Fenn's contributions specifically related to the development of electrospray ionization, now a commonly used technique for large molecules and routine liquid chromatography-tandem mass spectrometry.

Early in his career, he studied the field of jet propulsion at Project SQUID and focused on molecular beams.

He worked in industry at Monsanto and at private research labs before moving to academic posts including Yale and Virginia Commonwealth University.

The decision pleased the university, but provoked mixed responses from some people affiliated with the institution, who were disappointed with the treatment of a Nobel Prize winner with such a long history at the school.

[4] When Fenn was considering graduate school, he was advised to take additional mathematics courses by Henry Bent, then a chemistry professor at Harvard University.

[4] After completing graduate school, Fenn's first job was with Monsanto, working in the Phosphate Division and producing polychlorinated biphenyls (PCBs).

[4] Fenn worked briefly at a small company named Sharples Chemicals that focused on the production of amyl chloride derivatives.

[4] During this period, Fenn started his work developing supersonic atomic and molecular beam sources, which are now widely used in chemical physics research.

"[9] While Fenn was working with Monsanto, the company's research was focused on the production of phosphoric acid and polychlorinated biphenyls (PCBs).

[4] Fenn and his colleagues at Monsanto were largely unaware of the health hazards posed by PCBs, indeed because of their inertness, they "practically bathed in the stuff".

[10] The liquid sample is introduced into an electrospray source (at atmospheric pressure) and desolvated with a flow of heated nitrogen gas.

[13] Fenn's work with electrospray ionization was at the center of a lawsuit pitting him against his alma mater and former employer, Yale University.

In 1993, a private company seeking to license the use of electrospray technology traced its invention to Yale, when the university discovered that Fenn held the patent.

"[15] Fenn claimed that he owned the technology because the work was completed after he had been forced to downsize at the university's mandatory retirement age.

[15] Yale University entered into its own licensing agreement with a private company, leading Fenn to file a lawsuit against the school in 1996.

In 2005, U.S. District Judge Christopher Droney ruled against Fenn, awarding Yale $545,000 in royalties and $500,000 in legal fees.

"[15] Evidence presented in the case indicated that Fenn had served on panels at Yale University that reviewed the institution's policy on intellectual property.

"[16] Fenn shared the 2002 Nobel Prize in Chemistry with Koichi Tanaka and Kurt Wüthrich "for the development of methods for identification and structure analyses of biological macromolecules.

"[17] Fenn and Tanaka split half of the award for their work in developing ionization techniques for using mass spectrometry to analyze large biological molecules.

Wüthrich was honored for his work in developing nuclear magnetic resonance techniques to analyze similar molecules in solution.