UC San Diego

In 1886, physicist Eugen Goldstein discovered Kanalstrahlen or "canal rays," rays that moved from anode to cathode and determined that these rays were composed of positively charged particles. Twelve years later, another physicist named Wilhelm Wien demonstrated that canal rays, in the presence of strong electric and magnetic fields, could be deflected and that different rays travel different parabolic paths depending on their charge-to-mass ratios. It was at this time that the first mass spectrometers were born. Fast forward to present day, we now have numerous ways to generate ions, a variety of mass analyzers, and seemingly limitless applications for mass spectrometry---mass spectrometers are even being sent to Mars! To make a long story short, modern mass spectrometers have come a very, very long way from their ancestors in the late 1800’s. Mass specs are faster, more sensitive, and capable of more advanced analysis than ever before, however, the difficult problem of molecular identification still remains in the field of natural products and metabolomics. Chemistries produced by the natural world are complex messes of complicated molecular structures and biochemical transformations that always make understanding the world a difficult task. The work presented in this dissertation are applications of mass spectrometry and molecular networking, which are only small steps in the direction of simplifying molecular identification. The chemical repertoire of hundreds bacteria belonging to the same genus are explored, four new molecules are discovered, and a reference index of compounds has been created to aid future studies of the bacterial genus Pseudomonas. Lastly, this dissertation applies mass spectrometry and molecular networking in an attempt to deconvolute the metabolic exchange factors that take place in predator-prey interactions. It appears that the predator leaves specific signatures belonging to breakdown products of a key molecule involved in photosynthesis---a signature that could be used for crop protection in the production of alternative liquid fuels.