英文核酸课件

1、英文核酸BIOCHEMISTRYNEUCLEIC ACIDS英文核酸CONTENTS 4.1 Two Nucleic Acids: DNA and RNA 4.2 Propertie of nucleotides 核苷酸核苷酸 4.3 Primary Structure of Nucleic Acids 核酸的核酸的一级结构一级结构 4.4 Secondary Structure and tertiary Structure of Nucleic Acids 核酸的二级结构和三级结构核酸的二级结构和三级结构 4.5 Stability of Secondary and Tertiary Str

2、ucture核酸的二级结构和三级结构的稳定性核酸的二级结构和三级结构的稳定性英文核酸英文核酸4.2 NucleotidesNucleotides = Base + Sugar + Phosphate Nucleoside= Sugar + Base (no phosphate) PRdRPbasebaseRibose or deoxyribose(核糖或脱氧核糖）脱氧核糖）英文核酸adenine（腺嘌呤）urecil（尿嘧啶）thymine（胸腺嘧啶）cytosine（胞嘧啶）guanine（鸟嘌呤）Purine bases Pyrimidine Bases英文核酸Standard Nucle

3、otides： 5- adenosine monophosphate 5-AMP （ 5-腺苷酸腺苷酸） 5- guanosine monophosphate 5-GMP （ 5-鸟苷酸鸟苷酸） 5- cytidine monophosphate 5-CMP （ 5-胞苷酸胞苷酸） 5- uridine monophosphate 5-UMP （ 5-脲苷酸脲苷酸） 5- deoxyadenosine monophosphate 5-dAMP （ 5 -脱氧腺苷酸脱氧腺苷酸） 5- deoxyguanosine monophosphate 5-dGMP （5-脱氧鸟苷酸脱氧鸟苷酸） 5- de

4、oxycytidine monophosphate 5-dCMP （5-脱氧脱氧胞苷酸胞苷酸） 5-deoxythymidine monophosphate） 5-dTMP （5-脱氧胸腺苷酸脱氧胸腺苷酸英文核酸英文核酸Minor Bases or Modified bases(稀有碱基或修饰碱基稀有碱基或修饰碱基)英文核酸Nucleotide polyphosphateNucleotide polyphosphate多磷酸核苷多磷酸核苷 8 NDPs （ 5-nucleotide diphosphate 5-核苷核苷二磷酸二磷酸） 8 NTPs （ 5-nucleotide triphosp

5、hate 5-核核苷三磷酸苷三磷酸）ATP英文核酸Cyclic Nucleotides英文核酸CoA、NAD + （P）and FAD Co-enzyme A（CoA） Nicotinamide adenine dinucleotide （NAD+）烟酰胺腺嘌呤二核苷酸、 Flavin Adenine Dinucleotide （FAD）黄素腺嘌呤二核苷酸英文核酸NAD英文核酸NADP英文核酸FAD英文核酸Nucleotide propertics 1. Dissociation in waterThe phosphate group of a nucleotide acts as a str

6、ong acid (pKa 1), The amine groups of the purine and pyrimidine bases can be protonated.英文核酸2.Tautomerization of the bases The bases can tautomerize(互变异构）; that is, the bases can redistribute positions of hydrogens and double bonds 英文核酸Unusual base pair见于酵母苯丙氨酰tRNA英文核酸1-methyladenine =T英文核酸Nucleotid

7、e propertics3. Spectrum Nucleotides absorb light strongly in the near-ultraviolet region of the spectrum. 英文核酸 260（X104） AMP 1.54 GMP 1.17 CMP 0.75 dTMP 0.92 UMP 0.99.英文核酸Biological functions of nucleotides 1、The monomeric units of nucleic acids 2、Energy carrier：ATP、GTP、CTP、UTP 3、signals ：cAMP、cGMP

8、4、coenzymes：FAD、NAD、CoA英文核酸4.3 Primary Structure of Nucleic Acids The primary structure is the sequence of nucleoside monophosphates Directionality ：53 IndividualitypGGTA, pGpGpTpA, GGTApGGTA（OH）英文核酸Significance of Primary Structure Genetic information stored in nucleotide sequence of DNA Gene is a

9、particular DNA sequence英文核酸 DNA is genetic substance.Avery, MacLeod, McCarty 英文核酸Hershey and Chase - Bacteriophage T2 transfers DNA to bacteria 英文核酸4.4 Secondary structure of DNA The secondary structure refers to the shape a nucleic acid assumes as a result of the primary structure. B-DNA : predomin

10、ant form in the aqueous environment of the cell A-DNA Z-DNA : purine/pyrimidine tracts英文核酸Secondary structure of DNA11/ 0.23nm10/ 0.34nm12/ 0.38nmMajor grooveMinor groove英文核酸 英文核酸 Structure of B-DNA The two chains in the double helix are antiparallel Phosphate groups link together the sugar backbone

11、 via phosphodiester bonds. The bases on the two chains pair in a complementary fashion. A=T，G=C Hydrogen bonds between bases hold the double helix together. (A=T，G C)B-DNA:d= 2 nm，pitch = 3.4 nm , 10 bp / turn of the helix英文核酸DNA base pair英文核酸DNA base pair英文核酸DNA base pairPrictice:Write the sequence

12、 .英文核酸The discovery of DNA double helix Chargaffs Rule (A=T, G=C in DNA) Franklin, Wilkins: X-ray DiffractionRefined Structure 英文核酸Watson, Crick英文核酸Significance of DNA double helixsemi-conservative model of DNA replication英文核酸Meselson and Stahl experiment 1958英文核酸Application of Complementarity DNA半保

13、留复制核酸分子杂交实验 Molecule hybridization英文核酸Unusual Secondary Structures of DNA Palindromes(回文结构）Cruciform formation in palindrome sequencesGGCGCGCCCCGCGCGG英文核酸H-DNA purines/pyrimidines on one strand 英文核酸英文核酸4.5 Tertiary structure of DNA Tertiary structure refers to large-scale folding in a linear polymer

14、 that is at a higher order than secondary structure. The tertiary structure is the specific three-dimensional shape into which an entire chain is folded.英文核酸Tertiary structure of DNA英文核酸Circular DNA and Supercoiling Circular DNAs Supercoiling : Positive(+)-additional twists added beyond the normal a

15、mount for linear DNA negative (-)-reduced numbers of twists compared to linear DNA.英文核酸Supercoiling Twists(T, 缠绕数缠绕数): The total number of times the two strands of the helix cross over each other, excluding writhing. Twist is a measure of how tightly the helix is wound. Writhes (W,扭曲数扭曲数): The numbe

16、r of times the helix as a whole crosses over itself - that is, the number of superhelical turns that are present Linking number (L ,连接数连接数): The total number of times two strands of a DNA helix cross each other by means of either twist or writhe L = T + W The superhelical density : L/L0, where L0 is

17、 the linking number of the DNA in its unstrained (relaxed state).英文核酸英文核酸 Besides writhing, unwinding DNA, cruciform formation (via palindromes), triple helix formation (H-DNA), and Z-DNA formation, can all reduce superhelical tension, too. 英文核酸Ethidium bromide(溴乙溴乙锭锭)change DNA supercoil英文核酸problem

18、 set 1. 计算一个计算一个260bps的环状的环状DNA在松弛态和在松弛态和w=-2的的L和和超螺旋密度。松弛态：松弛态：L= T=260/10=26超螺旋：超螺旋：T=26；L=T+W=26+（-2）=24； =-2/24=-0.08 2. (已知自然界存在大多数DNA分子的superhelical density（超螺旋密度）是-0.06，一个10000bpDNA分子，假定是B型构像，将形成多少圈超螺旋？ 3 .为什么DNA倾向形成负超螺旋而不是正超螺旋？英文核酸RNA英文核酸tRNA英文核酸4.6 The Biological Functions of Nucleic Acids

19、1、Genome 2、Transcription 3、Translation: rRNA(ribosome: Rizyme, Structure) mRNA tRNA英文核酸分子生物学中心分子生物学中心法则法则英文核酸英文核酸M1RNA and SRP M1RNA ： 是E.coli的RNaseI的组成成分，该酶参与转录的RNA加工。 SRP: 信号识别颗粒M1RNA英文核酸4.7 Stability of Nucleic Acid Secondary and Tertiary Structure Stability and Denaturation Denaturation: (1) The

20、 electrostatic repulsion of the negative charges on the phosphate groups. (2)The higher entropy of the denatured state (the denatured form has more possible conformations than the double helix form, so the denatured form has greater randomness).Stability: (1)hydrogen bonds(2) The van der Waals inter

21、actions between the planar bases英文核酸英文核酸Factors favoring dissociation of double helices to random coils1、Hypochromism - absorption of light by bases reduced when in helix = denaturation causes increase in absorbance of light at 260 nm. Melting Temperature(Tm)：英文核酸 The factors affecting on Tm： G-C（0.15mol/LNaCl/0.15mol/L sodium citrate） Tm=69.3+0.41（G+C） DNA purity pH, 英文核酸问题问题 1、如何保存DNA？A. 无水乙醇中；b.纯水中；c. 75%乙醇中； 2、应该如何配制DNA溶液，可使其比较稳定？A. 纯水配制；b. 1mol/LNaCl配制；c. 0.01mol/LNaCl配制；d. 0.5mol/LNaOH配制。英文核酸 溶解度：溶于水溶解度：溶于水 酸碱性：生理酸碱性：生理pH带负电荷带负电荷 分子量和形状：分子量和形状：DNA 1081012，d/l=10-7， “柔柔性棒性棒”高黏度