Anion‐Assisted Self‐Assembly

Fyfe, Matthew C. T.; Glink, Peter T.; Menzer, Stephan; Stoddart, J. Fraser; White, Andrew J. P.; Williams, David J.

doi:10.1002/anie.199720681

Cited by 199 publications

(105 citation statements)

References 34 publications

(3 reference statements)

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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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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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“…Some examples of them are met already among Borromean rings 11 or 12, see also 19 ( Figure 8). Some examples like [5]-rotaxane 20 (Figure 8), 32 which had been obtained under a certain approximation, obey quasi-Brunnian property (L = λ = 1). 33 Such cases I suggest to classify as the ones with the multiple mechanical bonds.…”

Section: Multiple Mechanical Bondsmentioning

confidence: 99%

On sublinks and their connections within the graphs of the mechanically bound molecules

Vysotsky¹

2009

Arkivoc

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The concept of sublinks has been further developed and has been used in the new form for the analysis of the graphs of complex mechanically bound molecules. This analysis is additionally supported by the Brunnian numbers M, µ for topologically non-trivial and their complements L and λ for topologically trivial systems (like [n]-rotaxanes). The detailed topological analysis has been thus performed for more than thirty topologically different structures. The different orders of (sub)links, single and multiple mechanical bonds ought to be discerned to analyze connections within the larger structures. The new nomenclature recommendations developed suggest to indicate the number of the mechanical bonds, their (highest) multiplicities together with the number of covalent units and the number of interlocked rings or rings and dumbbells.

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“…Provided sufficient thermal energy is available to break the intercomponent interactions at each site, the ring moves randomly between the two stations. On average, however, the macrocycle spends more time on the station with the higher binding affinity (i.e., the molecule tends to adopt a particular preferred co-conformation [7]). …”

Section: Molecular Mechanical Switchesmentioning

confidence: 99%

Beyond switches: Rotaxane- and catenane-based synthetic molecular motors

Kay

Leigh

2008

Pure and Applied Chemistry

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Nature uses molecular motors and machines in virtually every significant biological process, but learning how to design and assemble simpler artificial structures that function through controlled molecular-level motion is a major challenge for contemporary physical science. The established engineering principles of the macroscopic world can offer little more than inspiration to the molecular engineer who creates devices for an environment where everything is constantly moving and being buffeted by other atoms and molecules. Rather, experimental designs for working molecular machines must follow principles derived from chemical kinetics, thermodynamics, and nonequilibrium statistical physics. The remarkable characteristics of interlocked molecules make them particularly useful for investigating the control of motion at the molecular level. Yet, the vast majority of synthetic molecular machines studied to date are simple two-state switches. Here we outline recent developments from our laboratory that demonstrate more complex molecular machine functions. This new generation of synthetic molecular machines can move continuously and progressively away from equilibrium, and they may be considered true prototypical molecular motors. The examples discussed exemplify two, fundamentally different, "Brownian ratchet" mechanisms previously developed in theoretical statistical physics and realized experimentally in molecular-level devices for the first time in these systems.

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Anion‐Assisted Self‐Assembly

Cited by 199 publications

References 34 publications

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

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

On sublinks and their connections within the graphs of the mechanically bound molecules

Beyond switches: Rotaxane- and catenane-based synthetic molecular motors

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