生化课件2013-04.ppt

Nucleic acids ? History of DNA ? Nucleotides are the building blocks of nucleic acids ? DNA Structure ? Nucleic Acid Properties History of Nucleic Acids 1869 – Swiss physician and biologist Friedrich Miescher discovered “ nuclein ” from nuclei of white blood cells. 1889 – The term “ nucleic acid ” was first used by Richard Altmann 1920s – the tetranucleotide hypothesis is introduced 1938 – Astbury and Bell publish first X-ray diffraction pattern of DNA, indicated periodicity 1944 – Avery, MacLeod, and McCarty demonstrate DNA could “ transform ” cells. Some doubt remained. Late 1940s – Erwin Chargaff used paper chromatography for separation of DNA hydrolysates . Amount of adenine is equal to amount of thymine and amount of guanine is equal to amount of cytosine. 1952 – Hershey and Chase confirm DNA is a molecule of heredity. 1951 – Furberg published the crystal structure of a nucleoside ( cytidine ) 1953 – Watson and Crick determine the structure of DNA History of DNA ?1869 DNA was first identified by Friedrich Miescher , a Swiss biologist. He called the substance nuclein , noted the presence of phosphorous, and separated the substance into an acidic part (which we now know is DNA) and a basic part (a class of basic proteins that bind to basic DNA). ?1889 – The term “ nucleic acid ” was first used by Richard Altmann , a German pathologist and histologist. Friedrich Miescher ’s discovery ? He examined used bandages obtained from a hospital caring for the wounded of the Crimean War (克里米亚战争) in hope of finding something interesting ? He discovered a substance containing both phosphorus and nitrogen, made up of molecules that were apparently very large, in the nuclei of white blood cells found in pus ? Named the substance nuclein because it seemed to come from cell nuclei. In 1874 when Miescher separated it into a protein and an acid molecule . It is now known as deoxyribonucleic acid (DNA) Hoppe- Seyler ? Thi