Generating novel proteins with new functions is a hallmark of protein engineering. Exploration of this field led to the invention of biologically important tools, easing the investigation of complex biological systems.

These tools include creating novel protein conformational switches, adopting various conformations upon different input signals, new classes of protein sensors aiding the determination of the physiological concentration of ions or ligands inside the cell, optogenetic tools to study and control biological systems with light, novel fluorescence tags for cell live imaging, new model systems, and creating new contrast agents for molecular imaging as diagnostic tools.

The aim of this Special Issue is to collate original research and review articles from researchers with various backgrounds in protein chemistry, with a focus on the novel applications of protein engineering and design across biology and chemistry.

Potential topics include but are not limited to the following:

• Engineering protein sensors and conformational switches with in vitro and in vivo applications
• Designing new optogenetic protein tools for controlling various biological systems with light
• Protein fluorescence tags with cell-live imaging applications
• New metalloenzymes and their applications in catalysis
• Proteins as contrast agents for diagnostic molecular imaging