Two‐Component Fibers/Gels and Vesicles Formed from Hetero‐Double‐Helices of Pseudoenantiomeric Ethynylhelicene Oligomers with Branched Side Chains

Saito, Nozomi; Shigeno, Masanori; Yamaguchi, Masahiko

doi:10.1002/chem.201200280

Cited by 33 publications

(39 citation statements)

References 91 publications

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“…The structure of the hetero‐double‐helix ( P )‐ 5 /( M )‐ 4 in the precipitates was determined by using CD and UV/Vis analyses in the solid state, which was compared with those of the hetero‐double‐helix previously obtained in a solution from ( P )‐ 5 and the ( M )‐tetramer ( M )‐bD‐ 4 with branched side chains8c (Figure 4). The ( P )‐nanoparticle precipitates obtained in the above experiment (Figure 3) were placed on a quartz plate.…”

Section: Resultsmentioning

confidence: 99%

Helicene‐Grafted Silica Nanoparticles Capture Hetero‐Double‐Helix Intermediates during Self‐Assembly Gelation

Miyagawa

Yamaguchi

2015

Chemistry A European J

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A mixture of a pseudoenantiomeric ethynylhelicene (M)-tetramer and a (P)-pentamer forms a hetero-double-helix in a solution, which self-assembles and gelates solvents. When gelation was conducted in the presence of chiral silica (P)-nanoparticles grafted with (P)-helicene, the resulting hetero-double-helix intermediate was adsorbed on the (P)-nanoparticles, and was removed from the solution by aggregation and precipitation. The resulting precipitates contained only the hetero-double-helix, not random coil or clusters of the hetero-double-helix. (P)-Nanoparticles did not extract the hetero-double-helix from the self-assembly gels. The hetero-double-helix was then isolated by liberating it from the precipitates in 2-bromopropionic acid, and was crystallized from the solution. The crystalline hetero-double-helices were isolated for several other combinations of pseudoenantiomeric ethynylhelicene oligomers.

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Section: Resultsmentioning

confidence: 99%

Helicene‐Grafted Silica Nanoparticles Capture Hetero‐Double‐Helix Intermediates during Self‐Assembly Gelation

Miyagawa

Yamaguchi

2015

Chemistry A European J

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“…[14,15] In this study, a gel formed for the tetrameric aab'b' aggregate of the (M)-A4(M)-E5/(M)-A4(P)-E4 mixture in toluene. [14,15] In this study, a gel formed for the tetrameric aab'b' aggregate of the (M)-A4(M)-E5/(M)-A4(P)-E4 mixture in toluene.…”

Section: Methodsmentioning

confidence: 91%

“…It competes with the entropic effect, in which dimeric aggregates are most favorable, because the entropic loss is minimal. [14] Also, no aggregation occurs between the amido domain (M)-A4 and the ethynyl domain (M/P)-E5. Specific tetrameric aabb heteroaggregate formation should include a concept not known at present.…”

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confidence: 99%

“…The method exploits the different stabilities of the homo-and heteroaggregates at the amido tetramer domain (M)-A4 and the ethynyl pentamer domains (M/P)-E5 (Figure 1). [14] Also, no aggregation occurs between the amido domain (M)-A4 and the ethynyl domain (M/P)-E5. The homoaggregation of (M)-A4 is much stronger than that of (M)-E5, and the heteroaggregation of (M)-E5 and (P)-E5 is much stronger than the homoaggregation.…”

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confidence: 99%

“…[13] Herein, bidomain oligomers (M)-A4(M/P)-E5 were used for tetrameric aabb heteroaggregate formation. [14] Also, no aggregation occurs between the amido domain (M)-A4 and the ethynyl domain (M/P)-E5. [14] Also, no aggregation occurs between the amido domain (M)-A4 and the ethynyl domain (M/P)-E5.…”

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Tetrameric ααββ Aggregate Formation by Stereoisomeric Bidomain Helicene Oligomers

2013

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Proteins form quaternary structures by the heteroaggregation of several subunits and exhibit functions as whole aggregates, [1] which structurally can be dimeric, trimeric, tetrameric, and higher aggregates with various modes of homoand heteroaggregation. Hemoglobin, which transports oxygen in red blood cells, forms a tetrameric aabb heteroaggregate from two a-subunits and two b-subunits, and exhibits physiologically important allosteric interactions between these subunits.[2] Tetrameric aabb heteroaggregates were observed in coiled coil peptides [3] and rigid-rod b-barrels, [4] which are formed by peptide-peptide interactions. The aggregation was highly dependent on the amino acid residue.From the enthalpic view, polymerized structures are favorable, because multiple aggregation gains a large free energy. It competes with the entropic effect, in which dimeric aggregates are most favorable, because the entropic loss is minimal. However, it may not be sufficient to explain tetrameric aabb aggregate formation simply by the balance of enthalpy and entropy, because such a balance most likely gives a complex mixture of aggregates. Specific tetrameric aabb heteroaggregate formation should include a concept not known at present. Thus, the development of a method of forming tetrameric aabb heteroaggregates using synthetic compounds is desirable to promote our understanding of protein functions and the development of novel drugs and biomaterials that interact with proteins.In this study, we present a general method of specifically constructing aabb heteroaggregates without forming other homo-and heteroaggregates of dimeric, trimeric, pentameric, and polymeric structures. The method entails the aggregation of multidomain oligomers. Synthetic small-domain compounds [5][6][7][8] and block copolymers [9] form polymeric heteroaggregates; however, the formation of specific higher aggregates such as the aabb tetrameric heteroaggregate is not yet known.We have recently reported the dimeric homoaggregate formation of the bidomain oligomer (P)-A4(P)-E7, [10] which contained the (P)-amidohelicene [11] tetramer domain (P)-A4 and the (P)-ethynylhelicene [12] heptamer domain (P)-E7, and dimeric heteroaggregate formation of the tridomain oligomers (P)-A4(P)-E5(P)-A4 and (P)-A4(M)-E5(P)-A4. [13] Herein, bidomain oligomers (M)-A4(M/P)-E5 were used for tetrameric aabb heteroaggregate formation. The method exploits the different stabilities of the homo-and heteroaggregates at the amido tetramer domain (M)-A4 and the ethynyl pentamer domains (M/P)-E5 (Figure 1). The stabilities are in the order: (M)-A4 and (M)-A4 > (M)-E5 and (P)-E5 > (M)-E5 and (M)-E5. The homoaggregation of (M)-A4 is much stronger than that of (M)-E5, and the heteroaggregation of (M)-E5 and (P)-E5 is much stronger than the homoaggregation.[14] Also, no aggregation occurs between the amido domain (M)-A4 and the ethynyl domain (M/P)-E5. Otherwise, complex mixtures of aggregates would form.With regards to solvent effects, it is known that the amido domain in (P)-A4(P)-E7 for...

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Structure and Property Diversity of Chiral Helicene Oligomers

Saito

Shigeno

Yamaguchi

2015

Encyclopedia of Polymer Science and Technology

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alkylthio, and perfluoroalkyl groups. In addition, cyclization of helicene oligomers provides another method of obtaining diversity.A notable aspect in the diversity of helicene oligomers is that they can be connected to provide multidomain oligomers (Fig. 4). When two helicene oligomers are connected, they are referred to herein as homo-bidomain oligomers. Cyclic homo-bidomain oligomers are also conceivable. Hetero-multidomain oligomers can be obtained by connecting different structures of oligomers. Such manipulations provide a large diversity of structures.Because helicene can generate characteristic π−π interactions, helicene oligomers often form bimolecular, trimolecular, tetramolecular, and polymolecular aggregates in which homoaggregation and heteroaggregation can also occur. Such aggregates self-assemble to form fibrils, vesicles, liquid crystals, and surface monolayers. These noncovalent bonding interactions provide diversity of the structure of helicene oligmers. Diverse Properties of Helicene OligomersStructural diversity is directly related to diversity of properties, and the properties of a helicene oligomer can be varied by structural modifications. In addition, multidomain oligomers can be designed, in which properties A and B of each domain can be combined. Such compounds exhibit property A + B or even another property C, a result regarded as the "synthesis of a property or function." Aggregation and self-assembly of helicene oligomers further increase property diversity, which covers materials with a broad range of sizes from subnanometersized molecules through nano-and micrometer-sized molecular aggregates and molecular self-assemblies to macroscopic bulk materials. Helicene oligomers are sensitive to changes in the environment such as temperature, solvent, and concentration. Different properties appear in dilute solution, in concentrated Amidohelicene oligomers: (a) acylcic oligomers (P)-1 (n = 1−9) with dianiline spacer, cyclic oligomers (P)-2 (n = 1−10) with dianiline spacer, (b) acyclic oligomers (P)-3 (n = 1−9) with m-phenylene spacer, and acyclic reverse oligomers (P)-4 (n = 1−4). (c) Schematic representation of reversible change between helix dimer and random coils of (P)-3 and (P)-4. solution, in the crystalline state, in the amorphous state, on the solid surface, at the solid-liquid interface, in fiber assemblies, in liquid crystals, and in gels. Dynamic properties of helicene oligomers are also interesting, and structural changes are largely affected by the environment, providing a stimulus response or possible molecular switching materials. It is also noteworthy that the process of a structure change can produce unusual transient phenomena. Amidohelicene OligomersStudies on helicene oligomers were initiated with amide derivatives (Fig. 5a, top), in which the spacer has a bent shape and includes both hydrogen bonding donor and acceptor moieties (24). (P)-5,8-Helicenedicarboxylate was reacted with bis(2,6-dimethylanilino)cyclohexane to give a series of acyclic helicene oligomers 1 up t...

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Two‐Component Fibers/Gels and Vesicles Formed from Hetero‐Double‐Helices of Pseudoenantiomeric Ethynylhelicene Oligomers with Branched Side Chains

Cited by 33 publications

References 91 publications

Helicene‐Grafted Silica Nanoparticles Capture Hetero‐Double‐Helix Intermediates during Self‐Assembly Gelation

Helicene‐Grafted Silica Nanoparticles Capture Hetero‐Double‐Helix Intermediates during Self‐Assembly Gelation

Tetrameric ααββ Aggregate Formation by Stereoisomeric Bidomain Helicene Oligomers

Structure and Property Diversity of Chiral Helicene Oligomers

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