@article {387, title = {DNA double helix, a tiny electromotor}, journal = {Nature Nanotechnology}, volume = {18}, year = {2023}, month = {12/2022}, pages = {238{\textendash}242}, chapter = {238}, abstract = {

Flowing fluid past chiral objects has been used for centuries to power rotary motion in man-made machines. By contrast, rotary motion in nanoscale biological or chemical systems is produced by biasing Brownian motion through cyclic chemical reactions. Here we show that a chiral biological molecule, a DNA or RNA duplex rotates unidirectionally at billions of revolutions per minute when an electric field is applied along the duplex, with the rotation direction being determined by the chirality of the duplex. The rotation is found to be powered by the drag force of the electro-osmotic flow, realizing the operating principle of a macroscopic turbine at the nanoscale. The resulting torques are sufficient to power rotation of nanoscale beads and rods, offering an engineering principle for constructing nanoscale systems powered by electric field.

}, issn = {1748-3387}, doi = {10.1038/s41565-022-01285-z}, url = {https://www.nature.com/articles/s41565-022-01285-z}, author = {Maffeo, Christopher and Quednau, Lauren and Wilson, James and Aksimentiev, Aleksei} } @article {360, title = {Synthetic Macrocycle Nanopore for Potassium-Selective Transmembrane Transport}, journal = {Journal of the American Chemical Society}, volume = {143}, year = {2021}, month = {08/2021}, pages = {15975-15983}, chapter = {15975}, abstract = {

Reproducing the structure and function of biological membrane channels, synthetic nanopores have been developed for applications in membrane filtration technologies and biomolecular sensing. Stable stand-alone synthetic nanopores have been created from a variety of materials, including peptides, nucleic acids, synthetic polymers, and solid-state membranes. In contrast to biological nanopores, however, furnishing such synthetic nanopores with an atomically defined shape, including deliberate placement of each and every chemical group, remains a major challenge. Here, we introduce a chemosynthetic macromolecule,\ extended pillararene macrocycle (EPM) as a chemically defined transmembrane nanopore that exhibits selective transmembrane transport. Our ionic current measurements reveal stable insertion of individual EPM nanopores into a lipid bilayer membrane and remarkable cation type-selective transport, with up to a 21-fold selectivity for potassium over sodium ions. Taken together, direct chemical synthesis offers a path to de novo design of a new class of synthetic nanopores with custom transport functionality imprinted in their atomically defined chemical structure.\ 

}, keywords = {Electrical conductivity, MD Simulations, Nanopores, Potassium Ions Selectivity}, doi = {10.1021/jacs.1c04910}, author = {Qiao, Dan and Joshi, Himanshu and Zhu, Huangtianzhi and Wang, Fushi and Xu, Yang and Gao, Jia and Huang, Feihe and Aleksei Aksimentiev and Feng, Jiandong} } @article {340, title = {Chiral Systems Made from DNA}, journal = {Advanced Science}, volume = {8}, year = {2021}, month = {01/2021}, pages = {2003113}, type = {Progress Report}, chapter = {2003113}, abstract = {

The very chemical structure of DNA that enables biological heredity and evolution has non-trivial implications for the self-organization of DNA molecules into larger assemblies and provides limitless opportunities for building functional nanostructures. This progress report discusses the natural organization of DNA into chiral structures and recent advances in creating synthetic chiral systems using DNA as a building material. How nucleic acid chirality naturally comes into play in a diverse array of situations is considered first, at length scales ranging from an individual nucleotide to entire chromosomes. Thereafter, chiral liquid crystal phases formed by dense DNA mixtures are discussed, including the ongoing efforts to understand their origins. The report then summarizes recent efforts directed toward building chiral structures, and other structures of complex topology, using the principle of DNA self-assembly. Discussed last are existing and proposed functional man-made nanostructures designed to either probe or harness DNA{\textquoteright}s chirality, from plasmonics and spintronics to\ biosensing.

}, doi = {10.1002/advs.202003113}, url = {https://doi.org/10.1002/advs.202003113}, author = {D Winogradoff and Pin-Yi Li and H Joshi and L Quednau and C Maffeo and Aleksei Aksimentiev} } @article {297, title = {Effect of temperature and hydrophilic ratio on the structure of poly(N-vinylcaprolactam)-block-poly(dimethylsiloxane)-block-poly(N-vinylcaprolactam) polymersomes}, journal = {ACS Applied Polymer Materials}, volume = {1}, year = {2019}, month = {04/2019}, pages = {722--736}, chapter = {722}, abstract = {

Nanosized polymeric vesicles (polymersomes) assembled from ABA triblock copolymers of poly(N-vinylcaprolactam)-poly(dimethylsiloxane)-poly(N-vinylcaprolactam) (PVCL-PDMS-PVCL) are a promising platform for biomedical applications, as the temperature-responsiveness of the PVCL blocks enables reversible vesicle shrinkage and permeability of the polymersome shell at elevated temperatures. Herein, we explore the effects of molecular weight, polymer block weight ratios, and temperature on the structure of these polymersomes via electron microscopy, dynamic light scattering, small angle neutron scattering (SANS), and all-atom molecular dynamic methods. We show that the shell structure and overall size of the polymersome can be tuned by varying the hydrophilic (PVCL) weight fraction of the polymer: at room temperature, polymers of smaller hydrophilic ratios form larger vesicles that have thinner shells, whereas polymers with higher PVCL content exhibit interchain aggregation of PVCL blocks within the polymersome shell above 50 {\textdegree}C. Model fitting and model-free analysis of the SANS data reveals that increasing the mass ratio of PVCL to the total copolymer weight from 0.3 to 0.56 reduces the temperature-induced change in vesicle diameter by a factor of 3 while simultaneously increasing the change in shell thickness by a factor of 1.5. Finally, by analysis of the shell structures and overall size of polymersomes with various PVCL weight ratios and those without temperature-dependent polymer components, we bring into focus the mechanism of temperature-triggered drug release reported in a previous study. This work provides new fundamental perspectives on temperature-responsive polymersomes and elucidates important structure-property relationships of their constituent polymers.

}, doi = {10.1021/acsapm.8b00259}, url = {https://pubs.acs.org/doi/pdf/10.1021/acsapm.8b00259}, author = {Yiming Yang and Aaron Alford and Kozlovskaya, Veronika and Zhao, Shidi and Joshi, Himanshu and Kim, Eunjung and Qian, Shuo and Urban, Volker and Cropek, Donald and Aleksei Aksimentiev and Kharlampieva, Eugenia} }