Tag Archives: PointProbe Plus

articles on the PointProbe Plus AFM probe series

5′-(CGA)n sequence-assisted pH-controlled assembly of supramolecular DNA nanostructure

In the research article “5′-(CGA)n sequence-assisted pH-controlled assembly of supramolecular DNA nanostructure” Yuting Yan, Yanwei Cao, Chunsheng Xiao, Yang Li, Xiaoxuan Xiang and Xinhua Guo demonstratethat the connection of duplex-forming sequences with a G-quadruplex-forming sequence (G6) could be used to construct DNA supramolecular nanostructures with alternating B-duplex and G-quadruplex structures. Their results demonstrate that the TT linker between B-duplex and G-quadruplex structures are necessary for the construction of such nanostructures, because the TT linker can provide structural flexibility for the bending of duplexes at the terminal of G-quadruplex.*

The formation of DNA supramolecular nanostructures was directly observed through AFM measurements.  Atomic force microscopy (AFM) was performed using NANOSENSORS™ PointProbe® Plus PPP-NCHR tapping mode AFM probes.

Figure 5. from “5′-(CGA)n sequence-assisted pH-controlled assembly of supramolecular DNA nanostructure” by Yuting Yan et al.: AFM images of the nanostructures formed by DNA G-quadruplexes self-assembly in KOAc buffer solution; (a,b) SG2 at pH 9.0, (c,d) SG2 at pH 4.5, (e,f) a mixture of SG2 and CSG2 at pH 4.5, (g,h) a mixture of SG2 and CSG2 at pH 9.0. The length of side is 2 µm and the scale bar is 500 nm. NANOSENSORS™ PointProbe® Plus PPP-NCHR AFM probes were used for all AFM images.
Figure 5. from “5′-(CGA)n sequence-assisted pH-controlled assembly of supramolecular DNA nanostructure” by Yuting Yan et al.: AFM images of the nanostructures formed by DNA G-quadruplexes self-assembly in KOAc buffer solution; (a,b) SG2 at pH 9.0, (c,d) SG2 at pH 4.5, (e,f) a mixture of SG2 and CSG2 at pH 4.5, (g,h) a mixture of SG2 and CSG2 at pH 9.0. The length of side is 2 µm and the scale bar is 500 nm.

AFM microscopy was performed on the fresh mica surfaces with the help of magnesium ions which can bind negatively charged DNA strands. The DNA samples were annealed at 100 µM in 100 mM K+ solution at 4°C for one week. Then aliquots were diluted with 2 mM MgCl2 aqueous solution to give a 20 µl analyte containing 1.5 µM DNA. The analytes were spread evenly on the mica surface for 5–8 min. Subsequently, the mica surface was washed with Milli-Q water to wipe off the excess salt, and finally dried in the air.*

*Yuting Yan, Yanwei Cao, Chunsheng Xiao, Yang Li, Xiaoxuan Xiang, Xinhua Guo
5′-(CGA)n sequence-assisted pH-controlled assembly of supramolecular DNA nanostructure
Royal Society Open Science, 1 August 2018, Volume 5, Issue 8
DOI: https://doi.org/10.1098/rsos.180123

Open Access: The article “5′-(CGA)n sequence-assisted pH-controlled assembly of supramolecular DNA nanostructure” by  Yuting Yan et al. 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/.

Injection and controlled motion of conducting domain walls in improper ferroelectric Cu-Cl boracite

NANOSENSORS PPP-EFM AFM tips were used in the research for this article. Have a look at the abstract or follow the external link to the full article.

Figure 1: Crystal structure and domains in boracites. From: Injection and controlled motion of conducting domain walls in improper ferroelectric Cu-Cl boracite
Figure 1: Crystal structure and domains in boracites.
From: Injection and controlled motion of conducting domain walls in improper ferroelectric Cu-Cl boracite

Raymond G.P. McQuaid, Michael P. Campbell, Roger W. Whatmore, Amit Kumar, J. Marty Gregg
Injection and controlled motion of conducting domain walls in improper ferroelectric Cu-Cl boracite. Nat. Commun. 8, 15105 doi: 10.1038/ncomms15105 (2017).

Abstract:
Ferroelectric domain walls constitute a completely new class of sheet-like functional material. Moreover, since domain walls are generally writable, erasable and mobile, they could be useful in functionally agile devices: for example, creating and moving conducting walls could make or break electrical connections in new forms of reconfigurable nanocircuitry. However, significant challenges exist: site-specific injection and annihilation of planar walls, which show robust conductivity, has not been easy to achieve. Here, we report the observation, mechanical writing and controlled movement of charged conducting domain walls in the improper-ferroelectric Cu3B7O13Cl. Walls are straight, tens of microns long and exist as a consequence of elastic compatibility conditions between specific domain pairs. We show that site-specific injection of conducting walls of up to hundreds of microns in length can be achieved through locally applied point-stress and, once created, that they can be moved and repositioned using applied electric fields.

Please follow this external link for the full article: https://www.nature.com/articles/ncomms15105

Creative Commons BYThe article “Injection and controlled motion of conducting domain walls in improper ferroelectric Cu-Cl boracite” by McQuaid, R. G. P. et al. is licensed under a Creative Commons Attribution 4.0 International License. The images or other third party material in this article are included in the article’s Creative Commons license, unless indicated otherwise in the credit line; if the material is not included under the Creative Commons license, users will need to obtain permission from the license holder to reproduce the material. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

NANOSENSORS™ Ultrastiff AFM Probes for Atomic Resolution

Dr. Oliver Krause, product developer at NANOSENSORS™ is talking in this screencast about AFM probes for dynamic AFM with sub-nanometer amplitudes enabling imaging with atomic and sub-nanometer resolution

Dynamic AFM with extremely small oscillation amplitudes of the probing tip enables Atomic Force Microscopy with atomic and even sub-atomic resolution. By adjusting the oscillation amplitude to the regime of short-range forces the impact of long-range forces on the detection mechanism can be suppressed effectively.
For stable operation the bending forces of the cantilever must be able to overcome the attractive tip-sample forces. Dynamic AFM with sub-nanometre amplitudes requires cantilevers with a force constant larger than 300N/m. The force constants of typical AFM probes for intermittent contact (Tapping Mode) are in the order of a few tens of N/m. Therefore, amplitudes of at least a few nanometres are required for stable operation.
Ultrastiff AFM cantilever probes with integrated sharp tips have been fabricated based on the well-established NANOSENSORS™ PointProbePlus® process. Cantilever geometries of 100µm length and 7 or even 10µm thickness have been realized resulting in force constants of 600 and 2000 N/m.