Single molecule protein sequencing would represent a disruptive burst in proteomic research with important biomedical impacts. Due to their success in DNA sequencing, nanopore based devices have been recently proposed as possible tools for the sequencing of peptide chains. One of the open questions in nanopore protein sequencing concerns the ability of such devices to provide different signals for all the 20 standard amino acids. Here, using equilibrium all-atom molecular dynamics simulations, we estimated the pore clogging in α -Hemolysin nanopore associated to 20 different homopeptides, one for each standard amino acid. Our results show that pore clogging is affected by amino acid volume, hydrophobicity and net charge. The equilibrium estimations are also supported by non-equilibrium runs for calculating the current blockades for selected homopeptides. Finally, we discuss the possibility to modify the α -Hemolysin nanopore, cutting a portion of the barrel region close to the trans side, to reduce spurious signals and, hence, to enhance the sensitivity of the nanopore.

The synergy of life sciences discoveries, biomolecular and protein engineering advances, and groundbreaking nanofabrication technologies, has introduced over the past years the wide use of the nanopore-based investigations of matter at the molecular level. This review focuses on the fundamental principles of α-hemolysin (α-HL) protein-based nanopores, as sensitive investigative tools that combine single-molecule detection with the ability to simultaneously manipulate single molecules, in otherwise complex samples. Herein, there are presented some of the efforts directed to control the capture dynamics and translocation speed of tailored polypeptides through the α-HL nanopore, by harnessing the electro-osmotic flow and nanopore-tweezing influence on individual molecules, which are engineered to resemble macrodipoles. The reported applications of this approach suggest a solution to enhance the temporal resolution of nanopore detection, prove the capability of the system in distinguishing between groups of distinct amino acids from the studied poly peptides, and propose a strategy to translate such single-molecule sensors in devices suitable for polypeptide sequencing at unimolecular level.

Research on batteries mostly focuses on electrodes and electrolytes while few activities regard separator membranes. However, they could be used as a toolbox for injecting chemical functionalities to capture unwanted species and enhance battery lifetime. Here, we report the use of biological membranes hosting a nanopore sensor for electrical single molecule detection and use aqueous sodium polysulfides encountered in sulfur-based batteries for proof of concept. By investigating the host-guest interaction between polysulfides of different chain-lengths and cyclodextrins, via combined chemical approaches and molecular docking simulations, and using a selective nanopore sensor inserted into a lipid membrane, we demonstrate that supramolecular polysulfide/cyclodextrin complexes only differing by one sulfur can be discriminated at the single molecule level. Our findings offer innovative perspectives to use nanopores as electrolyte sensors and chemically design membranes capable of selective speciation of parasitic molecules for battery applications and therefore pave the way towards smarter electrochemical storage systems.

No abstract