| 1. |
- Almqvist, Nils, et al.
(författare)
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Methods for fabricating and characterizing a new generation of biomimetic materials
- 1999
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Ingår i: Materials science & engineering. C, biomimetic materials, sensors and systems. - 0928-4931 .- 1873-0191. ; 7:1, s. 37-43
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Tidskriftsartikel (refereegranskat)abstract
- Bringing together current ideas in the fields of biomineralization and composite laminate materials, we have attempted to fabricate model materials that mimic abalone nacre through the rapid assembly of inorganic tablets, such as talc. Several physical methods were tested to aid the orientation of the talc tablets in fluid suspensions with a low percentage, 10% by dry weight, of organic binding material. The orientation of talc tablets in the synthesized composites was characterized by X-ray diffraction and scanning electron microscopy. The modulus of rupture of the materials was measured in a three-point bending test. We demonstrate that the alignment of tablets increases by the use of physical methods and from chemical surface treatment. Important factors to consider in making materials that mimic abalone nacre are discussed. Important factors to consider in making materials that mimic abalone nacre are discussed.
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| 2. |
- Schitter, Georg, et al.
(författare)
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Design and Modeling of a High-Speed AFM-Scanner
- 2007
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Ingår i: IEEE Transactions on Control Systems Technology. - 1558-0865. ; 15:5, s. 906-915
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Tidskriftsartikel (refereegranskat)abstract
- A new mechanical scanner design for a high-speed atomic force microscope (AFM) is presented and discussed in terms of modeling and control. The positioning range of this scanner is 13 mum in the X- and Y-directions and 4.3 mum in the vertical direction. The lowest resonance frequency of this scanner is above 22 kHz. This paper is focused on the vertical direction of the scanner, being the crucial axis of motion with the highest precision and bandwidth requirements for gentle imaging with the AFM. A second- and a fourth-order mathematical model of the scanner are derived that allow new insights into important design parameters. Proportional-integral (Pl)-feedback control of the high-speed scanner is discussed and the performance of the new AFM is demonstrated by imaging a calibration grating and a biological sample at 8 frames/s.
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| 3. |
- Schäffer, Tilman E, et al.
(författare)
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Does abalone nacre form by heteroepitaxial nucleation or by growth through mineral bridges?
- 1997
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Ingår i: Chemistry of Materials. - : American Chemical Society (ACS). - 0897-4756 .- 1520-5002. ; 9:8, s. 1731-1740
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Tidskriftsartikel (refereegranskat)abstract
- We present experimental support for a model of abalone nacre growth that is based on mineral bridges between successive aragonite tablets rather than on heteroepitaxial nucleation. Interlamellar sheets of organic polymers delineate the aragonite tablets but allow the tablets to grow mineral bridges through pores in the sheets. Atomic force microscope images of interlamellar organic sheets from flat pearls made by Haliotis rufescens (red abalone; marine gastropod mollusk) reveal a fibrous core and holes of 5-50 nm in diameter. Scanning ion conductance microscopy shows that these holes are actually pores through the interlamellar sheets. With the help of statistical analysis we can associate the pore-to-pore spacings in the interlamellar sheets with the observed offsets of successive nacre tablets. These results, supplemented by AFM, SEM, and TEM images, support and extend the model of biofabrication of gastropod nacre which is based on mineral bridges between the aragonite tablets.
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| 4. |
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| 5. |
- Thomson, Neil H., et al.
(författare)
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Oriented, active Escherichia coli RNA polymerase : an atomic force microscope study
- 1999
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Ingår i: Biophysical Journal. - 0006-3495 .- 1542-0086. ; 76:2, s. 1024-1033
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Tidskriftsartikel (refereegranskat)abstract
- RNA polymerase (RNAP) molecules to be imaged under aqueous buffer using tapping-mode atomic force microscopy (AFM). Recombinant RNAP molecules containing histidine tags (hisRNAP) on the C-terminus were specifically immobilized on ultraflat gold via a mixed monolayer of two different Ω-functionalized alkanethiols. One alkanethiol was terminated in an ethylene-glycol (EG) group, which resists protein adsorption, and the other was terminated in an N-nitrilotriacetic acid (NTA) group, which binds the histidine tag through two coordination sites with a nickel ion. AFM images showed that these two alkanethiols phase-segregate. Specific binding of the hisRNAP molecules was followed in situ by injecting proteins directly into the AFM fluid cell. The activity of the hisRNAP bound to the NTA groups was confirmed with a 42-base circular single-stranded DNA template (rolling circle), which the RNAP uses to produce huge RNA transcripts. These transcripts were imaged in air after the samples were rinsed and dried, since RNA also has low affinity for the EG-thiol and cannot be imaged under the buffers we used.
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