分子生物學(xué)48742850-在線瀏覽
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【正文】 ckground information on the mechanisms of heredity. ? Experimental evidence that identified DNA as the geic material. ? Properties of DNA as the geic material, including storage, transmission, stability, and mutation. Molecular Biology 大連理工大學(xué) The Key Experiments Contributes to Identifying DNA as the Primary Geic Material ? 1928 F. Griffith/ Transformation ? 1944 . Avery/ Further Confirmation ? 1952 . Hershey and M. Chase/ Phage Labeling Molecular Biology 大連理工大學(xué) 1928 F. Griffith Transformation ? Streptococcus pneumoniae (pneumococci) growing as colonies on the surface of a culture medium. –Left: The presence of a capsule(包膜） around the bacterial cells gives the colonies a glistening（發(fā)亮） , smooth (S) appearance. –Right: Pneumococci lacking capsules have produced these rough (R) colonies. Molecular Biology 大連理工大學(xué) The Experiments ? Something in the heatkilled S cells transformed the Rtype bacteria into Stype cells. Molecular Biology 大連理工大學(xué) The Conclusions ? There was a transforming agent in the the heat treated wild type bacteria (smooth) which transformed the live mutant (rough) type bacteria to be able to produce wild type bacteria capsule. Molecular Biology 大連理工大學(xué) . Avery’s Testify ? Background: – In 1944, Oswald Avery and his colleagues at The Rockefeller Institute in New York City eventually showed that the something was DNA. – Avery extracted relatively pure nucleic acids (DNA+RNA) from pneumococcus to determine what was the transforming agent observed in Griffith39。Molecular Biology 大連理工大學(xué) Noncovalent interactions that determine the threedimensional structure of macromolecules ? The biological properties of macromolecule are mainly determined by activating interactions that results in each molecule acquiring a unique threedimensional structure. ? These noncovalent interactions are much weaker than typical covalent bonds, and for any given type of macromolecule, several of these weaker interactions may play a role in determining threedimensional structure. Molecular Biology 大連理工大學(xué) Noncovalent interactions ? The Random coil 纏 繞 – Linear polypeptide and polynucleotide chains contain bonds about which there is free rotation. – In the absence of any intrastrand（分子內(nèi)） interactions, each monomer would be free to rotate with respect to its adjacent monomers – Few, if any, nucleic acid or protein molecules exist in nature as random coils because of many interactions between elements of the chains – Noncovalent interactions ? Hydrogen bonds 氫鍵 ? The hydrophobic interaction 疏水作用 ? Ionic bonds 離子鍵 ? Van der waals attraction 范德華力 Molecular Biology 大連理工大學(xué) effects of noncovalent interactions ? Determine the three dimensional structures of macromolecules. – Constrain(約束 ) a linear chain to fold in such a way that different regions of the chain, are brought together. ? Disulfide bonds(二硫鍵 。 covalent) also affects the molecular properties of proteins. Molecular Biology 大連理工大學(xué) Macromolecule isolation and characterization ? Proteins – Molecular sieves 分子篩 : molecular weight – Chromatography 層析 : charge (positively or negatively charged) or affinity properties – Electrophoresis 電泳： SDSPAGE, charge and size。s experiments Molecular Biology 大連理工大學(xué) Avery’s Transformation Experiment 1944 Determined that DNA was the geic material responsible for Griffith’s results (not RNA). Molecular Biology 大連理工大學(xué) ? In 1952, A. D. Hershey and M. Chase performed another experiment that
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