The tube cement of Phragmatopoma californica: a solid foam

Abstract

SUMMARY Phragmatopoma californica is a marine polychaete that builds protective tubes by joining bits of shell and sand grains with a secreted proteinaceous cement. The cement forms a solid foam (closed cells) via covalent crosslinking, as revealed by electron and laser scanning confocal microscopy. The cement contains extractable calcium and magnesium,and non-extractable phosphorus. Amino acid analysis demonstrated that the phosphorus is in the form of phosphoserine and that >90% of serine in the cement (i.e. 28 mol% of residues) is phosphorylated. In addition to previously identified basic proteins, the cement contains a highly acidic polyphosphoserine protein as a major component. We propose a model for the structure and bonding mechanism of the cement that has the following major features: (1) within the secretory pathway of cement gland cells, the electrostatic association of the oppositely charged proteins and divalent cations (Ca2+ and Mg2+) condense the cement proteins into dehydrated secretory granules; (2) the condensation of the cement leads to the separation of the solution into two aqueous phases (complex coacervation) that creates the closed cell foam structure of the cement; (3)rehydration of the condensed cement granules after deposition onto tube particles contributes to the displacement of water from the mineral substrate to facilitate underwater adhesion; and (4) after secretion, covalent cross-linking through oxidative coupling of DOPA gradually solidifies the continuous phase of the cement to set the porous structure.

Tick attachment cement – reviewing the mysteries of a biological skin plug system

“…The cementing material, which adheres sand and shell fragments together, is produced in bilateral glands and secreted from a special organ (Jensen & Morse, 1988). The cement bonds and the whole tubular construction must be strong and stable to withstand the turbulent, high‐energy environment of the intertidal zone (Stewart et al ., 2004). After secretion, the cement appears creamy white or light tan and turns reddish to dark brown as it ages (Jensen & Morse, 1988; Stewart et al ., 2004).…”

“…The cement bonds and the whole tubular construction must be strong and stable to withstand the turbulent, high‐energy environment of the intertidal zone (Stewart et al ., 2004). After secretion, the cement appears creamy white or light tan and turns reddish to dark brown as it ages (Jensen & Morse, 1988; Stewart et al ., 2004). It sets in only 30 s, but takes several hours to cure into a solid foam (Stevens et al ., 2007).…”

“…It sets in only 30 s, but takes several hours to cure into a solid foam (Stevens et al ., 2007). The adhesive material is largely proteinaceous containing 59.5% of total amino acid residues as short‐chain amino acids (alanine, glycine, serine) and 2.6% DOPA which is thought to act as a cross‐linker, stabilizing (tanning) the cement (Jensen & Morse, 1988; Stewart et al ., 2004; Stevens et al ., 2007). In addition, the cement also contains considerable amounts of phosphorus, calcium, magnesium and sulfur (Stewart et al ., 2004; Sun et al ., 2007; Wang & Stewart, 2013).…”

“…The adhesive material is largely proteinaceous containing 59.5% of total amino acid residues as short‐chain amino acids (alanine, glycine, serine) and 2.6% DOPA which is thought to act as a cross‐linker, stabilizing (tanning) the cement (Jensen & Morse, 1988; Stewart et al ., 2004; Stevens et al ., 2007). In addition, the cement also contains considerable amounts of phosphorus, calcium, magnesium and sulfur (Stewart et al ., 2004; Sun et al ., 2007; Wang & Stewart, 2013). Several charged polyelectrolytic proteins are present mainly composed of glycine, lysine, tyrosine (mostly as DOPA) and (phospho)‐serine (Waite, Jensen & Morse, 1992; Zhao et al ., 2005; Endrizzi & Stewart, 2009).…”

Acorn Barnacles Secrete Phase‐Separating Fluid to Clear Surfaces Ahead of Cement Deposition

“…Hydroxylation (e.g., tyrosine to DOPA) and phosphorylation (e.g., serine to phosphoserine) are post‐translational modifications commonly used by marine organisms to modify the adhesive properties of their cement proteins 7, 8, 27, 28, 29. As previously mentioned, barnacle cement does not contain DOPA;10, 11, 12 however, Gohad et al and Dickinson et al demonstrated that cyprid cement and the barnacle cementing apparatus are phosphorylated, respectively 14, 30.…”