What Bioconjugation is a strategy that links a protein with different substrates; enabling modulation of the properties of proteins in a desired direction. An effective conjugation technology has to control both the location and the number of molecules being incorporated in the protein. This imperative is of substantial importance, and development of new selective methodologies is crucial to the further advancement of bioconjugation and its applications in numerous fields like medicine and materials. In the current project, novel approaches for the preparation of well-defined conjugates will be developed. Thus, the knowledge gained from this work should be of considerable value in the design and production of bioconjugates with specific biological/chemical profiles. Why Synthetically modified proteins (bioconjugates) can have diverse functionalities, such as storing energy of sunlight, probing complex biological processes, and targeted drug delivery. Traditional strategies rely on the side-chain reactivity of one amino acid in a wild-type protein. A typical protein contains 200-300 amino acids and with only 20 proteinogenic amino acids available, these strategies will unavoidably be associated with non-selectivity resulting in heterogeneous product mixtures (that is, variation in the number of molecules incorporated and their locations on the protein), limits their widespread application. This project will address this problem, by developing novel approaches for 'site-selective' conjugation, hereby improving their application in medicine and materials. How Each bioconjugation technology will be identified through peptide library synthesis and reactivity screening with electrophilic partners. Peptides will be synthesized using well-established solid-phase synthesis strategies, which will allow us to synthesize and test reactivity of a broad range of peptides with a variety of suitable electrophiles in a short time. After successful development of the conjugation strategies, we plan to testify the full potential of the technologies by demonstrating the use in a real biomedical application. As a proof-of-concept, we will demonstrate the use of the novel conjugation strategies for attachment of the linker-drug component to the antibody in the preparation of antibody-drug conjugates for cancer treatment. SSR The bioconjugation tools developed during this project would have traits to potentially become market leading based on unmatched efficacy and selectivity profile. The bioconjugation technologies may conceivably be applied to a wide range of biomolecules. Such modified biomolecules (bioconjugates) can potentially be used in a broad range of chemical applications, such as storing the energy of sunlight, probing complex biological processes, diagnostic tools, as well as targeted drug delivery. As such, the proposed research may contribute to solving a broad range of fundamental challenges in the society, including unsustainable energy use, climate change/destruction of nature and global health issues.