Background: SV40 DNA replication system is a very useful tool to understand the mechanism of replication, which is a tightly regulated process. Many environmental and cellular factors can induce cell cycle arrest or apoptosis by inhibiting DNA replication. In the course of our search for bioactive metabolites from the marine sponges, psammaplin A was found to have some anticancer properties, the possible mechanism of which was studied. Methods: Cell viability was determined by Cell Counting Kit-8 (CCK-8) to count living RAW264.7 cells by combining 2-(2-methoxy-4-nitrophenyl)-3-(4-nitrophenyl)-5-(2,4-disulfophenyl)-2Htetrazolium (WST-8) and 1-methoxy-phenazine methosulfate (1-methoxy-PMS). The effect of psammaplin A on DNA replication was carried out in SV40 DNA replication system in vitro. The activities of topoisomerase I and polymerase α-primase were measured by the relaxation of superhelical plasmid DNA and the incorporation of [3H]dTTP to the template respectively. The ssDNA binding activity of RPA was assessed by Gel Mobility Shift Assay (GMSA). Results: We have found that psammaplin A delivers significant cytotoxic activity against the RAW264.7 cell line. It was also found that psammaplin A could substantially inhibit SV40 DNA replication in vitro, in which polymerase α-primase is one of its main targets. Conclusion: Taken together, we suggest that psammaplin A-induced cytotoxicity may correlate with its inhibition on DNA replication. Psammaplin A has the potential to be developed as an anticancer drug.

Cortical neuronal cultures were exposed to total ginkgolides (TG) in order to find out whether TG could rescue cultured cortical neurons from neurotoxicity damages. The cellular injuries were induced in the cells after 10 days in vitro by exposure to 1 mM L-glutamate (Glu) for 6–12 hr in serum-free medium, to 0.2 mM hydrogen peroxide (H2O2) for 6-12 hr, and then to free-glucose and hypoxia medium (an ischaemia model in vitro) for 4 hr. TG (0.01 to 100 ug/ml) was added to the growth medium 12 hr prior to or simultaneously the damage protected cortical neurons from toxic damages. Neuronal viability was confirmed by the assay of 3-(4,5-dimethyl thiazol-2-yl)-2,5-diphenyl tetrazolium (MTT). The lactate dehydrogenase (LDH) release from the cultured medium was also detected. The results of present study demonstrated that TG protected cortical neurons from toxic damages induced by Glu, H2O2 or free-glucose and hypoxia.

目的酿酒酵母（Saccharomyces cerevisiae）丙酮酸脱羧酶（PDC）基因的克隆和表达。方法利用PCR技术从酿酒酵母的总cDNA中钓取出PDCsc基因，构建其高效表达质粒，利用Ion和ompT蛋白酶缺陷株Escherichia coli BL21（DE3）进行表达。结果扩增出长约1.7kb的PDCsc基因，成功构建其表达质粒pSC-22b，对转化菌株的SDS-PAGE分析结果显示：该基因获得高效表达，表达蛋白占细胞总蛋白的18.6%。结论成功构建高效表达PDCsc基因的工程菌株，为实现利用PDCsc进行的生物转化奠定基础。

主要介绍了酿酒酵母和移动单孢中丙酮酸脱羧酶的结构、性质及其在手性合成中的应用，包括反应的机理、底物范围和影响反应的因素。

用BamH I和Xba I两种限制酶酶切质粒pKG27，获得了编码F26G（F26G：furostanol gly-coside 26-O-β-glucosidase）的cDNA，然后将期重组到表达载体pET-22b上而得到pET-22b-CSF26G，利用大肠杆菌E.coli BL21进行表达，用胞内可溶蛋白进行酶反应，通过TLC、HPLC分析证明重组菌表达出高活性的F26G酶，并实现了呋甾皂苷的体外生物转化。