The Princeton Environmental Institute (PEI) (http://web.princeton.edu/sites/PEI/) has an opening for a postdoctoral or more senior researcher to study microbial biogeochemistry of the nitrogen cycle. As part of a NASA funded project to Zhang (http://scholar.princeton.edu/xinningz/home) and Kopf (http://kopflab.org) labs, the research aims to characterize the mechanism of nitrogen stable isotope (15N/14N) fractionation during biological nitrogen fixation using in vitro assays containing purified nitrogenases. The cross-disciplinary work will be synergistic with ongoing in vivo studies in the Zhang and Kopf labs and require close coordination with collaborators in nitrogenase biochemistry and nitrogen cycle biogeochemistry.Required qualifications include a Ph.D. in Environmental Chemistry, Geosciences, Biochemistry or a related field, and expertise in analytical chemistry and/or stable isotope geochemistry. The appointment is for one year, with possibility for renewal. Interested applicants should provide a cover letter, curriculum vitae with publication list, a brief statement of research interest, and contact information for three references. All applications must be submitted using the Princeton University Academic Hiring website athttps://www.princeton.edu/acad-positions/position/11441.This position is subject to the University's background check policy. Princeton University is an equal opportunity employer/affirmative action employer and all qualified applicants will receive consideration for employment without regard to age, race, color, religion, sex, sexual orientation, gender identity or expression, national origin, disability status, protected veteran status, or any other characteristic protected by law.