Letter from Kai O. Pedersen to Michael Heidelberger

In this letter the physical chemist Kai Pedersen reported on experiments designed to separate and analyze antibody molecules based on physical characteristics such as size, shape, or isoelectric point (the pH at which a molecule carries no net electrical charge) by ultracentrifugation and electrophoresis. These experimental techniques were developed by the Nobel Prize winners Theodor Svedberg and Arne Tiselius, respectively, at the University of Uppsala in Sweden. Heidelberger had received a Guggenheim fellowship to spend the summer of 1934 at Uppsala in order to use ultracentrifugation to determine the size of antibodies.