Chemical Modification of Silk Protein via Palladium-Mediated Suzuki-Miyaura Reactions

Suzuki-Miyaura cross-coupling reactions were used to modify the tyrosine residues on Bombyx mori silkworm silk proteins using a water-soluble palladium catalyst. Utilizing this cross-coupling reaction, molecules with specific functions can be introduced to silk in order to broaden the capabilities of silk proteins in biological systems. Model reactions using tyrosine derivatives were first screened to optimize reaction conditions. For these reactions, a variety of aryl boronic acids, solvents, buffers and temperature ranges were explored. Qualitative information on the reaction progress was collected via high performance liquid chromatography (HPLC), mass spectrometry (MS) and nuclear magnetic resonance (NMR). Reactions were then applied to silk proteins. Iodination and cross-coupling modifications of silk were characterized with NMR, UV-vis, ion-exchange chromatography (IEC) and infrared spectroscopy (IR). Overall, the research demonstrates the ability to modify silk fibroin using Suzuki-Miyaura reactions following successful iodination of the protein.