How We Came to Know the Molecules of Life: Ten Scientists From X-ray Diffraction to DNA Replication

In 1912 Laue predicted and, with collaborators, confirmed that a crystal lattice diffracts X-rays the way a grating diffracts light, which showed that X-rays are waves and that crystals are regular arrangements of atoms. Every later stop on this path depends on that effect.

With his son he built the X-ray spectrometer that turned Laue's effect into a systematic method for locating atoms inside a crystal. The two shared the 1915 Nobel Prize in Physics for founding X-ray crystallography.

While still a student in 1912 to 1913 he derived the law linking diffraction angles to the spacing of atomic planes, and with his father used it to solve the first crystal structures, including table salt. He was twenty-five when the prize came, still its youngest laureate.

Hodgkin carried the method from minerals to biochemical molecules, determining the structures of penicillin in 1945 and vitamin B12 in 1955 and finishing insulin in 1969 after thirty-five years of work. Her 1964 Nobel Prize in Chemistry recognised those X-ray determinations.

Between 1945 and 1955 Sanger worked out the complete amino acid sequence of bovine insulin using a reagent that labels each chain's terminal amino acid. It proved that a protein has one exact, fixed sequence, a different kind of structural knowledge from a crystal picture.

Around 1950 Wilkins turned King's College London's X-ray diffraction equipment on DNA and, with Raymond Gosling, produced some of the first patterns showing it had a regular, helical structure. He shared the 1962 Nobel Prize in Physiology or Medicine for the molecular structure of nucleic acids.

In 1952, with Martha Chase, Hershey showed that a bacteriophage injects its DNA into a bacterium while its protein coat stays outside. That was evidence that DNA, not protein, carries hereditary information, and it earned him a share of the 1969 Nobel Prize in Physiology or Medicine.

Chase did the bench work of the 1952 experiment: protein labeled with radioactive sulfur, DNA with radioactive phosphorus, and a kitchen blender to shear phage bodies from infected bacteria. The DNA was what entered the cells. She was listed as co-author, though her contribution went largely unrecognised in her lifetime.

In 1958 Meselson and Franklin Stahl grew bacteria in a heavy nitrogen isotope to track DNA across generations. Each new molecule held one original strand and one new strand, the semiconservative replication the double helix model had predicted.

Stahl was Meselson's partner in the 1958 replication experiment at the California Institute of Technology. He later spent most of his career at the University of Oregon studying genetic recombination in bacteriophages and fungi.