Ionic liquids in analytical chemistry.

Solid-state nanopores are capable of the label-free analysis of single molecules. It is possible to add biochemical selectivity by anchoring a molecular receptor inside the nanopore, but it is difficult to maintain single-molecule sensitivity in these modified nanopores. Here, we show that metallized silicon nitride nanopores chemically modified with nitrilotriacetic acid receptors can be used for the stochastic sensing of proteins. The reversible binding and unbinding of the proteins to the receptors is observed in real time, and the interaction parameters are statistically analysed from single-molecule binding events. To demonstrate the versatile nature of this approach, we detect His-tagged proteins and discriminate between the subclasses of rodent IgG antibodies.

Stochastic sensing of proteins with receptor-modified solid-state nanopores

Solid-state and biological nanopore for real-time sensing of single chemical and sequencing of DNA

/pdf/nanopore-based-fourth-generation-dna-sequencing-technology-2cavwwctne.pdf

Nanopore-based Fourth-generation DNA Sequencing Technology

Applications of biological pores in nanomedicine, sensing, and nanoelectronics.

Here we report a rapid, label-free method for monitoring peptide cleavage. Monitoring peptide translocation through an engineered ion channel in the absence and the presence of an enzyme allowed quantitative chemical kinetics information on enzymatic processes to be obtained. In addition to its potential application in disease diagnostics and drug discovery, this peptide/protein cleavage approach is envisioned for further development as a novel rapid, label-free protein sequencing technique.

Real-Time Monitoring of Peptide Cleavage Using a Nanopore Probe

One of the key challenges to nanopore DNA sequencing is to slow down DNA translocation. Here, we report that the translocation velocities of various DNA homo- and copolymers through protein pores could be significantly decreased by using electrolyte solutions containing organic salts. Using a butylmethylimidazolium chloride (BMIM-Cl) solution instead of the commonly used KCl solution, DNA translocation rates on the order of hundreds of microseconds per nucleotide base were achieved. The much enhanced resolution of the nanopore coupled with different event blockage amplitudes produced by different nucleotides permits the convenient differentiation between various DNA molecules.

Slowing DNA translocation through nanopores using a solution containing organic salts.

Peptides play important roles in a variety of biological processes. Here, we studied the transport of peptides containing mainly aromatic amino acids in protein pores engineered with aromatic binding sites. With an increase in the length of the peptide, both the event mean dwell time and the current blockage amplitude increased. The dissociation rate constants k(off) decreased significantly, while the association rate constants k(on) decreased slowly as the peptide length increased. Thus, the overall reaction formation constants K(f), and hence the binding affinities of various peptides to the protein pore, are largely dependent upon the dissociation rate constants rather than the association rate constants. Furthermore, in a protein channel modified with aromatic binding sites, aromatic amino acid components contributed more to the dwell time and current blockage of the events than other types of amino acids, although the van der Waals volumes of amino acids also affected the event signatures. The effect of protein structure on peptide translocation was also investigated. With more aromatic binding sites engineered inside the lumen of the protein pore, a stronger binding affinity between peptides and the pore was observed. With the much enhanced resolution of the engineered protein pore, a series of short peptides, including those differing by a single amino acid, was successfully differentiated and simultaneously quantified. In addition to providing a rapid and cost-effective method for the peptide detection, the engineered protein pore approach offers the potential for peptide and protein sequencing.

Study of peptide transport through engineered protein channels.

Stochastic nanopore sensors for the detection of terrorist agents: Current status and challenges

We report a rapid and sensitive stochastic nanopore sensing method for the detection of monovalent cations and liquid explosive components and their sensitizers. The sensing element is a wild-type α-hemolysin protein pore with boromycin as a molecular adaptor, while a solution containing an ionic liquid was used as the background electrolyte. The analyte−boromycin complexes showed significantly different signatures. Specifically, their event mean dwell times and amplitudes were sufficiently distinct to permit the convenient differentiation and even simultaneous detection of liquid explosive components in aqueous environments. In addition, the results also demonstrate that the usage of specific ionic liquid salt solutions instead of NaCl or KCl solution as supporting electrolyte provides a useful means to greatly enhance the sensitivity of the nanopore for some analytes in stochastic sensing.

Qitao Zhao

Papers

Real-Time Monitoring of Peptide Cleavage Using a Nanopore Probe

Slowing DNA translocation through nanopores using a solution containing organic salts.

Study of peptide transport through engineered protein channels.

Stochastic nanopore sensors for the detection of terrorist agents: Current status and challenges

Nanopore stochastic detection of a liquid explosive component and sensitizers using boromycin and an ionic liquid supporting electrolyte.