Self-Assembling Capsules

Conn, M. Morgan; Rebek, Julius

doi:10.1021/cr9603800

Cited by 1,095 publications

(459 citation statements)

References 137 publications

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“…9) and previously reported hexameric aggregates (13 a-c) 6 and (14a) 6 (16)(17)(18). As shown in Table 1, the polystyrenederived M n values were consistent with formation of hexamer from 7b and 7c [see (7Ј) 6 ] and formation of a dodecamer such as 17 (Fig. 10) from 7a.…”

Section: Resultssupporting

confidence: 57%

“…Inspired by nature's ability to create extraordinarily complex systems from comparatively simple information codes, and with an eye toward creating nanoscale devices (2), chemists have sought to develop small molecules capable of self-assembling into larger structures (3)(4)(5)(6)(7)(8)(9)(10). Molecular recognition sites within these small molecules carry the code that guide the assembly.…”

mentioning

confidence: 99%

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Discrete and polymeric self-assembled dendrimers: Hydrogen bond-mediated assembly with high stability and high fidelity

Corbin

Lawless

et al. 2002

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

170

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Hydrogen bond-mediated self-assembly is a powerful strategy for creating nanoscale structures. However, little is known about the fidelity of assembly processes that must occur when similar and potentially competing hydrogen-bonding motifs are present. Furthermore, there is a continuing need for new modules and strategies that can amplify the relatively weak strength of a hydrogen bond to give more stable assemblies. Herein we report quantitative complexation studies on a ureidodeazapterin-based module revealing an unprecedented stability for dimers of its self-complementary acceptoracceptor-donor-donor (AADD) array. Linking two such units together with a semirigid spacer that carries a first-, second-, or third-generation Fré chet-type dendron affords a ditopic structure programmed to self assemble. The specific structure that is formed depends both on the size of the dendron and the solvent, but all of the assemblies have exceptionally high stability. The largest discrete nanoscale assembly is a hexamer with a molecular mass of about 17.8 kDa. It is stabilized by 30 hydrogen bonds, including six AADD⅐DDAA contacts. The hexamer forms and is indefinitely stable in the presence of a hexamer containing six ADD⅐DAA hydrogen-bonding arrays. A t the most fundamental level, the readout of stored information in biochemical systems requires both a code and the machinery for expressing the code (1). Distinction at the molecular level is critical in such processes and in its simplest form involves a molecular recognition event. The code may be, for example, the primary sequence of a polypeptide, which through a series of recognition events folds into a specific secondary or tertiary structure, or it may be a linear array of recognition sites that are sequentially processed through a distinctive engagement at each site. However, a distinctive chemical process alone (e.g., DNA base pairing) is not sufficient. It must be coupled with a biological process (e.g., replication) to be considered authentic information retrieval.Inspired by nature's ability to create extraordinarily complex systems from comparatively simple information codes, and with an eye toward creating nanoscale devices (2), chemists have sought to develop small molecules capable of self-assembling into larger structures (3-10). Molecular recognition sites within these small molecules carry the code that guide the assembly. Thus, the information retrieval process is expressed through the formation of the self-assembled structure, which can further manifest itself through the bulk properties of the material formed (11,12). Despite the many successful examples that have appeared over the past decade, the power of this biomimetic self-assembly strategy has not been fully realized largely because of the limited number of recognition motifs available, and, in particular, their relatively low stability (4, 13). Moreover, nearly all self-assembling systems reported to date use a single type of distinction. Developing systems where bi-or polyinstructional codes guide ...

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Section: Resultssupporting

confidence: 57%

mentioning

confidence: 99%

Discrete and polymeric self-assembled dendrimers: Hydrogen bond-mediated assembly with high stability and high fidelity

Corbin

Lawless

et al. 2002

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

170

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“…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. Two other sandwich-type anion complexes of artificial receptors have been described quite recently (27,28).…”

mentioning

confidence: 77%

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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“…The design of host molecules which efficiently bind small nonpolar guests is a great challenge as dispersion interactions of small guests are less intense owing to their small number of atoms. For binding such guests cage compounds are most suitable as they are able to fully enclose molecules and thereby increase the quantity of dispersion interactions [7][8][9] . Prominent examples for cage compounds are cryptophanes [10][11][12] .…”

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confidence: 99%

Strongly underestimated dispersion energy in cryptophanes and their complexes

2014

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Cryptophanes, composed of two bowl-shaped cyclotriveratrylene subunits linked by three aliphatic linker groups, are prototypal organic host molecules which bind reversibly neutral small guest compounds via London forces. The binding constants for these complexes are usually measured in tetrachloroethane and are in the range of 10 2 -10 3 M À 1 . Here we show that tetrachloroethane is-in contrast to the scientific consensus-enclosed by the cryptophane-E cavity. By means of NMR spectroscopy we show that the binding constant for CHCl 3 @cryptophane-E is in larger solvents two orders of magnitudes higher than the one measured before. Ab initio calculations reveal that attractive dispersion energy is responsible for high binding constants and for the formation of imploded cryptophanes which seem to be more stable than cryptophanes with empty cavities.

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Self-Assembling Capsules

Cited by 1,095 publications

References 137 publications

Discrete and polymeric self-assembled dendrimers: Hydrogen bond-mediated assembly with high stability and high fidelity

Discrete and polymeric self-assembled dendrimers: Hydrogen bond-mediated assembly with high stability and high fidelity

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

Strongly underestimated dispersion energy in cryptophanes and their complexes

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