Our goal is to use mass spectrometry to determine the structure of proteins, the production of which is upregulated when human placental cytotrophoblasts are cultured in an hypoxia environment. In normal pregnancy, fetal cytotrophoblasts invade maternal (uterine) arterioles, thus bringing oxygenated blood to the placenta. In preeclampsia, cytotrophoblast invasion is abnormally shallow and the cells become hypoxic. Current data suggest that the maternal syndrome (proteinuria, malignant hypertension) is caused by toxic factors released by hypoxic cytotrophoblasts. By 2-dimensional gel analysis we showed that culturing cytotrophoblasts under hypoxic conditions results in upregulated production of 7 discrete proteins. Knowing their structure is the first step in assessing their involvement in the etiology of preeclampsia. The University of California San Francisco Mass Spectrometry Facility, where the proposed work will be carried out, promotes the use of advanced techniques of computerized mass spectrometry in solving biomedical research problems of recognized scientific interest. This program is proactive in bringing to clinical and basic scientists the experimental benefits of state-of-the-art instrumentation with particular emphasis on the development of micro-sample handling, derivitization and separation methodologies and the pursuit of ultimate sensitivities in tandem mass spectrometry. One particular area of emphasis is the sequencing of proteins isolated from 2-dimensional gels, the principal approach proposed here.