Silk, glue proteins in worm's cement.

By extracting the contents of cement glands from thousands of marine worms, scientists have identified a component of silk and two unusual proteins used for making the worms' tubes.

These polychaete worms build large reef-like mounds made up of single-worm tube shelters. The worms glue together sand particles they collect from water washing over them. Like mussel glue, this tough, waterproof worm cement intrigues chemists studying adhesives (SN: 1/5/91, p.8).

To begin the identification, Rebecca A. Jensen of the University of California, Santa Barbara, allowed worms brought into the laboratory to use only very tiny silica beads for building their tubes. When she and her colleagues analyzed pieces of the worm tunnels, they could separate out the silica f rom the rest of the chemicals. In this way, they determined that the glue contains a lot of L-dopa, a modified amino acid, says Herbert Waite, a biochemist at the University of Delaware's College of Marine Studies in Lewes. The researchers were then able to isolate two dopa-rich proteins from the cement glands, they report in the June 30 Biochemistry.

The L-dopa forms hydrogen bonds more readily than water and so may displace water molecules that would otherwise block adhesion, Waite says. Also, L-dopa may help form links between protein molecules to harden the cement.