Barnacles are a class of marine crustaceans with an external shell (there are over 1,200 different species). The creatures attach permanently to a surface and feeds by filtering particles from the water using its modified feathery legs. When barnacles attach to boats, they affect flow resistance. In turn this leads to worse fuel consumption and the performance of the boat is adversely affected.
Barnacles have two nektonic (active swimming) larval stages. Once the larvae find a surface that is suitable they enter a permanent attachment (what is referred to as the sessile or nonmotile state).
When barnacles come into contact with the hull of a ship, the larvae of the barnacle leave tiny traces of proteins. These are extruded in order to test if the ship surface is attractive for long-term attachment. If the indication is positive, barnacles attach. If the signal is negative, then surface attachment does not occur. Researchers think that by knowing more about this attachment mechanism signals can be produced that deter barnacles from adhering to the hulls of boats.
The research is geared around the measurement of different surfaces and coatings to determine the likelihood of attachment. Measurements are undertaken using modified Atomic Force Microscopy. With this, a tiny ball is glued to the cantilever of the microscope and the extent of protein molecule attraction can be assessed.
What researchers are most interested in is the iso-electric point. This is defined as the pH-value at which the protein has net zero electric charge. The optimal threshold determines whether or not protein will be attracted to a given surface. Understanding this allows different surfaces to be assessed and predictions made as to whether protein will be attracted or repelled.
To date, tests have been conducted, at A*STAR in Singapore, on different proteins including fibrinogen, myoglobine and bovine albumin. These are proteins associated with barnacle attraction. The data gathered will allow researchers to select the appropriate the paint that is used on a ship hull.
The research findings have been published in the journal Nature Nanotechnology. The research paper is titled “Measuring protein isoelectric points by AFM-based force spectroscopy using trace amounts of sample.”
