construct were secreted extracellularly, indicating that the CTPP is necessary for targeting of AP24 to the vacuoles. Similar results were obtained for vacuolar chitinases and -1,3-glucanases of tobacco. The extracellularly targeted mutant proteins were shown to have retained their biological activity. Together, these results suggest that within all vacuolar pathogenesis-related proteins the targeting information resides in a short carboxyl-terminal propeptide which is removed during or after transport to the plant vacuole.     

大陈岛海域浮游动物群落季节变化及其影响因素

为探究大陈岛海域浮游动物群落的季节变化,于2020年9月（夏季）、11月（秋季）和2021年1月（冬季）、4月（春季）分别对大陈岛海域的浮游动物及环境因子进行了4个航次的调查。结果共鉴定浮游动物90种,包括浮游幼体15类,其中夏季种类数最多（68种）,冬季最少（20种）,常见的优势种有：百陶箭虫（Sagitta bedoti）、微刺哲水蚤（Canthocalanus pauper）、中华哲水蚤（Calanus sinicus）等12种（Y>0.02）。浮游动物的年平均丰度和生物量分别为（153.40±214.73）个/m³、（411.93±561.76） mg/m³,二者存在明显的季节变化,平均丰度为春季（380.17±296.14）个/m³>夏季（135.30±112.59）个/m³>秋季（67.88±90.52）个/m³>冬季（25.30±19.11）个/m³;平均生物量为夏季（895.01±802.54） mg/m³>春季（623.39±358.73） mg/m³>秋季（91.08±82.36） mg/m³>冬季（45.96±84.95） mg/m³。多样性指数（H''）和均匀度指数（J''）的年平均值分别为1.71±0.96和0.53±0.20,均表现出夏秋季较高、冬春季较低的特征。聚类分析结果表明调查海域的浮游动物可划分为夏季类群、秋季类群、冬季类群和春季类群4组类群。Pearson相关性分析和冗余分析（RDA）结果表明,海水温度、盐度、叶绿素a浓度是影响大陈岛海域浮游动物群落特征的重要环境因素。此外,夏季大陈岛海域水母类浮游动物暴发的现象值得关注。研究结果将为大陈岛海域的生物多样性保护及渔业资源可持续开发利用提供可参考的数据资料。     

Alcaloides du Strychnos tchibangensis

The structure of a new bisindole alkaloid has been elucidated by chemical correlation and analysis of ¹³C NMR spectra.     

Structure des caboxines: Alcaloïdes oxindoliques du Cabucala fasciculata

The structures of three new 11-monomethoxy pentacyclic oxindole alkaloids have been elucidated by chemical correlations with reserpinine: caboxine-A was assigned to the allo C₁₉-méthyl α series: 3S, 4R, 7S, 19S; isocaboxine-A and B to the epi-allo C₁₉-methyl α series and have, respectively, the following configurations 3R, 4S, 7S, 19S and 3R, 4S, 7R, 19S.