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First published online December 3, 2004
Journal of Experimental Biology 207, 4727-4734 (2004)
Published by The Company of Biologists 2004
doi: 10.1242/jeb.01330

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The tube cement of Phragmatopoma californica: a solid foam

Russell J. Stewart¹, James C. Weaver², Daniel E. Morse³ and J. Herbert Waite^3,*

¹ Department of Bioengineering, University of Utah, Salt Lake City, UT 84112
² Institute for Collaborative Biotechnologies and the Materials Research Laboratory, University of California, Santa Barbara, CA 93106, USA
³ Marine Science Institute and MCDB Department, University of California, Santa Barbara, CA 93106, USA

View larger version (78K): [in a new window]   Fig. 1. Representative SEM micrographs of cement disks on 0.5 mm glass beads removed from a reconstructed P. californica tube. (A) Intact cement disks on beads separated from a section of reconstructed tube in a hydrated state. Scale bar, 100 µm. (B,C) Fractured cement disks on beads separated after lyophilization. Scale bars, 10 µm.

View larger version (69K): [in a new window]   Fig. 2. Representative optical cross-sections through three separate intact cement disks in seawater by laser scanning confocal microscopy. The cement was visualized by auto-fluorescence. (A) Overlay of images acquired with FITC and Cy5 filter sets, (B,C) overlay of images acquired with FITC, Cy3 and Cy5 filter sets; excitation 488, 543 and 633 nm, emission filters 505-525, 560-600, and >600 nm. Scale bars, 10 µm.

View larger version (15K): [in a new window]   Fig. 3. Representative EDS spectra. (A) From a glue disk washed in de-ionized water (open curve). From a bare region of the same bead adjacent to the glue disk (grey-filled peaks). (B) From a glue disk washed with 0.5 mol l-1 NaEDTA, pH 8.0 (open peaks). Bare surface of silica bead (grey-filled peaks). keV, kiloelectron volts.

View larger version (93K): [in a new window]   Fig. 4. SEM and EDS spatial maps of a glue disk washed with de-ionized water. Scale bar, 25 µm.

View larger version (90K): [in a new window]   Fig. 5. SEM and EDS spatial maps of a glue disk washed with 0.5 mol l-1 NaEDTA. Scale bar, 50 µm.

View larger version (20K): [in a new window]   Fig. 6. Amino acid chromatograms from acid hydrolysis time course. (A) 3 h, (B) 28 h. Loss of pSer (3.2 min) is accompanied by gain of Ser (13.2 min).

View larger version (8K): [in a new window]   Fig. 7. pSer fraction (pSer/Ser+pSer) during cement acid hydrolysis time course.

View larger version (27K): [in a new window]   Fig. 8. Complex coacervation model of foam cement formation. (A) Macroanion (red) and macrocation (blue), pH 5. Mg2+ and Ca2+ are pumped in to neutralize excess polyanion charges. (B) Neutralization leads to phase separation of the coacervate (CO) from the equilibrium solution (E). CO is an enriched blend of anion, cation and Mg2+. Both phases are fluid although CO is viscous. (C) As volume of CO phase increases and CO desolvation proceeds, more vacuoles of E form within CO instead of diffusing to E phase. (D) Upon secretion into seawater at pH 8, electrostatic interaction of Mg2+ and Ca2+ with phosphate groups becomes ionic due to low solubility, increasing the viscosity of CO. (E) Oxidation of Dopa to quinones leads to cement solidification by cross-linking.