Metallopolymer–Peptide Hybrid Materials: Synthesis and Self‐Assembly of Functional,Polyferrocenylsilane–Tetrapeptide Conjugates

Conjugates of poly(ferrocenyldimethylsilane) (PFDMS) with Ac‐(GA)₂‐OH, Ac‐A₄‐OH, Ac‐G₄‐OH and Ac‐V₄‐OH have been prepared by reaction of the tetrapeptide units with the amino‐terminated metallopolymer. The number average degree of polymerisation (DP_n) of the PFDMS was approximately 20 and comparable materials with shorter (DP_n≈10) and/or amorphous chains have been prepared by the same procedure. Poly(ferrocenylethylmethylsilane) (PFEMS) was employed for the latter purpose. All conjugates were characterised by GPC, MALDI‐TOF MS, NMR and IR spectroscopy. With the exception of Ac‐V₄‐PFDMS₂₀, all materials exhibited some anti‐parallel β‐sheet structure in the solid state. The self‐assembly of the conjugates was studied in toluene by DLS. The vast majority of the materials, irrespective of peptide sequence or chain crystallinity, afforded fibres consisting of a peptidic core surrounded by a PFS corona. These fibres were found in the form of cross‐linked networks by TEM and AFM. The accessibility of the chemically reducing PFS corona has been demonstrated by the localised formation of silver nanoparticles on the surface of the fibres.     

Artificial Multienzyme Supramolecular Device: Highly Ordered Self‐Assembly of Oligomeric Enzymes In Vitro and In Vivo

A strategy for scaffold‐free self‐assembly of multiple oligomeric enzymes was developed by exploiting enzyme oligomerization and protein–protein interaction properties, and was tested both in vitro and in vivo. Octameric leucine dehydrogenase and dimeric formate dehydrogenase were fused to a PDZ (PSD95/Dlg1/zo‐1) domain and its ligand, respectively. The fusion proteins self‐assembled into extended supramolecular interaction networks. Scanning‐electron and atomic‐force microscopy showed that the assemblies assumed two‐dimensional layer‐like structures. A fluorescence complementation assay indicated that the assemblies were localized to the poles of cells. Moreover, both in vitro and in vivo assemblies showed higher NAD(H) recycling efficiency and structural stability than did unassembled structures when applied to a coenzyme recycling system. This work provides a novel method for developing artificial multienzyme supramolecular devices and for compartmentalizing metabolic enzyme cascades in living cells.     

A Supramolecular Polymer as a Self‐Assembling Polyvalent Scaffold

Binding bacteria : Discotic molecules self‐assemble into columnar supramolecular polymers that show strong polyvalent binding to bacteria by virtue of mannose ligands attached at their periphery (orange; see picture). The reversible formation of the supramolecular polymers allows simple mixing of differently substituted monomers and the optimization of bacterial aggregation.

     

STM Insight into Hydrogen‐Bonded Bicomponent 1 D Supramolecular Polymers with Controlled Geometries at the Liquid–Solid Interface

Bicomponent supramolecular polymers , consisting of two alternating molecules bridged through six H‐bonds, are observed by STM at the solid–liquid interface. Control of the geometry of the 1D architecture was obtained by using two different connecting molecules with different conformational rigidity, affording either linear (see picture, left) or zigzag (right) motifs.

     

Functionalized Soft Nanoporous Materials through Supramolecular Assembly of End‐Functionalized Polymer Blends

Supramolecular assembly through complementary interaction between molecular subgroups belonging to phase‐separating polymer species offers a great opportunity, not only for constructing nanoscale soft templates reminiscent of conventional block copolymer morphologies, but also for tailoring surface properties by facile removal of one of the structure components by cleaving complementary interactions. Herein we report the fabrication of a novel, organic, nanoporous film through supramolecular assembly of two complementarily, end‐interacting, mono‐end‐functionalized polymers under solvent annealing. The film of end‐functionalized polymer blends under solvent annealing yielded phase‐separated nanodomains that resemble nanoscopically ordered structures of block copolymers, but that are more advantageous due to easily cleavable and exchangeable links between the phase‐separated domains. The removal of one of the components of the precursor structure formed from the end‐functionalized polymers through cleavage of complementary interactions allowed us to fabricate mono‐ or multilayered nanoporous structures in which the chemically useful end‐functionalities of the remnant polymers are rich on the surface of the pores. The resultant, organic, nanoporous films with tailored surface functionality offer a useful platform for various chemical and biological applications.     

Easy Fabrication and Morphology Control of Supramolecular Liquid‐Crystalline Polymer Microparticles

A novel kind of supramolecular liquid‐crystalline polymer (SLCP) microparticles was successfully fabricated with an azopyridyl polymer and sebacic acid by combining a simple self‐organized precipitation method with hydrogen bonding interactions. Upon slow evaporation of a mixed solution of a volatile good solvent and a nonvolatile poor one, walnutlike microparticles showing wrinkled surfaces and LC natures were obtained. The diacid might play a crucial role in the formation of SLCP particles. Without addition of the diacid, neither wrinkled surfaces nor LC natures were observed in azopyridyl polymer microparticles. The fabricated SLCP microparticle possessed not only photoresponsive properties (due to azopyridyl groups) but also LC ordering, which might enable them to find advanced applications.

     

A Supramolecular Hydrogen‐Bonded Network as a Diffusion Barrier for Metal Adatoms

Confined in a molecular corral : A supramolecular network changes the mechanism by which underpotential deposition (UPD) of copper proceeds on a gold electrode modified by a self‐assembled monolayer (SAM). Lateral diffusion of Cu adatoms is suppressed between adjacent cells of a network/SAM hybrid structure. Instead, UPD occurs by direct deposition into the SAM filled pores of the network, where the Cu adatoms are confined.

     

Aromatic Gain in a Supramolecular Polymer

The synergy of aromatic gain and hydrogen bonding in a supramolecular polymer is explored. Partially aromatic bis(squaramide) bolaamphiphiles were designed to self‐assemble through a combination of hydrophobic, hydrogen‐bonding, and aromatic effects into stiff, high‐aspect‐ratio fibers. UV and IR spectroscopy show electron delocalization and geometric changes within the squaramide ring indicative of strong hydrogen bonding and aromatic gain of the monomer units. The aromatic contribution to the interaction energy was further supported computationally by nucleus‐independent chemical shift (NICS) and harmonic oscillator model of aromaticity (HOMA) indices, demonstrating greater aromatic character upon polymerization: at least 30 % in a pentamer. The aromatic gain–hydrogen bonding synergy results in a significant increase in thermodynamic stability and a striking difference in aggregate morphology of the bis(squaramide) bolamphiphile compared to isosteres that cannot engage in this effect.     

Reversible Assembly of a Supramolecular Cage Linked by Boron–Nitrogen Dative Bonds

Boron–nitrogen dative bonds provide a suitable motif for reversible, yet strong and directed interactions, leading to the highly efficient self‐assembly of small organic building blocks into supramolecular cage structures. A bipyramidal [2+3] assembly, as the first example of a supramolecular cage mediated by B?N dative bonds that exists as a discrete species in solution, is quantitatively obtained from a tribenzotriquinacene‐based trisboronate ester and 1,4‐diazabicyclo[2.2.2]octane. Thermodynamic equilibria of cage formation are investigated by isothermal titration calorimetry and fully reversible cage opening can be observed at elevated temperatures.     

Carboxylate‐Driven Supramolecular Assemblies of Protonated meso‐Aryl‐Substituted Dipyrrolylpyrazoles

Dipyrrolylpyrazole (dpp) derivatives possessing an aryl ring at the pyrazole 4‐position were synthesized. Upon protonation, modified dpp derivatives formed a variety of assembled structures through complexation with carboxylates, as observed by single‐crystal X‐ray and synchrotron XRD analyses. In particular, the complexation of protonated dpp species possessing long alkyl chains with dicarboxylates resulted in highly ordered assembled structures, the packing modes of which as lamellar structures were controlled by the lengths of the spacer units between two carboxylate moieties. The charge‐carrier transporting properties of the solid materials were also controlled by bound anions, including dicarboxylates.     

An AAA–DDD Triply Hydrogen‐Bonded Complex Easily Accessible for Supramolecular Polymers

For a complementary hydrogen‐bonded complex, when every hydrogen‐bond acceptor is on one side and every hydrogen‐bond donor is on the other, all secondary interactions are attractive and the complex is highly stable. AAA–DDD (A=acceptor, D=donor) is considered to be the most stable among triply hydrogen‐bonded sequences. The easily synthesized and further derivatized AAA–DDD system is very desirable for hydrogen‐bonded functional materials. In this case, AAA and DDD, starting from 4‐methoxybenzaldehyde, were synthesized with the Hantzsch pyridine synthesis and Friedländer annulation reaction. The association constant determined by fluorescence titration in chloroform at room temperature is 2.09×10⁷ M ^?1. The AAA and DDD components are not coplanar, but form a V shape in the solid state. Supramolecular polymers based on AAA–DDD triply hydrogen bonded have also been developed. This work may make AAA–DDD triply hydrogen‐bonded sequences easily accessible for stimuli‐responsive materials.     

Supramolecular Proteoglycan Aggregate Mimics: Cyclodextrin‐Assisted Biodegradable Polymer Assemblies for Electrostatic‐Driven Drug Delivery

Self‐assembled, noncovalent polymeric biodegradable materials mimicking proteoglycan aggregates were synthesized from inclusion complexes of cationic surfactants with γ‐cyclodextrin and the natural anionic polymer hyaluronan. The amorphous structure of this ternary system was proven by X‐ray diffraction and thermal analysis. Light‐scattering measurements showed that there was a competition between hyaluronic acid and the surfactant for the cyclodextrin cavity. These self‐assembled supramolecular matrices were loaded with both hydrophilic and lipophilic drug substances for dissolution studies. The release of the entrapped drugs was found to be controlled by cations in the surrounding media and by biodegradation. Slow drug release in an ion‐free medium became faster in physiological salt solution in which the macroscopic polymer matrix was disassembled. In contrast, the enzymatic degradation of hyaluronan was hindered in the polymeric matrix. The supramolecular systems consisting of γ‐cyclodextrin as a macrocyclic host, a cationic surfactant guest, and hyaluronic acid as the anionic polymer electrostatically cross‐linked by the inclusion complex of the first two was found to be a novel drug‐delivery system for the controlled release of traditional drugs such as curcumin and ketotifen and proteins such as bovine serum albumin.