Quadrangular Prism: A Unique Self‐Assembly from Amphiphilic Hyperbranched PMA‐b‐PAA

The novel hyperbranched poly(methyl acrylate)‐block‐poly(acrylic acid)s (HBPMA‐b‐PAAs) are successfully synthesized via single‐electron transfer‐living radical polymerization (SET‐LRP), followed with hydrolysis reaction. The copolymer solution could spontaneously form unimolecular micelles composed of the hydrophobic core (PMA) and the hydrophilic shell (PAA) in water. Results show that the size of spherical particles increases from 8.18 to 19.18 nm with increased pH from 3.0 to 12.0. Most interestingly, the unique regular quadrangular prisms with the large microstructure (5.70 μm in length, and 0.47 μm in width) are observed by the self‐assembly of unimolecular micelles when pH value is below 2. Such self‐assembly behavior of HBPMA‐b‐PAA in solution is significantly influenced by the pH cycle times and concentration, which show that increased polymer concentration favors aggregate growth.

     

Carbonic Anhydrase Immobilized on Encapsulated Magnetic Nanoparticles for CO2 Sequestration

Bovine carbonic anhydrase (BCA) was covalently immobilized onto OAPS (octa(aminophenyl)silsesquioxane)‐functionalized Fe₃O₄/SiO₂ nanoparticles by using glutaraldehyde as a spacer. The Fe₃O₄ nanoparticles were coated with SiO₂, onto which was grafted OAPS, and the product was characterized using SEM, TEM, XRD, IR, X‐ray photoelectron spectroscopy (XPS), and magnetometer analysis. The enzymatic activities of the free and Fe₃O₄/SiO₂/OAPS‐conjugated BCA (Fe? CA) were investigated by hydrolyzing p‐nitrophenylacetate (p‐NPA), and hydration and sequestration of CO₂ to CaCO₃. The CO₂ conversion efficiency and reusability of the Fe? CA were studied before and after washing the recovered Fe? CA by applying a magnetic field and quantifying the unreacted Ca²⁺ ions by using ion chromatography. After 30 cycles, the Fe? CA displayed strong activity, and the CO₂ capture efficiency was 26‐fold higher than that of the free enzyme. Storage stability studies suggested that Fe? CA retained nearly 82 % of its activity after 30 days. Nucleation of the precipitated CaCO₃ was monitored by using polarized light microscopy, which revealed the formation of two phases, calcite and valerite, at pH 10 upon addition of serine. The magnetic nanobiocatalyst was shown to be an excellent reusable catalyst for the sequestration of CO_2.     

Solid‐State Scrolls from Hierarchical Self‐Assembly of T‐Shaped Rod–Coil Molecules

On a roll : Attachment of flexible coils to the middle of a rigid rod generates T‐shaped rod–coil molecules that self‐assemble into layers that roll up to form filled cylindrical and hollow tubular scrolls, depending on the coil length, in the solid state (see picture); the rods are arranged parallel to the layer plane.

     

Structurally Homogeneous Nanosheets from Self‐Assembly of a Collagen‐Mimetic Peptide

A collagen‐mimetic peptide, NSIII, has been designed with three sequential blocks having positive, neutral, and negative charges, respectively. The non‐canonical imino acid, (2S,4S)‐4‐aminoproline (amp), was used to specify the positive charges at the Xaa positions of (Xaa‐Yaa‐Gly) triads in the N‐terminal domain of NSIII. Peptide NSIII underwent self‐assembly from aqueous solution to form a highly homogeneous population of nanosheets. Two‐dimensional crystalline sheets formed in which the length of the peptide defined the height of the sheets. These results contrasted with prior results on a similar multi‐domain collagen‐mimetic polypeptides in which the sheets had highly polydisperse distribution of sizes in the (x/y)‐ and (z)‐dimensions. The structural differences between the two nanosheet assemblies were interpreted in terms of the relative stereoelectronic effects of the different aminoproline derivatives on the local triple helical conformation of the peptides.     

Self‐Assembly of Amphiphilic Nanocrystals

Amphiphilic hybrid materials are formed from polymer‐coated semiconductor nanoparticles that simulate a surfactant‐like response (see picture). The strength and density of the surface coating are the key assembling forces driving a transition from single particles to cylindrical or vesicular superstructures.

     

Nonionic Dendritic and Carbohydrate Based Amphiphiles: Self‐Assembly and Transport Behavior

Herein, a new series of non‐ionic dendritic and carbohydrate based amphiphiles is synthesized employing biocompatible starting materials and studied for supramolecular aggregate formation in aqueous solution. The dendritic amphiphiles 12 and 13 possessing poly(glycerol) [G2.0] as hydrophilic unit and C‐10 and C‐18 hydrophobic alkyl chains, respectively, exhibit low critical aggregation concentration (CAC) in the order of 10⁻⁵m and hydrodynamic diameters in the 8–10 nm range and supplemented by cryogenic transmission electron microscopy. Ultraviolet‐visible (UV‐Vis) and fluorescence spectroscopy suggests the effective solubilization of hydrophobic guests by the self‐assembled architectures, with the nanotransporters 12 and 13 possessing the highest encapsulation efficiency of 80.74 and 98.03% for curcumin. Efficient uptake of encapsulated curcumin in adenocarcinomic human alveolar basal epithelial (A549) cells is observed by confocal laser scanning microscopy. Amphiphiles 12 and 13 are non‐cytotoxic at the concentrations studied, however, curcumin encapsulated samples efficiently reduce the viability of A549 cells in vitro. Experimental studies indicate the ability of amphiphile 13 to encapsulate 1‐anilinonaphthalene‐8‐sulfonic acid (ANS) and curcumin with binding constant of 1.16 × 105⁵m ⁻¹ and 1.43 × 10⁶m ⁻¹, respectively. Overall, our findings demonstrate the potential of these dendritic amphiphiles for the development of prospective nanocarriers for the solubilization of hydrophobic drugs.     

A Self‐Assembly Phase Diagram from Amphiphilic Perylene Diimides

Supramolecular forces govern self‐assembly and further determine the final morphologies of self‐assemblies. However, how they control the morphology remains hitherto largely unknown. In this paper, we have discovered that the self‐assembled nanostructures of rigid organic semiconductor chromophores can be finely controlled by the secondary forces by fine‐tuning the surrounding environments. In particular, we used water/methanol/hydrochloric acid to tune the environment and observed five different phases that resulted from versatile molecular self‐assemblies. The representative self‐assembled nanostructures were nanotapes, nanoparticles and their 1D assemblies, rigid microplates, soft nanoplates, and hollow nanospheres and their 1D assemblies, respectively. The specific nanostructure formation is governed by the water fraction, R_w, and the concentration of hydrochloric acid, [HCl]. For instance, nanotapes formed at low [HCl] and R_w values, whereas hollow nanospheres formed when either the HCl concentration is high, or the water fraction is low, or both. The significance of this paper is that it provides a useful phase diagram by using R_w and [HCl] as two variables. Such a self‐assembly phase diagram maps out the fine control that the secondary forces have on the self‐assembled morphology, and thus allows one to guide the formation toward a desired nanostructure self‐assembled from rigid organic semiconductor chromophores by simply adjusting the two key parameters of R_w and [HCl].     

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.     

Dendronized Triangular Oligo(phenylene ethynylene) Amphiphiles: Nanofibrillar Self‐Assembly and Dye Encapsulation

Triangular‐shaped oligo(phenylene ethynylene) amphiphiles 1 a and 1 b decorated in their periphery with two‐ and four‐branched hydrophilic triethyleneglycol dendron wedges, have been synthesized and their self‐assembling properties in solution and onto surfaces investigated. The steric demand produced by the dendritic substituents induces a face‐to‐face rotated π stacking of the aromatic moieties. Studies on the concentration and temperature dependence confirm this mechanism and provide binding constants of 1.2×10⁵ and 1.7×10⁵ M ^?1 in acetonitrile for 1 a and 1 b , respectively. Dynamic and static light scattering measurements complement the study of the self‐assembly in solution and demonstrate the formation of rod‐like supramolecular structures in aqueous solution. The nanofibers formed in solution can be efficiently transferred onto surfaces. Thus, TEM images reveal the presence of strands of various thickness, with the most common being several micrometers long and with diameters of around 70 nm. Some of these nanofibers present folded edges that are indicative of their ribbon‐like nature. Interestingly, compound 1 b can also form thick filaments with a rope‐like appearance, which points to a chiral arrangement of the fibers. AFM images under highly diluted conditions also reveal long fibers with height profiles that fit well with the molecular dimensions calculated for both amphiphiles. Finally, we have demonstrated the intercalation of the hydrophobic dye Disperse Orange 3 within the filaments and its subsequent release upon increasing the temperature.     

Mechanism of Crystalline Self‐Assembly in Aqueous Medium: A Combined Cryo‐TEM/Kinetic Study

Understanding the crystallization of organic molecules is a long‐standing challenge. Herein, a mechanistic study on the self‐assembly of crystalline arrays in aqueous solution is presented. The crystalline arrays are assembled from perylene diimide (PDI) amphiphiles bearing a chiral N‐acetyltyrosine side group connected to the PDI aromatic core. A kinetic study of the crystallization process was performed using circular dichroism spectroscopy combined with time‐resolved cryogenic transmission electron microscopy (cryo‐TEM) imaging of key points along the reaction coordinate, and molecular dynamics simulation of the initial stages of the assembly. The study reveals a complex self‐assembly process starting from the formation of amorphous aggregates that are transformed into crystalline material through a nucleation–growth process. Activation parameters indicate the key role of desolvation along the assembly pathway. The insights from the kinetic study correlate well with the structural data from cryo‐TEM imaging. Overall, the study reveals four stages of crystalline self‐assembly: 1) collapse into amorphous aggregates; 2) nucleation as partial ordering; 3) crystal growth; and 4) fusion of smaller crystalline aggregates into large crystals. These studies indicate that the assembly process proceeds according to a two‐step crystallization model, whereby initially formed amorphous material is reorganized into an ordered system. This process follows Ostwald’s rule of stages, evolving through a series of intermediate phases prior to forming the final structure, thus providing an insight into the crystalline self‐assembly process in aqueous medium.     

Use of Side‐Chain Incompatibility for Tailoring Long‐Range p/n Heterojunctions: Photoconductive Nanofibers Formed by Self‐Assembly of an Amphiphilic Donor–Acceptor Dyad Consisting of Oligothiophene and Perylenediimide

To tailor organic p/n heterojunctions with molecular‐level precision, a rational design strategy using side‐chain incompatibility of a covalently connected donor–acceptor (D–A) dyad has been successfully carried out. An oligothiophene–perylenediimide dyad, when modified with triethylene glycol side chains at one terminus and dodecyl side chains at the other ( 2 Amphi ), self‐assembles into nanofibers with a long‐range D/A heterojunction. In contrast, when the dyad is modified with dodecyl side chains at both termini ( 2 Lipo ), ill‐defined microfibers result. In steady‐state measurements using microgap electrodes, a cast film of the nanofiber of 2 Amphi displays far better photoconducting properties than that of the microfiber of 2 Lipo . Flash‐photolysis time‐resolved microwave conductivity measurements, in conjunction with transient absorption spectroscopy, clearly indicate that the nanofiber of 2 Amphi intrinsically allows for better carrier generation and transport properties than the microfibrous assembly of 2 Lipo .     

Amphiphilic Janus Gold Nanoparticles Prepared by Interface‐Directed Self‐Assembly: Synthesis and Self‐Assembly

Materials with Janus structures are attractive for wide applications in materials science. Although extensive efforts in the synthesis of Janus particles have been reported, the synthesis of sub‐10 nm Janus nanoparticles is still challenging. Herein, the synthesis of Janus gold nanoparticles (AuNPs) based on interface‐directed self‐assembly is reported. Polystyrene (PS) colloidal particles with AuNPs on the surface were prepared by interface‐directed self‐assembly, and the colloidal particles were used as templates for the synthesis of Janus AuNPs. To prepare colloidal particles, thiol‐terminated polystyrene (PS‐SH) was dissolved in toluene and citrate‐stabilized AuNPs were dispersed in aqueous solution. Upon mixing the two solutions, PS‐SH chains were grafted to the surface of AuNPs and amphiphilic AuNPs were formed at the liquid–liquid interface. PS colloidal particles decorated with AuNPs on the surfaces were prepared by adding the emulsion to excess methanol. On the surface, AuNPs were partially embedded in the colloidal particles. The outer regions of the AuNPs were exposed to the solution and were functionalized through the grafting of atom‐transfer radical polymerization (ATRP) initiator. Poly[2‐(dimethamino)ethyl methacrylate] (PDMAEMA) on AuNPs were prepared by surface‐initiated ATRP. After centrifugation and dissolving the colloidal particles in tetrahydrofuran (THF), Janus AuNPs with PS and PDMAEMA on two hemispheres were obtained. In acidic pH, Janus AuNPs are amphiphilic and are able to emulsify oil droplets in water; in basic pH, the Janus AuNPs are hydrophobic. In mixtures of THF/methanol at a volume ratio of 1:5, the Janus AuNPs self‐assemble into bilayer structures with collapsed PS in the interiors and solvated PDMAEMA at the exteriors of the structures.     

Cover Picture: Solid‐State Scrolls from Hierarchical Self‐Assembly of T‐Shaped Rod–Coil Molecules (Angew. Chem. Int. Ed. 9/2009)

Solid scrolls are reversibly formed by self‐assembly of rod‐shaped molecules with laterally attached coil units, in contrast to the layered structures formed from self‐assembly of planar molecules. As described by M. Lee and co‐workers in their Communication on page 1664 ff., the core structure of the scrolls, which are either filled cylinders or hollow tubes, can be controlled by variation of the length of the coil unit. The cover picture shows aligned tubular scrolls displaying well‐defined in‐plane ordering of the rod segments.

     

Self‐Assembled Vesicles with Functionalized Membranes

Biological membranes play a key role for the function of living organisms. Thus, many artificial systems have been designed to mimic natural cell membranes and their functions. A useful concept for the preparation of functional membranes is the embedding of synthetic amphiphiles into vesicular bilayers. The dynamic nature of such noncovalent assemblies allows the rapid and simple development of bio‐inspired responsive nanomaterials, which find applications in molecular recognition, sensing or catalysis. However, the complexity that can be achieved in artificial functionalized membranes is still rather limited and the control of their dynamic properties and the analysis of membrane structures down to the molecular level remain challenging.     

Dynamic Formation of Hybrid Peptidic Capsules by Chiral Self‐Sorting and Self‐Assembly

Owing to their versatility and biocompatibility, peptide‐based self‐assembled structures constitute valuable targets for complex functional designs. It is now shown that artificial capsules based on β‐barrel binding motifs can be obtained by means of dynamic covalent chemistry (DCC) and self‐assembly. Short peptides (up to tetrapeptides) are reversibly attached to resorcinarene scaffolds. Peptidic capsules are thus selectively formed in either a heterochiral or a homochiral way by simultaneous and spontaneous processes, involving chiral sorting, tautomerization, diastereoselective induction of inherent chirality, and chiral self‐assembly. Self‐assembly is shown to direct the regioselectivity of reversible chemical reactions. It is also responsible for shifting the tautomeric equilibrium for one of the homochiral capsules. Two different tautomers (keto‐enamine hemisphere and enol‐imine hemisphere) are observed in this capsule, allowing the structure to adapt for self‐assembly.