University of California

Paresh Agarwal

Carolyn Ruth Bertozzi

Ellen May Sletten

Aldehyde- and ketone-functionalized proteins are promising new substrates for the development of chemically modified biotherapeutics and protein-based materials. Their reactive carbonyl groups are typically conjugated with a-effect nucleophiles, such as substituted hydrazines and alkoxyamines, to generate hydrazones and oximes, respectively. However, the resulting C&#x2550;N linkages are susceptible to hydrolysis under physiologically relevant conditions, which limits their utility in biological systems. Here we introduce a Pictet-Spengler ligation that is based on the classic Pictet-Spengler reaction of aldehydes and tryptamine nucleophiles. The ligation exploits the bioorthogonal reaction of aldehydes and alkoxyamines to form an intermediate oxyiminium ion; this intermediate undergoes intramolecular C&#x2014;C bond formation with an indole nucleophile to form an oxacarboline product that is hydrolytically stable. The reaction was utilized for site-specific chemical modification of glyoxal- and formylglycine-functionalized proteins, including an aldehyde-tagged variant of the therapeutic monoclonal antibody Herceptin. In conjunction with techniques for site-specific introduction of aldehydes into proteins, the Pictet-Spengler ligation offers a new means to generate stable bioconjugates for medical and materials applications.

Growing community of inventors

Berkeley, CA, United States of America

Paresh Agarwal