英文ppt课件-核酸.ppt
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1、BIOCHEMISTRYNEUCLEIC ACIDSCONTENTS4.1 Two Nucleic Acids:DNA and RNA4.2 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 Structure核酸的二级结构和
2、三级结构的稳定性核酸的二级结构和三级结构的稳定性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)adenine(腺嘌呤)urecil(尿嘧啶)thymine(胸腺嘧啶)cytosine(胞嘧啶)guanine(鸟嘌呤)Purine bases Pyrimidine BasesStandard Nucleotides:5-adenosine monophosphate 5-AMP(5-
3、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-deoxycytidine monophosphate 5-dCMP(5-脱氧脱氧胞苷酸胞苷酸)5-deoxythymidine mono
4、phosphate)5-dTMP(5-脱氧胸腺苷酸脱氧胸腺苷酸Minor Bases or Modified bases(稀有碱基或修饰碱基稀有碱基或修饰碱基)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 triphosphate 5-核核苷三磷酸苷三磷酸)ATPCyclic NucleotidesCoA、NAD+(P)and FADCo-enzyme A(CoA)Nicotinamide ade
5、nine 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NADNADPFADNucleotide propertics1.Dissociation in waterThe phosphate group of a nucleotide acts as a strong acid(pKa 1),The amine groups of the purine and pyrimidine bases can be protonated.2.Tautomerization of the bases The b
6、ases can tautomerize(互变异构);that is,the bases can redistribute positions of hydrogens and double bonds Unusual base pair见于酵母苯丙氨酰tRNA1-methyladenine=TNucleotide propertics3.Spectrum Nucleotides absorb light strongly in the near-ultraviolet region of the spectrum.260(X104)AMP 1.54 GMP 1.17 CMP 0.75 dTM
7、P 0.92 UMP 0.99.Biological functions of nucleotides1、The monomeric units of nucleic acids 2、Energy carrier:ATP、GTP、CTP、UTP3、signals:cAMP、cGMP4、coenzymes:FAD、NAD、CoA4.3 Primary Structure of Nucleic Acids The primary structure is the sequence of nucleoside monophosphates Directionality:53Individuality
8、pGGTA,pGpGpTpA,GGTApGGTA(OH)Significance of Primary Structure Genetic information stored in nucleotide sequence of DNAGene is a particular DNA sequence DNA is genetic substance.Avery,MacLeod,McCarty Hershey and Chase-Bacteriophage T2 transfers DNA to bacteria 4.4 Secondary structure of DNAThe second
9、ary structure refers to the shape a nucleic acid assumes as a result of the primary structure.B-DNA:predominant form in the aqueous environment of the cellA-DNAZ-DNA:purine/pyrimidine tractsSecondary structure of DNA11/0.23nm10/0.34nm12/0.38nmMajor grooveMinor groove Structure of B-DNA The two chain
10、s in the double helix are antiparallel Phosphate groups link together the sugar backbone 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
11、DNA base pairDNA base pairDNA base pairPrictice:Write the sequence.The discovery of DNA double helixChargaffs Rule(A=T,G=C in DNA)Franklin,Wilkins:X-ray DiffractionRefined Structure Watson,CrickSignificance of DNA double helixsemi-conservative model of DNA replicationMeselson and Stahl experiment195
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