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Webb SJ, Monk CS, Nelson CA. Mechanisms of postnatal neurobiological development: implications for human development. Dev Neuropsychol 2002; 19:147-71. [PMID: 11530973 DOI: 10.1207/s15326942dn1902_2] [Citation(s) in RCA: 183] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
This review focuses on the postnatal neuroanatomical changes that arise during the first years of human life. Development is characterized by 2 major organizational periods. The first period begins at conception and includes the major histogenetic events such as neurulation, proliferation, migration, and differentiation. It has been proposed that these events may be controlled by genetic and epigenetic events, which give rise to neural structures that are amenable to external influence. The second period is a time of reorganization in the human cortex. These events occur during gestation and continue postnatally, possibly through the 2nd decade of life. This stage is characterized by dendritic and axonal growth, synapse production, neuronal and synaptic pruning, and changes in neurotransmitter sensitivity. Although the initiation of these events is influenced by endogenous signals, further neural maturation is primarily influenced by exogenous signals. To illustrate both the progressive and regressive events during the postnatal period, we use examples from the development of the human cortex.
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De Poli M, Zawodny W, Quinonero O, Lorch M, Webb SJ, Clayden J. Conformational photoswitching of a synthetic peptide foldamer bound within a phospholipid bilayer. Science 2016; 352:575-80. [PMID: 27033546 DOI: 10.1126/science.aad8352] [Citation(s) in RCA: 140] [Impact Index Per Article: 15.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2015] [Accepted: 02/24/2016] [Indexed: 12/17/2022]
Abstract
The dynamic properties of foldamers, synthetic molecules that mimic folded biomolecules, have mainly been explored in free solution. We report on the design, synthesis, and conformational behavior of photoresponsive foldamers bound in a phospholipid bilayer akin to a biological membrane phase. These molecules contain a chromophore, which can be switched between two configurations by different wavelengths of light, attached to a helical synthetic peptide that both promotes membrane insertion and communicates conformational change along its length. Light-induced structural changes in the chromophore are translated into global conformational changes, which are detected by monitoring the solid-state (19)F nuclear magnetic resonance signals of a remote fluorine-containing residue located 1 to 2 nanometers away. The behavior of the foldamers in the membrane phase is similar to that of analogous compounds in organic solvents.
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Research Support, Non-U.S. Gov't |
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140 |
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57 |
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Doyle EL, Hunter CA, Phillips HC, Webb SJ, Williams NH. Cooperative binding at lipid bilayer membrane surfaces. J Am Chem Soc 2003; 125:4593-9. [PMID: 12683831 DOI: 10.1021/ja021048a] [Citation(s) in RCA: 85] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The binding of copper(II) ions to membrane-bound synthetic receptors has been investigated. Complexation fitted a 4:1 receptor:copper(II) model, and the observed binding constants are significantly enhanced at the membrane relative to solution; these effects can be explained by the lower polarity of the membrane-water interface and the concentrating effect of the membrane, with no observed contribution from receptor preorganization. The stoichiometry of the complex formed is very sensitive to the concentration of the receptor in the membrane, and at low concentrations, binding is reduced relative to solution controls. This implies that by increasing or decreasing the number of receptors in their membranes, cells can finely tune biological responses such as chemotaxis that depend on the size of the receptor-ligand clusters formed.
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Jones EJH, Venema K, Earl R, Lowy R, Barnes K, Estes A, Dawson G, Webb SJ. Reduced engagement with social stimuli in 6-month-old infants with later autism spectrum disorder: a longitudinal prospective study of infants at high familial risk. J Neurodev Disord 2016; 8:7. [PMID: 26981158 PMCID: PMC4791854 DOI: 10.1186/s11689-016-9139-8] [Citation(s) in RCA: 84] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/09/2015] [Accepted: 02/17/2016] [Indexed: 11/18/2022] Open
Abstract
Background Autism spectrum disorder (ASD) is a neurodevelopmental disorder that affects more than 1 % of the population and close to 20 % of prospectively studied infants with an older sibling with ASD. Although significant progress has been made in characterizing the emergence of behavioral symptoms of ASD, far less is known about the underlying disruptions to early learning. Recent models suggest that core aspects of the causal path to ASD may only be apparent in early infancy. Here, we investigated social attention in 6- and 12-month-old infants who did and did not meet criteria for ASD at 24 months using both cognitive and electrophysiological methods. We hypothesized that a reduction in attention engagement to faces would be associated with later ASD. Methods In a prospective longitudinal design, we used measures of both visual attention (habituation) and brain function (event-related potentials to faces and objects) at 6 and 12 months and investigated the relationship to ASD outcome at 24 months. Results High-risk infants who met criteria for ASD at 24 months showed shorter epochs of visual attention, faster but less prolonged neural activation to faces, and delayed sensitization responses (increases in looking) to faces at 6 months; these differences were less apparent at 12 months. These findings are consistent with disrupted engagement of sustained attention to social stimuli. Conclusions These findings suggest that there may be fundamental early disruptions to attention engagement that may have cascading consequences for later social functioning. Electronic supplementary material The online version of this article (doi:10.1186/s11689-016-9139-8) contains supplementary material, which is available to authorized users.
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Journal Article |
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Thornton PD, Mart RJ, Webb SJ, Ulijn RV. Enzyme-responsive hydrogel particles for the controlled release of proteins: designing peptide actuators to match payload. SOFT MATTER 2008; 4:821-827. [PMID: 32907188 DOI: 10.1039/b714750c] [Citation(s) in RCA: 81] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
We report on enzyme-responsive hydrogel particles for the controlled release of proteins. Amino-functionalised poly(ethylene glycol acrylamide) (PEGA) hydrogel particles were functionalised with peptide actuators that cause charge-induced swelling and payload release when triggered enzymatically. Peptide-based actuators were designed to match the specificity of the target enzyme, while also matching the charge properties of the to-be released protein payload, thereby uniquely allowing for tuneable release profiles. Fluorescently labelled albumin and avidin, proteins of similar size but opposite charge, were released at a rate that was governed by the peptide actuator linked to the polymer carrier, offering a highly controlled release mechanism. Release profiles were analysed using a combination of fluorescence spectroscopy of the solution and two-photon fluorescence microscopy to analyse enzymatically triggered molecular events within hydrogel particles during the initial stages of release.
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Webb SJ, Harrison DJ, Wyllie AH. Apoptosis: an overview of the process and its relevance in disease. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 1997; 41:1-34. [PMID: 9204139 DOI: 10.1016/s1054-3589(08)61052-2] [Citation(s) in RCA: 81] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
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Review |
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81 |
10
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Mart RJ, Liem KP, Wang X, Webb SJ. The Effect of Receptor Clustering on Vesicle−Vesicle Adhesion. J Am Chem Soc 2006; 128:14462-3. [PMID: 17090021 DOI: 10.1021/ja0657612] [Citation(s) in RCA: 77] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
As part of our studies into how the localization of cell adhesion molecules into lipid rafts may affect cell adhesion, we developed Cu(1), a synthetic copper(iminodiacetate)-capped receptor able to phase separate from fluid phospholipid bilayers. The extent to which Cu(1) clustered into adhesive patches on the surface of vesicles could be controlled by changing vesicle composition. Extensive receptor phase separation significantly enhanced vesicle-vesicle adhesion; only vesicles with adhesive patches (blue fluorescence) adhered to their conjugate histidine-coated vesicles (red fluorescence) to form large vesicle aggregates (shown).
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Jones JE, Diemer V, Adam C, Raftery J, Ruscoe RE, Sengel JT, Wallace MI, Bader A, Cockroft SL, Clayden J, Webb SJ. Length-Dependent Formation of Transmembrane Pores by 310-Helical α-Aminoisobutyric Acid Foldamers. J Am Chem Soc 2016; 138:688-95. [PMID: 26699898 PMCID: PMC4752191 DOI: 10.1021/jacs.5b12057] [Citation(s) in RCA: 63] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
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The synthetic biology toolbox lacks
extendable and conformationally
controllable yet easy-to-synthesize building blocks that are long
enough to span membranes. To meet this need, an iterative synthesis
of α-aminoisobutyric acid (Aib) oligomers was used to create
a library of homologous rigid-rod 310-helical foldamers,
which have incrementally increasing lengths and functionalizable N-
and C-termini. This library was used to probe the inter-relationship
of foldamer length, self-association strength, and ionophoric ability,
which is poorly understood. Although foldamer self-association in
nonpolar chloroform increased with length, with a ∼14-fold
increase in dimerization constant from Aib6 to Aib11, ionophoric activity in bilayers showed a stronger length
dependence, with the observed rate constant for Aib11 ∼70-fold
greater than that of Aib6. The strongest ionophoric activity
was observed for foldamers with >10 Aib residues, which have end-to-end
distances greater than the hydrophobic width of the bilayers used
(∼2.8 nm); X-ray crystallography showed that Aib11 is 2.93 nm long. These studies suggest that being long enough to
span the membrane is more important for good ionophoric activity than
strong self-association in the bilayer. Planar bilayer conductance
measurements showed that Aib11 and Aib13, but
not Aib7, could form pores. This pore-forming behavior
is strong evidence that Aibm (m ≥ 10) building blocks can span bilayers.
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Journal Article |
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Sardzík R, Noble GT, Weissenborn MJ, Martin A, Webb SJ, Flitsch SL. Preparation of aminoethyl glycosides for glycoconjugation. Beilstein J Org Chem 2010; 6:699-703. [PMID: 20978609 PMCID: PMC2956404 DOI: 10.3762/bjoc.6.81] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/26/2010] [Accepted: 07/21/2010] [Indexed: 11/23/2022] Open
Abstract
The synthesis of a number of aminoethyl glycosides of cell-surface carbohydrates, which are important intermediates for glycoarray synthesis, is described. A set of protocols was developed which provide these intermediates, in a short number of steps, from commercially available starting materials.
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Journal Article |
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Redmore SM, Rickard CEF, Webb SJ, Wright LJ. Ruthenium Complexes of a Simple Tridentate Ligand Bearing Two "Distal" Pyridine Bases. Inorg Chem 1997; 36:4743-4748. [PMID: 11670151 DOI: 10.1021/ic961534x] [Citation(s) in RCA: 58] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Treatment of N,N'-bis(6-methyl-2-pyridinyl)-2,6-pyridinedicarboxamide (1) (H(2)LMe(2)) with RuCl(2)(PPh(3))(3) in toluene yields the complex RuCl(2)(PPh(3))(LMe(2){H}(2)) (2) in which the ruthenium atom is coordinated to the nitrogen atoms of the two deprotonated amides and the central pyridine of 1. The two pendant pyridines in 2 are both protonated, and hydrogen bonds are formed to the coordinated chloride positioned in the molecular cleft between these two groups. Both of the chlorides in 2 can be replaced by other anions in simple metathesis reactions, and treatment of 2 with excess SCN(-) or CH(3)CO(2)(-) yields the corresponding complexes RuX(2)(PPh(3))(LMe(2){H}(2)) (X: SCN(-), 3; CH(3)CO(2)(-), 4). Treatment of 2 with NO(2)(-) also results in displacement of the chlorides, but in this case, the protons on the pendant pyridines are lost and the nitrosyl-containing complex Ru(NO(2))(NO)(PPh(3))(LMe(2)) (5) is formed. Single-crystal X-ray structure determinations have been carried out for the following compounds: 1, space group C2/c, a = 13.588(6) Å, b = 11.518(2) Å, c = 12.731(3) Å, Z = 4, V = 1826.7 Å(3); 2, space group P&onemacr;, a = 10.482(5) Å, b = 11.349(8) Å, c = 15.710(4) Å, Z= 2, V = 1689(2) Å(3); 5, space group P&onemacr;, a = 12.204(2) Å, b = 13.065(3) Å, c = 14.722(6) Å, Z = 2, V = 1973.9(10) Å(3).
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Brioche J, Pike S, Tshepelevitsh S, Leito I, Morris GA, Webb SJ, Clayden J. Conformational Switching of a Foldamer in a Multicomponent System by pH-Filtered Selection between Competing Noncovalent Interactions. J Am Chem Soc 2015; 137:6680-91. [PMID: 25915163 PMCID: PMC4520694 DOI: 10.1021/jacs.5b03284] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2015] [Indexed: 12/26/2022]
Abstract
Biomolecular systems are able to respond to their chemical environment through reversible, selective, noncovalent intermolecular interactions. Typically, these interactions induce conformational changes that initiate a signaling cascade, allowing the regulation of biochemical pathways. In this work, we describe an artificial molecular system that mimics this ability to translate selective noncovalent interactions into reversible conformational changes. An achiral but helical foldamer carrying a basic binding site interacts selectively with the most acidic member of a suite of chiral ligands. As a consequence of this noncovalent interaction, a global absolute screw sense preference, detectable by (13)C NMR, is induced in the foldamer. Addition of base, or acid, to the mixture of ligands competitively modulates their interaction with the binding site, and reversibly switches the foldamer chain between its left and right-handed conformations. As a result, the foldamer-ligand mixture behaves as a biomimetic chemical system with emergent properties, functioning as a "proton-counting" molecular device capable of providing a tunable, pH-dependent conformational response to its environment.
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research-article |
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Birchall LS, Ulijn RV, Webb SJ. A combined SPS–LCD sensor for screening protease specificity. Chem Commun (Camb) 2008:2861-3. [DOI: 10.1039/b805321a] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Monk CS, Webb SJ, Nelson CA. Prenatal neurobiological development: molecular mechanisms and anatomical change. Dev Neuropsychol 2002; 19:211-36. [PMID: 11530976 DOI: 10.1207/s15326942dn1902_5] [Citation(s) in RCA: 38] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/31/2022]
Abstract
During prenatal development, the central nervous system is transformed from a thin layer of unspecified tissue into a complex system that can process information and organize actions. There are 8 general mechanisms that permit this transformation: neural induction, neurulation, proliferation, migration, axonal outgrowth, synaptogenesis, differentiation, and apoptosis. These processes as well as the anatomical changes they cause are described. Future research with humans, such as in utero MRI as well as behavioral and electrophysiological testing of infants following specific prenatal perturbations, is suggested to link the findings from molecular approaches to developmental neuropsychology.
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Review |
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Noble GT, Craven FL, Voglmeir J, Šardzík R, Flitsch SL, Webb SJ. Accelerated Enzymatic Galactosylation of N-Acetylglucosaminolipids in Lipid Microdomains. J Am Chem Soc 2012; 134:13010-7. [DOI: 10.1021/ja302506t] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/17/2023]
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Wilson CP, Boglio C, Ma L, Cockroft SL, Webb SJ. Palladium(II)-Mediated Assembly of Biotinylated Ion Channels. Chemistry 2011; 17:3465-73. [DOI: 10.1002/chem.201002031] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2010] [Revised: 10/12/2010] [Indexed: 11/10/2022]
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Noble GT, Flitsch SL, Liem KP, Webb SJ. Assessing the cluster glycoside effect during the binding of concanavalin A to mannosylated artificial lipid rafts. Org Biomol Chem 2009; 7:5245-54. [DOI: 10.1039/b910976e] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
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Abstract
Based on recent models of the ontogeny of memory (Nelson, 1995), we hypothesize that 6-month-old infants should show evidence of repetition priming. Event-related potentials were recorded from 11 scalp sites to novel and primed upright and inverted faces. In Experiment 1 (n = 24), 6-month-old infants viewed faces that were repeated after 6 to 12 images. Overall, repeated faces demonstrated greater negativity than novel faces and upright faces demonstrated greater negativity than inverted faces. In order to ground these results in an adult model, a group of adults (n = 30) was tested in a similar experiment. Here we observed effects of repetition at an early positive component labeled the P150 as well as at the P300, with repeated images being more positive than novel images. These data support the idea that infants at 6 months are capable of revealing electrophysiological evidence of perceptual priming.
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Comparative Study |
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Abstract
Energy levels exist in mammalian cells which result in the absorption of microwaves between 66 and 76 gigahertz. Many of these energy levels occur when water molecules associate with the various chemical groups of macromolecules. The absorption spectra of cells between 66 and 76 gigahertz, therefore, is determined by the structure of in vivo water lattices, and these seem to reflect indirectly the structural makeup of macromolecules or macromolecular complexes. Tumor cells absorb 66-, 68-, and 70-gigahertz microwaves less strongly and 69-, 72-, and 75-gigahertz microwaves more strongly than normal cells. These differences in the strength of attenuation at each frequency suggest that either the ratio of RNA to DNA or the relative number of certain types of chemical groups in tumor cells is different from that in normal cells.
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Tomsett M, Maffucci I, Le Bailly BAF, Byrne L, Bijvoets SM, Lizio MG, Raftery J, Butts CP, Webb SJ, Contini A, Clayden J. A tendril perversion in a helical oligomer: trapping and characterizing a mobile screw-sense reversal. Chem Sci 2017; 8:3007-3018. [PMID: 28451368 PMCID: PMC5380885 DOI: 10.1039/c6sc05474a] [Citation(s) in RCA: 33] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2016] [Accepted: 01/24/2017] [Indexed: 11/21/2022] Open
Abstract
Helical oligomers of achiral monomers adopt domains of uniform screw sense, which are occasionally interrupted by screw-sense reversals. These rare, elusive, and fast-moving features have eluded detailed characterization. We now describe the structure and habits of a screw-sense reversal trapped within a fragment of a helical oligoamide foldamer of the achiral quaternary amino acid 2-aminoisobutyric acid (Aib). The reversal was enforced by compelling the amide oligomer to adopt a right-handed screw sense at one end and a left-handed screw sense at the other. The trapped reversal was characterized by X-ray crystallography, and its dynamic properties were monitored by NMR and circular dichroism, and modelled computationally. Raman spectroscopy indicated that a predominantly helical architecture was maintained despite the reversal. NMR and computational results indicated a stepwise shift from one screw sense to another on moving along the helical chain, indicating that in solution the reversal is not localised at a specific location, but is free to migrate across a number of residues. Analogous unconstrained screw-sense reversals that are free to move within a helical structure are likely to provide the mechanism by which comparable helical polymers and foldamers undergo screw-sense inversion.
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research-article |
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August D, Borsley S, Cockroft SL, della Sala F, Leigh DA, Webb SJ. Transmembrane Ion Channels Formed by a Star of David [2]Catenane and a Molecular Pentafoil Knot. J Am Chem Soc 2020; 142:18859-18865. [PMID: 33084320 PMCID: PMC7745878 DOI: 10.1021/jacs.0c07977] [Citation(s) in RCA: 33] [Impact Index Per Article: 6.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2020] [Indexed: 12/19/2022]
Abstract
A (FeII)6-coordinated triply interlocked ("Star of David") [2]catenane (612 link) and a (FeII)5-coordinated pentafoil (51) knot are found to selectively transport anions across phospholipid bilayers. Allostery, topology, and building block stoichiometry all play important roles in the efficacy of the ionophoric activity. Multiple FeII cation coordination by the interlocked molecules is crucial: the demetalated catenane exhibits no anion binding in solution nor any transmembrane ion transport properties. However, the topologically trivial, Lehn-type cyclic hexameric FeII helicates-which have similar anion binding affinities to the metalated Star of David catenane in solution-also display no ion transport properties. The unanticipated difference in behavior between the open- and closed-loop structures may arise from conformational restrictions in the linking groups that likely enhances the rigidity of the channel-forming topologically complex molecules. The (FeII)6-coordinated Star of David catenane, derived from a hexameric cyclic helicate, is 2 orders of magnitude more potent in terms of ion transport than the (FeII)5-coordinated pentafoil knot, derived from a cyclic pentamer of the same building block. The reduced efficacy is reminiscent of multisubunit protein ion channels assembled with incorrect monomer stoichiometries.
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research-article |
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