Category: News

Adhesion strategies of Dictyostelium discoideum – a force spectroscopy study

“Motile cells require reversible adhesion to solid surfaces to accomplish force transmission upon locomotion. In contrast to mammalian cells, Dictyostelium discoideum ( a soil dwelling amoeba) cells do not express integrins forming focal adhesions but are believed to rely on more generic interaction forces that guarantee a larger flexibility; even the ability to swim has been described for Dictyostelium discoideum (D.d.).”*

In order to understand the origin of D.d. adhesion, Nadine Kamprad, Hannes Witt, Marcel Schröder, Christian Titus Kreis, Oliver Bäumchen, Andreas Janshoff and Marco Tarantola  describe in their publication “Adhesion strategies of Dictyostelium discoideum – a force spectroscopy study”* how they realized and modified a variety of conditions for the amoeba comprising the absence and presence of the specific adhesion protein Substrate Adhesion A (sadA), glycolytic degradation, ionic strength, surface hydrophobicity and strength of van der Waals interactions by generating tailored model substrates. By employing AFM-based single cell force spectroscopy (using NanoWorld Arrow-TL2 tipless cantilevers) they could show that experimental force curves upon retraction exhibit two regimes described in detail in the article cited above. The study describes a versatile mechanism that allows the cells to adhere to a large variety of natural surfaces under various conditions.

Fig. 2 A from "Adhesion strategies of Dictyostelium discoideum – a force spectroscopy study": Cell parametrization: β, angle between the normal on the cell membrane and the cell axis; R1, contact radius between the cell and substrate; R0, equatorial cell radius; R2, contact radius between the cell and cantilever, ϕ1 contact angle towards the substrate; ϕ2, contact angle between the cell and cantilever, in the background is a section of the confocal image in B. B: morphology of the carA-1-GFP labelled D.d. cell attached to the cantilever subjected to a pulling force of 0.2 nN. NanoWorld Arrow-TL2 tipless cantilevers were used.
Fig. 2 A from “Adhesion strategies of Dictyostelium discoideum – a force spectroscopy study” by N. Kamprad et al.: Cell parametrization: β, angle between the normal on the cell membrane and the cell axis; R1, contact radius between the cell and substrate; R0, equatorial cell radius; R2, contact radius between the cell and cantilever, ϕ1 contact angle towards the substrate; ϕ2, contact angle between the cell and cantilever, in the background is a section of the confocal image in B. B: morphology of the carA-1-GFP labelled D.d. cell attached to the cantilever subjected to a pulling force of 0.2 nN.

*Nadine Kamprad, Hannes Witt, Marcel Schröder, Christian Titus Kreis, Oliver Bäumchen, Andreas Janshoff, Marco Tarantola
Adhesion strategies of Dictyostelium discoideum – a force spectroscopy study
Nanoscale, 2018, 10, 22504-22519
DOI: 10.1039/C8NR07107A

To read the full article follow this external link: https://pubs.rsc.org/en/content/articlehtml/2018/nr/c8nr07107a

Open Access The article “Adhesion strategies of Dictyostelium discoideum – a force spectroscopy study” by Nadine Kamprad, Hannes Witt, Marcel Schröder, Christian Titus Kreis, Oliver Bäumchen, Andreas Janshoff and Marco Tarantola is licensed under a Creative Commons Attribution 3.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/3.0/.

In Situ Molecular-Level Observation of Methanol Catalysis at the Water–Graphite Interface

“Methanol occupies a central role in chemical synthesis and is considered an ideal candidate for cleaner fuel storage and transportation. It can be catalyzed from water and volatile organic compounds, such as carbon dioxide, thereby offering an attractive solution for reducing carbon emissions.”*

In “In Situ Molecular-Level Observation of Methanol Catalysis at the Water–Graphite Interface” the authors show that graphite immersed in ultrapure water is able to spontaneously catalyze methanol from volatile organic compounds in ambient conditions. Using single-molecule resolution atomic force microscopy (AFM) in liquid, they directly observe the formation and evolution of methanol–water nanostructures at the surface of graphite.*
The findings described in this article could have a significant impact on the development of organic catalysts and on the function of nanoscale carbon devices

NanoWorld ARROW-UHFAuD AFM probes were used for the Atomic Force Microscopy imaging in liquid.

Figure 1 from “In Situ Molecular-Level Observation of Methanol Catalysis at the Water–Graphite Interface” by W. Foster et al.: High-resolution amplitude modulation AFM imaging of HOPG immersed in initially ultrapure water. (a) A solid-like patch formed by the self-assembly of molecules (dashed white outline) nucleates from an atomic step at the HOPG surface (dashed black line). The molecular self-assembly is observed here in situ as it progressively grows across the HOPG surface over a period of 9 min, with the patch edges moving away from the step. Rowlike structures with a periodicity of 4.30 ± 0.28 nm as visible within the patch. (b) Sub-nanometer imaging of other structures reveals detailed features (0.79 ± 0.08 nm periodicity, red arrows) perpendicular to the main rows (periodicity 2.45 ± 0.08 nm, white arrow). The exact molecular arrangement is not known, but strongly reminiscent of the alternated water–methanol nanoribbons recently reported by our group.(22) The white scale bars are 100 nm in (a) and 1 nm in (b). The purple color scale bar represents a topographic variation of 20 Å in (a) and 1 Å nm in (b). The blue scale bar represents a phase variation of 20° in (a) and 10° in (b). In (a) the time lapse between the first and second frames is 1 min and then 4 min elapses between the subsequent frames. NanoWorld Arrow-UHFAuD AFM probes were used.
Figure 1 from “In Situ Molecular-Level Observation of Methanol Catalysis at the Water–Graphite Interface” by W. Foster et al.: High-resolution amplitude modulation AFM imaging of HOPG immersed in initially ultrapure water. (a) A solid-like patch formed by the self-assembly of molecules (dashed white outline) nucleates from an atomic step at the HOPG surface (dashed black line). The molecular self-assembly is observed here in situ as it progressively grows across the HOPG surface over a period of 9 min, with the patch edges moving away from the step. Rowlike structures with a periodicity of 4.30 ± 0.28 nm as visible within the patch. (b) Sub-nanometer imaging of other structures reveals detailed features (0.79 ± 0.08 nm periodicity, red arrows) perpendicular to the main rows (periodicity 2.45 ± 0.08 nm, white arrow). The exact molecular arrangement is not known, but strongly reminiscent of the alternated water–methanol nanoribbons recently reported by our group.(22) The white scale bars are 100 nm in (a) and 1 nm in (b). The purple color scale bar represents a topographic variation of 20 Å in (a) and 1 Å nm in (b). The blue scale bar represents a phase variation of 20° in (a) and 10° in (b). In (a) the time lapse between the first and second frames is 1 min and then 4 min elapses between the subsequent frames

*William Foster, Juan A. Aguilar, Halim Kusumaatmaja, Kislon Voϊtchovsky
In Situ Molecular-Level Observation of Methanol Catalysis at the Water–Graphite Interface
ACS Appl. Mater. Interfaces, 2018, 10 (40), pp 34265–34271
DOI: 10.1021/acsami.8b12113

Please follow this external link for the full article: https://pubs.acs.org/doi/full/10.1021/acsami.8b12113

Open Access The article “In Situ Molecular-Level Observation of Methanol Catalysis at the Water–Graphite Interface” by William Foster, Juan A. Aguilar, Halim Kusumaatmaja and Kislon Voϊtchovsky is licensed under a Creative Commons Attribution 4.0 International License, which permits use, sharing, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in a credit line to the material. If material is not included in the article’s Creative Commons license and your intended use is not permitted by statutory regulation or exceeds the permitted use, you will need to obtain permission directly from the copyright holder. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/.