Anion Helicates:  Double Strand Helical Self-Assembly of Chiral Bicyclic Guanidinium Dimers and Tetramers around Sulfate Templates

Sánchez‐Quesada, Jorge; Seel, Christian; Prados, and Pilar; Mendoza, Javier de; and, Ionara Dalcol; Giralt, Ernest

doi:10.1021/ja953243d

Cited by 218 publications

(118 citation statements)

References 23 publications

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“…As shown in Figure 3 a, cells incubated with CF-(VRLPPP) 3 presented the highest fluorescence intensity. This result could be attributed to the ability of guanidinium groups to interact strongly with bidentate anions, [21] present here in the form of phosphate diester in the outer part of the cell membranes (Figure 1 d) and, it is in agreement with several reported examples. [22] A dose-response analysis was then undertaken, by incubating HeLa cells with the peptides at different concentrations.…”

supporting

confidence: 92%

Potential Peptide Carriers: Amphipathic Proline‐Rich Peptides Derived from the N‐Terminal Domain of γ‐Zein

et al. 2004

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supporting

confidence: 92%

Potential Peptide Carriers: Amphipathic Proline‐Rich Peptides Derived from the N‐Terminal Domain of γ‐Zein

et al. 2004

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“…Such a complex formation resembles the anion-induced selfassociation that has also been described for other systems (14)(15)(16)(17)(18). Furthermore, the structure of the complexes formed are comparable to those of the molecular capsules described by the groups of Rebek (19)(20)(21)(22) or Böhmer (23)(24)(25)(26), but because both cyclopeptide subunits in the complex are held together only by the anion and not by additional intermolecular interactions, the term sandwich complex is more appropriate.…”

supporting

confidence: 54%

Conformation and anion binding properties of cyclic hexapeptides containing l -4-hydroxyproline and 6-aminopicolinic acid subunits

Kubik

Goddard

2002

Proc. Natl. Acad. Sci. U.S.A.

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Two cyclic hexapeptides containing alternating all R and all S configured L-(4R͞S)-hydroxyproline and 6-aminopicolinic acid subunits are presented, and the influence of the hydroxyl groups on the solubility, conformation, and receptor properties is investigated. Cyclopeptide 2, containing the natural 4R configured hydroxyproline, adopts a conformation similar to that of the unsubstituted peptide 1, which is able to bind anions such as halides and sulfate in aqueous solution. 2 also interacts with these anions, but whereas 1 forms sandwich type 2:1 complexes, in which the anion is bound by two cyclopeptide moieties, 2 forms 1:1 complexes. The stabilities of the halide and sulfate complexes of 2 range between 10 0 and 10 2 M ؊1 in 80% D2O͞CD3OD. Complex formation is detectable even in water, but with slightly smaller stability constants. Using this information a quantitative evaluation of the stability of the 2:1 complexes of 1, for which overall stability constants in the order 10 4 to 10 5 M ؊2 in 80% D2O͞CD3OD were observed, was made. In contrast to 2, the conformation of 3, containing the non-natural 4S configured hydroxyproline, is strongly affected by the presence of the hydroxyl groups. In d 6-DMSO and methanol͞water mixtures a slow conformational equilibrium between two C3-symmetrical conformers is observed, and 3 is thus much less preorganized for anion binding than either 1 or 2.T he crystal structures of anion binding proteins with the substrate resting in the active site have provided valuable information on the principles nature uses for the recognition of negatively charged compounds (1). Important binding interactions are, for example, multiple hydrogen bonds formed between the substrate and NH groups of the protein backbone or hydrogen bond donors in amino acid side chains (2, 3). A way of mimicking these interactions in an artificial system is to arrange amide or urea NH groups around the cavity of a suitable host molecule. This strategy has led to the development of many artificial hosts for anions, some of which possess remarkable substrate affinity, even in highly competitive solvents such as DMSO or acetonitrile (4-12). The ultimate goal has, of course, been the design of receptors that bind anions by hydrogen bonds in water. However, despite the recent advances in the development of anion receptors (4-7), most systems described so far require strong electrostatic or coordinative interactions to be effective in this solvent. One of the few exceptions is the cyclic hexapeptide 1 that has recently been described by us (13). This neutral macrocyclic receptor interacts with anions such as halides or sulfate even in water͞methanol mixtures, a behavior that can largely be attributed to the special geometry of the complexes formed. We have found that the presence of a suitable anion in solution induces an aggregation of two cyclopeptide molecules, whereby a cavity is formed into which the anion is included (Fig. 1). In this complex, the anion is shielded from the surrounding solvent and can thus inte...

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“…[6] We hypothesized that oligomer 1 would fold in a manner similar to other linear, flexible oligomers [7] to provide a model cavity by which to explore the intermolecular interactions between the electropositive CH side of 1,4-triazoles and electron-rich guests such as anions ( Figure 1). Our expectations were buoyed by previous reports of anion-induced folding, [8,9] in particular by a recent demonstration by Jeong and co-workers [8] that the folding of oligoindoles can be directed through a helical arrangement of NH···anion hydrogen bonds. Herein, we report 1) that 1:1 interactions between diaryl triazoles and chloride ions in acetone are directional and sufficiently strong as to be observable by 1 H NMR spectroscopy, 2) that the strength of the interaction increases with the generation of triazole-containing oligomer, and 3) that CH···anion contacts guide the folding of aryl triazole oligomers in solution and in the solid state.…”

mentioning

confidence: 60%

1,2,3‐Triazole CH⋅⋅⋅Cl⁻ Contacts Guide Anion Binding and Concomitant Folding in 1,4‐Diaryl Triazole Oligomers

et al. 2008

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Manipulation of weak intermolecular interactions guides the rational design [1] of sensors, drugs, and foldamers-synthetic, [2] nonnatural backbones that fold into an ordered, biomimetic array. 1,4-Substituted 1,2,3-triazoles, which are readily accessible through the Cu I -catalyzed Huisgen 1,3-dipolar cycloaddition of azides and alkynes, [3] are seemingly universal ligation tools [4] whose capacity for independent function has received far less attention. Recent reports, however, indicate that the size and dipole moment ( % 5 D) of triazoles make them interesting candidates for amide bond surrogates, [5] and Arora and co-workers have reported the contributions of triazoles to the conformational preferences of peptidotriazole oligomers. [6] We hypothesized that oligomer 1 would fold in a manner similar to other linear, flexible oligomers [7] to provide a model cavity by which to explore the intermolecular interactions between the electropositive CH side of 1,4-triazoles and electron-rich guests such as anions ( Figure 1). Our expectations were buoyed by previous reports of anion-induced folding, [8,9] in particular by a recent demonstration by Jeong and co-workers [8] that the folding of oligoindoles can be directed through a helical arrangement of NH···anion hydrogen bonds. Herein, we report 1) that 1:1 interactions between diaryl triazoles and chloride ions in acetone are directional and sufficiently strong as to be observable by 1 H NMR spectroscopy, 2) that the strength of the interaction increases with the generation of triazole-containing oligomer, and 3) that CH···anion contacts guide the folding of aryl triazole oligomers in solution and in the solid state.While the "click" coupling of alkyl azides with alkynes is highly efficient, [10] the formation of diaryl triazoles has, until recently, been relatively more difficult and less efficient. [11] Nonetheless, under modified conditions, the Cu I -catalyzed cycloaddition produces acceptable yields of the desired 1,4-diaryl-1,2,3-triazole-containing compounds 1-3. A tetraethylene glycol unit was introduced outside of the cavity for solubility.Oligomer 1 has appreciable conformational freedom only around the arene-triazole single bonds. Molecular modeling [12] suggested no significant preference for a particular rotamer, a prediction that is supported by NOESY spectra of 1 in [D 6 ]acetone (Figure 2 a). Modeling studies also show that complexation of 1 with Cl À aligns the electropositive triazole CH units toward the interior of a helix, within which the Cl À is bound.The computer modeling holds true in solution, where the chloride-induced folding of 1 is revealed by 1 H NMR spectroscopy. The 1 H NMR spectrum of 1 changes considerably upon the addition of tetrabutylammonium chloride

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Anion Helicates: Double Strand Helical Self-Assembly of Chiral Bicyclic Guanidinium Dimers and Tetramers around Sulfate Templates

Cited by 218 publications

References 23 publications

Potential Peptide Carriers: Amphipathic Proline‐Rich Peptides Derived from the N‐Terminal Domain of γ‐Zein

Potential Peptide Carriers: Amphipathic Proline‐Rich Peptides Derived from the N‐Terminal Domain of γ‐Zein

Conformation and anion binding properties of cyclic hexapeptides containing l -4-hydroxyproline and 6-aminopicolinic acid subunits

1,2,3‐Triazole CH⋅⋅⋅Cl⁻ Contacts Guide Anion Binding and Concomitant Folding in 1,4‐Diaryl Triazole Oligomers

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Anion Helicates: Double Strand Helical Self-Assembly of Chiral Bicyclic Guanidinium Dimers and Tetramers around Sulfate Templates

Cited by 218 publications

References 23 publications

Potential Peptide Carriers: Amphipathic Proline‐Rich Peptides Derived from the N‐Terminal Domain of γ‐Zein

Potential Peptide Carriers: Amphipathic Proline‐Rich Peptides Derived from the N‐Terminal Domain of γ‐Zein

Conformation and anion binding properties of cyclic hexapeptides containing l -4-hydroxyproline and 6-aminopicolinic acid subunits

1,2,3‐Triazole CH⋅⋅⋅Cl− Contacts Guide Anion Binding and Concomitant Folding in 1,4‐Diaryl Triazole Oligomers

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1,2,3‐Triazole CH⋅⋅⋅Cl⁻ Contacts Guide Anion Binding and Concomitant Folding in 1,4‐Diaryl Triazole Oligomers