Rudolf Schoenheimer (May 10, 1898 – September 11, 1941) was a German-American biochemist who developed the technique of isotope labelling of biomolecules, enabling detailed study of metabolism.

[4] In 1933, following the rise of the Nazis to power he emigrated from Germany to the Columbia University to join the department of Biological Chemistry.

[1] Working with David Rittenberg, from the radiochemistry laboratory of Harold C. Urey and later together with Konrad Bloch, they used stable isotopes to tag foodstuffs and trace their metabolism within living things.

His M.D dissertation was titled "Über die experimentelle Cholesterinkrankheit der Kaninchen" ("About the experimental cholesterol disease of rabbits").

[3] The program was aided by the Rockefeller Foundation and taught by Karl Thomas, professor of physiological chemistry at the University of Leipzig.

[4] After his studies at Leipzig had ended, he began a year of work at the Moabit Hospital in Berlin as the resident pathologist.

[4] In April 1933, Schoenheimer emigrated to the United States in response to the Nazi regime's policy for the dismissal of Jewish faculty in universities.

[4] He was offered work at Columbia University as an assistant professor, where he continued his research on metabolism and cholesterol synthesis, alongside Walter M. Sperry and David Rittenberg.

[4] In 1933, Germany entered a political crisis and saw the rise of Hitler and the Nazi Party, which led Schoenheimer into emigrating to the United States.

[1] At Columbia Schoenheimer was among others that shared similar interests in Biochemistry and wanted it to move in the direction of organic chemistry.

[1] Rabbits are sensitive to a diet which includes cholesterol, and their bodily responses particularly that of the aorta demonstrates a change that similarly resembles the Human atherosclerosis.

[11] One of the methods used in the experiment involved heavy water administered into animals in order to analyse the deuterium present in the different constituents of the body.

[10] This suggested which type of substances were utilising the hydrogen present in body fluids and revealed the role water posed in metabolic processes.

[6] Schoenheimer and his colleague David Rittenberg, analysed how synthesised amino acids containing nitrogen would operate within an animal's body.

They used adult rats as the subject of their experiment and added amino acids synthesised from isotopic ammonia to their diet.

[6] When these diets were applied in nitrogen equilibrium it was found they were incorporated into tissue proteins at an intensive and rapid rate.

[6]  There was also evidence of chemical transformation as heavy nitrogen was present in amino acids, which were isolated from protein, following ingestion.

[12] This method of isotope labelling molecules enabled Schoenheimer and his colleagues to investigate various issues in intermediary metabolism.

[6] At the height of his career he committed suicide by ingesting potassium cyanide at his home in Yonkers, having struggled with depression for multiple years.

[4] Schoenheimer's scientific work and his development of isotope tagging techniques enabled biochemists to discover the various metabolic pathways of the body.

[13] The methods and techniques used by Schoenheimer also provided a means to measure quantities of substances within the body prior to the advent of the technologies and software for dynamic modeling.

[13] Schoenheimer's 1933 metabolic balance study in animals presented early evidence of "end-product feedback inhibition of cholesterol synthesis".