THE ROLE OF ATOMIC FORCE MICROSCOPY IN ADVANCING DIATOM RESEARCH INTO THE NANOTECHNOLOGY ERA - Life at the Nanoscale: Atomic Force Microscopy of Live Cells - page 410

supramolecular assemblies of different nanoibres (ANFs I, II, II), each with
their own modular properties, and aligned domains which can all unfold -

refold in registry and (3) they have an additional lexible polymer region
and adhesive motif to enable the ANF to extend beyond the cell surface and
adhere to surfaces. Energy dispersive X-ray analysis and Fourier transform
infrared spectroscopy showed that the adhesive contained mainly protein,
carbohydrate, sulphate, calcium and magnesium. 29 Further analysis of soluble
EDTA extracts suggested that the ANFs composed sulphated high-molecular-
mass glycoproteins cross-linked by calcium and magnesium ions. The cross-
linking was proposed to enable domains of the adjacent protein backbones
to unbind and refold in register. Although the exact modular structure of the
ANFs was unknown, the force proile had the characteristic ingerprint of
a true modular protein such as the muscle protein titin. Synthesis of a titin
assembly consisting of several modular constructs in parallel was proven
to unfold in registry, further supporting the proposed ANF supramolecular
modular mechanism.

30

References

1. Hoagland, K. D., Rosowski, J. R., Gretz, M. R., and Roemer, S. C. (1993) Diatom

extracellular polymeric substances: function, ine structure, chemistry and
physiology, J. Phycol. , 29 , 537-566.

2. Pickett-Heaps, J. D., Schmid, A. M., and Edgar, L. A. (1990) The cell biology of the

diatom valve formation, Prog. Phycol. Res ., 7 , 1-168.

3. Wetherbee, R., Lind, J. L., Burke, J., and Quatrano, R. S. (1998) The irst kiss:

establishment and control of initial adhesion by raphid diatoms, J. Phycol. , 34 ,

9-15.

4. Hildebrand, M. (2008) Diatoms, biomineralization processes, and genomics,

Chem. Rev. , 108 , 4855-4874.

5. Hamm, C. E., Merkel, R., Springer, O., Jurkojc, P., Maier, C., Prechtel, K., and

Smetacek, V. (2003) Architecture and material properties of diatom shells
provide effective mechanical protection,

Nature , 421 , 841-843.

6. Nelson, D. M., Tréguer, P., Brzezinski, M. A., and Leynaert, A. (1995) Production

and dissolution of biogenic silica in the ocean: revised global estimates,
comparison with regional data and relationship to biogenic sedimentation,
Global Biogeochem. Cycles , 9 , 359-372.

7. Falkowski, P. G., and Oliver, M. J. (2007) Mix and match: how climate selects

phytoplankton, Nat. Rev. Microbiol. , 5 , 813-819.

8. Sterrenburg, F. A. S. (2005) Crystal palaces—diatoms for engineers, J. Nanosci.

Nanotechnol. , 5 , 100-107.