UC San Diego

Natural products are a crucial component in drug discovery because of their considerable pharmaceutical properties. Cyclic non-ribosomally peptides are one category of natural products featured by containing non-standard amino acids and lactam or lactone structures, thus increasing the complexity of the resulting tandem mass spectrometry data. Cyclosporin, microcystins and nodularins all are well-known examples and have notable pharmacologically importance. In this current work, by collaborating with Dr. Pevzner bioinformatics group, a program was developed for the annotation and characterization of tandem mass spectra obtained from cyclic peptides. This program, MS- CPA is available as a web tool (http://lol.ucsd.edu/ms- cpa_v1/Input.py). The second half of this thesis will be focused on a ribosomally encoded peptide antibiotic trifolitoxin produced by a rhizobium strain. This peptide undergoes multiple unknown post-translational modifications results in a loss of 24 Da masses. Mass spectrometry based strategies as well as in vivo reconstitution experiments were used to partially characterize trifolitoxin structure.