With the world's focus on reducing our dependency on fossil-fuel energy, the scientific community can investigate new plastic materials that are much less dependent on petroleum than are conventional plastics. Given increasing environmental issues, the idea of replacing plastics with water-based gels, so-called hydrogels, seems reasonable. Here we report that water and clay (2-3 per cent by mass), when mixed with a very small proportion (<0.4 per cent by mass) of organic components, quickly form a transparent hydrogel. This material can be moulded into shape-persistent, free-standing objects owing to its exceptionally great mechanical strength, and rapidly and completely self-heals when damaged. Furthermore, it preserves biologically active proteins for catalysis. So far no other hydrogels, including conventional ones formed by mixing polymeric cations and anions or polysaccharides and borax, have been reported to possess all these features. Notably, this material is formed only by non-covalent forces resulting from the specific design of a telechelic dendritic macromolecule with multiple adhesive termini for binding to clay.

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Molecular analogues of a variety of mechanical devices such as shuttles, brakes, unidirectional rotors and tweezers have been created. But these 'molecular machines' have not yet been used to mechanically manipulate a second molecule in a controlled and reversible manner. Here we show that light-induced scissor-like conformational changes of one molecule can give rise to mechanical twisting of a non-covalently bound guest molecule. To realize this coupling of molecular motions, we use a previously designed system: a ferrocene moiety with an azobenzene strap, each end of which is attached to one of the two cyclopentadienyl rings of the ferrocene unit, acts as a pivot so that photoisomerization of the strap rotates the ferrocene rings relative to each other and thereby also changes the relative position of two 'pedal' moieties attached to the ferrocene rings. We translate this effect into intermolecular coupling of motion by endowing the pedals with binding sites, which allow the host system to form a stable complex with a bidentate rotor molecule. Using circular dichroism spectroscopy, we show that the photoinduced conformational changes of the host are indeed transmitted and induce mechanical twisting of the rotor molecule. This design concept, which significantly extends the successful coupling of motion beyond the intramolecular level seen in synthetic allosteric receptors, might allow for the remote control of molecular events in larger interlocked molecular systems.

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The first example of "light-driven chiral molecular scissors" (1), which consists of 1,1',3,3'-tetraarylferrocene as a pivot part and azobenzene as a driving part, was synthesized. Absorption, circular dichroism (CD), and 1H NMR spectral studies on the photoinduced isomerization process of an enantiomer of 1 agreed well with a prediction by a DFT calculation, where a motion of the handles via light-driven contraction/expansion of the connecting azobenzene strap was transformed, through a pivotal motion of the ferrocene unit, into an open-close motion of the blade parts.

Supramolecular interaction of fullerenes with cyclic dimers of metalloporphyrins (1‐M, M=central metal ions) showed a pronounced dependence on the nature of the metal ions, whereby 1‐RhMe/fullerene systems displayed extremely high association constants (ca. 108 M−1) and low dissociation activities. Crystal‐structure analysis and NMR data suggested a charge‐transfer interaction and van der Waals interactions between the host and guest.

The development of nanocarriers that selectively release guest molecules on sensing a particular biological signal is being actively pursued in nanomedicine for diagnostic and therapeutic purposes. Here we report a protein-based nanocarrier that opens in the presence of intracellular adenosine-5'-triphosphate (ATP). The nanocarrier consists of multiple barrel-shaped chaperonin units assembled through coordination with Mg(2+) into a tubular structure that protects guest molecules against biological degradation. When its surface is functionalized with a boronic acid derivative, the nanocarrier is able to enter cells. The hydrolysis of intracellular ATP into adenosine-5'-diphosphate (ADP) induces conformational changes of the chaperonin units, which in turns generate a mechanical force that leads to the disassembly of the tube and release of the guests. This scission occurs with a sigmoidal dependence on ATP concentration, which means that the nanocarrier can differentiate biological environments in terms of the concentration of ATP for selective guest release. Furthermore, biodistribution tests reveal preferential accumulation of the nanocarriers in a tumour tissue.

Various properties of semiconductor nanoparticles, including photoluminescence and catalytic activity, make these materials attractive for a range of applications. As nanoparticles readily coagulate and so lose their size-dependent properties, shape-persistent three-dimensional stabilizers that enfold nanoparticles have been exploited. However, such wrapping approaches also make the nanoparticles insensitive to external stimuli, and so may limit their application. The chaperonin proteins GroEL (from Escherichia coli) and T.th ('T.th cpn', from Thermus thermophilus HB8) encapsulate denatured proteins inside a cylindrical cavity; after refolding, the encapsulated proteins are released by the action of ATP inducing a conformational change of the cavity. Here we report that GroEL and T.th cpn can also enfold CdS semiconductor nanoparticles, giving them high thermal and chemical stability in aqueous media. Analogous to the biological function of the chaperonins, the nanoparticles can be readily released from the protein cavities by the action of ATP. We expect that integration of such biological mechanisms into materials science will open a door to conceptually new bioresponsive devices.