Regioselective reactions for programmable resveratrol oligomer synthesis

Although much attention has been devoted to resveratrol, a unique polyphenol produced by plants and credited as potentially being responsible for the 'French paradox'--the observation that French people have a relatively low incidence of coronary heart disease, even though their diet is high in saturated fats--the oligomers of resveratrol have been largely ignored despite their high biological activity. Challenges in achieving their isolation in sufficient quantity from natural sources, coupled with an inability to prepare them easily synthetically, are seen as the main obstacles. Here we report a programmable, controlled and potentially scalable synthesis of the resveratrol family via a three-stage design. The synthetic approach requires strategy- and reagent-guided chemical functionalizations to differentiate two distinct cores possessing multiple sites with the same or similar reactivity, ultimately leading to five higher-order natural products. This work demonstrates that challenging, positionally selective functionalizations of complex materials are possible where biosynthetic studies have indicated otherwise, it provides materials and tools with which to unlock the full biochemical potential of this family of natural products, and it affords an intellectual framework within which other oligomeric families could potentially be accessed.     

Complete nucleotide sequence of an influenza virus haemagglutinin gene from cloned DNA

A synthetic fowl plague virus (FPV) haemagglutinin gene has been cloned in bacteria and the complete sequence of the RNA gene deduced. It is 1,742 nucleotides long and the mRNA codes for 56.3 amino acids in an uninterrupted sequence. The nature of some of the important domains in the haemagglutinin has been established, and their structure is discussed in relation to their function. Extensive amino acid sequence homologies exist between FPV and human influenza haemagglutinins.     

耐热DNA聚合酶介导的DNA酶促自发合成

构建了无模板引物的“类ＰＣＲ体系”。该体系在适当温度保温一段时间之后，能检测到产物出现，利用热变性分析等手段，初步研究了产物的性质，发现这些产物是随机合成的具有一些特殊构型的ＤＮＡ。本文报道三种构型，两类碱基组成比例，并通过改变反应条件观察对酶促自发合成的影响，探讨耐热ＤＮＡ聚合酶的非特异聚合活性以及介导的酶促自发合成的机理和意义。     

从两个实例看实验设计的正确性原则

对两例错误的实验设计进行了讨论,说明正确的物理实验设计必须以物理理论为依据.     

用于基因疫苗接种的气动式基因枪

为解决现有各种基因枪在微弹制备方面存在的问题并减小冲击波影响,提出一种基因枪结构。将裹着基因疫苗的微弹吸附在不锈钢网上,并将不锈钢网放置在加速通道中加速微弹。在数值模拟的基础上,研制了实验装置,测试了装置的性能,并利用该装置将pEGFG质粒导入H e la细胞。实验结果表明:这种结构的基因枪在0.3M Pa的气压下就可以把微弹加速到300m/s以上,且微弹在靶面分布均匀;射入H e la细胞的pEGFG质粒也得到了表达,能满足基因疫苗接种的要求。     

Cell-surface expression of influenza haemagglutinin from a cloned DNA copy of the RNA gene

By replacing either the eight early or the late genes of SV40 with a cloned copy of the influenza virus haemagglutinin gene we have constructed recombinant viruses which, in infected cells, express large quantities of haemagglutinin. This glycoprotein, over 10(8) molecules of which are produced per cell, is identical in molecular weight to authentic influenza virus haemagglutinin, accumulates at the cell surface and displays haemabsorbing activity.     

DNA synthesis provides the driving force to accelerate DNA unwinding by a helicase

Helicases are molecular motors that use the energy of nucleoside 5'-triphosphate (NTP) hydrolysis to translocate along a nucleic acid strand and catalyse reactions such as DNA unwinding. The ring-shaped helicase of bacteriophage T7 translocates along single-stranded (ss)DNA at a speed of 130 bases per second; however, T7 helicase slows down nearly tenfold when unwinding the strands of duplex DNA. Here, we report that T7 DNA polymerase, which is unable to catalyse strand displacement DNA synthesis by itself, can increase the unwinding rate to 114 base pairs per second, bringing the helicase up to similar speeds compared to its translocation along ssDNA. The helicase rate of stimulation depends upon the DNA synthesis rate and does not rely on specific interactions between T7 DNA polymerase and the carboxy-terminal residues of T7 helicase. Efficient duplex DNA synthesis is achieved only by the combined action of the helicase and polymerase. The strand displacement DNA synthesis by the DNA polymerase depends on the unwinding activity of the helicase, which provides ssDNA template. The rapid trapping of the ssDNA bases by the DNA synthesis activity of the polymerase in turn drives the helicase to move forward through duplex DNA at speeds similar to those observed along ssDNA.     

Accurate whole-genome sequencing and haplotyping from 10 to 20 human cells

Recent advances in whole-genome sequencing have brought the vision of personal genomics and genomic medicine closer to reality. However, current methods lack clinical accuracy and the ability to describe the context (haplotypes) in which genome variants co-occur in a cost-effective manner. Here we describe a low-cost DNA sequencing and haplotyping process, long fragment read (LFR) technology, which is similar to sequencing long single DNA molecules without cloning or separation of metaphase chromosomes. In this study, ten LFR libraries were made using only ～100?picograms of human DNA per sample. Up to 97% of the heterozygous single nucleotide variants were assembled into long haplotype contigs. Removal of false positive single nucleotide variants not phased by multiple LFR haplotypes resulted in a final genome error rate of 1 in 10?megabases. Cost-effective and accurate genome sequencing and haplotyping from 10-20 human cells, as demonstrated here, will enable comprehensive genetic studies and diverse clinical applications.