Proteins, Processing, and Properties of Adhesive Fluid Condensates Purified from Mussels

Abstract Humans struggle to design effective underwater adhesives, yet they are essential for numerous technical and biomedical applications. In contrast, biological organisms—most notably mussels—have evolved glues that excel in aquatic environments. While researchers have drawn inspiration from mussels, the resulting materials remain limited by a poor understanding of the native mussel glue formation process. Here, the contents of glue secretory vesicles extracted from mussels are investigated, revealing fluid condensates comprised of the various protein components of the glue. Proteomic analysis confirms the presence of several previously unconfirmed glue proteins in the vesicles, as well as several enzymatic components that may play a role in regulating glue oxidation and cross‐linking. Mimicking vesicle conditions, a method is developed to maintain the vesicle proteins in a reconstituted bulk fluid condensate, enabling in vitro analysis and hypothesis testing. A combination of proteomics, vibrational spectroscopy, and nanomechanical adhesion testing reveals the crucial contributions of several physicochemical factors (e.g., pH, sulfate and vanadium ions, sulfhydryls) for the processing and performance of mussel glues as they transition from fluid condensates to microporous solid glues. These findings are crucial for understanding biological glues and the development of next generation bio‐inspired underwater adhesives.