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Chemical Reviews Jul 2023Anionic species are omnipresent and involved in many important biological processes. A large number of artificial anion receptors has therefore been developed. Some of... (Review)
Review
Anionic species are omnipresent and involved in many important biological processes. A large number of artificial anion receptors has therefore been developed. Some of these are capable of mediating transmembrane transport. However, where transport proteins can respond to stimuli in their surroundings, creation of synthetic receptors with stimuli-responsive functions poses a major challenge. Herein, we give a full overview of the stimulus-controlled anion receptors that have been developed thus far, including their application in membrane transport. In addition to their potential operation as membrane carriers, the use of anion recognition motifs in forming responsive membrane-spanning channels is discussed. With this review article, we intend to increase interest in transmembrane transport among scientists working on host-guest complexes and dynamic functional systems in order to stimulate further developments.
Topics: Receptors, Artificial; Biological Transport; Anions
PubMed: 37342028
DOI: 10.1021/acs.chemrev.3c00039 -
Chemical Society Reviews Oct 2010This tutorial review provides a summary of anion-mediated folding of linear and cyclic oligomers as well as anion-responsive behaviours of related polymeric... (Review)
Review
This tutorial review provides a summary of anion-mediated folding of linear and cyclic oligomers as well as anion-responsive behaviours of related polymeric architectures. Anions have emerged as a significant focus of the supramolecular community and here we review their impact on directing the secondary structures of synthetic oligomers and polymers while modulating physical properties e.g. molecular recognition. Oligomers and polymers responsive to anionic guests are typically constructed with hydrogen bond donors complementary to the target anions. Anion binding within the cavities leads to folding and helical wrapping of linear and cyclic oligomers as well as control over macromolecular properties of polymers. This review covers the impact of anion binding on guiding the secondary structures of single-stranded folded oligomers (foldamers) and cyclic oligomers (macrocycles), and on modulating the physical properties of select polymer architectures.
Topics: Anions; Indoles; Polymers; Pyrroles; Triazoles; Urea
PubMed: 20730154
DOI: 10.1039/b926162c -
Accounts of Chemical Research Nov 2017Anion receptors often rely on coordinative or multiple ionic interactions to be active in water. In the absence of such strong interactions, anion binding in water can... (Review)
Review
Anion receptors often rely on coordinative or multiple ionic interactions to be active in water. In the absence of such strong interactions, anion binding in water can also be efficient, however, as demonstrated by a number of anion receptors developed in recent years. The cyclopeptide-derived receptors comprising an alternating sequence of l-proline and 6-aminopicolinic acid subunits are an example. These cyclopeptides are neutral and, at first sight, can only engage in hydrogen-bond formation with an anionic substrate. Nevertheless, they even interact with strongly solvated sulfate anions in water. The intrinsic anion affinity of these cyclopeptides can be related to structural aspects of their highly preorganized concave binding site, which comprises a wall of hydrophobic proline units arranged around the peptide NH groups at the cavity base. When anions are incorporated into this cavity they can engage in hydrogen-bonding interactions to the NH groups, and complex formation also benefits from cavity dehydration. Formation of 1:1 complexes, in which an anion binds to a single cyclopeptide ring, is associated with only small stability constants, however, whereas significantly more stable complexes are formed if the anion is buried between two cyclopeptide molecules. A major contribution to the formation of these sandwich complexes derives from the addition of the second ring to the initially formed 1:1 cyclopeptide-anion complex. This step brings the apolar proline residues of both cyclopeptides in close proximity, which causes the resulting structure to be stabilized to a large extent by hydrophobic effects. Solvent dependent binding studies provided an estimate to which degree these solvent effects contribute to the overall complex stability. In these studies, bis(cyclopeptides) were used, featuring two cyclopeptide rings covalently connected via linkers that enable both rings to simultaneously interact with the anion. Bis(cyclopeptides) with additional solubilizing groups allowed binding studies in a wide range of solvents, including in water. The systematic analysis of the solvent dependence of anion affinity yielded a quantitative correlation between complex stability and parameters relating to the solvation of the anions and solvent properties, confirming that solvent effects contribute to anion binding. Interestingly, the thermodynamic signature of complex formation in water mirrors that of sulfate binding to a protein complex but is opposite to that of other recently described anion receptors, which also do not engage in ionic or coordinative interactions with the substrate. These receptors not only differ in terms of the thermodynamics of binding from the cyclopeptides but also possess a characteristically different anion selectivity in that they prefer to bind weakly coordinating anions but fail to bind sulfate. Solvent effects likely control the anion binding of both receptors types but their impact on complex formation and anion selectivity seems to be profoundly different. Future work in the area of anion coordination chemistry will benefit from the deeper understanding of these effects and how they can be controlled.
Topics: Anions; Hydrogen Bonding; Hydrophobic and Hydrophilic Interactions; Molecular Conformation; Peptides, Cyclic; Picolinic Acids; Proline; Receptors, Artificial; Thermodynamics; Water
PubMed: 29125287
DOI: 10.1021/acs.accounts.7b00458 -
Organic & Biomolecular Chemistry Nov 2022The anion recognition ability of 2,4,6-triisopropylphenylsilanetriol 5 has been evaluated by H NMR titrations in MeCN-. The anion recognition ability of silanetriol 5...
The anion recognition ability of 2,4,6-triisopropylphenylsilanetriol 5 has been evaluated by H NMR titrations in MeCN-. The anion recognition ability of silanetriol 5 was greater than those of the structurally related silanediols and silanemono-ol, although less effective than those of 1,3-disiloxane-1,3-diol and 1,3-disiloxane-1,1,3,3-tetraol. From the comparison of the association constants and DFT calculations, all three silanol groups of 5 cooperatively hydrogen bonded to anionic species. The catalytic ability of silanetriol 5 for the addition of indole to β-nitrostyrene in CHCl has also been evaluated. Silanetriol 5 acts as a more effective organocatalyst than the corresponding silanediol in this reaction.
Topics: Anions; Acetonitriles
PubMed: 36321688
DOI: 10.1039/d2ob01596j -
Nature Communications Aug 2022The quantification of anion binding by molecular receptors within lipid bilayers remains challenging. Here we measure anion binding in lipid bilayers by creating a...
The quantification of anion binding by molecular receptors within lipid bilayers remains challenging. Here we measure anion binding in lipid bilayers by creating a fluorescent macrocycle featuring a strong sulfate affinity. We find the determinants of anion binding in lipid bilayers to be different from those expected that govern anion binding in solution. Charge-dense anions HPO and Cl that prevail in dimethyl sulfoxide fail to bind to the macrocycle in lipids. In stark contrast, ClO and I that hardly bind in dimethyl sulfoxide show surprisingly significant affinities for the macrocycle in lipids. We reveal a lipid bilayer anion binding principle that depends on anion polarisability and bilayer penetration depth of complexes leading to unexpected advantages of charge-diffuse anions. These insights enhance our understanding of how biological systems select anions and guide the design of functional molecular systems operating at biomembrane interfaces.
Topics: Anions; Dimethyl Sulfoxide; Lipid Bilayers; Sulfates
PubMed: 35941124
DOI: 10.1038/s41467-022-32403-z -
Chemistry (Weinheim An Der Bergstrasse,... Jan 2022Since its discovery two decades ago, anion-π interaction has been increasingly recognized as an important driving force. Extensive theoretical and experimental efforts...
Since its discovery two decades ago, anion-π interaction has been increasingly recognized as an important driving force. Extensive theoretical and experimental efforts on the ground-state anion-π binding and recognition have laid the bases for exploring its relevance in catalysis. Accordingly, the concept of "anion-π catalysis" that employing an electron-deficient π surface (π-acidic surface) for anionic reaction intermediate and transition state stabilization has emerged. This article shortly reviews the emergence and development of this concept, aiming to provide an emphasis on the general concept and key progress in this exciting area. To highlight the essential contribution of anion-π interactions, the contents are organized according to their role engaged in catalytic process, for example from both ground-state and transition-state stabilization to solely transition-state stabilization, mainly by a single π-face, and to cooperative π-face activation. A concluding remark and outlook on future development of this field is also given.
Topics: Anions; Catalysis; Electrons; Models, Molecular
PubMed: 34658085
DOI: 10.1002/chem.202103303 -
International Journal of Molecular... Jan 2019Integral membrane proteins of the divalent anion/Na⁺ symporter (DASS) family are conserved from bacteria to humans. DASS proteins typically mediate the coupled uptake... (Review)
Review
Integral membrane proteins of the divalent anion/Na⁺ symporter (DASS) family are conserved from bacteria to humans. DASS proteins typically mediate the coupled uptake of Na⁺ ions and dicarboxylate, tricarboxylate, or sulfate. Since the substrates for DASS include key intermediates and regulators of energy metabolism, alterations of DASS function profoundly affect fat storage, energy expenditure and life span. Furthermore, loss-of-function mutations in a human DASS have been associated with neonatal epileptic encephalopathy. More recently, human DASS has also been implicated in the development of liver cancers. Therefore, human DASS proteins are potentially promising pharmacological targets for battling obesity, diabetes, kidney stone, fatty liver, as well as other metabolic and neurological disorders. Despite its clinical relevance, the mechanism by which DASS proteins recognize and transport anionic substrates remains unclear. Recently, the crystal structures of a bacterial DASS and its humanized variant have been published. This article reviews the mechanistic implications of these structures and suggests future work to better understand how the function of DASS can be modulated for potential therapeutic benefit.
Topics: Amino Acid Sequence; Animals; Anions; Binding Sites; Biological Transport; Humans; Protein Binding; Protein Conformation; Protein Multimerization; Sodium; Structure-Activity Relationship; Symporters
PubMed: 30669552
DOI: 10.3390/ijms20020440 -
Chemical Communications (Cambridge,... Jul 2016Oligo-(thio)ureas have proven to be a promising class of receptors that are widely applied in anion recognition. This article aims to present some recent progress in the... (Review)
Review
Oligo-(thio)ureas have proven to be a promising class of receptors that are widely applied in anion recognition. This article aims to present some recent progress in the construction of oligoureas and their anion coordination (recognition) chemistry. Typical examples of metal-coordination assisted and covalently connected oligo-(thio)urea receptors are summarized, with focus on geometry characteristics required for achieving complementary binding of a target anion. Special emphasis is given to ortho-phenylene-connected oligoureas in the application of anion binding and the self-assembly of important supramolecular architectures, including helicates, tetrahedral cages, and so on.
Topics: Anions; Models, Molecular; Molecular Structure; Urea
PubMed: 27352298
DOI: 10.1039/c6cc03761e -
Chemical Society Reviews Mar 2014The ability of cationic coordination cages to act as anion receptors is reviewed, with an emphasis on the anion encapsulation chemistry and the dynamics of cage... (Review)
Review
The ability of cationic coordination cages to act as anion receptors is reviewed, with an emphasis on the anion encapsulation chemistry and the dynamics of cage assembly, anion exchange, and other anion-induced structural transformations. The first part of the review describes various examples of anion-encapsulating coordination cages, categorized on the basis of their M(x)L(y) stoichiometry (M = metal cation; L = organic ligand). The second part deals with the dynamic aspects of anion encapsulation, including the kinetics and mechanism of anion binding, release, and exchange, as well as the structural evolution of the coordination complexes involved.
Topics: Anions; Coordination Complexes; Crystallography, X-Ray; Kinetics; Models, Molecular; Molecular Structure
PubMed: 24384869
DOI: 10.1039/c3cs60371g -
Macromolecular Rapid Communications Jan 2012In biological systems, the selective and high-affinity recognition of anionic species is accomplished by macromolecular hosts (anion-binding proteins) that have been... (Review)
Review
In biological systems, the selective and high-affinity recognition of anionic species is accomplished by macromolecular hosts (anion-binding proteins) that have been "optimized" through evolution. Surprisingly, it is only recently that chemists have systematically attempted to develop anion-responsive synthetic macromolecules for potential applications in medicine, national security, or environmental monitoring. Recent results indicating that unique features of polymeric systems such as signal amplification, multivalency, and cooperative behavior may be exploited productively in the context of anion recognition and sensing are documented. The wide variety of interactions-including Lewis acid/base, ion-pairing, and hydrogen bonding-that have been employed for this purpose is reflected in the structural diversity of anion-responsive macromolecules identified to date.
Topics: Anions; Binding Sites; Molecular Structure; Polymers
PubMed: 22038843
DOI: 10.1002/marc.201100528