Barnacle cement: a polymerization model based on evolutionary concepts.
Date
2009-11
Author
Advisors
Rittschof, Daniel
Forward, Richard
Barber, Richard
McClellan-Green, Patricia
Holm, Eric
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Abstract
The tenacity by which barnacles adhere has sparked a long history of scientific investigation
into their adhesive mechanisms. To adhere, barnacles utilize proteinaceous cement
that rapidly polymerizes and forms adhesive bonds underwater, and is insoluble once
polymerized. Although progress has been made towards understanding the chemical properties
of cement proteins, the biochemical mechanisms of cement polymerization remain largely
unknown. In this dissertation, I used evolutionary concepts to elucidate barnacle
cement polymerization. Well-studied biological phenomena (blood coagulation in vertebrates
and invertebrates) were used as models to generate hypotheses on proteins/biochemical
mechanisms involved in cement polymerization. These model systems are under similar
selective pressures to cement polymerization (life or death situations) and show similar
chemical characteristics (soluble protein that quickly/efficiently coagulates). I
describe a novel method for collection of unpolymerized cement. Multiple, independent
techniques (AFM, FTIR, chemical staining for peroxidase and tandem mass spectroscopy)
support the validity of the collection technique. Identification of a large number
of proteins besides ‘barnacle cement proteins’ with mass spectrometry, andobservations
of hemocytes in unpolymerized cement inspired the hypothesis that barnacle cement
is hemolymph. A striking biochemical resemblance was shown between barnacle cement
polymerization and vertebrate blood coagulation. Clotted fibrin and polymerized cement
were shown to be structurally similar (mesh of fibrous protein) but biochemically
distinct. Heparin, trypsin inhibitor and Ca2+ chelators impeded cement polymerization,
suggesting trypsin and Ca2+ involvement in polymerization. The presence/activity of
a cement trypsin-like serine protease was verified and shown homologous to bovine
pancreatic trypsin. Protease activity may activate cement structural precursors, allowing
loose assembly with other structural proteins and surface rearrangement. Tandem mass
spectrometry and Western blotting revealed a homologous protein to human coagulation
factor XIII (fibrin stabilizing factor: transglutaminase that covalently cross-links
fibrin monomers). Transglutaminase activity was verified and may covalently cross-link
assembled cement monomers.
Similar to other protein coagulation systems, heritable defects occur during cement
polymerization. High plasma protein concentration combined with sub-optimal enzyme,
and/or cofactor concentrations and sub-optimal physical/muscular parameters (associated
with hemolymph release) results in improperly cured cement in certain individuals
when polymerization occurs in contact with low surface energy silicone and its associated
leached molecules.
Type
DissertationDepartment
EcologySubject
Amino Acid SequenceAnimals
Biological Evolution
Calcium
Cattle
Humans
Microscopy, Atomic Force
Models, Biological
Molecular Sequence Data
Polymers
Proteins
Tandem Mass Spectrometry
Thoracica
Transglutaminases
Trypsin
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https://hdl.handle.net/10161/653Citation
Dickinson, Gary H. (2009). Barnacle cement: a polymerization model based on evolutionary concepts. Dissertation, Duke University. Retrieved from https://hdl.handle.net/10161/653.Collections
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