Biochemical analyses of the cement float of the goose barnacle Dosima fascicularis – a preliminary study

Abstract

The goose barnacle Dosima fascicularis produces an excessive amount of adhesive (cement), which has a double function, being used for attachment to various substrata and also as a float (buoy). This paper focuses on the chemical composition of the cement, which has a water content of 92%. Scanning electron microscopy with EDX was used to measure the organic elements C, O and N in the foam-like cement. Vibrational spectroscopy (FTIR, Raman) provided further information about the overall secondary structure, which tended towards a β-sheet. Disulphide bonds could not be detected by Raman spectroscopy. The cystine, methionine, histidine and tryptophan contents were each below 1% in the cement. Analyses of the cement revealed a protein content of 84% and a total carbohydrate content of 1.5% in the dry cement. The amino acid composition, 1D/2D-PAGE and MS/MS sequence analysis revealed a de novo set of peptides/proteins with low homologies with other proteins such as the barnacle cement proteins, largely with an acidic pI between 3.5 and 6.0. The biochemical composition of the cement of D. fascicularis is similar to that of other barnacles, but it shows interesting variations.

Keywords:

• barnacle adhesive/cement
• 1D/2D PAGE
• FTIR/Raman spectroscopy
• protein primary/secondary structure
• hydrogel
• carbohydrate

Acknowledgements

The authors thank Cornelius Luetz and Stuart Fegan for critically reading the manuscript. They also thank Sascha Thies, Paul Hagedorn und Thomas Montforts for their help with the protein and peptide analyses and helpful discussions. They are grateful to Dr Patrick Flammang who provided histological sections of Sabellaria alveolata as positive controls in the L-DOPA test. The authors would also like to thank the anonymous reviewers for their constructive and helpful comments. This research was carried out with the financial support of the Austrian Science Fund (FWF) [P21767-B17 to Waltraud Klepal] and of the Fraunhofer-Gesellschaft zur Foerderung der angewandten Forschung e.V., Germany. A scholarship was granted to Vanessa Zheden from the German Academic Exchange Service (DAAD). This work was also supported by COST action TD0906 ‘Biological Adhesives: from Biology to Biomimetics’.