John Fenn, a chemist, shared half the Nobel Prize in Chemistry with Kohichi Tanaka "for their development of soft desorption ionisation methods for mass spectrometric analyses of biological macromolecules." John Fenn developed a technique for mass spectrometry measurements of macromolecules. To make any measurements with a mass spectrometer you need to first put the substance into a vapor phase and then ionize it (remove electrons). At the time, it was not possible to put protein molecules into a gas phase without destroying them, as was true for most macromolecules. Fenn’s method was to mix the macromolecule into a charged solution and then spray the solution, like a water hose, but in a much smaller stream. As the stream goes along, droplets form and begin to evaporate. As the droplets get smaller from evaporation, the charges residing on the surface of the droplets begin to push harder on each other until the droplet bursts because of the repulsion between the charges on its surface. As the droplets break up, they contain fewer of the macromolecules, until finally you are left with single charged macromolecules with minimal breaking of the macromolecules.
