UC Berkeley

Chemically modified proteins have been of great use in both the pharmaceutical industry and in academic research. Development of new reactions is necessary to further increase the diversity of protein-based biological agents available to researchers and physicians. In particular, high efficiency reactions that can site-specifically modify proteins are sought by the research community. In this thesis, a new reaction that oxidiatively couples o-aminophenols and anilines at very high rates was presented, as the MS2 viral capsid coat protein was fully modified site-specifically with a small molecule in under 30 s. The products of the reaction were characterized using small molecule model compounds and a reaction mechanism was posulated based on the available information.

Further, the reaction was used to synthesize of variety of protein-peptide or protein-polymer conjugates. Over 100 copies of 2k or 5k molecular weight poly(ethyleneglycol) (PEG) were attached to a 28 nm diameter MS2 virus-like particle in under 2 min using this new oxidative coupling reaction. In addition, several small peptides were also attached in the same way with similar results. The reaction was also utilized for modification of other proteins such as lysozyme to show its general applicability.

Finally, the reaction was applied to labeling proteins with radioactive Fluorine-18 for the purpose of positron emission tomography (PET). Fluorine-18 was incorporated into a small molecule prosthetic group to form [18F]-p-fluoroaniline ([18F]-FA). 18F-FA was successfully coupled to both lysozyme and MS2 virus-like particles containing aminophenol functionality. Again the reaction reached completion in under 2 min and gave excellent yields.

It is our hope that this reaction will be utilized by other protein chemists looking for a highly efficient way to assemble challenging protein bioconjugates.