Our current research focus is on a group of gas-filled protein nanostructures named gas vesicles (GVs). GVs were evolved in certain photosynthetic microbes, which need to float to the surface of water to maximize their photosynthesis. Under this evolutionary pressure, GVs emerged as intracellular hollow nanostructures of a few hundred nanometers in size. GVs are made entirely from proteins, which form a 2-nanometer shell that is permeable to gas but excludes liquid water. Note that the design principle of GVs is fundamentally different from that of bubbles. In the case of a bubble, the gas inside is usually insulated from the outside by a layer of polymers. For GVs, however, both gas and water molecules are allowed to freely exchange between the inside and outside. Instead, GVs make their inner surface hydrophobic and thus prevents water molecular from undergoing heterogeneous condensation into liquid droplets. Meanwhile, the sub-micron size of the air compartment substantially reduces the chance of homogeneous condensation, the formation of droplets in a cavity. By cutting off these two routes of condensation, GVs manage to keep inside dry and stay physically stable for months in an aqueous solution. To learn more, here is our recent review paper on biomolecular ultrasound and GVs (Annu. Rev. Chem. Biomol. Eng. 9, 229), and our protocol paper on the preparation of GVs for molecular imaging (Nature Protocol 12, 2050). Comprehensive reviews on the biology of GVs were written before by Anthony Walsby and Felicitas Pfeifer.
We recently published one of the first systematic protein-protein interaction map of GV proteins. This represents the first step to unravel the intriguing cellular process to assemble these protein organelles, and we anticipate the work will lay the foundation to solve the molecular mechanism of GV assembly. See “GV assembly roadmap” in the publication tab (http://lulab.rice.edu/#publication).