Single Adhesive Nanofibers from a Live Diatom Have the Signature Fingerprint of Modular Proteins

• Published in: Biophysical journal Vol. 89; no. 6; pp. 4252 - 4260
• Main Authors: Dugdale, T.M., Dagastine, R., Chiovitti, A., Mulvaney, P., Wetherbee, R.
• Format: Journal Article
• Language: English
• Published: United States Elsevier Inc 01.12.2005; Biophysical Society
• Subjects: Adhesiveness; Algal Proteins - chemistry; Algal Proteins - ultrastructure; Atoms & subatomic particles; Bacillariophyceae; Cell adhesion & migration; Cell Adhesion Molecules - chemistry; Cell Adhesion Molecules - ultrastructure; Cells, Cultured; Chemicals; Computer Simulation; Diatoms - enzymology; Elasticity; Enzyme Activation; Mechanical properties; Microscopy; Models, Chemical; Models, Molecular; Nanostructures - chemistry; Nanostructures - ultrastructure; Particle Size; Peptide Mapping; Physical properties; Plankton; Protein Conformation; Proteins; Scientific apparatus & instruments; Spectroscopy, Imaging, Other Techniques; Tensile Strength
• ISSN: 0006-3495; 1542-0086
• DOI: 10.1529/biophysj.105.062489

The adhesive and mechanical properties of a cell-substratum adhesive secreted by live diatom cells were examined in situ using atomic force microscopy. The resulting force curves have a regular saw-tooth pattern, the characteristic fingerprint of modular proteins, and when bridged between tip and surface can repeatedly be stretched and relaxed resulting in precisely overlaying saw-tooth curves (up to ∼600 successive cycles). The average rupture force of the peaks is 0.794 ± 0.007 (mean ± SE) nN at a loading rate of 0.8 μm/s and the average persistence length is 0.026 ± <0.001 (mean ± SE) nm (fit using the worm-like chain model). We propose that we are pulling on single adhesive nanofibers, each a cohesive unit composed of a set number of modular proteins aligned in register. Furthermore, we can observe and differentiate when up to three adhesive nanofibers are pulled based upon multimodal distributions of force and persistence length. The high force required for bond rupture, high extensibility (∼1.2 μm), and the accurate and rapid refolding upon relaxation, together provide strong and flexible properties ideally suited for the cell-substratum adhesion of this fouling diatom and allow us to understand the mechanism responsible for the strength of adhesion.