Tag Archives: SPM probes

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/.

Room Temperature Polarization Phenomena in Nanocrystalline and Epitaxial Thin Films of Gd-Doped Ceria Studied by Kelvin Probe Force Microscopy

In their study “Room Temperature Polarization Phenomena in Nanocrystalline and Epitaxial Thin Films of Gd-Doped Ceria Studied by Kelvin Probe Force Microscopy” Kerstin Neuhaus, Giuliano Gregori and Joachim Maier show that “the combined polarization-KPFM method is able to produce consistent results for evaluation of room temperature chemical diffusion processes. In the future, a compilation of similar experiments with variation of temperature, humidity, gas surrounding etc. could also help to further study not only the role of the microstructure but also the influence of the environment on the polarization properties of other industrially relevant oxides.” *

“The samples were first mapped in the pristine state for reference. Subsequently, the sample was polarized with up to±5 V (with regard to the AFM tip) for up to 300 s. Directly after the end of the polarization experiment continuous surface potential mapping was started.”*

“For polarization and KPFM mapping, the samples were contacted with a silver paste back contact and Pt wire. The working contact for the polarization was an AFM tip (PPP-NCSTPt) with Pt coating, which was used simultaneously as probe during KPFM mapping (cf. Fig. 1).”*

Figure 1 from "Room Temperature Polarization Phenomena in Nanocrystalline and Epitaxial Thin Films of Gd-Doped Ceria Studied by Kelvin Probe Force Microscopy": Schematic of the experimental setup, NANOSENSORS PPP-NCST-Pt AFM probes were used
Figure 1 from “Room Temperature Polarization Phenomena in Nanocrystalline and Epitaxial Thin Films of Gd-Doped Ceria Studied by Kelvin Probe Force Microscopy”: Schematic of the experimental setup

*Kerstin Neuhaus, Giuliano Gregori, Joachim Maier
Room Temperature Polarization Phenomena in Nanocrystalline and Epitaxial Thin Films of Gd-Doped Ceria Studied by Kelvin Probe Force Microscopy
ECS Journal of Solid State Science and Technology,7 (8) P362-P368 (2018)
DOI: 10.1149/2.0011808jss

The article “Room Temperature Polarization Phenomena in Nanocrystalline and Epitaxial Thin Films of Gd-Doped Ceria Studied by Kelvin Probe Force Microscopy” by Neuhaus et. al. is an open access article distributed under the terms of the Creative Commons Attribution 4.0 License. To view a copy of this license, visit http://creativecommons.org/ licenses/by/4.0/.