《生物化学原理》之核酸

第四章 核苷酸和核酸 核苷酸和核酸的共价结构 DNA的结构 RNA的结构 核酸的性质 ? ? 脱氧核糖核酸： deoxyribonucleic acid DNA 核糖核酸： ribonucleic acid RNA 信使核糖核酸：messenger RNA mRNA 转移核糖核酸：transfer RNA tRNA 核糖体核糖核酸：ribosomal RNA rRNA 一、核酸与核苷酸的基本结构 核酸的基本组成单位：核苷酸 核苷酸是由磷酸、戊糖和含氮碱基（嘌呤，嘧啶）组成的 74 BASES The bases are nitrogen-containing ring compounds, either pyrimidines or purines. C C CHC N H NH O O C CHC N H N O NH2 H3C C CHC N H NH O O HC HC U C T uracil cytosine thymine N N 1 2 3 4 5 6 N N 1 2 3 4 5 6N N 7 8 9 O N N H C C C C N NH NH2 HC N N H C C C CH N N HC NH2 adenine guanine A G PYRIMIDINEPURINE PHOSPHATES The phosphates are normally joined to the C5 hydroxyl of the ribose or deoxyribose sugar (designated 5). Mono-, di-, and triphosphates are common. O O O O PCH2 O O O P O O O PCH2O O O O P O O PO O O O PCH2O as in AMP as in ADP as in ATP The phosphate makes a nucleotide negatively charged. NUCLEOTIDES A nucleotide consists of a nitrogen-containing base, a five-carbon sugar, and one or more phosphate groups. N N O NH2 O O O O PCH2 OHOH O BASE PHOSPHATE SUGAR Nucleotides are the subunits of the nucleic acids. BASIC SUGAR LINKAGE N O C H SUGAR BASE 1 2 3 4 5 N-glycosidic bond The base is linked to the same carbon (C1) used in sugarsugar bonds. SUGARS Each numbered carbon on the sugar of a nucleotide is followed by a prime mark; therefore, one speaks of the “5-prime carbon,” etc. OHOH O HH HOCH2OH HH OHH O HH HOCH2OH HH PENTOSE a five-carbon sugar O 4 32 1 C 5 two kinds are used ?-D-ribose used in ribonucleic acid ?-D-2-deoxyribose used in deoxyribonucleic acid PANEL 26 A survey of the nucleotides 磷酸 碱基 戊糖 74 BASES The bases are nitrogen-containing ring compounds, either pyrimidines or purines. C C CHC N H NH O O C CHC N H N O NH2 H3C C CHC N H NH O O HC HC U C T uracil cytosine thymine N N 1 2 3 4 5 6 N N 1 2 3 4 5 6N N 7 8 9 O N N H C C C C N NH NH2 HC N N H C C C CH N N HC NH2 adenine guanine A G PYRIMIDINEPURINE PHOSPHATES The phosphates are normally joined to the C5 hydroxyl of the ribose or deoxyribose sugar (designated 5). Mono-, di-, and triphosphates are common. O O O O PCH2 O O O P O O O PCH2O O O O P O O PO O O O PCH2O as in AMP as in ADP as in ATP The phosphate makes a nucleotide negatively charged. NUCLEOTIDES A nucleotide consists of a nitrogen-containing base, a five-carbon sugar, and one or more phosphate groups. N N O NH2 O O O O PCH2 OHOH O BASE PHOSPHATE SUGAR Nucleotides are the subunits of the nucleic acids. BASIC SUGAR LINKAGE N O C H SUGAR BASE 1 2 3 4 5 N-glycosidic bond The base is linked to the same carbon (C1) used in sugarsugar bonds. SUGARS Each numbered carbon on the sugar of a nucleotide is followed by a prime mark; therefore, one speaks of the “5-prime carbon,” etc. OHOH O HH HOCH2OH HH OHH O HH HOCH2OH HH PENTOSE a five-carbon sugar O 4 32 1 C 5 two kinds are used ?-D-ribose used in ribonucleic acid ?-D-2-deoxyribose used in deoxyribonucleic acid PANEL 26 A survey of the nucleotides 74 BASES The bases are nitrogen-containing ring compounds, either pyrimidines or purines. C C CHC N H NH O O C CHC N H N O NH2 H3C C CHC N H NH O O HC HC U C T uracil cytosine thymine N N 1 2 3 4 5 6 N N 1 2 3 4 5 6N N 7 8 9 O N N H C C C C N NH NH2 HC N N H C C C CH N N HC NH2 adenine guanine A G PYRIMIDINEPURINE PHOSPHATES The phosphates are normally joined to the C5 hydroxyl of the ribose or deoxyribose sugar (designated 5). Mono-, di-, and triphosphates are common. O O O O PCH2 O O O P O O O PCH2O O O O P O O PO O O O PCH2O as in AMP as in ADP as in ATP The phosphate makes a nucleotide negatively charged. NUCLEOTIDES A nucleotide consists of a nitrogen-containing base, a five-carbon sugar, and one or more phosphate groups. N N O NH2 O O O O PCH2 OHOH O BASE PHOSPHATE SUGAR Nucleotides are the subunits of the nucleic acids. BASIC SUGAR LINKAGE N O C H SUGAR BASE 1 2 3 4 5 N-glycosidic bond The base is linked to the same carbon (C1) used in sugarsugar bonds. SUGARS Each numbered carbon on the sugar of a nucleotide is followed by a prime mark; therefore, one speaks of the “5-prime carbon,” etc. OHOH O HH HOCH2OH HH OHH O HH HOCH2OH HH PENTOSE a five-carbon sugar O 4 32 1 C 5 two kinds are used ?-D-ribose used in ribonucleic acid ?-D-2-deoxyribose used in deoxyribonucleic acid PANEL 26 A survey of the nucleotides 74 BASES The bases are nitrogen-containing ring compounds, either pyrimidines or purines. C C CHC N H NH O O C CHC N H N O NH2 H3C C CHC N H NH O O HC HC U C T uracil cytosine thymine N N 1 2 3 4 5 6 N N 1 2 3 4 5 6N N 7 8 9 O N N H C C C C N NH NH2 HC N N H C C C CH N N HC NH2 adenine guanine A G PYRIMIDINEPURINE PHOSPHATES The phosphates are normally joined to the C5 hydroxyl of the ribose or deoxyribose sugar (designated 5). Mono-, di-, and triphosphates are common. O O O O PCH2 O O O P O O O PCH2O O O O P O O PO O O O PCH2O as in AMP as in ADP as in ATP The phosphate makes a nucleotide negatively charged. NUCLEOTIDES A nucleotide consists of a nitrogen-containing base, a five-carbon sugar, and one or more phosphate groups. N N O NH2 O O O O PCH2 OHOH O BASE PHOSPHATE SUGAR Nucleotides are the subunits of the nucleic acids. BASIC SUGAR LINKAGE N O C H SUGAR BASE 1 2 3 4 5 N-glycosidic bond The base is linked to the same carbon (C1) used in sugarsugar bonds. SUGARS Each numbered carbon on the sugar of a nucleotide is followed by a prime mark; therefore, one speaks of the “5-prime carbon,” etc. OHOH O HH HOCH2OH HH OHH O HH HOCH2OH HH PENTOSE a five-carbon sugar O 4 32 1 C 5 two kinds are used ?-D-ribose used in ribonucleic acid ?-D-2-deoxyribose used in deoxyribonucleic acid PANEL 26 A survey of the nucleotides 尿嘧啶 胞嘧啶 胸腺嘧啶 腺嘌呤 鸟嘌呤 脱氧核糖核苷酸 DNA 核糖核苷酸 RNA 生物体内还有一些游离的核苷酸 AMP，ADP，ATP cAMP 核苷酸的生 物学功能 75 NUCLEIC ACIDS Nucleotides are joined together by a phosphodiester linkage between 5 and 3 carbon atoms to form nucleic acids. The linear sequence of nucleotides in a nucleic acid chain is commonly abbreviated by a one-letter code, AGCTTACA, with the 5 end of the chain at the left. O O O P O O PO O O O PO NOMENCLATURE The names can be confusing, but the abbreviations are clear. BASE adenine guanine cytosine uracil thymine NUCLEOSIDE adenosine guanosine cytidine uridine thymidine ABBR. A G C U T Nucleotides are abbreviated by three capital letters. Some examples follow: AMP dAMP UDP ATP = adenosine monophosphate = deoxyadenosine monophosphate = uridine diphosphate = adenosine triphosphate sugar base sugar base BASE + SUGAR = NUCLEOSIDE BASE + SUGAR + PHOSPHATE = NUCLEOTIDE O OH sugar base CH2 H2O O O O PO + O OH sugar base CH2 O O O PO O sugar base CH2 O O O PO O sugar base CH2 P O O O O 5 OH3 3 end of chain 3 5 phosphodiester linkage 5 end of chain example: DNA NUCLEOTIDES HAVE MANY OTHER FUNCTIONS O CH2 N N N N NH2 OHOH 1 They carry chemical energy in their easily hydrolyzed phosphoanhydride bonds. O O O P O CH2 N N N N NH2 OH 2 They combine with other groups to form coenzymes. O O POOCCCCNCCCNCCHS OO H H H H HH H H H HH HH HOCH3 example: coenzyme A (CoA) CH3 3 They are used as signaling molecules in the cell. O O O P O CH2 N N N N NH2 OOH example: cyclic AMP phosphoanhydride bonds example: ATP (or ) O PO O O ATP 75 NUCLEIC ACIDS Nucleotides are joined together by a phosphodiester linkage between 5 and 3 carbon atoms to form nucleic acids. The linear sequence of nucleotides in a nucleic acid chain is commonly abbreviated by a one-letter code, AGCTTACA, with the 5 end of the chain at the left. O O O P O O PO O O O PO NOMENCLATURE The names can be confusing, but the abbreviations are clear. BASE adenine guanine cytosine uracil thymine NUCLEOSIDE adenosine guanosine cytidine uridine thymidine ABBR. A G C U T Nucleotides are abbreviated by three capital letters. Some examples follow: AMP dAMP UDP ATP = adenosine monophosphate = deoxyadenosine monophosphate = uridine diphosphate = adenosine triphosphate sugar base sugar base BASE + SUGAR = NUCLEOSIDE BASE + SUGAR + PHOSPHATE = NUCLEOTIDE O OH sugar base CH2 H2O O O O PO + O OH sugar base CH2 O O O PO O sugar base CH2 O O O PO O sugar base CH2 P O O O O 5 OH3 3 end of chain 3 5 phosphodiester linkage 5 end of chain example: DNA NUCLEOTIDES HAVE MANY OTHER FUNCTIONS O CH2 N N N N NH2 OHOH 1 They carry chemical energy in their easily hydrolyzed phosphoanhydride bonds. O O O P O CH2 N N N N NH2 OH 2 They combine with other groups to form coenzymes. O O POOCCCCNCCCNCCHS OO H H H H HH H H H HH HH HOCH3 example: coenzyme A (CoA) CH3 3 They are used as signaling molecules in the cell. O O O P O CH2 N N N N NH2 OOH example: cyclic AMP phosphoanhydride bonds example: ATP (or ) O PO O O ATP 75 NUCLEIC ACIDS Nucleotides are joined together by a phosphodiester linkage between 5 and 3 carbon atoms to form nucleic acids. The linear sequence of nucleotides in a nucleic acid chain is commonly abbreviated by a one-letter code, AGCTTACA, with the 5 end of the chain at the left. O O O P O O PO O O O PO NOMENCLATURE The names can be confusing, but the abbreviations are clear. BASE adenine guanine cytosine uracil thymine NUCLEOSIDE adenosine guanosine cytidine uridine thymidine ABBR. A G C U T Nucleotides are abbreviated by three capital letters. Some examples follow: AMP dAMP UDP ATP = adenosine monophosphate = deoxyadenosine monophosphate = uridine diphosphate = adenosine triphosphate sugar base sugar base BASE + SUGAR = NUCLEOSIDE BASE + SUGAR + PHOSPHATE = NUCLEOTIDE O OH sugar base CH2 H2O O O O PO + O OH sugar base CH2 O O O PO O sugar base CH2 O O O PO O sugar base CH2 P O O O O 5 OH3 3 end of chain 3 5 phosphodiester linkage 5 end of chain example: DNA NUCLEOTIDES HAVE MANY OTHER FUNCTIONS O CH2 N N N N NH2 OHOH 1 They carry chemical energy in their easily hydrolyzed phosphoanhydride bonds. O O O P O CH2 N N N N NH2 OH 2 They combine with other groups to form coenzymes. O O POOCCCCNCCCNCCHS OO H H H H HH H H H HH HH HOCH3 example: coenzyme A (CoA) CH3 3 They are used as signaling molecules in the cell. O O O P O CH2 N N N N NH2 OOH example: cyclic AMP phosphoanhydride bonds example: ATP (or ) O PO O O ATP 核酸是由核苷酸通过3，5磷酸二酯键连接而成的 75 NUCLEIC ACIDS Nucleotides are joined together by a phosphodiester linkage between 5 and 3 carbon atoms to form nucleic acids. The linear sequence of nucleotides in a nucleic acid chain is commonly abbreviated by a one-letter code, AGCTTACA, with the 5 end of the chain at the left. O O O P O O PO O O O PO NOMENCLATURE The names can be confusing, but the abbreviations are clear. BASE adenine guanine cytosine uracil thymine NUCLEOSIDE adenosine guanosine cytidine uridine thymidine ABBR. A G C U T Nucleotides are abbreviated by three capital letters. Some examples follow: AMP dAMP UDP ATP = adenosine monophosphate = deoxyadenosine monophosphate = uridine diphosphate = adenosine triphosphate sugar base sugar base BASE + SUGAR = NUCLEOSIDE BASE + SUGAR + PHOSPHATE = NUCLEOTIDE O OH sugar base CH2 H2O O O O PO + O OH sugar base CH2 O O O PO O sugar base CH2 O O O PO O sugar base CH2 P O O O O 5 OH3 3 end of chain 3 5 phosphodiester linkage 5 end of chain example: DNA NUCLEOTIDES HAVE MANY OTHER FUNCTIONS O CH2 N N N N NH2 OHOH 1 They carry chemical energy in their easily hydrolyzed phosphoanhydride bonds. O O O P O CH2 N N N N NH2 OH 2 They combine with other groups to form coenzymes. O O POOCCCCNCCCNCCHS OO H H H H HH H H H HH HH HOCH3 example: coenzyme A (CoA) CH3 3 They are used as signaling molecules in the cell. O O O P O CH2 N N N N NH2 OOH example: cyclic AMP phosphoanhydride bonds example: ATP (or ) O PO O O ATP 二、DNA的结构 DNA是携带遗传信息的大分子 DNA的结构 DNA的碱基组成特征 dAMP, dCMP, dTMP, dGMP A+G=T+C 嘌呤和嘧啶碱基等量 A/T=G/C DNA的二级结构 Rosalind Franklin A structure this pretty just had to exist -James Waston, The double helix, 1968 DNA双螺旋结构的特征： （1）两条反向平行的DNA链绕同一个中心 轴旋转，相互缠绕，形成右手螺旋。 （2）DNA链的磷酸核糖骨架位于螺旋的外 侧。碱基包含在螺旋内部，碱基平面与中心 轴垂直，糖环平面与中心轴平行，其中A与 T，G与C分别以氢键配对。 （3）右手螺旋的平均直径是2.0nm，两个相 邻的碱基对之间的纵向距离是0.34nm，每个 螺旋的螺距为3.4nm。每个螺旋含10对脱氧 核苷酸。 （4）在双螺旋的表面，存在两个大小不同 的沟槽，称为大沟和小沟。 A T G C 维持DNA双螺旋结构的作用力： （1）碱基堆积力：是最主要的作用力。 （2）两条DNA链间互补碱基对之间的氢键。 DNA二级结构的其他形式 几种特殊的DNA序列 1?1?D?A?D?A?0?0? ?N?N? ?8?8 ? 镜像重复 1?1?D?A?D?A?0?0? ?N?N? ?8?8 ? ? ? 三股螺旋H-DNA DNA的超螺旋结构：DNA的三级结构 缠绕式超螺旋 线圈式超螺旋 DNA在体内的包装：染色质和染色体 细胞周期 有丝分裂期 核小体nucleosome是染色质的基本结构