PHI 31 Lecture Notes - Lecture 3: Linus Pauling, Physical Chemistry, Scale Model
Document Summary
Watson and crick (1651-1953): episode in science. X-ray pictures of crystallized dna allowed dna structure to be studied. Making models theoretical, analog, and scale models. Backbones inside, bases outside - dry molecule; not good fit to reality. Backbones outside, bases inside - wet molecule; good fit . Theoretical model (or structure of dna) - two polynucleotide chains w/ backbones twisted around each other. Linus pauling found protein w/ -helix spiral structure. Watson: perhaps dna has spiral structure too! Models serve as tools for thinking about structures. A way of thinking about a structure may or may not be good way to think about details/may not be good fit to reality. B form-dna pointed to helix pattern. Picture served as model that didn"t immediately resemble. X-ray scattering by atoms regularly spaces on infinite helix. Helps understand the experimental set-up of x-ray scattering experiments w/ helical molecules. Able to use his expertise in x-ray scattering to interpret franklin"s picture.
