@article {370, title = {Fluorofoldamer-Based Salt- and Proton-Rejecting Artificial Water Channels for Ultrafast Water Transport.}, journal = {Nano Lett}, volume = {22}, year = {2022}, month = {2022 06 22}, pages = {4831-4838}, abstract = {

Here, we report on a novel class of fluorofoldamer-based artificial water channels (AWCs) that combines excellent water transport rate and selectivity with structural simplicity and robustness. Produced by a facile one-pot copolymerization reaction under mild conditions, the best-performing channel (AWC ) is an n-CH-decorated foldamer nanotube with an average channel length of 2.8 nm and a pore diameter of 5.2 {\r A}. AWC demonstrates an ultrafast water conduction rate of 1.4 {\texttimes} 10 HO/s per channel, outperforming the archetypal biological water channel, aquaporin 1, while excluding salts (i.e., NaCl and KCl) and protons. Unique to this class of channels, the inwardly facing C(sp2)-F atoms being the most electronegative in the periodic table are proposed as being critical to enabling the ultrafast and superselective water transport properties by decreasing the channel{\textquoteright}s cavity and enhancing the channel wall smoothness via reducing intermolecular forces with water molecules or hydrated ions.

}, keywords = {Aquaporins, Biological Transport, Protons, Sodium Chloride, Water}, issn = {1530-6992}, doi = {10.1021/acs.nanolett.2c01137}, author = {Shen, Jie and Roy, Arundhati and Joshi, Himanshu and Samineni, Laxmicharan and Ye, Ruijuan and Tu, Yu-Ming and Song, Woochul and Skiles, Matthew and Kumar, Manish and Aleksei Aksimentiev and Zeng, Huaqiang} } @article {351, title = {Foldamer-Based Ultrapermeable and Highly Selective Artificial Water Channels that Exclude Protons}, journal = {Nature Nanotechnology}, volume = {16}, year = {2021}, month = {08/2021}, pages = {911-917}, chapter = {911}, abstract = {

The outstanding capacity of aquaporins (AQPs) for mediating highly selective superfast water transport has inspired the recent development of supramolecular monovalent ion-excluding artificial water channels (AWCs). AWC-based bioinspired membranes are proposed for desalination, water purification, and other separation applications. While some recent progress has been made in synthesizing AWCs that approach the water permeability and ion selectivity of AQPs, a hallmark feature of AQPs{\textemdash}high water transport while excluding protons-has not been reproduced. We report a class of biomimetic, helically folded pore-forming polymeric foldamers that can serve as long-sought-after highly selective ultrafast water-conducting channels with performance exceeding those of AQPs (1.1 {\texttimes} 1010 water molecules per second for AQP1, with high water-over- monovalent-ion transport selectivity (~108 water molecules over Cl-\ ion) conferred by the modularly tunable hydrophobicity of the interior pore surface. The best-performing AWC reported here delivers water transport at an exceptionally high rate, namely, 2.5 times that of AQP1, while concurrently rejecting salts (NaCl and KCl) and even protons.

}, doi = {10.1038/s41565-021-00915-2}, author = {Roy, Arundhati and Shen, Jie and Joshi, Himanshu and Song, Woochul and Tu, Yu-Ming and Chowdhury, Ratul and Ruijuan, Ye and Li, Ning and Ren, Changliang and Kumar, Manish and Aleksei Aksimentiev and Zeng, Huaqiang} } @article {121, title = {Filling Up the Heme Pocket Stabilizes Apomyoglobin and Speeds Up Its Folding.}, journal = {J Phys Chem B}, year = {2014}, month = {02/2014}, abstract = {

Wild type apomyoglobin folds in at least two steps: the ABGH core rapidly, followed much later by the heme-binding CDEF core. We hypothesize that the evolved heme-binding function of the CDEF core frustrates its folding: it has a smaller contact order and is no more complex topologically than ABGH, and thus, it should be able to fold faster. Therefore, filling up the empty heme cavity of apomyoglobin with larger, hydrophobic side chains should significantly stabilize the protein and increase its folding rate. Molecular dynamics simulations allowed us to design four different mutants with bulkier side chains that increase the native bias of the CDEF region. In vitro thermal denaturation shows that the mutations increase folding stability and bring the protein closer to two-state behavior, as judged by the difference of fluorescence- and circular dichroism-detected protein stability. Millisecond stopped flow measurements of the mutants exhibit refolding kinetics that are over 4 times faster than the wild type{\textquoteright}s. We propose that myoglobin-like proteins not evolved to bind heme are equally stable, and find an example. Our results illustrate how evolution for function can force proteins to adapt frustrated folding mechanisms, despite having simple topologies.

}, issn = {1520-5207}, doi = {10.1021/jp412459z}, author = {Goodman, J S and Shu-Han Chao and Pogorelov, T V and Martin Gruebele} }