Researchers at the Physics laboratory of ENS de Lyon (CNRS/ENS de Lyon) have recreated artificial pores that mimic the functioning of two types of biological pore, paving the way for the manufacture of selective nano-pumps and nano-filters. Results published in the journals PNAS (July 2022) and Nano Letters (May 2023).

Thermally Switchable Nanogate Based on Polymer Phase Transition

Abstract

Mimicking and extending the gating properties of biological pores is of paramount interest for the fabrication of membranes that could be used in filtration or drug processing. Here, we build a selective and switchable nanopore for macromolecular cargo transport. Our approach exploits polymer graftings within artificial nanopores to control the translocation of biomolecules. To measure transport at the scale of individual biomolecules, we use fluorescence microscopy with a zero-mode waveguide set up. We show that grafting polymers that exhibit a lower critical solution temperature creates a toggle switch between an open and closed state of the nanopore depending on the temperature. We demonstrate tight control over the transport of DNA and viral capsids with a sharp transition (∼1 °C) and present a simple physical model that predicts key features of this transition. Our approach provides the potential for controllable and responsive nanopores in a range of applications.

Reference : Thermally Switchable Nanogate Based on Polymer Phase Transition. Pauline J. Kolbeck, Dihia Benaoudia, Léa Chazot-Franguiadakis, Gwendoline Delecourt, Jérôme Mathé, Sha Li, Romeo Bonnet, Pascal Martin, Jan Lipfert, Anna Salvetti, Mordjane Boukhet, Véronique Bennevault, Jean-Christophe Lacroix, Philippe Guégan and Fabien Montel. Nano Letters, May 22, 2023.     
DOI : 10.1021/acs.nanolett.3c00438 
Open archive HAL: hal-04131308

Experimental study of a nanoscale translocation ratchet

Significance

Some classes of biological motors like the Sec61 complex or the bacterial type IV pilus can achieve directional transport of biomolecules through nanopores, according to an out-of-equilibrium process called translocation ratchet, which biases thermal fluctuation toward a preferential direction. Despite its biological relevance, this process has never been reproduced into an artificial system. In this frame, we developed an artificial translocation ratchet at nanoscale, able to perform directional transport of DNA molecules through synthetic nanopores. We quantified the effect of both geometrical and kinetic parameters of this system on its ability to enhance the DNA transport and found the length of the DNA to be the main parameter likely to change the ratcheting effect; specifically, we observed a minimal length to trigger the ratchet mechanism that has never been described before.

Abstract

Despite an extensive theoretical and numerical background, the translocation ratchet mechanism, which is fundamental for the transmembrane transport of biomolecules, has never been experimentally reproduced at the nanoscale. Only the Sec61 and bacterial type IV pilus pores were experimentally shown to exhibit a translocation ratchet mechanism. Here we designed a synthetic translocation ratchet and quantified its efficiency as a nanopump. We measured the translocation frequency of DNA molecules through nanoporous membranes and showed that polycations at the trans side accelerated the translocation in a ratchet-like fashion. We investigated the ratchet efficiency according to geometrical and kinetic parameters and observed the ratchet to be only dependent on the size of the DNA molecule with a power law N^−0.6. A threshold length of 3 kbp was observed, below which the ratchet did not operate. We interpreted this threshold in a DNA looping model, which quantitatively explained our results.

Reference

Experimental study of a nanoscale translocation ratchet. Bastien Molcrette, Léa Chazot-Franguiadakis, François Liénard, Zsombor Balassy, Céline Freton, Christophe Grangeasse and Fabien Montel. PNAS, July 18, 2022. 
DOI : 10.1073/pnas.2202527119 
Open archive HAL: hal-03841871