Nanocrystalline cellulose/β-casein conjugated nanoparticles prepared by click chemistry

Functionalized nanoparticles are promising building blocks for well-defined nanomaterials with unique properties. Site-specific or regio-selective functionalization of those nanoparticles and organization into high-order assemblies is a major challenge in materials research. Here, we demonstrate site-specific immobilization of a model protein at one tip of nanocrystalline cellulose (NCC), single-crystalline rod-like shaped nanoparticles that are isolated by acid hydrolysis of bulk cellulose. Click reaction between reducing end functionalized NCC bearing azide groups and β-casein micelles bearing acetylene groups results in mushroom-like conjugated nanoparticles in different arrangements. The strategy developed here to design hybrid polysaccharide–protein nanoparticles could be useful for building novel functional self-assembled nanobiomaterials and have potential in nanomedicine, immunoassay and drug delivery applications.     

Intrinsic Fluorescence of Metabolite Amyloids Allows Label‐Free Monitoring of Their Formation and Dynamics in Live Cells

The formation of apoptosis‐inducing amyloidal structures by metabolites has significantly extended the “amyloid hypothesis” to include non‐proteinaceous, single metabolite building blocks. However, detection of metabolite assemblies is restricted compared to their larger protein‐based counterparts owing to the hindrance of external labelling and limited immunohistochemical detection tools. Herein, we present the detection of the formation, dynamics, and cellular distribution of metabolite amyloid‐like structures and provide mechanistic insights into the generation of supramolecular chromophores. Moreover, the intrinsic fluorescence properties allow the detection of metabolite assemblies in living cells without the use of external dyes. Altogether, this intrinsic fluorescence of metabolite assemblies further verifies their amyloidal nature, while providing an important tool for further investigation of their pathological role in inborn error of metabolism disorders.     

Functionalized Carbon Nanoparticles,Blacks and Soots as Electron‐Transfer Building Blocks and Conduits

Functionalized carbon nanoparticles (or blacks) have promise as novel active high‐surface‐area electrode materials, as conduits for electrons to enzymes or connections through lipid films, or as nano‐building blocks in electroanalysis. With previous applications of bare nanoblacks and composites mainly in electrochemical charge storage and as substrates in fuel cell devices, the full range of benefits of bare and functionalized carbon nanoparticles in assemblies and composite (bio)electrodes is still emerging. Carbon nanoparticles are readily surface‐modified, functionalized, embedded, or assembled into nanostructures, employed in bioelectrochemical systems, and incorporated into novel electrochemical sensing devices. This focus review summarizes aspects of a rapidly growing field and some of the recent developments in carbon nanoparticle functionalization with potential applications in (bio)electrochemical, photoelectrochemical, and electroanalytical processes.     

Self-assembly of supramolecular platinum complexes with bis-4-pyridyl cavitands

The design and self-assembly of six new supramolecular complexes (four triangles and two 2+2 assemblies) are described. These assemblies incorporate two new bispyridyl cavitand building blocks and were prepared in excellent yields (85-95%). The assemblies and building blocks were characterized with multinuclear NMR spectroscopy, electrospray ionization mass spectrometry, and elemental analysis. Isotopically resolved mass spectrometry along with NMR data confirms the existence of the six assemblies.     

Synthesis of multimetallic dendrimers through non-covalent interactions

Hexa-ammonium functionalized Dendriphos ligands and mono-sulfonate functionalized metal complexes have been used as building blocks for the preparation of multimetallic dendritic assemblies. These metallodendrimers consist of a single metal centre surrounded by an oligocationic shell formed by the coordinated Dendriphos ligands and multiple associated anionic organometallic complexes.     

Synthesis and reactions of the first cyclopentadienyl isonitriles

6-Azidofulvenes without a further substituent in the exocyclic position were transformed into new 1-isocyano- and 2-isocyanocyclopenta-1,3-dienes by photolysis in methanol. These novel functionalized cyclopentadienes are useful building blocks, e.g. as dienes in Diels-Alder reactions.     

pH tunable self-assembly of chicoric acid and their biocompatibility studies

We report for the first time, the pH tunable self-assembly of chicoric acid, an HIV-I integrase inhibitor, which displayed a remarkable tendency to self-assemble at room temperature into varying nano- and microstructures. Furthermore, those assemblies were then functionalised with gold (Au) nanoparticles. We then investigated the biocompatibility of the materials by conducting in vitro cell attachment and cytotoxicity studies using normal rat kidney cells. The studies revealed that the biomaterials were non-toxic and biocompatible, and showed considerable adhesion to the cells. These results suggest that the assemblies could potentially be used for a variety of applications, such as carriers for targeted drug delivery as well as optoelectronics and sensors. Furthermore, the formation of highly organised nano- and microstructures of medicinally significant phytohormones such as chicoric acid is of particular interest as it might help in further understanding the supramolecular assembly mechanism of higher organised biological structures for the development of building blocks for various device fabrications.     

Multicomponent assembly of boron-based dendritic nanostructures

A new synthetic strategy for the construction of boron-based macrocycles and dendrimers is described. Condensation of aryl- and alkylboronic acids with 3,4-dihydroxypyridine is shown to give pentameric macrocycles in which five boronate esters are connected by dative B-N bonds. Three macrocycles have been characterized crystallographically. The boron atoms of these assemblies represent chiral centers, and the assembly process is highly diastereoselective. Attachment of amino or aldehyde groups in the meta position of the arylboronic acid building blocks does not interfere with macrocyclization. This allows performing multicomponent assembly reactions between functionalized boronic acids, dihydroxypyridine ligands, and amines or aldehydes, respectively. Reaction of 3,5-diformylphenylboronic acid, 3,4-dihydroxypyridine, and a primary amine R-NH2 (R=Ph, Bn) gives dendritic nanostructures having a pentameric macrocyclic core and 10 amine-derived R groups in their periphery. Combination of 3,5-diformylphenylboronic acid with 2,3-dihydroxypyridine and the dendron 3,5-(benzyloxy)benzylamine, on the other hand, results in formation of a dendrimer with a tetrameric macrocyclic core and eight dendrons in its periphery.     

An Engineered Aryl Acid Adenylation Domain with an Enlarged Substrate Binding Pocket

Adenylation (A) domains act as the gatekeepers of non‐ribosomal peptide synthetases (NRPSs), ensuring the activation and thioesterification of the correct amino acid/aryl acid building blocks. Aryl acid building blocks are most commonly observed in iron‐chelating siderophores, but are not limited to them. Very little is known about the reprogramming of aryl acid A‐domains. We show that a single asparagine‐to‐glycine mutation in an aryl acid A‐domain leads to an enzyme that tolerates a wide range of non‐native aryl acids. The engineered catalyst is capable of activating non‐native aryl acids functionalized with nitro, cyano, bromo, and iodo groups, even though no enzymatic activity of wild‐type enzyme was observed toward these substrates. Co‐crystal structures with non‐hydrolysable aryl‐AMP analogues revealed the origins of this expansion of substrate promiscuity, highlighting an enlargement of the substrate binding pocket of the enzyme. Our findings may be exploited to produce diversified aryl acid containing natural products and serve as a template for further directed evolution in combinatorial biosynthesis.     

由D-Erythorbic Acid合成新的多官能团C4手性筑块

手性C4筑块是合成许多天然产物 Leukotrienes, Pyrrolizidine alkaloids及前列腺素A2等的重要合成子[1～3]. 然而到目前为止, 手性C4筑块只有从少数几种手性源如酒石酸, L-苏糖, D-赤藓糖等中才能得到[2～7]. 我们在以D-erythorbic acid为原料合成新型手性配体的过程中[8～10], 发现了一种简便获得选择性保护的多官能团手性C4筑块(化合物4, 5)的新途径(Scheme 1).     

Iron‐Catalyzed Direct Diazidation for a Broad Range of Olefins

Reported herein is a new iron‐catalyzed diastereoselective olefin diazidation reaction which occurs at room temperature (1–5 mol % of catalysts and d.r. values of up to >20:1). This method tolerates a broad range of both unfunctionalized and highly functionalized olefins, including those that are incompatible with existing methods. It also provides a convenient approach to vicinal primary diamines as well as other synthetically valuable nitrogen‐containing building blocks which are difficult to obtain with alternative methods. Preliminary mechanistic studies suggest that the reaction may proceed through a new mechanistic pathway in which both Lewis acid activation and iron‐enabled redox‐catalysis are crucial for selective azido‐group transfer.     

Anion modules: building blocks of supramolecular assemblies by combination with π-conjugated anion receptors

Dipyrrolyldiketone boron complexes, as π-conjugated acyclic anion receptors, act as building subunits of various assemblies through noncovalent interactions in the form of receptor-anion complexes. Instead of, or in addition to, the modification of receptor structures, the introduction of anion modules as building blocks for the assemblies was found to be useful in forming various soft materials. Gallic carboxylate derivatives 3-n (n = 16, 18, 20), as tetrabutylammonium (TBA) salts, form receptor-anion-module complexes that can be used to fabricate supramolecular assemblies. Combinations of aliphatic anion modules 3-n and receptors 1a,b along with a TBA cation afforded products with mesophases, which were indicated by differential scanning calorimetry and polarized optical microscopy. X-ray diffraction measurements of the solid states and mesophases of 1a·3-n·TBA and 1b·3-n·TBA revealed highly ordered structures including lamellar structures, which could be modulated by the lengths of the alkyl chains of the modules. Functional materials exhibiting electrical conductivity were fabricated by using combinations of anionic building blocks that form assemblies by themselves and π-conjugated acyclic receptors.     

Star polymers composed entirely of amino acid building blocks: a route towards stereospecific, biodegradable and hierarchically functionalized stars

Highly functionalized water soluble core cross-linked star (CCS) polymers having degradable cores and hierarchical functionalities spanning from the peripheral groups along the arms to the core have been synthesized entirely from amino acid building blocks. The core-isolated moieties were shown to undergo further reactions, such as click chemistry, as well as being capable of encapsulating water-insoluble drugs.     

Syntheses of dibenzo[b,e][1,4]dioxin derivatives via iron complexes, and further functionalizations via directed metallation

Double nucleophilic aromatic substitution reactions between (cyclopentadienyl)(η⁶-1,2-dichlorobenzene)iron(1 + ) salts and substituted 1,2benzenediols have been carried out under mild conditions to prepare [η⁶-dibenzo[b,e][1,4]dioxin]iron(1 + ) complexes functionalized in the 1- or 2-position with an alkyl, aldehyde, carboxylic acid, methoxycarbonyl, carboxamide, or hydroxy group. 3-Methyl- and 4-methyl-(η⁶-1,2-dichlorobenzene)iron complexes were treated with substituted 1,2-benzenediols to effect functionalization of both aromatic rings of the heterocycle. The dibenzodioxin ligands were liberated routinely by irradiation with ultraviolet light. Directed deprotonation of the free functionalized dibenzodioxins with an alkyllithium reagent followed by quenching with a variety of electrophiles yielded further derivatives, including two new isoindolone systems.     

Order from Chaos: Self‐Assembly of Nanoprism from a Mixture of Tetratopic Terpyridine‐Porphyrin Conformers

Porphyrins have been widely used in the self‐assembly of metallo‐supramolecules. In this study, we introduced 2,2':6,2"‐terpyridine (tpy) into a porphyrin core to synthesize a tetratopic building block with multiple conformers. During the self‐assembly with Zn(II), such a mixture of conformers was able to form a discrete nanoprism with all building blocks in one conformation. Detailed characterizations, including NMR, ESI‐MS and traveling‐wave ion mobility‐mass spectrometry (TWIM‐MS), all supported the formation of the desired assemblies. AFM and TEM further confirmed the dimensions of assembled nanoprisms. Moreover, the photophysical properties of the ligands and complexes were noticeably different depending upon size and metal ion center.     

Amyloids: not only pathological agents but also ordered nanomaterials

Amyloid fibers constitute one of the most abundant and important naturally occurring self-associated assemblies. A variety of protein and peptide molecules with various amino acid sequences form these highly stable and well-organized assemblies under diverse conditions. These assemblies display phase states ranging from liquid crystals to rigid nanotubes. The potential applications of these supramolecular assemblies exceed those of synthetic polymers since the building blocks may introduce biological function in addition to mechanical properties. Here we review the structural characteristics of amyloidal supramolecular assemblies, their potential use as either natural or de novo designed sequences, and the range of applications that have been demonstrated so far.     

Four-arm oligonucleotide Ni(II)-cyclam-centered complexes as precursors for the generation of supramolecular periodic assemblies

The development of a multiarm metal-centered DNA building block as a precursor for the construction of supramolecular assemblies has relied upon the preparation of a Ni(II)-1,4,8,11-tetrazacyclotetradecane ligand (cyclam) functionalized with four linkers. This complex can be incorporated into a support-bound DNA sequence and the remaining three linkers can then be elongated by DNA synthesis. The result is a Ni(II)-cyclam complex tethering four 20-mer DNA strands. This building block, designed to be tetrahedral in nature, can in principle be used to form tetrahedral assemblies. These assemblies can be designed to be of known size and composition or permitted to grow into complexes of essentially infinite size, ideally the macroscopic version of a crystal.     

Inorganic Self-assembly: Going Bio

The use of self-assembly for building complex functional structures is a current topic of interest in supramolecular chemistry. In this context, the use of biomolecule-based building blocks has paved the way for the development of intracellular assemblies. Currently, the potential functionality of such assemblies in biomedical applications is being disclosed. On the other hand, the use of inorganic (metal-based) building blocks is still in its infancy. The construction of inorganic self-assemblies in-bio is particularly challenging and demands great efforts to reach applications. However, the plethora of thinkable advantages related to the use of inorganic self-assembly in living cells must fuel new discoveries in this area. This Concept reviews the current advances, perspectives, and challenges in inorganic self-assembly in living systems.     

Self-assembly of inorganic nanoparticle vesicles and tubules driven by tethered linear block copolymers

Controllable self-assembly of nanoscale building blocks into larger specific structures provides an effective route for the fabrication of new materials with unique optical, electronic, and magnetic properties. The ability of nanoparticles (NPs) to self-assemble like molecules is opening new research frontiers in nanoscience and nanotechnology. We present a new class of amphiphilic "colloidal molecules" (ACMs) composed of inorganic NPs tethered with amphiphilic linear block copolymers (BCPs). Driven by the conformational changes of tethered BCP chains, such ACMs can self-assemble into well-defined vesicular and tubular nanostructures comprising a monolayer shell of hexagonally packed NPs in selective solvents. The morphologies and geometries of these assemblies can be controlled by the size of NPs and molecular weight of BCPs. Our approach also allows us to control the interparticle distance, thus fine-tuning the plasmonic properties of the assemblies of metal NPs. This strategy provides a general means to design new building blocks for assembling novel functional materials and devices.     

Direct synthesis of enaminone functionalized biaryl ethers by CuI-catalyzed O-arylation of enaminone functionalized phenols

The O-arylation of o-enaminone functionalized phenols, namely, (E)-3-(dimethylamino)-1-(2-hydroxyphenyl)prop-2-en-1-ones, has been achieved via a self-promoted process in the presence of CuI, which provided a class of new biaryl ethers bearing a reactive enaminone fragment. The reactions were performed under mild conditions and the functionalized biaryl ether products have been found as useful building blocks for the assembly of heterocyclic compounds.