Carbon Building Blocks Research Articles

Salvage of ribose from uridine or RNA supports glycolysis in nutrient-limited conditions

Glucose is vital for life, serving as both a source of energy and carbon building block for growth. When glucose is limiting, alternative nutrients must be harnessed. To identify mechanisms by which cells can tolerate complete loss of glucose, we performed nutrient-sensitized genome-wide genetic screens and a PRISM growth assay across 482 cancer cell lines. We report that catabolism of uridine from the medium enables the growth of cells in the complete absence of glucose. While previous studies have shown that uridine can be salvaged to support pyrimidine synthesis in the setting of mitochondrial oxidative phosphorylation deficiency1, our work demonstrates that the ribose moiety of uridine or RNA can be salvaged to fulfil energy requirements via a pathway based on: (1) the phosphorylytic cleavage of uridine by uridine phosphorylase UPP1/UPP2 into uracil and ribose-1-phosphate (R1P), (2) the conversion of uridine-derived R1P into fructose-6-P and glyceraldehyde-3-P by the non-oxidative branch of the pentose phosphate pathway and (3) their glycolytic utilization to fuel ATP production, biosynthesis and gluconeogenesis. Capacity for glycolysis from uridine-derived ribose appears widespread, and we confirm its activity in cancer lineages, primary macrophages and mice in vivo. An interesting property of this pathway is that R1P enters downstream of the initial, highly regulated steps of glucose transport and upper glycolysis. We anticipate that ‘uridine bypass’ of upper glycolysis could be important in the context of disease and even exploited for therapeutic purposes.

Regio- and diastereoselective synthesis of diverse spirocyclic indenes by cyclization with indene-dienes as two carbon building blocks.

We report a base-promoted cyclization with indene-dienes as two carbon building blocks toward diverse spirocyclic indene scaffolds including hexacyclic spiroindenes bearing benzo pyran motifs and pentacyclic spiroindenes containing oxindole units in high yields with excellent diastereoselectivities.

The simultaneous synthesis of carbon dots and carbon spheres with tunable sizes using a vertical chemical vapour deposition method

Herein we report on the direct synthesis of solid hydrophobic carbon dots (CDs) and simultaneously carbon spheres (CSs), using a vertical chemical vapour deposition (CVD) reactor. The HRTEM data indicated that the CDs and CSs originated from different carbon building blocks indicated that the CDs and CSs originated from different carbon building blocks. The CDs were obtained by reacting acetylene (C2H2) and Ar mixtures at high flow rates (>500 sccm) and high temperatures (800-1000 °C). TEM studies indicated that the CDs produced were graphene-like quantum dots that increased in size from c. 3 nm to 8 nm as the Ar flow rate (constant C2H2 flow rate) was decreased, while small solid CSs (c. 100 nm) were also synthesised in the process. The CSs had a typical spherical layered structure with no graphitic core. A mechanism to rationalise the observation that the CDs and CSs grew simultaneously by different pathways with no formation of intermediate-sized particles is given.

Superior toughness and hardness in graphite–diamond hybrid induced by coherent interfaces

Finding a material with both a high hardness and toughness is a key area of research in materials science and condensed matter physics. Herein, we propose a new kind of superior mechanical material, a graphite–diamond hybrid (termed Gradia, Nature, 2022, 607, 486), consisting of diamond and graphite nanodomains interlocked via coherent interfaces using first-principles calculations. Upon strain, unusual sequential structural transitions appear in the Gradia, driven by the movement of coherent graphite–diamond interfaces towards the diamond units. This feature allows Gradia to withstand large strains and absorb more energy before structural collapse, leading to superior toughness. More interestingly, Gradia has the potential to be a superhard material based on the estimated Vickers hardness above 40 GPa. This work could play an exemplary role in the exploration of excellent mechanical materials through the modulation of the linking styles of carbon building blocks.

Mechanism-based ligand design for copper-catalysed enantioconvergent C(sp3)-C(sp) cross-coupling of tertiary electrophiles with alkynes.

In contrast with the well-established enantioconvergent radical C(sp3)-C cross-coupling of racemic secondary alkyl electrophiles, the corresponding coupling of tertiary electrophiles to forge all-carbon quaternary stereocentres remains underexplored. The major challenge arises from the steric hindrance and the difficult enantio-differentiation of three distinct carbon substituents of prochiral tertiary radicals. Here we demonstrate a general copper-catalysed enantioconvergent C(sp3)-C(sp) cross-coupling of diverse racemic tertiary alkyl halides with terminal alkynes (87 examples). Key to the success is the rational design of chiral anionic N,N,N-ligands tailor-made for the computationally predicted outer-sphere radical group transfer pathway. This protocol provides a practical platform for the construction of chiral C(sp3)-C(sp/sp2/sp3) bonds, allowing for expedient access to an array of synthetically challenging quaternary carbon building blocks of interest in organic synthesis and related areas.

CO2 utilization: a brief review of main routes and the potential to Brazilian scenario industry

Within the chemical and fuel production chains, four raw materials are basically used as a source of carbon: oil, natural gas, coal and biomass, the latter being a renewable source. But, taking into account the objective of reducing the effects caused by greenhouse gases (GHG), it is necessary to develop processes and technological concepts that aim to recycle carbon dioxide (CO2) emitting mainly large stationary sources. In addition to carbon capture and storage, the concept of "CO2 utilization" makes room for recycling CO2 avoiding its atmospheric emission and, in addition, a new carbon building block for chemicals and fuels. In this context, the Brazilian scenario stands out for industrial cases with high CO2 purity, such as the sugar-energy sector where new technologies for converting CO2 into valuable chemicals can be tested. Thus, this review presents an overview of the main routes developed for the conversion of CO2, ranging from those with low level of technological readiness (TRL) such as photochemistry and plasma catalysis to the most advanced ones such as thermocatalytic and biological conversions, polymerizations and mineralizations.

Au(I)-Catalyzed Oxidative Functionalization of Yndiamides.

Yndiamides, underexplored cousins of ynamides, offer rich synthetic potential as doubly nitrogenated two carbon building blocks. Here we report a gold-catalyzed oxidative functionalization of yndiamides to access unnatural amino acid derivatives, using a wide range of nucleophiles as a source of the amino acid side chain. The transformation proceeds under mild conditions, is highly functional group tolerant, and displays excellent regioselectivity through subtle steric differentiation of the yndiamide nitrogen atom substituents.

Alkynylation‐Desilylation‐Alkynylation‐Cycloisomerization (ADAC) Three‐Component Synthesis of 2,2′‐Biindolyls – Concise Synthesis of Tjipanazole I

AbstractA sequentially Pd/Cu‐catalyzed alkynylation‐desilylation‐alkynylation‐cycloisomerization (ADAC) process in the sense of a consecutive three‐component reaction using TIPS‐butadiyne as a four carbon building block gives a rapid and efficient access to 2,2′‐biindolyls in a one‐pot fashion. This facile entry to unsymmetrically substituted title compounds has been employed in a concise two‐step synthesis of the alga alkaloid tjipanazole I.

Hierarchically Nanoporous 3D Assembly Composed of Functionalized Onion-Like Graphitic Carbon Nanospheres for Anode-Minimized Li Metal Batteries.

Despite the recent attention for Li metal anode (LMA) with high theoretical specific capacity of ≈3860 mA h g-1 , it suffers from not enough practical energy densities and safety concerns originating from the excessive metal load, which is essential to compensate for the loss of Li sources resulting from their poor coulombic efficiencies (CEs). Therefore, the development of high-performance LMA is needed to realize anode-minimized Li metal batteries (LMBs). In this study, high-performance LMAs are produced by introducing a hierarchically nanoporous assembly (HNA) composed of functionalized onion-like graphitic carbon building blocks, several nanometers in diameter, as a catalytic scaffold for Li-metal storage. The HNA-based electrodes lead to a high Li ion concentration in the nanoporous structure, showing a high CE of ≈99.1%, high rate capability of 12 mA cm-2 , and a stable cycling behavior of more than 750 cycles. In addition, anode-minimized LMBs are achieved using a HNA that has limited Li content (≈0.13 mg cm-2 ), corresponding to 6.5% of the cathode material (commercial NCM622 (≈2 mg cm-2 )). The LMBs demonstrate a feasible electrochemical performance with high energy and power densities of ≈510 Wh kgelectrode -1 and ≈2760 W kgelectrode -1 , respectively, for more than 100 cycles.

Green Pathway in Utilizing CO2 via Cycloaddition Reaction with Epoxide—A Mini Review

Carbon dioxide (CO2) has been anticipated as an ideal carbon building block for organic synthesis due to the noble properties of CO2, which are abundant renewable carbon feedstock, non-toxic nature, and contributing to a more sustainable use of resources. Several green and proficient routes have been established for chemical CO2 fixation. Among the prominent routes, this review epitomizes the reactions involving cycloaddition of epoxides with CO2 in producing cyclic carbonate. Cyclic carbonate has been widely used as a polar aprotic solvent, as an electrolyte in Li-ion batteries, and as precursors for various forms of chemical synthesis such as polycarbonates and polyurethanes. This review provides an overview in terms of the reaction mechanistic pathway and recent advances in the development of several classes of catalysts, including homogeneous organocatalysts (e.g., organic salt, ionic liquid, deep eutectic solvents), organometallic (e.g., mono-, bi-, and tri-metal salen complexes and non-salen complexes) and heterogeneous supported catalysts, and metal organic framework (MOF). Selection of effective catalysts for various epoxide substrates is very important in determining the cycloaddition operating condition. Under their catalytic systems, all classes of these catalysts, with regard to recent developments, can exhibit CO2 cycloaddition of terminal epoxide substrates at ambient temperatures and low CO2 pressure. Although highly desired conversion can be achieved for internal epoxide substrates, higher temperature and pressure are normally required. This includes fatty acid-derived terminal epoxides for oleochemical carbonate production. The production of fully renewable resources by employment of bio-based epoxy with biorefinery concept and potential enhancement of cycloaddition reactions are pointed out as well.

Fructose metabolism in Chromohalobacter salexigens: interplay between the Embden\u2013Meyerhof\u2013Parnas and Entner\u2013Doudoroff pathways

BackgroundThe halophilic bacterium Chromohalobacter salexigens metabolizes glucose exclusively through the Entner–Doudoroff (ED) pathway, an adaptation which results in inefficient growth, with significant carbon overflow, especially at low salinity. Preliminary analysis of C. salexigens genome suggests that fructose metabolism could proceed through the Entner–Doudoroff and Embden–Meyerhof–Parnas (EMP) pathways. In order to thrive at high salinity, this bacterium relies on the biosynthesis and accumulation of ectoines as major compatible solutes. This metabolic pathway imposes a high metabolic burden due to the consumption of a relevant proportion of cellular resources, including both energy molecules (NADPH and ATP) and carbon building blocks. Therefore, the existence of more than one glycolytic pathway with different stoichiometries may be an advantage for C. salexigens. The aim of this work is to experimentally characterize the metabolism of fructose in C. salexigens.ResultsFructose metabolism was analyzed using in silico genome analysis, RT-PCR, isotopic labeling, and genetic approaches. During growth on fructose as the sole carbon source, carbon overflow was not observed in a wide range of salt concentrations, and higher biomass yields were reached. We unveiled the initial steps of the two pathways for fructose incorporation and their links to central metabolism. While glucose is metabolized exclusively through the Entner–Doudoroff (ED) pathway, fructose is also partially metabolized by the Embden–Meyerhof–Parnas (EMP) route. Tracking isotopic label from [1-13C] fructose to ectoines revealed that 81% and 19% of the fructose were metabolized through ED and EMP-like routes, respectively. Activities of enzymes from both routes were demonstrated in vitro by 31P-NMR. Genes encoding predicted fructokinase and 1-phosphofructokinase were cloned and the activities of their protein products were confirmed. Importantly, the protein encoded by csal1534 gene functions as fructose bisphosphatase, although it had been annotated previously as pyrophosphate-dependent phosphofructokinase. The gluconeogenic rather than glycolytic role of this enzyme in vivo is in agreement with the lack of 6-phosphofructokinase activity previously described.ConclusionsOverall, this study shows that C. salexigens possesses a greater metabolic flexibility for fructose catabolism, the ED and EMP pathways contributing to a fine balancing of energy and biosynthetic demands and, subsequently, to a more efficient metabolism.

Nanoscale Crystalline Sheets and Vesicles Assembled from Nonplanar Cyclic π-Conjugated Molecules.

A fundamental challenge in chemistry and materials science is to create new carbon nanomaterials by assembling structurally unique carbon building blocks, such as nonplanar π-conjugated cyclic molecules. However, self-assembly of such cyclic π-molecules to form organized nanostructures has been rarely explored despite intensive studies on their chemical synthesis. Here we synthesized a family of new cycloparaphenylenes and found that these fully hydrophobic and nonplanar cyclic π-molecules could self-assemble into structurally distinct two-dimensional crystalline multilayer nanosheets. Moreover, these crystalline multilayer nanosheets could overcome inherent rigidity to curve into closed crystalline vesicles in solution. These supramolecular assemblies show that the cyclic molecular scaffolds are homogeneously arranged on the surface of nanosheets and vesicles with their molecular isotropic x-y plane standing obliquely on the surface. These supramolecular architectures that combined exact crystalline order, orientation-specific arrangement of π-conjugated cycles, controllable morphology, uniform molecular pore, superior florescence quench ability, and photoluminescence are expected to give rise to a new class of functional materials displaying unique photonic, electronic, and biological functions.

Meta-composites: NiO supported 3D carbon networks structured by 1D building blocks towards tailorable negative permittivity

Meta-composites have drawn significant attention due to their preferable applications in electronic devices and promising mass production-scale. Compared with metallic particles as common conductive units in metamaterials or meta-composites fabrication, one-dimensional (1D) carbonaceous building blocks [e.g. multi-walled carbon nanotubes (MWCNTs) or carbon fibers] could provide preferable alternations. In this paper, nickel-modified carbon fibers and MWCNTs were served as 1D building blocks to fabricate meta-composites. Negative permittivity behavior in meta-composites were investigated at radio-frequency region. Herein, two different types of negative permittivity (i.e. dipole-type and plasma-type) were observed and analyzed by Lorentz model and Drude model respectively. Different variation trends of alternative conductivity spectra were followed by Jonscher’s power law or Drude model, indicating conductive mechanism change from hopping conduction to metal-like conduction. Equivalent circuit analysis to impedance response of meta-composites manifested correspondence between inductive characteristic and negative permittivity. This work not only presents novel routes to meta-composites designations by 1D carbon building blocks, but also further clarifies negative permittivity generation mechanism, which will facilitate applications in impedance matching, electromagnetic shielding and multi-layer high-k capacitors etc.

Electrosynthesis of Bio-Based Dicarboxylic Acids

Currently, oil and gas are dominating feedstocks for bulk and fine chemicals. However, limited fossil resources and growing awareness for the environment requires sustainable alternatives [1]. One potential source for renewable raw materials is wood. In the pulping process of wood to cellulose, large amounts of lignin and also turpentine accumulate as a by-product. With the holistic use of waste streams in mind, lignin and the components of the turpentine fraction represent promising sources for carbon building blocks. α-Pinene, the major compound of the turpentine fraction, can be oxidized to a biogenic dicarboxylic acid which finds a potential application as a hardener in bio-based thermosets. For a fully sustainable application, the necessity for renewable resources goes hand in hand with the demand for green chemical processes, such as electrosynthesis [2]. The key step of a possible oxidation sequence of α-pinene to bio-based dicarboxylic acids is successfully performed by electrocatalytical conversion of pinanediol to pinonic acid. To establish this transformation as a green method, we developed a simple, high-yielding protocol for the anodic oxidation of pinanediol, while maintaining of the intrinsic stereogenic information, at nickel oxidehydroxide anodes in water, the least hazardous of all solvents. [1] C. Brandt, Chem. Unserer Zeit 2002, 36, 214–224. [2] A. Frontana-Uribe, R. D. Little, J. G. Ibanez, A. Palma, R. Vasquez-Medrano, Green Chem. 2010, 12, 2099–2199. Figure 1

A “fullerene-carbon nanotube” structure with tunable mechanical properties

Carbon-based nanostructures have drawn tremendous research interest and become promising building blocks for the new generation of smart sensors and devices. Utilizing a bottom-up strategy, the chemical interconnecting sp3 covalent bond between carbon building blocks is an efficient way to enhance its Young's modulus and ductility. The formation of sp3 covalent bond, however, inevitably degrades its ultimate tensile strength caused by stress concentration at the junction. By performing a molecular dynamics simulation of tensile deformation for a fullerene-carbon nanotube (FCNT) structure, we propose a tunable strategy in which fullerenes with various angle energy absorption capacities are utilized as building blocks to tune their ductile behavior, while still maintaining a good ultimate tensile strength of the carbon building blocks. A higher ultimate tensile strength is revealed with the reduction of stress concentration at the junction. A brittle-to-ductile transition during the tensile deformation is detected through the structural modification. The development of ductile behavior is attributed to the improvement of energy propagation ability during the fracture initiation, in which the released energy from bonds fracture is mitigated properly, leading to the further development of mechanical properties.

Rational design and synthesis of hierarchically structured SnO2 microspheres assembled from hollow porous nanoplates as superior anode materials for lithium-ion batteries

Herein, hierarchically structured SnO2 microspheres are designed and synthesized as an efficient anode material for lithium-ion batteries using hollow SnO2 nanoplates. Three-dimensionally ordered macroporous (3-DOM) SnOx-C microspheres synthesized by spray pyrolysis are transformed into hierarchically structured SnO2 microspheres by a two-step post-treatment process. Sulfidation produces hierarchically structured SnS-SnS2-C microspheres comprising tin sulfide nanoplate and carbon building blocks. A subsequent oxidation process produces SnO2 microspheres from hollow SnO2 nanoplate building blocks, which are formed by Kirkendall diffusion. The discharge capacity of the hierarchically structured SnO2 microspheres at a current density of 5 A·g−1 for the 600th cycle is 404 mA·h·g−1. The hierarchically structured SnO2 microspheres have reversible discharge capacities of 609 and 158 mA·h·g−1 at current densities of 0.5 and 30 A·g−1, respectively. The ultrafine nanosheets contain empty voids that allow excellent lithium-ion storage performance, even at high current densities.

Carbon Structure Originated Chirality in Carbon Nanotubes

The origin of single wall carbon nanotube chirality includes fundamental understanding on formation mechanism of tubular carbon topology and its interrelations with catalyst features. Elucidation of this mechanism is key for realizing untapped potentials of nanotubes, because nanotube chirality governs its physical properties. For more than two decades studies have revealed the essential contributions of a catalyst features (diameter, morphology, composition and structure) in chirality abundance of grown nanotubes. Thus, chirality origination by catalyst structure via an epitaxial relationship emerges as a dominant mechanism. However, it is easy to overlook the hypothesis that was speculated in early stages of nanotube discovery in which chirality originates from hemispherical fullerene end-cap. To address this long standing dispute, our strategy was to decouple grown carbon structure properties from the impact of catalyst features. To this end, we grew carbon nanotubes on liquid catalyst with isotropic surface and thereby eliminated the entire complex catalyst feature’s contributions mentioned above. We found that the tubes with chirality (11,1)/χ=4.31o grown on isotropic surface of catalyst, can be up to eightfold preferable than tubes with larger helix angle (9,4)/χ=17.48o, although having exactly same diameter d=9.156Å. Abundances of tubes grown on solid polyhedral catalysts with certain structure and shape follow completely different patterns. This finding suggests chirality origination in carbon nanotubes as an intrinsic property of carbon structure. It distinguishes between the chirality origination by carbon structure and amendment by catalyst and could lead to the comprehensive theory of chirality formation. The role and energetics of carbon flux density and the type of elementary carbon building blocks (dimers, trimers, chains, clusters …) that form the precursor for carbon nanotube cap, and thereby originate the chirality will be discussed.

Yeast as a cell factory: current state and perspectives.

The yeast Saccharomyces cerevisiae is one of the oldest and most frequently used microorganisms in biotechnology with successful applications in the production of both bulk and fine chemicals. Yet, yeast researchers are faced with the challenge to further its transition from the old workhorse to a modern cell factory, fulfilling the requirements for next generation bioprocesses. Many of the principles and tools that are applied for this development originate from the field of synthetic biology and the engineered strains will indeed be synthetic organisms. We provide an overview of the most important aspects of this transition and highlight achievements in recent years as well as trends in which yeast currently lags behind. These aspects include: the enhancement of the substrate spectrum of yeast, with the focus on the efficient utilization of renewable feedstocks, the enhancement of the product spectrum through generation of independent circuits for the maintenance of redox balances and biosynthesis of common carbon building blocks, the requirement for accurate pathway control with improved genome editing and through orthogonal promoters, and improvement of the tolerance of yeast for specific stress conditions. The causative genetic elements for the required traits of the future yeast cell factories will be assembled into genetic modules for fast transfer between strains. These developments will benefit from progress in bio-computational methods, which allow for the integration of different kinds of data sets and algorithms, and from rapid advancement in genome editing, which will enable multiplexed targeted integration of whole heterologous pathways. The overall goal will be to provide a collection of modules and circuits that work independently and can be combined at will, depending on the individual conditions, and will result in an optimal synthetic host for a given production process.

Reduced graphene oxide/carbon nanotube hybrid film as high performance negative electrode for supercapacitor

Interconnecting different carbon building blocks, such as 1-dimensional (1D) carbon nanotubes (CNTs) and 2-dimensional (2D) graphene sheets, is an effective way to build hybrid carbon architectures with fascinating new properties. Here we report the synthesis of a binder-free reduced graphene oxide/carbon nanotube (rGO/CNT) hybrid film and its capacitive behaviour in both positive and negative potential window with 1M Na2SO4 aqueous electrolyte. It is found that intercalating small amount of CNTs into rGO sheets result in excellent specific capacitance of 272Fg−1 at a scan rate of 5mVs−1 in negative potential window of −0.8 to 0V. In contrast, moderate specific capacitance of 132Fg−1 at the same scan rate is obtained in positive potential window of 0 to 0.8V. The reason of the enhanced capacitance in negative potential window is discussed. We propose that the remarkable improvement of capacitance in negative potential window is mainly due to the strong cation adsorption at the oxidized surface of rGO sheets. The addition of CNTs can significantly improve the rate capability and cyclic stability of the electrode compared to that of pure rGO electrode. As-synthesized rGO/CNT hybrid film shows great potential in neutral aqueous electrolyte based asymmetric supercapacitors as high performance negative electrode, and other applications such as flexible batteries, seawater desalination, and biomedical applications.

Bio‐Inspired Synthesis of High‐Performance Nanocomposite Catalysts for Hydrogen Oxidation

AbstractA biologically inspired synthesis method is presented as a new tool for the design of novel electrochemically active materials, focusing on the advantages for fuel cell development. The need for cost‐effective, high‐performance materials is driving contemporary fuel cell research, with the expectation that advances in synthetic methods will be necessary for commercialization of this energy technology. Highly active electrocatalysts for proton‐exchange‐membrane (PEM) fuel cells are being developed, by combining a kinetically controlled synthesis method of the nanocrystalline metal catalyst with the mesoscale assembly of two morphologically different carbon building blocks of the supporting matrix. These methods provide access to new combinations of porosity, conductivity and electrochemical hydrogen oxidation. The relationships between the porous morphologies of the carbon matrices, the sizes of the platinum nanocrystals and their resulting electrochemical activities are discussed, correlating these with the relevant fuel cell principles.