Isomers are different compounds that have the same molecular formula. Constitutional isomers are isomers that differ because their atoms are connected in a different order. Stereoisomers differ only in arrangement of their atoms in space.Stereoisomers are not constitutional isomers. Enantiomers are stereoisomers whose molecules are nonsuperposable mirror images of each other. Diastereomer are stereoisomers whose molecules are not mirror images of each other

An equimolar mixture of two enantiomers is called a racemic form (either a racemate or a racemic mixture). A racemic form shows no rotation of plane￾polarized light

Before 1951 only relative configurations of chiral molecules were known. Configurations of chiral molecules were related to each other through reactions of known stereochemistry. The standard compound was glyceraldehyde

糖是自然界存在的一大类有机化合物， 由绿色植物经光合作用合成。糖不仅为生物 有机体提供建筑材料（如纤维素）和能量来 源，而且还是高密度的信息载体，起到了重 要的细胞识别功能。糖和蛋白质、核酸、脂 类一起，被称为涉及生命活动本质的重要生 物分子，是维持生命机器正常运转的最根本 的物质基础

In both prokaryotes and eukaryotes, primary RNA transcripts undergo various alteration or processing events to become mature RNAs: The three commonest types are: 1, nucleotide removal by nucleases; 2, nucleotide addition to the 5’- or 3’-end, 3, nucleotide modification on the base or thesugar

一、 hnRNA 二、 pre-mRNAs 三、 hnRNP 四、 snRNPs 五、pre-mRNA processing The alternative mRNA processing is the conversion of pre-mRNA species into more than one type of mature mRNA

一、 一般特征 二、 DNA 聚合酶链反应 三、 细菌 DNA 的复制 1、E.coli 中的 DNA 聚合酶：3 种 2、复制起始点的特点：在 E.coli 中，只有一个复制点，oriC

一. 亲电加成反应 （一）. 亲电加成反应 (Electrophilic Addition) 1. 正碳离子机理 2. 翁型离子机理 3. 三分子加成机理 4. 炔烃的亲电加成 二. 亲电加成反应活性(Reactivity) 1. 底物 2. 试剂

一. 反应的类型 二. 反应机理 1. E1机理 2. 单分子共轭碱消除 (E1CB) 机理 3. E2机理 三.影响反应机理的因素 1. 底物 2. 碱 3. 离去基团 4. 溶剂

First order overall (一级反应) The reaction is a unimolecular nucleophilic substitution（单分子亲核取代反应）