Tag: AFMプローブ

Pectin Interaction with Immune Receptors is Modulated by Ripening Process in Papayas

Dietary fibers have been shown to exert immune effects via interaction with pattern recognition receptors (PRR) such as toll-like receptors (TLR) and nucleotide-binding oligomerization domain (NOD)-like receptors. Pectin is a dietary fiber that interacts with PRR depending on its chemical structure. Papaya pectin retains different chemical structures at different ripening stages. How this influences PRR signalling is unknown.*

The aim of the article “Pectin Interaction with Immune Receptors is Modulated by Ripening Process in Papayas” by Samira B. R. Prado, Martin Beukema, Eva Jermendi, Henk A. Schols, Paul de Vos and João Paulo Fabi was to determine how ripening influences pectin structures and their ability to interact with TLR2, 3, 4, 5 and 9, and NOD1 and 2.*

Papaya ripening is an enzymatic, biochemically driven process that occurs over a short period of time (five days) and involves the mobilization of pectin and the alteration of its chemical composition.

The authors evaluated the interaction of the water-soluble fractions rich in pectin extracted from unripe to ripe papayas. The pectin extracted from ripe papayas activated all the TLR and, to a lesser extent, the NOD receptors. The pectin extracted from unripe papayas also activated TLR2, 4 and 5 but inhibited the activation of TLR3 and 9.*

During papaya ripening, profound changes in pectin structures lead to differences in the biological effects. The data presented in the paper show that papaya pectin extracted from fruit pulp at different ripening points differently interacted with PRR in a ripening-dependent way. The longer chains of HG from unripe papayas pectin, which were less methyl-esterified, inhibited the activation of TLR3 and 9 and activated TLR2 and 4, in contrast to the ripe papaya’s pectin, which have smaller HG chains with medium methyl esterification thus activating TLR2, 3, 4, 5 and 9.*

This variation may represent new biological features of papaya pectin structures in addition to anticancer activities, possibly creating new and cost-effective approaches to extracting papaya pectin with desirable structural and biological features.*

These findings might lead to selection of ripening stages for tailored modulation of PRR to support or attenuate immunity in consumers.*

The changes in Molecular weight ( Mw ) can also be visualized by Atomic Force Microscopy (see Fig. 1C in the paper.)

The AFM images presented in the paper were acquired in tapping mode using an NanoWorld Pointprobe® NCHR AFM probe with a typical spring constant of 42 N/m and typically 320 kHz resonance frequency. The scan speed and scanning resolution were 0.5 Hz and 512 × 512 points, respectively.*

Figure 1 C from “Pectin Interaction with Immune Receptors is Modulated by Ripening Process in Papayas” by Samira B. R. Prado et al. 2020:
(C) Representative topographical AFM images of Un-1-WSF and R-2-WSF. White arrow indicates linear structures, black arrow aggregates and grey arrow the smaller structure from the R-2-WSF. Un-1-WSF: unripe – papaya from 1st day after harvest – water-soluble fraction; Un-2-WSF: unripe – papaya from 2nd day after harvest – water-soluble fraction; I-WSF: intermediate ripening time point – papaya from 3rd day after harvest – water-soluble fraction; R-1-WSF: ripe – papaya from 4th day after harvest – water-soluble fraction; R-2-WSF: ripe – papaya from 5th day after harvest – water-soluble fraction. Please have a look at the full article for the full figure.

*Samira B. R. Prado, Martin Beukema, Eva Jermendi, Henk A. Schols, Paul de Vos and João Paulo Fabi
Pectin Interaction with Immune Receptors is Modulated by Ripening Process in Papayas
Nature Scientific Reports volume 10, Article number: 1690 (2020)
DOI: https://doi.org/10.1038/s41598-020-58311-0

Please follow this external link to read the full article https://rdcu.be/b3Fnb .

Open Access The article “ Pectin Interaction with Immune Receptors is Modulated by Ripening Process in Papayas “ by Samira B. R. Prado, Martin Beukema, Eva Jermendi, Henk A. Schols, Paul de Vos and João Paulo Fabi 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/.

KPFM surface photovoltage measurement and numerical simulation

Kelvin Probe Force Microscopy ( KPFM ) is a scanning probe microscopy technique. It is a combination of the Kelvin probe and of Atomic Force Microscopy methods. The technique consists in evaluating the difference in work function between two conducting materials, by using a nanometer scale tip ( the “KPFMtip”), and placing it close to the material to be characterised, where a difference in work function leads to an electrostatic force developing between the two, which is translated as an oscillation of the tip’s cantilever. A bia sapplied via an external circuit is varied until the force and hence the electrostatic field between sample and KPFM tip is cancelled.*

In the article “KPFM surface photovoltage measurement and numerical simulation” Clément Marchat, James P. Connolly, Jean-Paul Kleider, José Alvarez, Lejo J. Koduvelikulathu and Jean Baptiste Puel present a method for the analysis of Kelvin probe force microscopy (KPFM) characterization of semiconductor devices.
It enables evaluation of the influence of defective surface layers. The model is validated by analysing experimental KPFM measurements on crystalline silicon samples of contact potential difference (VCPD) in the dark and under illumination, and hence the surface photovoltage (SPV). It is shown that the model phenomenologically explains the observed KPFM measurements. It reproduces the magnitude of SPV characterization as a function of incident light power in terms of a defect density assuming Gaussian defect distribution in the semiconductor bandgap. This allows an estimation of defect densities in surface layers of semiconductors and therefore increased exploitation of KPFM data.*

The KPFM measurements were performed using NanoWorld ARROW-EFM conductive AFM tips with a PtIr coating.
The tip work function didn’t require calibration because only SPV measurement were performed and studied. Measurements were performed in the KPFM amplitude modulation (AM)mode rather than the frequency modulation (FM) one. The AM mode was chosen because lateral resolution was not a problem on the homogeneous bulk samples studied, allowing focus on the superior surface potential resolution that can be achieved with the AM mode.*

Fig. 1 from “KPFM surface photovoltage measurement and numerical simulation” by Clément Marchat et al:
Kelvin probe force microscopy setup schematic. The conducting cantilever carrying the KPFM tip is scanned over a surface while AC + DC potential is applied. The AC signal is a sinusoid whose frequency matches the mechanical resonance of the cantilever. The four-quadrant detector provides feedback in order to minimise cantilever oscillation by varying the DC signal thereby yielding the sample work function compared to the tip one.

*Clément Marchat, James P. Connolly, Jean-Paul Kleider, José Alvarez, Lejo J. Koduvelikulathu and Jean Baptiste Puel
KPFM surface photovoltage measurement and numerical simulation
EPJ Photovoltaics10, 3 (2019)
DOI: https://doi.org/10.1051/epjpv/2019002

Please follow this external link to read the full article: https://www.epj-pv.org/articles/epjpv/abs/2019/01/pv180014/pv180014.html

Open Access The article “KPFM surface photovoltage measurement and numerical simulation “ by Clément Marchat, James P. Connolly, Jean-Paul Kleider, José Alvarez, Lejo J. Koduvelikulathu and Jean Baptiste Puel 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/.

Self-assembly of small molecules at hydrophobic interfaces using group effect

Although common in nature, the self-assembly of small molecules at sold–liquid interfaces is difficult to control in artificial systems. The high mobility of dissolved small molecules limits their residence at the interface, typically restricting the self-assembly to systems under confinement or with mobile tethers between the molecules and the surface. Small hydrogen-bonding molecules can overcome these issues by exploiting group-effect stabilization to achieve non-tethered self-assembly at hydrophobic interfaces. Significantly, the weak molecular interactions with the solid makes it possible to influence the interfacial hydrogen bond network, potentially creating a wide variety of supramolecular structures.*

In the paper “Self-assembly of small molecules at hydrophobic interfaces using group effect” William Foster, Keisuke Miyazawa, Takeshi Fukuma, Halim Kusumaatmaja and Kislon Voϊtchovsky investigate the nanoscale details of water and alcohols mixtures self-assembling at the interface with graphite through group-effect. They explore the interplay between inter-molecular and surface interactions by adding small amounts of foreign molecules able to interfere with the hydrogen bond network and systematically varying the length of the alcohol hydrocarbon chain. The resulting supramolecular structures forming at room temperature are then examined using atomic force microscopy with insights from computer simulations.*

The authors show that the group-based self-assembly approach investigated in the paper is general and can be reproduced on other substrates such as molybdenum disulphide and graphene oxide, potentially making it relevant for a wide variety of systems.*

NanoWorld Arrow UHF-AuD ultra high frequency cantilevers for High Speed AFM were used for the amplitude modulation atomic force microscopy described in this paper.


Figure 4 from “Self-assembly of small molecules at hydrophobic interfaces using group effect“ by William Foster et al.:
Impact of the backbone length of primary alcohols on interfacial self-assembly on HOPG. The basic monolayer motif is visible as expected in a 50 : 50 methanol : water mixture (a), here imaged by amplitude-modulation AFM (topography image). In a 50 : 50 ethanol : water mixture (b), two organised layers are visible both in topography and in the phase where it is more pronounced, outlined by a white dashed line (blue and red arrows). In phase, the self-assembled layers appear darker than the directly exposed graphite, where no structures are present (black arrow). The lower layer shows few resolvable features and is bordered by wide rows that have a separation of 5.89 ± 0.28 nm. In 50 : 50 1-propanol : water mixture (c), novel structures with long, straight edges emerge (red arrow) and grow on top of the exposed graphite (black arrow). The structures have a row periodicity of 5.86 ± 0.25 nm. The inset shows details of the longitudinal row structures near an edge. Further variance is seen in a 50 : 50 2-propanol : water mixture (d) where two types of domains form (red and blue arrows), both demonstrating a clear phase contrast with the graphite surface (black arrow). The domains have longitudinal rows with periodicities of 6.10 ± 0.35 nm (blue arrow) and 4.91 ± 0.45 nm (red arrow). Unlike for (c), higher resolution of the row (inset) evidence curved edges. The scale bars are 50 nm in (a) and (b), 100 nm in (c) and (d) main image and 20 nm in the insets. The purple colour scale bar represents a height variation of 1 nm in (a), (b) and (d), 3 nm in (c) and 0.5 nm in the insets. The blue scale bar represents a phase variation of 1.5° in (b), 2° in (c) and its inset and 15° in (d) and its inset.

*William Foster, Keisuke Miyazawa, Takeshi Fukuma, Halim Kusumaatmaja and Kislon Voϊtchovsky
Self-assembly of small molecules at hydrophobic interfaces using group effect
Nanoscale, 2020,12, 5452
DOI: 10.1039/c9nr09505e

Please follow this external link to read the full article: https://pubs.rsc.org/en/content/articlepdf/2020/nr/c9nr09505e

Open Access: The paper « Self-assembly of small molecules at hydrophobic interfaces using group effect»  by William Foster, Keisuke Miyazawa, Takeshi Fukuma, Halim Kusumaatmaja and Kislon Voϊtchovsky 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 https://creativecommons.org/licenses/by/3.0/.