清华大学：《生物化学》课程PPT教学课件（英文版）Nucleotides and Nucleic Acids（1/2）

Nucleotides and nucleic Acids 11/05/2002 Bing zhou, PhD Department of Biological Science and Biotechnology TSinghua University

Nucleotides and Nucleic Acids 11/05/2002 Bing Zhou, PhD Department of Biological Science and Biotechnology Tsinghua University

Functions of Nucleotides RNA and DNA components serving as energy stores for future use in phosphate transfer reactions. These reactions are predominantly carried out by ATP forming a portion of several important coenzymes such as NAD+, NADP+, FAD and coenzyme A second messengers in signal transduction events. The predominant second messenger is cyclic-AMP(CAMP), a cyclic derivative of amp formed from atp controlling numerous enzymatic reactions through allosteric effects on enzyme activity. serving as activated intermediates in numerous biosynthetic reactions. These activated intermediates include s- adenosylmethionine(s-AdoMet) involved in methyl transfer reactions as well as the many sugar coupled nucleotides involved in glycogen and glycoprotein synthesis

Functions of Nucleotides ► RNA and DNA components ► serving as energy stores for future use in phosphate transfer reactions. These reactions are predominantly carried out by ATP. ► forming a portion of several important coenzymes such as NAD+, NADP+, FAD and coenzyme A. ► second messengers in signal transduction events. The predominant second messenger is cyclic-AMP (cAMP), a cyclic derivative of AMP formed from ATP. ► controlling numerous enzymatic reactions through allosteric effects on enzyme activity. ► serving as activated intermediates in numerous biosynthetic reactions. These activated intermediates include S￾adenosylmethionine (S-AdoMet) involved in methyl transfer reactions as well as the many sugar coupled nucleotides involved in glycogen and glycoprotein synthesis

DNA as Genetic Material

DNA as Genetic Material

History of DNA 1. The Swiss biologist, Friedrich Miescher, isolated DNA from salmon sperm in 1868 2. In 1944, Oswald Avery, Colin MacLeod, and Maclyn McCarty showed that DNA from pathogenic strains of the bacterium Pneumococcus could be transferred into nonpathogenic strains, making them(and any succeeding generations) 3. Erwin Chargaff reported in 1947 that the quantitities of adenine and thymine in dNa were very close to the same value. Similarly, he observed that cytosine and guanine were also very close to equal in quantity. 4. In 1952, Alfred Hershey and Martha Chase showed T2 bacteriophage inject only DNA into cells and this is sufficient to make more T2 bacteriophage 5. James Watson and Francis Crick proposed the model of the double helix of dna in 1953 6. In 1965, Marshall Nirenburg, Philip Leder, and others, identified the genetic code by which protein is made from information in DNA

History of DNA ► 1. The Swiss biologist, Friedrich Miescher, isolated DNA from salmon sperm in 1868. ► 2. In 1944, Oswald Avery, Colin MacLeod, and Maclyn McCarty showed that DNA from pathogenic strains of the bacterium Pneumococcus could be transferred into nonpathogenic strains, making them (and any succeeding generations) pathogenic ► 3. Erwin Chargaff reported in 1947 that the quantitities of adenine and thymine in DNA were very close to the same value. Similarly, he observed that cytosine and guanine were also very close to equal in quantity. ► 4. In 1952, Alfred Hershey and Martha Chase showed T2 bacteriophage inject only DNA into cells and this is sufficient to make more T2 bacteriophage. ► 5. James Watson and Francis Crick proposed the model of the double helix of DNA in 1953. ► 6. In 1965, Marshall Nirenburg, Philip Leder, and others, identified the genetic code by which protein is made from information in DNA

Levene(1910)-tetranucleotide hypothesis nucleic acid is a repetitive polymer of four subunits A: C: G: T in the ratio 1: 1:1:1 structure seems too simple to carry information

Levene (1910) - tetranucleotide hypothesis nucleic acid is a repetitive polymer of four subunits A:C:G:T in the ratio 1:1:1:1 => structure seems too simple to carry information

A T C (Klug Cummings 1997) Levene's Tetranucleotide Hy pothesis Early experiments suggested that the four bases occur in DNA in equal ratios, possibly as a repeating tetramer. The implications was that the structure of DNA was too simple and too regular to contribute to hereditary variation: attention thereafter focussed on protein as the heredity substance

Levene's Tetranucleotide Hypothesis Early experiments suggested that the four bases occur in DNA in equal ratios, possibly as a repeating tetramer. The implications was that the structure of DNA was too simple and too regular to contribute to hereditary variation: attention thereafter focussed on protein as the heredity substance

Frederick Griffith In 1928 a scientist named frederick Griffith was working on a project that enabled others to point out that DNA was the molecule of inheritance. Griffiths experiment involved mice and two types of pneumonia, a virulent and a non-virulent kind. He injected the virulent pneumonia into a mouse and the mouse died. Next he injected the non-virulent pneumonia into a mouse and the mouse continued to live. After this, he heated up the virulent disease to kill it and then injected it into a mouse. The mouse lived on. Last he injected non-virulent pneumonia and virulent pneumonia, that had been heated and killed. into a mouse. This mouse died Why? Griffith thought that the killed virulent bacteria had passed on a characteristic to the non-virulent one to make it virulent. He thought that this characteristic was in the inheritance molecule. This passing on of the inheritance molecule was what he called transformation

Frederick Griffith In 1928 a scientist named Frederick Griffith was working on a project that enabled others to point out that DNA was the molecule of inheritance. Griffith's experiment involved mice and two types of pneumonia, a virulent and a non-virulent kind. He injected the virulent pneumonia into a mouse and the mouse died. Next he injected the non-virulent pneumonia into a mouse and the mouse continued to live. After this, he heated up the virulent disease to kill it and then injected it into a mouse. The mouse lived on. Last he injected non-virulent pneumonia and virulent pneumonia, that had been heated and killed, into a mouse. This mouse died. Why? Griffith thought that the killed virulent bacteria had passed on a characteristic to the non-virulent one to make it virulent. He thought that this characteristic was in the inheritance molecule. This passing on of the inheritance molecule was what he called transformation

Controls Living Ill (virulent) Living IIR t Heat-killed (avirulent) ⅢIS Inject Inject Inject Mouse dies Mouse lives Mouse lives ing IIR and Griffiths critical experiment eat-killed IlIS LivingⅢs Tissue recovered nect Mouse dies analyzed (Klug Cummings 1997) Griffith's Transformation Experiment Pneumococcus bacteria include two strains, a virulent IlIs strain with a Smooth coat that kills mice (left), and a non-virulent IIR Rough strain that does not (middle). Heating destroys the virulence of llIs (right). When heat-killed llIS is mixed with live IIR and injected into mice, the mouse dies, and its tissue contains living bacteria with smooth coats like Ils, and these bacteria are subsequently virulent to mice. Something in the heat-killed lls bacteria has transformed the biological and hereditary properties of the IIR bacteria

Griffith's Transformation Experiment Pneumococcus bacteria include two strains, a virulent IIIS strain with a Smooth coat that kills mice (left), and a non-virulent IIR Rough strain that does not (middle). Heating destroys the virulence of IIIS (right). When heat-killed IIIS is mixed with live IIR and injected into mice, the mouse dies, and its tissue contains living bacteria with smooth coats like IIIS, and these bacteria are subsequently virulent to mice. Something in the heat-killed IIIS bacteria has 'transformed' the biological and hereditary properties of the IIR bacteria

Oswald Avery Fourteen years later a scientist named Oswald Avery continued with Griffith's experiment to see what the nheritance molecule was. In this experiment he destroyed the lipids, ribonucleic acids, carbohydrates, and proteins of the virulent pneumonia. Transformation still occurred after this. Next he destroyed the deoxyribonucleic acid. Transformation did not occur. Avery had found the inheritance molecule, dNA

Oswald Avery Fourteen years later a scientist named Oswald Avery continued with Griffith’s experiment to see what the inheritance molecule was. In this experiment he destroyed the lipids, ribonucleic acids, carbohydrates, and proteins of the virulent pneumonia. Transformation still occurred after this. Next he destroyed the deoxyribonucleic acid. Transformation did not occur. Avery had found the inheritance molecule, DNA!

Klug Cummings 1997) Centrifuge Heat-kill Homogenize cells Recover IllS filtrate lIS cells spun to Extract carbohydrates, bottom of tube lipids, and proteins lIS cells in liquid culture medium Averys isolation of the"Transforming Principle Avery repeated Griffith 's experiment of combining heat-killed virulent IlIs bacteria with non-virulent IIR bacteria. In order to isolate the transforming substance, he fractionated the heat-killed llis cells and selectively removed carbohydrates and lipids, leaving behind proteins and nucleic acids

Avery's isolation of the "Transforming Principle" Avery repeated Griffith's experiment of combining heat-killed virulent IIIS bacteria with non-virulent IIR bacteria. In order to isolate the transforming substance, he fractionated the heat-killed IIIS cells and selectively removed carbohydrates and lipids, leaving behind proteins and nucleic acids