Unique Building Block Research Articles

Excimer based fluorescent pyrene-ferritin conjugate for protein oligomerization studies and imaging in living cells.

Ferritin self-assembly has been widely exploited for the synthesis of a variety of nanoparticles for drug-delivery and diagnostic applications. However, despite the crucial role of ferritin self-assembly mechanism for probes encapsulation, little is known about the principles behind the oligomerization mechanism. In the present work, the novel “humanized” chimeric Archaeal ferritin HumAfFt, displaying the transferrin receptor-1 (TfR1) recognition motif typical of human H homopolymer and the unique salt-triggered oligomerization properties of Archaeoglobus fulgidus ferritin (AfFt), was site-selectively labeled with N-(1-pyrenyl)maleimide on a topologically selected cysteine residue inside the protein cavity, next to the dimer interface. Pyrene characteristic fluorescence features were exploited to investigate the transition from a dimeric to a cage-like 24-meric state and to visualize the protein in vitro by two photon fluorescence microscopy. Indeed, pyrene fluorescence changes upon ferritin self-assembly allowed to establish, for the first time, the kinetic and thermodynamic details of the archaeal ferritins oligomerization mechanism. In particular, the magnesium induced oligomerization proved to be faster than the monovalent cation-triggered process, highly cooperative, complete at low MgCl2 concentrations, and reversed by treatment with EDTA. Moreover, pyrene intense excimer fluorescence was successfully visualized in vitro by two photon fluorescence microscopy as pyrene-labeled HumAfFt was actively uptaken into HeLa cells by human transferrin receptor TfR1 recognition, thus representing a unique nano-device building block for two photon fluorescence cell imaging.

Business Model Concept: An Integrative Framework Proposal

Every firm employs a particular business model seeking competitive advantage. However, this pursuit is difficult, and sometimes unsuccessful. The reasons for failure should be sought in the managers’ lack of understanding of their organisations’ business models, their unique building blocks, and the potential that they have. To help managers better understand business models, this paper reviews the extant literature and identifies the elements of business models cited therein. Further, considering the new needs on the changing markets and the prevailing search for sustainability beyond profit, this paper portrays essential business model elements in an integrated framework. An updated generic business model framework consists of four primary categories, namely, value proposition, value capture, value creation, and value network, and could be useful for a variety of organisations, profit and non-profit, with various mission and vision orientations and interaction with the environment.

Ionic Complexes of Metal Oxide Clusters for Versatile Self-Assemblies

The combination of rational design of building components and suitable utilization of driving force affords spontaneous molecular assemblies with well-defined nanostructure and morphology over multiple length scales. The serious challenges in constructing assemblies with structural advantages for the realization of functions programmed into the building components usually lie ahead since the process that occurs does not always follow the expected roadmap in the absence of external intervention. Thus, prefabricated intermediates that help in governing the target self-assemblies are developed into a type of unique building blocks. Metal oxide cluster polyanions are considered as a type of molecular nanoclusters with size scale and structural morphology similar to those of many known inorganic particles and clusters but possess distinctive characteristics. Following the understanding of these clusters in self-assembly and the rationalization of their most efficient design strategy and approach, the obtained fundamental principles can also be applied in common nanoparticle- and cluster-based systems. On the other hand, the deliberate synergy offered by organic countercations that support the self-assembly of these clusters greatly expands the opportunity for the functionalization of complex building units via control of multiple interactions. The ionic combination of the inorganic clusters with hydrophilicity and the cationic organic component with hydrophobicity leads to discrete properties of the complexes. Significantly, the core-shell structure with rigid-flexible features and amphiphilicity will pave the way for hierarchical self-assemblies of the obtained complexes, while the intrinsic characteristics of the metal oxide clusters can be modulated through external physicochemical stimuli. Within this context, over the past decade we have extensively explored the ionic combination of inorganic polyanionic clusters with cationic organic amphiphiles and devoted our efforts to establishing the general rules and structure-property relationships of the formed complexes for constructing self-assemblies at the interface, in solution, and in solid matrixes. Specific interest has been focused on the functional synergy deriving from the incompatible components in highly organized self-assemblies. In this Account, we describe the recent progress on the ionic complexation of polyoxometalate clusters with cationic amphiphiles and the construction of diverse self-assembled nanostructures. First, the fundamental structural characteristics and molecular geometries of the prepared complexes are analyzed. The construction principle and diversity of the self-assembly based on the complexes and the smart stimuli response are then discussed, subject to the adjustment of various non-covalent interactions occurring in the assemblies. Subsequently, we enumerate the functional applications of the ionic complexes assembling into organic, inorganic, and even biological matrixes. The inspiration from the construction of ionic complexation and self-assembly in this Account provides vivid profiles for the design of hybrid materials involving nanoclusters and/or nanoparticles with rich potentials in addition to polyoxometalate chemistry.

Biosynthesis of the β-Lactone Proteasome Inhibitors Belactosin and Cystargolide.

Belactosins and cystargolides are natural product proteasome inhibitors from Actinobacteria. Both feature dipeptidic backbones and a unique β-lactone building block. Herein, we present a detailed investigation of their biosynthesis. Identification and analysis of the corresponding gene clusters indicated that both compounds are assembled by rare single-enzyme amino acid ligases. Feeding experiments with isotope-labeled precursors and in vitro biochemistry showed that the formation of the β-lactone warhead is unprecedented and reminiscent of leucine biosynthesis, and that it involves the action of isopropylmalate synthase homologues.

Amyloid fibril systems reduce, stabilize and deliver bioavailable nanosized iron

Iron-deficiency anaemia (IDA) is a major global public health problem. A sustainable and cost-effective strategy to reduce IDA is iron fortification of foods, but the most bioavailable fortificants cause adverse organoleptic changes in foods. Iron nanoparticles are a promising solution in food matrices, although their tendency to oxidize and rapidly aggregate in solution severely limits their use in fortification. Amyloid fibrils are protein aggregates initially known for their association with neurodegenerative disorders, but recently described in the context of biological functions in living organisms and emerging as unique biomaterial building blocks. Here, we show an original application for these protein fibrils as efficient carriers for iron fortification. We use biodegradable amyloid fibrils from β-lactoglobulin, an inexpensive milk protein with natural reducing effects, as anti-oxidizing nanocarriers and colloidal stabilizers for iron nanoparticles. The resulting hybrid material forms a stable protein-iron colloidal dispersion that undergoes rapid dissolution and releases iron ions during acidic and enzymatic in vitro digestion. Importantly, this hybrid shows high in vivo iron bioavailability, equivalent to ferrous sulfate in haemoglobin-repletion and stable-isotope studies in rats, but with reduced organoleptic changes in foods. Feeding the rats with these hybrid materials did not result in abnormal iron accumulation in any organs, or changes in whole blood glutathione concentrations, inferring their primary safety. Therefore, these iron-amyloid fibril hybrids emerge as novel, highly effective delivery systems for iron in both solid and liquid matrices.

Boragen launches for boron fungicides

Boragen, the first start-up to launch from a new business accelerator focused on agriculture technology, has raised $10 million in its first round of venture funding. The firm will use the money to develop synthetic fungicides based on a group of boron-containing compounds. Cofounder and chief science officer Tony Liu, a synthetic chemist, first zeroed in on a group of compounds called benzoxaboroles while screening for pharmaceutical leads. Benzoxaboroles have been used in topical antibiotics and antifungals. “Boron is a unique building block that allows a lot of freedom to modulate geometry and charge,” Liu points out. “You can fine-tune the reactivity by changing what you put around it for a specific use.” Boragen’s lead candidate boasts a new mode of fungus-killing action, which will help prevent the emergence of resistant organisms, says CEO John W. Dombrosky. And it can be used in tiny amounts when combined with common fungicides,

One-Step Synthesis of a Unique Molecular Platform for the Selective Functionalization of Calix[6]arenes

High selectivity is crucial for the functionalization of macrocyclic platforms bearing multiple identical functions. In the case of calix[6]arenes, only a few examples of efficient homo-functionalization have been reported. Herein, we describe the one-step synthesis of a tri-differentiated calix[6]arene and its use as a key intermediate to selectively access various homo- and hetero-functionalization patterns. In combination with the ‘all-but-one’ carbamatation methodology, this unique building block gives access to sophisticated calix[6]arenes that, until now, were inaccessible.

The synthesis of an EDTA-like chelating peptidomimetic building block suitable for solid-phase peptide synthesis.

A novo trifunctional EDTA-like peptidomimetic amino acid is described. This unique building block, which is prepared in a straightforward manner from commercialized starting materials, contains three moieties: a hexadentate chelating unit similar to that present in EDTA, and amino and carboxylic groups, which facilitate its introduction into the backbone of peptides using conventional SPPS. As a proof of concept, this building block is introduced into a cyclic peptide inspired from the family of Gratisin analogues. The designed peptide contains the amino acid analogue in one of the turns, and chelates Ca2+ with nanomolar affinity at physiological pH.

3D hierarchical golden wattle-like TiO2 microspheres: polar acetone-based solvothermal synthesis and enhanced water purification performance

3D hierarchical TiO2 microsphere structures self-assembled from 1D nanostructures have attracted considerable research attention due to their unique microstructures and properties, and non-polar solvent-based solvothermal methods have been proved to be effective techniques to synthesize such structures. However, to the best of our knowledge, no successful products have been reported based on polar solvents in the available literature. Herein, for the first time, uniform and sophisticated golden wattle (Acacia pycnantha)-like TiO2 microsphere structures, self-assembled from highly crystallized and radially grown 1D rutile nanorods, were successfully synthesized via a template-free solvothermal reaction using only polar acetone as the solvent in the presence of hydrochloric acid (HCl). The obtained samples showed good water purification performance, even superior to Degussa P25, owing to their unique 1D nanorod building block structure, fast electron transfer rate, excellent light harvesting capability and good crystallinity. In addition, a three-step growth mechanism of the golden wattle-like TiO2 microspheres was proposed based on a time-dependent morphology and crystal form evolution process. The synthetic strategy for the golden wattle-like TiO2 microspheres employed in this study provides new insights into the design of 3D hierarchical TiO2 structures for practical environmental purification applications.

Hydrogenative ring-rearrangement of biomass derived 5-(hydroxymethyl)furfural to 3-(hydroxymethyl)cyclopentanol using combination catalyst systems of Pt/SiO2 and lanthanoid oxides

Combination catalyst systems composed of Pt/SiO2 and lanthanoid oxides efficiently catalyze the hydrogenative ring-rearrangement of 5-(hydroxymethyl)furfural in water to produce 3-(hydroxymethyl)cyclopentanol which can be a unique chemical building block derived from biomass.

Microscale vortex laser with controlled topological charge**Project supported by the “Youth 1000 Talent Plan” Fund, Ministry of Education of China (Grant No. 201421) and the National Natural Science Foundation of China (Grant Nos. 11574012 and 61521004).

A microscale vortex laser is a new type of coherent light source with small footprint that can directly generate vector vortex beams. However, a microscale laser with controlled topological charge, which is crucial for virtually any of its application, is still unrevealed. Here we present a microscale vortex laser with controlled topological charge. The vortex laser eigenmode was synthesized in a metamaterial engineered non-Hermitian micro-ring cavity system at exceptional point. We also show that the vortex laser cavity can operate at exceptional point stably to lase under optical pumping. The microscale vortex laser with controlled topological charge can serve as a unique and general building block for next-generation photonic integrated circuits and coherent vortex beam sources. The method we used here can be employed to generate lasing eigenmode with other complex functionalities.

Nucleophilic Tetrafluoroethylation Employing in Situ Formed Organomagnesium Reagents

Tetrafluoroalkyl bromides are metalated with equimolar iPrMgCl·LiCl (Turbo Grignard) to form organomagnesium compounds which are stable at low temperatures and react with various electrophiles (aldehydes, ketones, CO2, cyclic sulfate and sulfamidate, N-sulfonylimines, nitrone, chlorophosphate, nonaflyl azide) to afford novel functionalized tetrafluoroethylene-containing products. Ease of operation, excellent selectivity, high nucleophilicity, and enhanced stability of the reactive species together with a broad substrate scope comprise a highly attractive nucleophilic tetrafluoroethylation protocol affording unique synthetic building blocks.

Recent Advances in Understanding and Engineering Polyketide Synthesis.

Polyketides are a diverse group of natural products that form the basis of many important drugs. The engineering of the polyketide synthase (PKS) enzymes responsible for the formation of these compounds has long been considered to have great potential for producing new bioactive molecules. Recent advances in this field have contributed to the understanding of this powerful and complex enzymatic machinery, particularly with regard to domain activity and engineering, unique building block formation and incorporation, and programming rules and limitations. New developments in tools for in vitro biochemical analysis, full-length megasynthase structural studies, and in vivo heterologous expression will continue to improve our fundamental understanding of polyketide synthesis as well as our ability to engineer the production of polyketides.

Fine-Tuned Intrinsically Ultramicroporous Polymers Redefine the Permeability/Selectivity Upper Bounds of Membrane-Based Air and Hydrogen Separations.

Intrinsically ultramicroporous (<7 Å) polymers represent a new paradigm in materials development for membrane-based gas separation. In particular, they demonstrate that uniting intrachain "rigidity", the traditional design metric of highly permeable polymers of intrinsic microporosity (PIMs), with gas-sieving ultramicroporosity yields high-performance gas separation membranes. Highly ultramicroporous PIMs have redefined the state-of-the-art in large-scale air (e.g., O2/N2) and hydrogen recovery (e.g., H2/N2, H2/CH4) applications with unprecedented molecular sieving gas transport properties. Accordingly, presented herein are new 2015 permeability/selectivity "upper bounds" for large-scale commercial membrane-based air and hydrogen applications that accommodate the substantial performance enhancements of recent PIMs over preceding polymers. A subtle balance between intrachain rigidity and interchain spacing has been achieved in the amorphous microstructures of PIMs, fine-tuned using unique bridged-bicyclic building blocks (i.e., triptycene, ethanoanthracene and Tröger's base) in both ladder and semiladder (e.g., polyimide) structures.

Terminal versus Internal Diiodobenzyl Alcohol Derivatives via Regioselective Metal–Iodine Exchange of 1,2,3‐Triiodoarenes: Synthesis and Antibacterial Activity

AbstractA wide range of unique diiodobenzyl alcohol building blocks have been synthesized by regioselective metal‐iodine exchange (MIE) reactions using isopropylmagnesium chloride is reported. Remarkably, the regioselectivity of the MIE reaction is easily controlled by both the aldehydes and the 1,2,3‐triiodoarenes to provide either the internal or the terminal products in good yields and in a highly regioselective fashion. The synthesized diiodobenzyl alcohols were tested for in vitro antibacterial activity against two Gram‐positive strains, Micrococcus luteus (ATCC 934) and Staphylococcus aureus (ATCC 29213), and two Gram‐negative strains, Escherichia coli (ATCC 25922) and Serratia marcescens (ATCC 27117). The biological data clearly shows that all tested diiodobenzyl alcohols have selective antibacterial activity against Gram‐positive strains and no activity against Gram‐negative ones. This report discloses a facile protocol for the synthesis of hitherto unknown ortho‐diiodobenzyl alcohol and 2,3‐diiodobenzyl alcohol derivatives in only one step that is quite general in scope and scalable, with products that are hard to make by any other means.

Synthesis of fully protected, reverse N-prenylated (2S,3R)-3-hydroxytryptophan, a unique building block of the cyclomarins.

Reverse N-prenylated 3-hydroxytryptophan, the rather exotic amino acid of the cyclomarins, is obtained in enantio- and diastereomerically pure and fully protected form by a combination of a highly stereoselective addition of a zincated indole toward protected serinal and subsequent palladium-catalyzed N-prenylation.

Solution Processable Colloidal Nanoplates as Building Blocks for High-Performance Electronic Thin Films on Flexible Substrates

Low-temperature solution-processed electronic materials on plastic substrates are of considerable interest for flexible electronics. Solution dispersible inorganic nanostructures (e.g., zero-dimensional (0D) quantum dots or one-dimensional (1D) nanowires) have emerged as interesting ink materials for low-temperature solution processing of electronic thin films on flexible substrates, but usually with limited performance due to the large number of grain boundaries (0D) or incomplete surface coverage (1D). Here, we report two-dimensional (2D) colloidal nanoplates of layered materials as a new ink material for solution assembly of high-performance electronic thin films. The 2D colloidal nanoplates exhibit few dangling bonds and represent an ideal geometry for the assembly of highly uniform continuous thin films with greatly reduced grain boundaries dictated by large-area conformal plane-plane contact with atomically flat/clean interfaces. It can therefore promise efficient charge transport across neighboring nanoplates and throughout the entire thin film to enable unprecedented electronic performance. We show that Bi2Se3 and Bi2Te3 nanoplates can be synthesized with well-controlled thickness (6-15 nm) and lateral dimension (0.5-3 μm) and can be used for the assembly of highly uniform continuous thin films with a full surface coverage and an excellent room temperature carrier mobility >100 cm(2)·V(-1)·s(-1), approaching that of chemical vapor deposition grown materials. Our study demonstrates a general strategy to using 2D nanoplates as a unique building block for the construction of high-performance electronic thin films on plastic substrates for future flexible electronics and optoelectronics.

Processing‐Property Relationships in Electrospun Janus‐Type Biphasic Ceramic Nanofibers

Electrospinning provides a promising route to quickly produce high‐purity ceramic fibers from readily available sol–gel precursors. Recently, techniques have been developed to enable the production of biphasic nanocomposites on a single fiber, enabling the development of novel composites with connectivities that are difficult to obtain using existing methods. These “composites on a fiber” can be used as a unique anisotropic building block for creating more complex ordered structures. This work examines links between processing, structure, and properties for Janus‐type composite nanofibers for the magnetoelectric BaTiO3–CoFe2O4 system. Specifically, we show how altering the viscosity and conductivity of precursor solutions can provide a unique route to synthesize biphasic composites of a range of sizes and compositions. Furthermore, we show how altering these properties can impact the magnetic and magnetoelectric behavior of these fibers. While this work focuses specifically on the BaTiO3‐CoFe2O4 system, lessons learned can be applied to electrospinning biphasic ceramic materials from a variety of material systems and applications.

Enhanced photoabsorption in front-tapered single-nanowire solar cells.

Vertically aligned single-nanowire is verified to be a unique building block to realize the high-efficiency solar cell beyond Schockley-Queisser limit. We proposed a front-tapered vertically aligned single-nanowire solar cell (V-SNSC) and investigated numerically the possibility of this configuration to improve the photoabsorption efficiency compared to the conventional designs, by using 2.5D full-wave finite-element method. The influences of the feature sizes of aspect ratio, bottom radius, and nanowire length on the light-trapping properties were explored; the detailed field distribution and carrier generation rate were revealed as well based on the theory of dielectric resonant antenna, in order to elucidate the underlying physical mechanism. Results showed that, compared with the cylindrical counterparts, the absorption capability of V-SNSCs could be greatly enhanced by using a front-tapered configuration with less material utilized, and that such a positive effect can be further strengthened by increasing the nanowire length. The proposed configuration provides a promising approach to engineer the photoabsorption in the photovoltaic and other optoelectronic devices.

Self-Assembly of Polymer Brush-Functionalized Inorganic Nanoparticles: From Hairy Balls to Smart Molecular Mimics

New opportunities for complex and controllable self-organization of inorganic nanoparticles (e.g., quantum dots, plasmonic or magnetic nanoparticles) are provided when the stabilizing organic layer at the nanoparticle surface consists of a polymer brush of densely grafted chains. We highlight recent advances in the synthesis and self-assembly of these unique building blocks, termed polymer brush-functionalized nanoparticles (PBNPs). We show how the field has progressed from PBNPs with isotropic, single-component brushes showing limited self-assembly behavior to PBNPs with anisotropic brushes showing directional interactions and complex self-organization. We further discuss how PBNPs with isotropic multicomponent brushes, either mixed brushes or grafted block copolymers, can also exhibit the complex self-organization of molecular amphiphiles via rearrangements within the brush enabled by conformational flexibility. Through numerous examples, we show how established principles of polymer science and surface...