Key Experiments

Biochem

Avery ( Mclead & MacCarthy) 1944

• determined DNA was mol. of heredity

  • Based on Griffith Exp. w/mice and R/S strain

• When DNA was not present mouse lived

Watson and Crick - 1953

• Structure of DNA

• Based off

  • Chargaff: base pair ratios

  • Rosaling Franklin: DNA crystals w/ x-ray —> showed helix form

• hypothesised replication, semi-conservative

• most important discovery—> structure allows for any combination of bases

Medelson - Stahl Experiment

• Test semi-conservative hypothesis

• E-coli cells with N15 — Heavy

  • Cells with N14 — light

• Gen 0 — Heavy

• Gen 1 - intermediate ( mix)

• Gen 2 - intermediate ( mix) + light —> (50/50)

• Gen 3- intermediate ( mix) + light —> (75/25)

Fredrick Sanger - 1953

• looked at A.a sequence for insulin

• only L conformation found in sequence

Linus Pauling, R. Corey, H Branson - 1951

• defined a-helix, b-sheet, b-loop, and turn

  • all properties of the secondary structures found

Anfinsen - 1950s

• All information on folding is within primary A.a sequence

• ribonuclease

  • knew how it worked, smaller ( 4 disulfide bonds)

  • Urea —> break non-covalent bonds

  • B- mercaptoethanol —> break disulfide/covalent bonds

  • fully denatured, then placed in oxygenated solution, regained enzymatic activities

• If reoxidized with urea, it would be scrambled “ wrong disul. bonds form)

  • adding B- mercaptoethanol — would reform the right ones

  • driven by decrease in free energy