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Chapter 2 Nucleic Acid Chemistry

Chapter 2 Nucleic Acid Chemistry. Composation Structure Function DNA RNA. introduction. Francis Harry Compton Crick. 1868 Fridrich Miescher first isolated nuclein from pyocyte. 1944 O.Avery confirmed DNA is hereditary substance. 1953 J.Watson F.Crick discovered DNA double helix.

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Chapter 2 Nucleic Acid Chemistry

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  1. Chapter 2 Nucleic Acid Chemistry Composation Structure Function DNA RNA

  2. introduction Francis Harry Compton Crick 1868 Fridrich Miescher first isolated nuclein from pyocyte. 1944 O.Avery confirmed DNA is hereditary substance. 1953 J.Watson F.Crick discovered DNA double helix. 1968 Nirenberg found the genetic code . James Dewey Watson Marshall W. Nirenberg

  3. Nucleic acid is a polymer of nucleotide ,having and transfering genetic information, include deoxyribonucleic acid (DNA)and ribonucleic acid(RNA).

  4. Section 1 composition of nucleic acid

  5. Ribonucleoside核苷 The linkage of base with ribose(2-deoxyribose) by glycoside formed ribonucleoside(deoxynucleoside脱氧核苷). 核苷：腺苷AR,鸟苷GR,胞苷CR,尿苷UR。 脱氧核苷：脱氧腺苷dAR,脱氧鸟苷dGR,脱氧胞苷dCR,脱氧胸苷dTR。 cytidine胞苷CR guanine deoxyriboside 脱氧鸟苷dGR

  6. Nucleotide核苷酸 The product of ribonucleoside linking of phosphoric acid at 5’ position. 核苷酸： 腺苷酸AMP,鸟苷酸GMP,胞苷酸CMP,尿苷酸UMP。 脱氧核苷酸： 脱氧腺苷酸dAMP,脱氧鸟苷酸dGMP,脱氧胞苷酸dCMP,脱氧胸苷酸dTMP。 胞苷酸CMP 脱氧鸟苷酸dGMP

  7. Important nucleotide

  8. DNA DNA was formed by linking of deoxynucleotides with phosphodiester bond at 3’ position of one deoxynucleotide and 5’ position of another deoxynucleotide. So is the RNA formation mode, difference is the nucleotide.

  9. Section 2 Dimensional structure and function of DNA • 1.Double-stranded helix • The two strands are antiparallel. • The chain, phosphoric acid and deoxyribose, locate lateral of the helix, but bases are in the helix. • Pair strictly A to T, G to C. • A turn contains 10 nucleotides, with height 3.4nm. • Width 2.0nm. • Form a major groove and a minor groove. • Rotating right-handed. • The maintaining force of the structure is hydrogen-bond.

  10. Pairs bases

  11. 2.0 nm 小沟 大沟 The Nobel Prize in Physiology or Medicine 1962 (1953) Watson and Crick

  12. Versatility of DNA double helix A型结构 碱基平面倾斜20º，螺旋变粗变短，螺距2～3nm。 Z型结构 左手螺旋，只有小沟

  13. 2.Tertiary structure of DNA----supercoil Further coil of the DNA double helix. 正超螺旋 负超螺旋

  14. 3. Nucleosome 核小体 DNA: ~200bp Histone: H1, H2A,H2B H3,H4.

  15. 4.Function of DNA Containing genetic information, as the template of gene duplication , DNA finally directs protein biosynthesis. As a result, keeping hereditary characters of body. Gene refer to a segment of DNA chain which posseses a special biological function.

  16. Section3 spatial structure and function of RNA RNAs in animal cell

  17. mRNA --messenger RNA • 5’cap:m7GpppNm- • 3’Poly A tail：An n=20—200 • Single chain • half life time from munits to hours

  18. tRNA --transfer RNA • Stem-loop structure, cloverleaf pattern三叶草形. • 3 loop and 1 arm: DHU loop, anticoden loop, Tφloop, AA arm. • Anticoden and CCA-OH 3’end. • Contain rare bases 10%-20%.

  19. Rare bases Ψ I DHU mG Ψ：pseudouracil假尿嘧啶，I：hypoxanthine次黄嘌呤， DHU：dihydrouracil二氢尿嘧啶， mG：7-methylguanine7-甲基鸟嘌呤．

  20. tRNA tertiary structure: a inverse L like.

  21. tRNA functions as a amino acid transfer in protein biosynthesis.

  22. rRNA --ribosomal RNA • Weight 80% of total RNA in a cell. • Flower like. • Component of ribosome. • procaryote：5S,16S,23S; eukaryote: 18S,5S,5.8S,28S Eukaryote 18S rRNA

  23. Section 4. physical and chemical properties of nucleic acid • General character • acidity. • high viscosity of DNA • breaking easily

  24. 2. Ultraviolet absorption • Nucleic acids get their maximum absorption at 260nm. • DNA solution： A260／A280=1.8; RNA solution： A260／A280= 2.0 • OD260=1.0, equal to 50μg/ml DS DNA, 40μg/ml SS DNA or RNA.

  25. 3. DNA denaturation --the double chain change into single chain. Methods: heat, acid, base, urea, acetone Result: OD260↑, viscosity↓, activity lose.

  26. Tm --melting temperature, 解开链温度，融解温度，refer tothe middle point of temperature range of DNA thermal denaturation . • The temperature of 50% double chain undoing. • Tm=69.3+0.41(G+C)%

  27. 4.Renaturation and hybridization Renaturation: the single DNA chains recover their natural double helix structure. Annealing退火: renaturation of thermal denatural DNA, by way of slow cooling. Hybridization杂交：phenomenon of single chain DNA or RNA bind the chain different origin in renaturation process.

  28. Section 5. nucleases核酸酶 • Nuclease: hydrolysis of nucleic acid. • DNase: hydrolysis of DNA. • RNase: hydrolysis of RNA. • exonuclease外切酶： act at the end of the chain • endonuclease核酸内切酶：act at the inner part of the chain • restriction enzyme限制性内切酶：cut a special point of the chain. • ribozyme核酶：consists of RNA, not protein.

  29. 选择题练习 核酸化学

  30. 1. The element that could be used in nucleic acid quantitation is ( ) A. C B. O C. N D. H E. P

  31. 2. The basic unit composition of nucleic acid is ( ) A. Ribose and deoxyribose B. phosphoric acid and pentaglucose C. Pentaglucose and basic group D. mononucleotide E. phosphoric acid，pentose and basic group

  32. 3．脱氧核糖核苷酸彻底水解，生成的产物的产物是( ) A 核糖和磷酸 B 脱氧核糖和碱基 C 脱氧核糖和磷酸 D 磷酸，核糖和碱基 E 脱氧核糖，磷酸和碱基

  33. 4．在核酸分子中核苷酸之间的连接方式是( ) A. 3’,3’－磷酸二酯键 B. 糖苷键 C. 2’,5’ －磷酸二酯键 D. 肽键 E. 3’,5’－磷酸二酯键

  34. 5. The ultraviolet absorption maximum of nucleic acid is about ( ) A. 220nm B. 240nm C. 260nm D. 280nm E. 300nm

  35. 6. 含有稀有碱基比例较多的核酸是( ) A. mRNA B. DNA C. tRNA D. rRNA E. hnRNA

  36. 7. 核酸分子中储存、传递遗传信息的关键部分是( ) A. 核苷 B. 戊糖 C. 磷酸 D. 碱基序列 E. 戊糖磷酸骨架

  37. 8．DNA分子碱基含量关系哪种是错误的？ A. A+T=C+G B. A+G=C+T C. G=C D. A=T E. A/T=G/C

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