The influenza A viruses, which have instigated deadly pandemics in the past, still remain a major global public health problem until today. Molecules known as virulence factors are produced by bacteria, viruses, and fungi to help them to infect host cells. One of virulence factors found in ... more
Complete filling of batches of nanopipettes
Nanopipettes, in which a nanoscale channel is filled with a solution, are used in all kinds of nanotechnology applications, including scanning-probe microscopy. Bringing a solution into a nanopipette with a pore diameter below 10 nanometer is challenging, however, since capillary forces prevent the complete filling of a sub-10-nm nanopipette pore with a liquid. Now, Shinji Watanabe and colleagues from Kanazawa University have found a simple but efficient way for filling nanopipettes. The researchers show that the 'air bubble' that typically remains near the pipette's pore end can be removed by applying a temperature gradient along the pipette.
The scientists investigated their 'thermally-driven method' to a batch of 94 pipettes, aligned length-wise next to each other, all with a pore diameter of around 10 nm. The pipettes were put on a metal plate kept at a temperature of 80 °C, with their tips protruding from the plate, resulting in a temperature gradient.
Time-lapsed optical microscopy images of the filling process of the nanopipettes showed that after 1200 seconds, the tips are completely filled with solution, and that air bubbles are driven out of the pipettes.
In order to double-check that the pipettes were indeed bubble-free, Watanabe and colleagues performed so-called I-V measurements. Every pipette was filled with a solution of potassium chloride (KCl), which is conducting. Both pipette ends were then contacted with electrodes. If an electrical current runs between the ends -- specifically, if the pipette has an electrical conductivity below a few GΩ-- then filling with the solution is complete. The resesarchers observed electrical currents and therefore filling for the whole batch of pipettes.
The scientists also performed transmission electron microscopy (TEM) measurments of pipettes with pore diameters below 10 nm. Although the thermally-driven method leads to good electrical contacts, particle-like structures were observed inside the tips of the nanopipettes, demonstrating that (quoting the researchers) "TEM observation without inducing pipette deformation is important for accurately determining the characteristics of sub-10-nm nanopipettes."
Watanabe and colleagues concluded that their method is very practical and easy to introduce in nanopipette frabrication and that their study "will provide a significant contribution to various fields of nanoscience using nanopipettes.
Researchers at Kanazawa University have uncovered the role of lipids in facilitating a functional switch between two forms of a cellular enzyme: Peroxiredoxin (Prxs). Their study published in the Journal of Molecular Biology explains how negatively charged membrane lipids can bind to Prxs, ... more
A molecule adsorbed on a surface (Figure 1A) vibrates on the surface (Figure 1B). The vibration energy is determined by the mass of the molecule and by the restoring forces exerted on the molecule. The restoring force originates from the interaction within the molecule and with the surface. ... more
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