Mussels, adhesive used

Tonegawa et al. (2004) created a cationic polylysine with a tetrapeptide end sequence (glycine-tyrosine-glycine-lysine), which is a motif common to the consensus sequences of mussel adhesive proteins. They then cross-linked this with the anionic polysaccharide, gellan, enzymatically. The polyionic complexation between the cationic peptide and the anionic polysaccharide formed a hybrid fiber at the aqueous solution interface that, when cross-linked, mimicked the byssus gel that marine mussels use to adhere to surfaces, despite the presence of water and salt. 

Chemical modification with dopamine was also used as strength and water-resistance aids for SPI adhesives (Liu et al., 2002). Dopamine is an amino acid with two adjacent phenolic hydroxyl groups, and is the primary component responsible for marine adhesive properties. The Liu modification scheme creates an SPI that is similar to mussel proteins used for surface adhesion. Increased water-resistance compared to other stand-alone SPI adhesives was achieved. Bond strength depends on the phenolic functionality in the synthesized compounds (Liu, 2002). Much interest in this adhesive has developed because it is a strong and resilient adhesive, which is formaldehyde-free, making it suitable for interior wood products. 

Abstract Aqueous biocompatible tribosystems are desirable for a variety of tissue-contacting medical devices. L-3,4-dihydroxyphenylalanine (DOPA) and lysine (K) peptide mimics of mussel adhesive proteins strongly interact with surfaces and may be useful for surface attachment of lubricating polymers in tribosystems. Here, we describe a significant improvement in lubrication properties of poly (dimethylsiloxane) (PDMS) surfaces when modified with PEG-DOPA-K. Surfaces were characterized by optical and atomic force microscopy, contact angle, PM-IRRAS, and X-ray photoelectron spectroscopy. Sudi surfaces, tested over the course of 200 rotations ( 8 m in length), maintained an extremely low friction coefficient (p) (0.03 0.00) compared to bare PDMS (0.98 0.02). These results indicate... 

Figure 2.2 (a) Attachment of mussel to surface (like other mussels or rocks) by using byssal threads (Cha et al., 2008). (h) Scheme representing stmctures and proteins involved in mussel adhesion (Cha et al., 2008). (c) Mechanism of l-DOPA—mediated adhesion in mussels. The reduced DOPA hinds directly to surface resulting in adhesion (left). Cohesion is obtained by metal ion templating and oxidation chemistry (right) (Wilker, 2011). 

The sequence of oxidation steps which converts the mussel adhesive protein to underwater glue was investigated using model peptides. The three-dimensional structure of the protein was derived from the decapeptide sequence with the help of computer modeling studies. The oxidation chemistries were then applied to the three-dimensional protein structure to develop a mechanistic picture, at the molecular level, showing how the mussel attaches itself to solid surfaces. 

In addition to its ability to perform in an aggressive aqueous environment, the mussel adhesive protein is also attractive because it is nontoxic, durable and biocompatible. For these reasons, it will find extensive use in medical applications like wound closures, bone and dental repair and tissue bonding, which will eliminate the use of sutures during surgery. 

The chemical reactions discussed above are not by themselves sufficient to develop a mechanistic scheme for underwater glue formation unless they are reviewed in the context of the three-dimensional structure of the mussel adhesive protein. The structure of this protein however is not available. We therefore decided to derive its three-dimensional structure from the consensus decapeptide sequence in an incremental fashion using computer modeling and chemical intuition. It is well-known that the primary amino acid sequence determines the structure of a protein. However, predicting three-dimensional structures from an amino acid sequence is a risky venture unless there are experimental guide posts that support or reject the predicted structures. 

Toohey KS, Sottos NR, Lewis JA, Moore 1, White SR (2007) Self-healing materials with microvascular networks. Nat Mater 6 581-585 Vreeland V (2002) Recombinant minimal catalytic vanadium haloperoxidases and their uses. International patent no WO 02/00838 A2, 3 Jan Waite JH, Anderson NH, Jewhurst S, Sun C (2005) Mussel adhesion finding the tricks worth mimicking. JAdhes 81 1-21... 

A challenge with any of these is the ability to obtain sufficient for commercial use. These materials are usually made by the organism in very small quantities and harvesting in bulk would be difficult. Preferred approaches are therefore either to identify the essential active molecules and synthesize these (as with mussel adhesion) or to find a way of producing these by using genetic engineering processes. 

Figure 13.12. Using synthetic polymer mimics of mussel adhesives to bond together two strips of wet pig skin (left) and a cow tooth to aluminum (right). You can see the polymeric adhesive between the skin strips as well as between the tooth and metal.

The polyphenolic adhesive protein of the mussel Mytilus edulis is an unusual protein composed mainly of repetitive decapeptide and hexapeptide sequences. In the mussel, the protein is first produced in a precursor form and is converted to an adhesive by post-translation-al modification. To develop an efficient renewable resource for production of the polyphenolic protein, we have used genetic engineering technology. cDNA sequences encoding portions of the polyphenolic protein were identified and expressed in the yeast Saccharomyces cerevisiae. 

The cheiuical iugredieut used by mussels to auchor themselves to rocks is discovered, aud used to synthesize a waterproof adhesive Molecular-based logic gates are demoustrated to work better thau siUcou-based gates - au important precedent in the development of a molecular computer... 

Tyrosinase was reported to hydroxylate and oxidize tyrosine residues in proteins1231, which is important in the production of moisture-resistant adhesives. In fact, tyrosinase has been used for the production of synthetic glues with similar compositions to those of naturally occurring adhesives such as mussel glue1241. 

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