Biophysics of green algae: Euglena gracilis investigated by atomic force microscopy

C. Gruenberger, R. Ritter, I.C. Gebeshuber

Institut fuer Allgemeine Physik, Vienna University of Technology, Wien, AustriaAustrian Center of Competence for Tribology AC2T, Wiener Neustadt, Austria

http://www.ille.com

Overview

• Some properties of biological materials• Motivation to study algae• Introduction to Euglena gracilis• AFM of whole cells• AFM of cell organelles• Conclusions• Outlook (algae, biomaterials)

Properties of biological material• The hydrodynamic, aerodynamic, wetting and

adhesive properties of natural materials are remarkable.

• The results of evolution often converge on limited constituents or principles.

• For example, the same material component will be found just slightly but effectively varied to obey different functions in the same organism (e.g. collagen occurs in bones, skin, tendons and the cornea).

Properties of biological material

• One smart feature of natural materials concerns their beautiful organization in which structure and function are optimized at different length scales.

• Natural systems also show a high level of integration: miniaturization whose object is to accommodate a maximum of elementary functions in a small volume, hybridization between inorganic and organic components optimizing complementary possibilities and functions and hierarchy.

Properties of biological material

• Some biomolecules such as amino acids and thereby also proteins are defined in their structure down to the atomic level. They are materials built with molecular precision.

• In principle, each and every cell, plant, animal and person can be called a nanotechnological wonder.

• Nowadays, materials scientists have just started to make man-made materials of such precision.

Motivation for studying algae

• interesting material properties of E. gracilis• many TEM and SEM and optical microscopy

images available, AFM only sparsely (yields information not only on topography but also mechanical properties)

• AFM of photoreceptor ultimate goal

Introduction to E. gracilis

• green alga, length 20m-100m• single celled organism• typical model organism for plant researchers and

simple animal researchers• high pressure

resistant natural containers (200 bar)

Flagellar swelling:Euglena gracilis photoreceptor

• photoreceptor with single photon sensitivity at room temperature

• simple two state photocycle promising building block in biocomputers

Scale bar 100nm, © CNR Pisa

AFM of whole cells

AFM of whole cells

flagellum

reservoir

paramylon grain

Euglena pellicle

SEM© http://www.biol.tsukuba.ac.jp/~inouye/ino/e

TEM© Peter v. Sengbusch

• mechanical stability • flexible • interlocking ridges • slide against each other• biogenic lubricants

AFM of whole cells

© Barsanti et al., 1993, Vision Res. 33(15), 2043-2050

AFM of cell organelles:paramylon grain

AFM tapping mode, 2.5m*2.5m, height scale 353nm

AFM of cell organelles:crystalline lipid body

Conclusion

• development of preparation method • AFM of cell walls • AFM of mucus excretion pellicle pores• AFM of new surface features • AFM of crystalline cell organelles

Outlook I: Towards AFM of the photoreceptor

• The soluton of crystalline parts contains only few photoreceptors.

• Lipid bodies, paramylon grains and not completely dissolved cell tissue amount for a large portion of the solution.

• Combination with fluorescence microscopy is needed.

Outlook II: Biomaterials in material science

• Relating structure to function in biomaterials can only be the beginning of promising developments.

• The thermal and hydrolytic sensitivities of biological materials limit their applicability in many important synthetic materials applications.

• A real breakthrough requires an understanding of the basic building principles of living organisms and a study of the chemical and physical properties at the interfaces, to control the form, size and compaction of objects.