Catecholic 3,4-dihydroxyphenyl-l-alanine (Dopa) residues in mussel foot proteins (mfps) contribute critically to mussel (Mytilus californianus) plaque adhesion, but only if protected from oxidation at the adhesive-substratum interface. Dopa oxidation is thermodynamically favorable in seawater yet barely detectable in plaques; therefore, we investigated how plaques insulate Dopa-containing mfps against oxidation. Seawater sulfate triggers an mfp3 and mfp6 liquid-liquid phase separation (LLPS). By combining plaque cyclic voltammetry with electrophoresis, mass spectrometry, and redox-exchange chemistry, we show that Dopa-containing mfp3 and mfp6 in phase-separated droplets remain stable despite rapid oxidation in the surrounding equilibrium solution. The results suggest that a cohort of oxidation-prone proteins is endowed with phase-dependent redox stability. Moreover, in forming LLPS compartments, Dopa proteins become reservoirs of chemical energy.
The COVID-19 pandemic has created massive demand for widespread, distributed tools for detecting SARS-CoV-2 genetic material. The hurdles to scalable testing include reagent and instrument accessibility, availability of highly trained personnel, and large upfront investment. Here we showcase an orthogonal pipeline we call CREST (Cas13-based, Rugged, Equitable, Scalable Testing) that addresses some of these hurdles. Specifically, CREST pairs commonplace and reliable biochemical methods (PCR) with low-cost instrumentation, without sacrificing detection sensitivity. By taking advantage of simple fluorescence visualizers, CREST allows for a binary interpretation of results. CREST may provide a point-of-care solution to increase the distribution of COVID-19 surveillance.
The COVID-19 pandemic has created massive demand for widespread, distributed tools for detecting SARS-CoV-2 genetic material. The hurdles to scalable testing include reagent and instrument accessibility, availability of highly-trained personnel, and large upfront investment. Here we showcase an orthogonal pipeline we call CREST (Cas13-based, Rugged, Equitable, Scalable Testing) that addresses some of these hurdles. Specifically, CREST pairs commonplace and reliable biochemical methods (PCR) with low-cost instrumentation, without sacrificing detection sensitivity. By taking advantage of simple fluorescence visualizers, CREST allows for a binary interpretation of results. CREST may provide a pointof-care solution to increase the distribution of COVID-19 surveillance.
We demonstrate a universal approach to form bottlebrush polymer networks in both bulk and thin films by photo-crosslinking mixtures of well-defined bottlebrush precursors and bis-benzophenone-based additives. This strategy is compatible with a wide variety of different side-chain chemistries including poly(acrylates), poly(ethers), poly(esters), and poly(siloxanes) due to the indiscriminate C–H abstraction behavior of benzophenone upon exposure to ultraviolet light. The appropriate choice of molecular “linker” that bridges benzophenones is critical to solubilize the additive in a given bottlebrush precursor at room temperature without a solvent. Importantly, homogeneous mixtures can be achieved using two distinct types of linkers: telechelic polymers matched to the bottlebrush side-chain chemistry or small-molecule branched alkyl derivatives that are often synthetically more accessible. As evidenced by in situ UV shear rheology, the curing kinetics and mechanical properties of these amorphous or semicrystalline networks are controlled by bottlebrush precursor chemistry, architecture, and crosslinker loading. The influence of elastically effective and ineffective crosslinks, which arise in tandem from the statistical nature of benzophenone-induced radical reactions, is quantitatively captured by introducing a general model that relates crosslinker concentration and shear modulus. These results provide a conceptual framework that can be used to conveniently synthesize bottlebrush networks with tailored properties.
Marine mussels secrete proteins rich in residues containing catechols and cationic amines that displace hydration layers and adhere to charged surfaces under water via a cooperative binding effect known as catechol-cation synergy. Mussel-inspired adhesives containing paired catechol and cationic functionalities are a promising class of materials for biomedical applications, but few studies address the molecular adhesion mechanism(s) of these materials. To determine whether intramolecular adjacency of these functionalities is necessary for robust adhesion, a suite of siderophore analog surface primers was synthesized with systematic variations in intramolecular spacing between catechol and cationic functionalities. Adhesion measurements conducted with a surface forces apparatus (SFA) allow adhesive failure to be distinguished from cohesive failure and show that the failure mode depends critically on the siderophore analog adsorption density. The adhesion of these molecules to muscovite mica in an aqueous electrolyte solution demonstrates that direct intramolecular adjacency of catechol and cationic functionalities is not necessary for synergistic binding. However, we show that increasing the catechol-cation spacing by incorporating nonbinding domains results in decreased adhesion, which we attribute to a decrease in the density of catechol functionalities. A mechanism for catechol-cation synergy is proposed based on electrostatically driven adsorption and subsequent binding of catechol functionalities. This work should guide the design of new adhesives for binding to charged surfaces in saline environments.
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