We have updated our list of articles in the field of High-Speed AFM (HS-AFM) on the www.highspeedscanning.com website. If you would like to see what has been going on recently in the field of High-Speed AFM (HS-AFM) then you are welcome to have a look at: http://www.highspeedscanning.com/hs-afm-references.html
We are aware that this list is far from complete so if you have used one of our Ultra-Short Cantilevers (USC) for high speed atomic force microscopy in the research for your publication and your article isn’t listed yet then please let us know. We will be happy to add it to the list.
NanoWorld Ultra-Short Cantilevers (USC) for High-Speed AFM (HS-AFM)
Magnesium (Mg2+) is a key
divalent cation in biology. It regulates
and maintains numerous, physiological functions such as nucleic acid stability,
muscle contraction, heart rate and vascular tone, neurotransmitter release, and
serves as cofactor in a myriad of enzymatic reactions. Most
importantly, it coordinates with ATP, and is thus crucial for energy production
in mitochondria.*
In order to
store Mg2+ in the mitochondrial lumen it is imported via Mrs2 and
Alr2 ion channels that are closely related to CorA, the main Mg2+-importer in
bacteria. Although these Mg2+-transport proteins do not show much sequence
conservation, they all share two trans-membrane domains (TMDs) with the
signature motif Glycine-Methionine-Asparagine (GMN) at the extracellular loop.*
CorA, a divalent-selective channel in the
metal ion transport superfamily, is the major Mg2+-influx pathway in
prokaryotes. CorA structures in closed (Mg2+-bound), and open (Mg2+-free)
states, together with functional data showed that Mg2+-influx
inhibits further Mg2+-uptake completing a regulatory feedback loop.
While the closed state structure is a symmetric pentamer, the open state
displayed unexpected asymmetric architectures.*
In the
article “Real time dynamics of Gating-Related conformational changes in CorA” Martina
Rangl, Nicolaus Schmandt, Eduardo Perozo and Simon Scheuring used high-speed atomic force microscopy (HS-AFM), to explore
the Mg2+-dependent gating transition of single CorA channels: HS-AFM
movies during Mg2+-depletion experiments revealed the channel’s
transition from a stable Mg2+-bound state over a highly mobile and
dynamic state with fluctuating subunits to asymmetric structures with varying
degree of protrusion heights from the membrane.*
Their data shows that at Mg2+-concentration below Kd, CorA
adopts a dynamic (putatively open) state of multiple conformations that imply
structural rearrangements through hinge-bending in TM1. They also
discuss how these structural dynamics define the functional behavior of this
ligand-dependent channel.*
All Atomic Force Microscopy experiments described in the article were performed using NanoWorld Ultra-Short CantileversUSC-F1.2-k0.15 for high-speed Atomic Force Microscopy ( HS-AFM ). Videos of CorA membranes were recorded with imaging rates of ~1–2 frames s−1 and at a resolution of 0.5 nm pixel−1.
Figure 1 from “Real time dynamics of Gating-Related conformational changes in CorA”: Sample morphology of CorA reconstitutions for HS-AFM.
(a) HS-AFM overview topograph of densely packed CorA in a POPC/POPG (3:1) lipid bilayer exposing the periplasmic side and a loosely packed protein area with diffusing molecules exposing the intracellular face (full color scale: 20 nm). Left: Height histogram of the HS-AFM image with two peaks representative of the mica and the CorA surface (∆Height (peak-peak): 12 nm (20,500 height values)). The dashed line indicates the position of the cross-section analysis shown in (b). (b) Profile of the membrane shown in a), including a cartoon (top) of the membrane in side view. The height profile (~12 nm) corresponds well to the all-image height analysis (a, left) and the CorA structure (Matthies et al., 2016). (c) High-resolution image (top) and cross-section analysis along dashed line (bottom) of the periplasmic face. The height and dimension of the periplasmic face is in good agreement with the structure (left), and the periodicity (~14 nm, n = 40) corresponds well with the diameter of the intracellular face spacing the molecules on the other side of the membrane (full color scale: 2 nm). (d) HS-AFM image of densely packed CorA embedded in a DOPC/DOPE/DOPS (4:5:1) membrane. This reconstitution resulted in two stacked membrane layers, both exposing the CorA intracellular face. The dashed line indicates the position of the cross-section analysis shown in (e). Left: Height histogram of the HS-AFM image with two peaks at ~12 nm and ~17 nm (32,500 height values), corresponding to the proteins in two stacked membranes (full color scale: 20 nm). (e) Section profile of the membrane shown in d), including a cartoon (top) of the membrane in side view. (f) High-resolution view and cross-section analysis along dashed line (bottom) of the CorA intracellular face revealing the individual subunits of the pentamers (full color scale: 3 nm). Inset: 5-fold symmetrized average of CorA. The dimensions of CorA observed with HS-AFM are in good agreement with the structure (left: PDB 3JCF). The structures in (c) and (f) are shown in ribbon (top) and surface (bottom) representations, respectively.
*Martina Rangl, Nicolaus Schmandt, Eduardo Perozo, and Simon Scheuring Real time dynamics of Gating-Related conformational changes in CorA eLife. 2019; 8: e47322 DOI: 10.7554/eLife.47322
Open Access: The article “Real time dynamics of Gating-Related conformational changes in CorA” by Martina Rangl, Nicolaus Schmandt, Eduardo Perozo and Simon Scheuring 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/.
The properties of a polymer change significantly depending on the structure of the polymer chain, particularly, with branched structures, depending on the number of branches and the length of the branch.* However, the long-chain branch (LCB) structure of polyethylene was unclear, due particularly to the complex polymer structure and the limitations of its analysis methods.
In their study “Direct Observation of Long-Chain Branches in a Low-Density Polyethylene” Ken-ichi Shinohara, Masahiro Yanagisawa and Yuu Makida measured the chain length of LCBs and the distance between branch points of LDPE by atomic force microscopy.*
Figure 1 from “Direct Observation of Long-Chain Branches in a Low-Density Polyethylene “ by K. Shinohara et al.: Direct measurement of LCB in a tubular LDPE (F200-0 fractionated). (A) AFM image of a single molecule of LDPE on mica in DMTS at 25 °C. X: 279 nm, Y: 209 nm, Z: 18 nm. (B) Length of each chain of LDPE. (C) A wire model of self-shrinking structure of polymer chain of LDPE. Main chain: red wire. LCB: black wire. The model was created to be one tenth of the length of the extended chain based on AFM observation (B), MD simulation (Fig. S1), and the molecular weight determined by SEC-MALLS-Visc experiments (see Fig. 2).
*Ken-ichi Shinohara, Masahiro Yanagisawa, Yuu Makida Direct Observation of Long-Chain Branches in a Low-Density Polyethylene Nature Scientific Reportsvolume 9, Article number: 9791 (2019) doi: https://doi.org/10.1038/s41598-019-46035-9
Open Access: The article «Direct Observation of Long-Chain Branches in a Low-Density Polyethylene» by Ken-ichi Shinohara, Masahiro Yanagisawa and Yuu Makida 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/.
