Sponge enzyme could help chemists make organosiloxanes

Organosiloxanes end up in a wide range of consumer products as lubricants and coatings, and chemists use the molecules as protecting groups in organic synthesis. Currently, the way chemists form the Si-O bonds in these compounds is to start with chlorosilanes, which require a lot of energy to make and can lead to acidic waste. Also, there is no way to break down these bonds in polymeric organosiloxanes, making the materials unrecyclable. At the ACS national meeting in San Diego last week, chemists presented a possible way to fix both sustainability problems with help from marine sponges. These simple creatures build silica-based skeletons instead of calcium-based ones, as most other animals have. They use enzymes called silicateins to convert silicates they scavenge from the water into silica. Previous research showed that these enzymes could hydrolyze the Si-O bonds in some organosiloxanes. Now Lu Shin Wong at the University of Manchester and colleagues have put one silicatein from the sponge Suberites domuncula through its catalytic paces and demonstrated that it can hydrolyze a variety of organosiloxanes and form others without chlorosilanes. And the enzyme can do so in organic solvents at relatively high temperatures, sometimes with yields between 80 and 90%. Wong says the team is now working to understand the enzyme mechanism behind these reactions and to engineer the protein to be more soluble and active in solvents.