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Figure 6.1: A burst E. gracilis cell. The pellicle is torn apart and due to the inner pressure of the cell the cytoplasm including cell organelles is ejected. If the cell has not been fixated, enzymatic activity starts to dissolve tissue, making AFM investigation even more difficult. Intermittent contact mode AFM image, Amplitude trace. successful imaging. The proper balance is required for the residue to support the cell enough against bursting but not to cover it. Much better results were achieved following the steps from section 5.3.2, Fig. 5.7 (on page 75) to avoid too much and too little embedding of the cells. In Fig. 6.3 the basal part of a well embedded E. gracilis cell is shown. The material embedding the cell alters its surface roughness around 5 µm away from the cell. Such samples proved to be exellent for AFM imaging, especially in intermittent contact mode under ambient conditions and could well be used for for several days. It was assumed that scanning under liquid, because of the absence of a water meniscus between tip and sample (see section 3.2.1, page 27, could enhance image resolution but was found to pose another range of difficulties. Algal cells do hardly attach to even functionalized (e.g. poly-l-lysine or gelatin coated) glass supports, and a stable positioning of the scanned surface was not reached. The imprint in Fig. 6.4 was left by a E. gracilis cell that detached from a poly-l-lysine coated glass slide in liquid. The negative forms of the algal pellicular strips in the substrate surface can be well seen. A comparison of cell length usually measuring more than 40 − 80 µm and imprint length around 6 µm indicates a relatively small area of contact. A stable imaging surface however is a prerequisite for reproducible high resolution AFM imaging. 78
Figure 6.2: An embedded E. gracilis cell covered with remains of the nutrient solution after the drying process. The cell surface is not well suited for imaging with AFM. Intermittent contact mode AFM image, Amplitude trace. Sample stability is an important challenge when scanning under liquid. In general, cells are high structures (several micrometers) and this greatly reduces stability for the AFM scan as the scanned pellicle surface is far from the pellicle part attached to the substrate. The algal cell seen in Fig. 6.5 could not be imaged with satisfactory results. Its surface did not maintain a stable position during the scan, such that the AFM imaging resulted in a slightly blurred image. Additionally the cantilever images itself as its pyramidal shaped sides touch the cell long before being exactly above it. 79
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DIPLOMARBEIT Atomic Force Microscop
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»Later I have been asked many time
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Contents Abstract 4 1 Introduction
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5.2.1 Optical Microscopy and Fluore
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theory (see e.g. [1]). Now I call o
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understand phenomena at a larger sc
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of whole dried Euglena cells in air
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these assembly functions for us. 2
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Figure 2.2: Rise in public spending
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The presented three types of nanote
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2.4.1 Self-Assembly and Emergent St
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After diligent investigation such s
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1 µN) between a probe and the samp
Page 27 and 28: 3.2.1 Static Mode In Static Mode (a
Page 29 and 30: crystal and the cantilever tip (pha
Page 31 and 32: Figure 3.6: Highly ordered and fres
Page 33 and 34: Figure 3.8: Schematic drawing of th
Page 35 and 36: Figure 3.11: The cantilever deflect
Page 37 and 38: Figure 3.14: This force curve shows
Page 39 and 40: Figure 4.1: A group of Euglena orga
Page 41 and 42: several species with rigid pellicle
Page 43 and 44: Figure 4.2: The rightmost cell can
Page 45 and 46: cavity and is used for regulatory f
Page 47 and 48: as phobic reactions, because the ce
Page 49 and 50: Figure 4.7: Scheme of the photorece
Page 51 and 52: Figure 4.9: Measured monoclinic uni
Page 53 and 54: Figure 4.11: Twice the same Euglena
Page 55 and 56: 4.15), their ends are termed the (-
Page 57 and 58: Figure 4.15: Kinesin and dynein and
Page 59 and 60: Figure 4.17: (Image reproduced from
Page 61 and 62: into fully functional chloroplasts
Page 63 and 64: Figure 4.19: How a microtubule-kine
Page 65 and 66: Chapter 5 Materials and Methods The
Page 67 and 68: Cell Treatment - Demembranation In
Page 69 and 70: Figure 5.3: This image shows cells
Page 71 and 72: Figure 5.4: The AFM setup at the In
Page 73 and 74: Figure 5.6: If the user menu AFM_TU
Page 75 and 76: Figure 5.7: Single steps of the sam
Page 77: Chapter 6 Results High resolution t
Page 81 and 82: Figure 6.5: Scanning under liquid s
Page 83 and 84: Flagellum The flagellum of an E. gr
Page 85 and 86: Pellicle The pellicle of E. gracili
Page 87 and 88: Figure 6.11: The pellicle of an E.
Page 89 and 90: Crystalline Cell Parts Crystalline
Page 91 and 92: Figure 6.18: A layered structure th
Page 93 and 94: It might also be possible that comb
Page 95 and 96: Appendix A Acronyms SPM Scanning Pr
Page 97 and 98: [13] A. Junk, F. Riess: From an ide
Page 99 and 100: [45] J. Ruan, B. Bhushan: Atomic-sc
Page 101 and 102: [70] M. Rief, M. Gautel, F. Oesterh
Page 103 and 104: [97] P. Gualtieri, L. Barsanti: Alg
Page 105 and 106: Annex 1 This Igor script was used i
Page 107 and 108: w[i][j][laynr]=(w[i][j][3]-used_off
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