Fluids and Electrolytes under Confinement in Single-Digit Nanopores.

Confined fluids and electrolyte solutions in nanopores exhibit rich and surprising physics and chemistry that impact the mass transport and energy efficiency in many important natural systems and industrial applications. Existing theories often fail to predict the exotic effects observed in the narrowest of such pores, called single-digit nanopores (SDNs), which have diameters or conduit widths of less than 10 nm, and have only recently become accessible for experimental measurements. What SDNs reveal has been surprising, including a rapidly increasing number of examples such as extraordinarily fast water transport, distorted fluid-phase boundaries, strong ion-correlation and quantum effects, and dielectric anomalies that are not observed in larger pores.

Co-Assembly of Carbon Nanotube Porins into Biomimetic Peptoid Membranes.

Robust and cost-effective membrane-based separations are essential to solving many global crises, such as the lack of clean water. Even though the current polymer-based membranes are widely used for separations, their performance and precision can be enhanced by using a biomimetic membrane architecture that consists of highly permeable and selective channels embedded in a universal membrane matrix. Researchers have shown that artificial water and ion channels, such as carbon nanotube porins (CNTPs), embedded in lipid membranes can deliver strong separation performance.

Electric Field Induced Biomimetic Transmembrane Electron Transport Using Carbon Nanotube Porins.

Cells modulate their homeostasis through the control of redox reactions via transmembrane electron transport systems. These are largely mediated via oxidoreductase enzymes. Their use in biology has been linked to a host of systems including reprogramming for energy requirements in cancer.

Electrostatic gating of ion transport in carbon nanotube porins: A modeling study.

Carbon nanotube porins (CNTPs) are biomimetic membrane channels that demonstrate excellent biocompatibility and unique water and ion transport properties. Gating transport in CNTPs with external voltage could increase control over ion flow and selectivity. Herein, we used continuum modeling to probe the parameters that enable and further affect CNTP gating efficiency, including the size and composition of the supporting lipid membrane, slip flow in the carbon nanotube, and the intrinsic electronic properties of the nanotube.

Membrane fusion and drug delivery with carbon nanotube porins.

Drug delivery mitigates toxic side effects and poor pharmacokinetics of life-saving therapeutics and enhances treatment efficacy. However, direct cytoplasmic delivery of drugs and vaccines into cells has remained out of reach. We find that liposomes studded with 0.

Water-ion permselectivity of narrow-diameter carbon nanotubes.

Carbon nanotube (CNT) pores, which mimic the structure of the aquaporin channels, support extremely high water transport rates that make them strong candidates for building artificial water channels and high-performance membranes. Here, we measure water and ion permeation through 0.8-nm-diameter CNT porins (CNTPs)-short CNT segments embedded in lipid membranes-under optimized experimental conditions.

Strong Differential Monovalent Anion Selectivity in Narrow Diameter Carbon Nanotube Porins.

Inner pores of carbon nanotubes combine extremely fast water transport and ion selectivity that could potentially be useful for high-performance water desalination and separation applications. We used dye-quenching halide assays and stopped-flow spectrometry to determine intrinsic permeability of three small monovalent halide anions (chloride, bromide, iodide) and one pseudohalide anion (thiocyanate) through narrow 0.8 nm diameter carbon nanotube porins (CNTPs).

Strong Electroosmotic Coupling Dominates Ion Conductance of 1.5 nm Diameter Carbon Nanotube Porins.

Extreme confinement in nanometer-sized channels can alter fluid and ion transport in significant ways, leading to significant water flow enhancement and unusual ion correlation effects. These effects are especially pronounced in carbon nanotube porins (CNTPs) that combine strong confinement in the inner lumen of carbon nanotubes with the high slip flow enhancement due to smooth hydrophobic pore walls. We have studied ion transport and ion selectivity in 1.

Carbon Nanotube Porins in Amphiphilic Block Copolymers as Fully Synthetic Mimics of Biological Membranes.

Biological membranes provide a fascinating example of a separation system that is multifunctional, tunable, precise, and efficient. Biomimetic membranes, which mimic the architecture of cellular membranes, have the potential to deliver significant improvements in specificity and permeability. Here, a fully synthetic biomimetic membrane is reported that incorporates ultra-efficient 1.

Response to Comment on "Enhanced water permeability and tunable ion selectivity in subnanometer carbon nanotube porins".

Horner and Pohl argue that high water transport rates reported for carbon nanotube porins (CNTPs) originate from leakage at the nanotube-bilayer interface. Our results and new experimental evidence are consistent with transport through the nanotube pores and rule out a defect-mediated transport mechanism. Mechanistic origins of the high Arrhenius factor that we reported for narrow CNTPs at pH 8 require further investigation.

Enhanced water permeability and tunable ion selectivity in subnanometer carbon nanotube porins.

Fast water transport through carbon nanotube pores has raised the possibility to use them in the next generation of water treatment technologies. We report that water permeability in 0.8-nanometer-diameter carbon nanotube porins (CNTPs), which confine water down to a single-file chain, exceeds that of biological water transporters and of wider CNT pores by an order of magnitude.

Effect of arginine methylation on the RNA recognition and cellular uptake of Tat-derived peptides.

Arginine (Arg) methylation is a common post-translational modification that regulates gene expression and viral infection. The HIV-1 Tat protein is an essential regulatory protein for HIV proliferation, and is methylated in the cell. The basic region (residues 47-57) of the Tat protein contains six Arg residues, and is responsible for two biological functions: RNA recognition and cellular uptake.

Effect of charged amino acid side chain length at non-hydrogen bonded strand positions on β-hairpin stability.

β-Sheets have been implicated in various neurological disorders, and ∼20% of protein residues adopt a sheet conformation. Therefore, studies on the structural origin of sheet stability can provide fundamental knowledge with potential biomedical applications. Oppositely charged amino acids are frequently observed across one another in antiparallel β-sheets.