NEW YORK, Jan. 12 (UPI) -- Purdue University scientists claim to have unlocked a key and hitherto secret ingredient of the super-strong glues mussels use to latch onto boats and shores -- iron.
The knowledge of what makes shellfish stick could help keep barnacles off military and commercial ships, as well as prevent hull corrosion, thereby saving perhaps $1 billion a year or more, the investigators predict.
"The Navy alone spent a half-billion dollars in 1990 scraping barnacles off ships, applying new paint and extra fuel from increased drag caused by the barnacles," lead researcher Jonathan Wilker, a Purdue chemist in West Lafayette, Ind., told United Press International. "And that's just the Navy, not counting commercial ships. It's more than just a little curiosity -- it's a big problem."
Because iron plays a major role in how these glues work, it is possible they could be controlled with electronics and find their way into circuitry, Michael Clarke, a program officer and chemistry expert with the National Science Foundation in Arlington, Va., told UPI.
"This research is neat," said Clarke, who did not participate in the effort. "We now understand why these mussel glues work so well. That's probably been a mystery to mankind since boats have been built."
Wilker's interest in marine life glues emerged from scuba diving, where he witnessed reefs and other underwater structures covered in mussels resist even huge waves. Wilker and colleagues have been investigating adhesives from mussels, barnacles, kelp and oysters for four years. All have the uncanny ability to work underwater and stick to nearly anything -- even Teflon.
The researchers started off with the glues of the common blue mussel, Mytilus edulis. Scientists have known for years the animals generated proteins that, when smeared on a surface, link up into a hardened mesh.
"It's been known for a while what the glues are made of, but it's not been known how this cross-linking takes place -- what the reactions are, what the cross-links are, what the reagents that initiate the cross-links are, and what the final cross-linked products look like," Wilker said.
In a paper published in the Jan. 12 issue of the international chemistry journal Angewandte Chemie, Wilker and his team reveal the cross-linking agent that binds the proteins together: iron concentrated from seawater. Virtually all proteins are made from a set of 20 amino acids, but the adhesive proteins contain an unusual amino acid called DOPA, to which iron binds.
When the researchers mixed ingredients making up the glue with various chemicals, "we found iron seemed to work best," Wilker said. "And the iron content of the glues is quite high normally."
Understanding how the marine glues form and bind to surfaces could help develop coatings to prevent barnacles from sticking.
"Current anti-fouling paints rely upon releasing copper into the surrounding waters, thereby killing barnacles in their larval state," Wilker said. "We are hoping our results will help make anti-fouling paints that do not require the release of toxins into the marine environment. If you take some water from the Hudson River, copper levels are through the roof. Environmentally, that's not very satisfying."
Wilker said the glue has another possible use as a corrosion preventer. He said he has been receiving calls from companies -- such as Lord Corp. of Cary, N.C. -- inquiring about the glue's potential as a rustproof coating.
"If you talk to people who put a new piece of metal in seawater, you'll hear it rusts pretty quickly. Apparently when barnacles and mussels stick (to metal underwater), it's still shiny and not rusted underneath when you knock them off," he said. "It sounds like it would be a simple problem, but developing a synthetic polymer to prevent rusting is really tricky, especially if you can't use the chromium you put in stainless steel, which is really toxic and bad for the environment."
The mussel-based adhesives also could be used to develop strong, non-toxic glues to close wounds or surgical incisions. They would be safe to use in the body and work in watery environments.
"You really don't want to be using stitches, which are inherently traumatic, poking holes in the body," Wilker said. He noted ETHICON of Somerville, N.J., a Johnson & Johnson company, markets Dermabond adhesive, which glues skin together but does not work internally. ETHICON licensed Dermabond from its manufacturer, Closure Medical Corp., of Raleigh, N.C.
Improved adhesives could be used in internal surgical applications that involve "quite delicate work, (such as to) glue severed limbs or reconnect nerve trunks," he said.
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Charles Choi covers research for UPI Science News. E-mail [email protected]
