Archive for the ‘Hot Articles’ Category

Buckyball’s Hydrogen Spillover Effect at Ambient Temperature Observed Experimentally for the First Time

A group of scientists from Tohoku University, Japan experimentally demonstrated the hydrogen spillover effect of buckyball (a.k.a. fullerene or C60). They achieved this breakthrough using mass spectroscopy, and their findings were published recently in Chem. Commun.

Certain transition metal nanoparticles (e.g. Ru, Pt and Ni) can capture hydrogen molecules. The capture process generally involves three sequential steps. Firstly, hydrogen molecules split into hydrogen atoms on the metal surface. Secondly, the yielded hydrogen atoms migrate on the surface towards substrates under the metal nanoparticles and, finally, these atoms fix onto the substrates. The second step is termed the “spillover effect” (Figure 1a). Previous studies predicted that curved graphene sheets could enhance the hydrogen spillover effect at ambient temperatures, but solid experimental evidence has remained inadequate.

To gather evidence for this prediction, Nishihara et al. studied the material buckyball, a spherical carbon nanosphere that represents an extremely curved graphene sheet. The researchers selected ketjenblack (KB), a type of porous carbon sheet, as the substrate, and deposited Pt nanoparticles (1-3 nm in diameter) and buckyball molecules onto it (Figure 1b). They found that the Pt and buckyball-decorated KB stored a higher amount of hydrogen compared to the Pt-loaded KB. This observation indirectly confirmed the previous prediction, as hydrogen storage capacity may be improved by enhancing the spillover effect.

Figure 1. (a) A schematic illustration showing how a hydrogen molecule is split on Pt surface [process (1)] followed by the spillover effect [processes (2) and (2′)]. (b) A schematic illustration of the structure of Pt and buckyball-decorated KB. The inset panel displays two forms of hydrogen bound to the composite: the physically adsorbed di-hydrogen molecules, and the spillover hydrogen atoms anchored on the KB substrate and buckyballs.

 

The authors then sought time-of-flight mass spectroscopy to obtain more evidence. This spectroscopic technique is capable of identifying molecules with different mass to charge ratios (m/z). As shown in Figure 2, after treating the buckyball and Pt-loaded KB with deuterium molecules (D2), the spectrum (red) exhibited two additional peaks with m/z of ~723.5 and ~724.5 (highlighted by arrows in the figure) compared to those of the buckyball reference (black) and the buckyball and Pt-loaded KB prior to D2 dosage (blue). The authors ascribed these two new peaks to single D atom-adsorbed buckyballs with different amounts of carbon isotopes (12C and 13C). The presence of the two new peaks clearly showed that buckyballs could host hydrogen atoms to enhance the spillover effect. In addition, upon exposing the D-containing buckballs to air, both of the newly-merged peaks disappeared, suggesting that D atom adsorption was reversible.

Figure 2. The time-of-flight mass spectroscopy spectra of buckyball (black), Pt and buckyball-decorated KB before (blue) and after (red) exposure to D2, and after exposure to air (green). Pictures on the right show the molecular structure of a buckyball molecule and two deuterium-incorporated buckyball molecules (with different number of 13C isotope). Deuterium is used to avoid the interference from the 13C isotope.

This work could serve as a reference for future studies of the spillover effect induced by buckyballs interacting with other metal nanoparticles. The increasing availability of in-depth fundamental insight could refine our understanding of ambient-temperature hydrogen storage.

To find out more please read:

Enhanced Hydrogen Spillover to Fullerene at Ambient Temperature

Hirotomo Nishihara, Tomoya Simura and Takashi Kyotani

Chem. Commun. 2018, DOI: 10.1039/c8cc00265g

About the blogger:

Tianyu Liu obtained his Ph.D. (2017) in Physical Chemistry from University of California, Santa Cruz in United States. He is passionate about scientific communication to introduce cutting-edge research to both the general public and scientists with diverse research expertise. He is a blog writer for Chem. Commun. and Chem. Sci. More information about him can be found at http://liutianyuresearch.weebly.com/.

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An Organometallic Toolbox for the Study and Synthesis of Unique N-Heterocyclic Carbenes

N-heterocyclic carbenes (NHCs) are an interesting example of chemical curiosity turned commonplace. NHCs are stable singlet carbenes located within an N-heterocycle, in which the carbon centre bears an sp2 hybridised pair of electrons. As early as 1835 chemists were thinking about carbenes, with Dumas’ optimistic (if unsuccessful) attempt to synthesise the methylene carbene by dehydrating methanol. For many years the intentional study of carbenes was considered too demanding because of their instability, and so they remained in relative obscurity. A number of seminal papers changed this preconception; in particular, a report by Wanzlick in 1968 reporting the synthesis of the first NHC-metal complex using mercury and the first synthesis of a stable and isolable NHC by Arduengo in 1991.

Intensification in research and interest in NHCs over the past thirty years may have originated with these seminal reports, but it continues because of the success of NHCs in catalysis: both as strongly σ-donating metal ligands and nucleophilic organocatalysts. One of the most valuable features of NHCs is the ability to tailor their steric and electronic properties by altering the heterocyclic ring and N-bound substituents. Accordingly, the study of NHC reactivity and the development of methods to functionalise NHCs are essential for continued innovation in this field.

Drs Marina Uzelac and Eva Hevia at the University of Strathclyde, Scotland, have written a review article summarising organometallic methods to metallate N-heterocyclic carbenes. The work summarises metallation of all three components of the NHC: the carbenic carbon, the heterocyclic backbone and the N-bound substituents.

The lithiated complex (1), synthesised by treatment of the N-heterocyclic carbene NHC with nBuLi, can be transmetallated at the C4 position by a number of main group elements to give a variety of bimetallic complexes (2). These complexes can be selectively quenched to generate NHC complexes with unconventional regiochemistry (3).

The lithiated complex (1) can be transmetallated at the C4 position by a number of main group elements to give a variety of bimetallic complexes (2). These complexes can be selectively quenched to generate NHC complexes with unconventional regiochemistry (3).

To exemplify the breadth of research discussed; beginning with 2,6-diisopropylphenyl (dipp) substituted imidazole-2-ylidenes, the reactivity of the NHC can be unlocked by initial addition of an alkali metal such as lithium, sodium or potassium (see figure). Metallation at the C4 position occurs by deprotonation of the vinyl protons in the NHC backbone, while a second metal coordinates to the carbene electron pair at the C2 position. From this species (1) it is possible to transmetallate the C4 position with a less-polar metal such as zinc, aluminium, gallium, boron or iron to furnish a bi-metallic NHC (2). Interestingly, addition of an electrophilic methyl or proton source to this species exclusively quenches the C2 position, generating a suite of unconventional complexes (3) with the carbene electron pair positioned on the C4 carbon.

Lithiation of NHC complexes: a) deprotonation of the backbone of NHC-borane complex; b) co-complexation of NHC-zinc complex with alkyllithium affording lithium zincate; c) deprotonation of the abnormal carbene complex.

Reactivity of main-group NHC complexes towards lithiation.

Further studies investigate how different reagents influence the regioselectively and extent of metallation, how metallated NHCs can activate small-molecules such as carbon dioxide, conditions which can lead to the metallation of N-dipp substitutents, as well as products and speciation following treatment of NHCs with a variety of bimetallic reagents.

In addition to expanding the knowledge of NHC reactivity, the work summarised in this review provides a reference and inspiration to researchers seeking to tailor NHCs for unique applications in synthesis and catalysis.

To find out more please read:

Polar organometallic strategies for regioselective C-H metallation of N-heterocyclic carbenes

Marina Uzelac and Eva Hevia.
Chem. Commun., 2018, Advance Article
DOI: 10.1039/c8cc00049b

About the author:

Zoë Hearne is a PhD candidate in chemistry at McGill University in Montréal, Canada, under the supervision of Professor Chao-Jun Li. She hails from Canberra, Australia, where she completed her undergraduate degree. Her current research focuses on transition metal catalysis to effect novel transformations, and out of the lab she is an enthusiastic chemistry tutor and science communicator.

 

 

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Gold Rocks the Casbah

Researchers at the University of Texas have developed an inventive method to deliver molecules into the cell’s nucleus. Advances in gene therapy and the development of drugs that target DNA, the transcription machinery and other regulatory systems all rely on effective transport of molecules into the nucleus. Furthermore, achieving selective delivery of drugs reduces toxicity to non-target organs while maintaining the therapeutic effect.

Towards this aim, the authors delivered liposomes coated with clusters of gold nanoparticles into the cytoplasm. Laser irradiation of the cells heats the nanoparticles to high temperatures resulting in vapourisation of the water-based cytosol, and the transient formation of nanobubbles. The effect of this is an increase in the porosity of the nuclear envelope, enabling the transfer of various macromolecules from the cytoplasm into the nucleus. The authors describe this technique as ‘nanomechanical transduction’ because it is hypothesised that the mechanical effects brought on by the rapid growth and collapse (20 – 50 ns lifetimes) of the bubbles is responsible for the observed increase in porosity.

Local heating of gold nanoparticles and the subsequent formation of nanobubbles occurs due to ‘plasmon resonance’, whereby an electromagnetic field interacts with gold on the surface of the liposome and drives free-electron oscillation in resonance with the incident laser.

A diagram showing nanomechanical transduction. A gold-coated nanoparticle liposome enters the cell and, upon activation by a laser pulse, creates nanobubbles which causes mechanical disruptions in the cell and increased permeability of the nuclear membrane so molecules such as plasmids can enter.

A diagram showing nanomechanical transduction. A gold-coated liposome enters the cell and, upon activation by a laser pulse, creates nanobubbles and mechanical disruption within the cell, resulting in increased permeability of the nuclear membrane.

As a proof-of-concept the authors investigated whether nanomechanical transduction can improve the nuclear localisation of two different types of macromolecule: a dextran polymer labelled with a fluorescent dye, and a plasmid encoding the green fluorescent protein. In the first experiment, cells containing the dextran polymer were incubated with plasmonic liposomes and subjected to a near-infrared laser pulse. Up to 70% fluorescence intensity was observed in the nucleus compared to the cytoplasm, far exceeding the result from control experiments using electroporation to increase cell membrane permeability. In a similar way, nanomechanical transduction resulted in a 2.7 fold increase in the expression of the green-fluorescent protein compared to using electroporation, demonstrating efficient delivery of the plasmid into the nucleus.

The authors entitle their paper ‘rock the nucleus’ and, unintentional reference or not, I think a Casbah (one meaning is the central keep, or citadel, of a walled city) is a rather fitting analogy for the nucleus: the command post of the cell, and safeguard of genetic information. The authors of this work offer a sophisticated yet general method for molecules to breach the walls.

To find out more please read:

Rock the nucleus: significantly enhanced nuclear membrane permeability and gene transfection by plasmonic nanobubble induced nanomechanical transduction

Xiuying Li, Peiyuan Kang, Zhuo Chen, Sneha Lal, Li Zhang, Jeremiah J. Gassensmith and Zhenpeng Qin.
Chem. Commun., 2008, Advance Article
DOI: 10.1039/c7cc09613e

About the author:

Zoë Hearne is a PhD candidate in chemistry at McGill University in Montréal, Canada, under the supervision of Professor Chao-Jun Li. She hails from Canberra, Australia, where she completed her undergraduate degree. Her current research focuses on transition metal catalysis to effect novel transformations, and out of the lab she is an enthusiastic chemistry tutor and science communicator.

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Anchoring Arynes on Graphene with Microwave but No Solvents

Recently in ChemComm, an international team from Italy and Spain reported a non-conventional way to anchor arynes onto graphene surface using microwave. Their developed method is fast, efficient, mild and solvent-free.

Attaching functional groups onto graphene surface, i.e. functionalization, allows the physical and chemical properties of graphene to be fine-tuned, such as electrical conductivity and solubility. Conventional solvent-based functionalization strategies usually involve time-consuming reactions and tedious purification steps. The poor suspension stability of graphene in solvents, particularly in polar organic solvents, greatly hinders the overall functionalization efficiency. Therefore, establishing easy and solvent-free functionalization protocols for graphene is highly needed.

M. Prato, A. Criado and coworkers made a breakthrough in addressing this challenge by developing a microwave-assisted functionalization method. Their method to functionalize graphene consists of cycloaddition reactions between few-layer graphene (FLG) and arynes (Figure 1). These reactions proceed by mixing the dry powder of FLG and arylene anhydrides, the precursors of arynes, followed by rapid heating under microwave irradiation. The whole process is solvent-free and occurs within half a minute. It is also applicable to a variety of arynes (Figure 2).

Figure 1. The schematic illustration of the microwave-assisted functionalization of graphene with arynes. This process can be carried out within half a minute and is solvent-free.

Figure 2. A variety of arynes capable of being anchored on graphene surface. 1~6 represent the arylene anhydrides and f-G(7)~f-G(12) are corresponding arynes attached onto graphene.

The most unique feature of the demonstrated method is the dual role of FLG. In addition to being one of the reactants, FLG is capable of absorbing microwave energy, and enables its surface to rapidly reach high temperatures that significantly accelerate the cycloaddition reactions.

This microwave-assisted functionalization method shows great promise as a stepping stone for the fast and efficient modulation of graphene surface and subsequently, the performance of graphene-based electronics.

 

To find out more please read:

Microwave-Induced Covalent Functionalization of Few-Layer Graphene with Arynes Under Solvent-Free Conditions

V. Sulleiro, S. Quiroga, D. Peña, D. Pérez, E. Guitián, A. Criado and M. Prato

Chem. Commun. 2018, DOI: 10.1039/C7CC08676H

About the blogger:

Tianyu Liu obtained his Ph.D. (2017) in Physical Chemistry from University of California, Santa Cruz in United States. He is passionate about scientific communication to introduce cutting-edge research to both the general public and scientists with diverse research expertise. He is an online blog writer for Chem. Commun. and Chem. Sci. More information about him can be found at http://liutianyuresearch.weebly.com/.

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HOT ChemComm articles for January

All of the referee-recommended articles below are free to access until 5th March 2018.

Kinetic Stabilisation of a Molecular Strontium Hydride Complex using an Extremely Bulky Amidinate Ligand
Caspar N. de Bruin-Dickason, Thomas Sutcliffe, Carlos Alvarez Lamsfus, Glen B. Deacon, Laurent Maron and Cameron Jones
Chem. Commun., 2018,54, 786-789
DOI: 10.1039/C7CC09362D, Communication

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The antibacterial activity of polyoxometalates: Structures, antibiotic effects and future perspectives
Aleksandar Bijelic, Manuel Aureliano and Annette Rompel
Chem. Commun., 2018,54, 1153-1169
DOI: 10.1039/C7CC07549A, Feature Article

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Controlled Preparation of Amphiphilic Triblock-Copolyether in a Metal- and Solvent-Free Approach for Tailored Structure-Directing Agents
Alexander Balint, Marius Papendick, Manuel Clauss, Carsten Müller, Frank Giesselmann and Stefan Naumann
Chem. Commun., 2018, Advance Article
DOI: 10.1039/C7CC09031E, Communication

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Alkene functionalization for the stereospecific synthesis of substituted aziridines by visible-light photoredox catalysis
Wan-Lei Yu, Jian-Qiang Chen, Yun-Long Wei, Zhu-Yin Wang and Peng-Fei Xu
Chem. Commun., 2018, Advance Article
DOI: 10.1039/C7CC09151F, Communication

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Microwave-induced covalent functionalization of few-layer graphene with arynes under solvent-free conditions
M. V. Sulleiro, S. Quiroga, D. Peña, D. Pérez, E. Guitián, A. Criado and M. Prato
Chem. Commun., 2018, Advance Article
DOI: 10.1039/C7CC08676H, Communication

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Barbiturate end-capped non-fullerene acceptors for organic solar cells: tuning acceptor energetics to suppress geminate recombination losses
Ching-Hong Tan, Jeffrey Gorman, Andrew Wadsworth, Sarah Holliday, Selvam Subramaniyan, Samson A. Jenekhe, Derya Baran, Iain McCulloch and James R. Durrant
Chem. Commun., 2018, Advance Article
DOI: 10.1039/C7CC09123K, Communication

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Hiding Carbon Dioxide in Oxazolidinones

Sometimes it feels as though the pinnacle of synthetic achievement is represented by 20 step total syntheses (with 10 contiguous stereocentres and 5 fused rings…). The level of chemical complexity that can be fashioned from simple building blocks is undoubtedly impressive, but amid such feats it is important not to lose sight of the elegance and worth of simple chemistry, especially when it aims to play a part in resolving profound challenges. One such challenge, which will increasingly confront future generations, is how to reduce the load of carbon dioxide in the atmosphere. One solution is to ‘fix’ carbon dioxide by integrating it into chemical building blocks of added complexity in a sustainable way.

The porosity and high surface area of metal organic frameworks (MOFs), a class of three-dimensional coordination networks, proffers them as ideal materials for capture and storage of carbon dioxide. A team of researchers have designed a MOF which consumes carbon dioxide in a different way: by transformation into value-added chemicals. The group have developed a catalytic MOF embedded with lewis-acidic copper centres capable of converting aziridines to oxazolidinones by the addition of carbon dioxide. Oxazolidinones are used as auxiliaries in chiral synthesis, and are structural components of some antibiotics.

The MOF, termed MMPF-10, is a metal-metalloporphyrin framework constructed from a copper-bound porphyrin ring chemically modified to incorporate 8 benzoic acid moieties, generating an octatopic ligand. These carboxylic acids groups form a second complex with copper in situ, termed a ‘paddlewheel’ for its appearance, with the formula [Cu2(CO2)4]. The resulting network contains hexagonal channels measuring 25.6 x 15.6 Å flanked by four of each of the two copper complexes. With 0.625 % of the catalyst at room temperature, 1 bar CO2 pressure, and in a solvent free environment, MMPF-10 catalyses the transformation of 1-methyl-2-phenylaziridine to yield 63% of the product.

metal-metalloporphyrin MOF catalyses catalyzes carbon dioxide fixation aziridines to oxazolidinones

Topology of MMPF-10 showing hexagonal channels in a) and c), and pentagonal cavities in b). Turquoise: copper, red: oxygen, grey: carbon, blue: nitrogen.

This work, a simple reaction to prepare oxazolidinones, shows that carbon dioxide can be fixed in specialised synthetic building blocks in a sustainable way. This is the way the first paragraph ended, ‘in a sustainable way’, because the challenge of developing such a reaction is two-fold: it must use carbon dioxide, and the reaction conditions must be sustainable. There will be no beneficial offset if the reaction uses a lot of energy, requires many resources, or generates larges quantities of waste. In this reaction the researchers have remained mindful of developing a mild, solvent-free reaction with low catalyst loading employing an earth abundant metal, reflecting an earnest aim to develop practical and sustainable chemistry.

To find out more please read:

A metal-metalloporphyrin framework based on an octatopic porphyrin ligand for chemical fixation of CO2 with aziridines

Xun Wang, Wen-Yang Gao, Zheng Niu, Lukasz Wojtas, Jason A. Perman, Yu-Sheng Chen, Zhong Li, Briana Aguila and Shengqian Ma
Chem. Commun., 2018, Advance Article
DOI: 10.1039/c7cc08844b

About the Author

Zoë Hearne is a PhD candidate in chemistry at McGill University in Montréal, Canada, under the supervision of Professor Chao-Jun Li. She hails from Canberra, Australia, where she completed her undergraduate degree. Her current research focuses on transition metal catalysis to effect novel transformations, and out of the lab she is an enthusiastic chemistry tutor and science communicator.

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Single-Crystalline NiFe-Hydroxide Nanosheets for Catalyzing Oxygen Evolution

A group of scientists led by Prof. Shizhang Qiao has synthesized an oxygen evolution reaction (OER) catalyst combining the merit of low cost, excellent catalytic activity and long lifetime. This OER catalyst is composed of single-crystalline NiFe-hydroxide nanoflakes directly grown on nickel foams. The work has been published recently in ChemComm.

OER, the reaction of producing oxygen gas from water, is an indispensable component of electricity-generation devices using sustainable energy (e.g. fuel cells and photoelectrochemical water splitting cells). OER is usually the bottleneck limiting the overall energy conversion efficiency due to its sluggish kinetics and complex reaction pathways. As such, OER catalysts are needed to accelerate the OER reaction rate. Among the various OER catalysts, noble metal oxides stand out owing to their ultrahigh catalytic activity. However, the “shining” performance is dimmed by their high cost and short lifetime. Thus, obtaining alternatives with comparable OER catalytic activity as well as long-term stability is required to advance the utilisation of sustainable energy.

To address this challenge, the authors turned their attention to a low-cost transition metal, nickel. They developed a hydrothermal method using nickel foams to grow highly crystalline and near-vertically aligned NiFe-hydroxide nanosheets as OER catalysts (Figure 1a). The seamless integration between the hydroxide nanosheets and the nickel substrates reduces the contact resistance and facilitates interfacial electron transfer. The near-vertical orientation (Figure 1b) allows water molecules to fully contact the catalysts. Both of the characteristics render excellent OER catalytic activity. Additionally, the high crystallinity (Figure 1c) ensures the catalysts are robust enough to withstand extensive use without degradation in performance.

Figure 1. (a) The schematic illustration of the synthetic procedures of the NiFe-hydroxide [Fe-Ni(OH)2] nanosheets supported on nickel foams (NF). (b) The scanning electron microscopy image shows the near-vertically aligned nanosheets on a piece of nickel foam. (c) The transmission electron microscopy image reveals the crystallinity of the synthesized catalyst.

The NiFe-hydroxide nanosheets outperform most of the state-of-the-art OER catalysts, including those containing noble metal elements. Specifically, the nanosheets exhibit an onset potential of 1.497 V (Figure 2). The onset potential is a measure of the catalytic activity that equals the magnitude of potential required to yield a current density of 10 mA/cm2 (when appreciable amount of oxygen gas is evolved). Outstandingly, the onset potential of the NiFe-hydroxide is the smallest among the catalysts selected for comparison.

Figure 2. The polarisation curves of different OER catalysts. The onset potential is marked by the dotted line in the inset.

The catalytic activity is also highly stable, with no loss in performance after at least 100 h of measurement. Interestingly, the onset potential further shifts to a lower value of 1.465 V after 100 h. The authors attributed this observation to a “self-activation” process that involves the formation and accumulation of nickel oxyhydroxide (NiOOH) on the surface of the nanosheets.

The hydrothermal method demonstrated here could be used to synthesize other cost-effective crystalline catalysts to develop catalysts for reactions beyond OER, such as hydrogen evolution and carbon dioxide reduction.

To find out more please read:

Free-Standing Single-Crystalline NiFe-Hydroxide Nanoflake Arrays: A Self-Activated and Robust Electrocatalyst for Oxygen Evolution

Jinlong Liu, Yao Zheng, Zhenyu Wang, Zhouguang Lu, Anthony Vasileff and Shi-Zhang Qiao

Chem. Commun. 2017, DOI: 10.1039/c7cc08843d

About the blogger:

Tianyu Liu obtained his Ph.D. (2017) in Physical Chemistry from University of California, Santa Cruz in United States. He is passionate about scientific communication to introduce cutting-edge research to both the general public and scientists with diverse research expertise. He is a blog writer for Chem. Commun. and Chem. Sci. More information about him can be found at http://liutianyuresearch.weebly.com/.

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Shoot the Messenger: Circular DNA-Graphene Oxide Material Targets mRNA in Living Cells

Schematic of the circular DNA cDNA/GO graphene oxide platform fabrication for intracellular mRNA messenger RNA imaging and gene therapy.

Scheme showing how cDNA/GO enters the cell and interacts with mRNA

Did you know that the combined length of DNA in your body’s cells is a number so large that the only references I could find use cosmic distances as a reference? Try twice the diameter of the solar system, or the distance to the moon and back 1500 times. Despite the complexity and infinite detail encountered when studying science, it is often something so simple as size that gives us pause. How can DNA be both uncomprehendingly huge and tiny at the same time?

The major function of DNA is to encode proteins, a process which begins with the transcription of genes into single-stranded messenger RNA (mRNA) molecules. It is mRNA that is directly translated into the strands of amino acids which fold to form proteins.

A team of researchers at Fuzhou University in China have developed a graphene oxide and circularised single-stranded DNA (cDNA/GO) hybrid material capable of penetrating living cells and binding mRNA. The material’s utility is shown in two practical applications: mRNA imaging and nucleotide therapeutics. The authors chose the mRNA of survivin and c-raf kinase as targets, because the enzymes are involved in carcinogenesis, and the mRNA are overexpressed in cancer cells and can be used as biomarkers.

cDNA was chosen for its increased stability over linear single-stranded DNA, which is rapidly degraded in vivo by exonucleases. For mRNA imaging the material is designed with a fluorescent dye coupled to the cDNA. GO was chosen as a hydrophilic delivery scaffold capable of adsorbing cDNA and quenching the dye. When cDNA/GO was incubated with HeLa cells (a cancer cell strain) a time-dependent increase in fluorescence was observed in the cytoplasm. Fluorescence is restored when cDNA encounters the target and desorbs from the GO to form a duplex with the mRNA.

CLSM images acquired for HeLa cells treated with both survivin and c-raf targeted cDNA/GO for duplexed intracellular mRNA imaging

The mRNA of both survivin and c-raf kinase can be imaged in living cells with cDNA/GO.

The researchers also probed whether the material might serve as a therapeutic agent: if formation of the cDNA-mRNA duplex blocks translation it may reduce the load of c-raf kinase and survivin in the cell and influence cancer cell growth. Accordingly, the researchers found that when the HeLa cells were incubated with cDNA/GO, cell proliferation was inhibited in a dose-dependent manner.

This research contributes a robust design which can be applied to diverse mRNA targets because optimisable properties such as stability, bioavailability and selectivity are largely independent of the sequence of nucleotides.

To find out more please read:

Circular DNA: a stable probe for highly efficient mRNA imaging and gene therapy in living cells

Jingying Li, Jie Zhou, Tong Liu, Shan Chen, Juan Li and Huanghao Yang
Chem. Commun., 2018, Advance Article
DOI: 10.1039/C7CC08906F

About the author

Zoë Hearne is a PhD candidate in chemistry at McGill University in Montréal, Canada, under the supervision of Professor Chao-Jun Li. She hails from Canberra, Australia, where she completed her undergraduate degree. Her current research focuses on transition metal catalysis to effect novel transformations, and out of the lab she is an enthusiastic chemistry tutor and science communicator.

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Tuning the Size of Metal-Organic Framework Crystals by Decoupling Nucleation and Growth Processes

A group of scientists from Tsinghua University in China have made a breakthrough in enhancing the controllability of the metal-organic framework (MOF) crystal size.

MOF represents a family of microporous crystals consisting of metal node-organic ligand coordination networks. They have shown potential in versatile applications including hydrogen storage, catalysis and electrochemical energy storage. Since their performance strongly correlates to the crystal size, synthesizing MOF crystals with tunable sizes and high yields is necessary to allow fundamental studies on the size-performance relationship. Unfortunately, the conventional size-controlling methods either require complex operations or exhibit low yields.

Now in ChemComm, Tiefeng Wang and coworkers demonstrate a method that can easily tune the size of MOF crystals. The mechanism is based on decoupling nucleation and growth processes. Unlike traditional strategies that mingle all metal precursors and organic ligands together in a solvent, this newly developed protocol initially mixes only a small portion of metal precursors with organic ligands. The metal precursors quickly coordinate with surrounding ligands to form small MOF clusters (the “nucleation” stage). Due to the limited supply of the metal precursors, the growth of these clusters into large crystals is unfavorable. Subsequently, the remaining metal precursors are introduced into the cluster-containing solution. The clusters then continue to grow into MOF crystals (the “growth” stage). Because the crystals develop directly from the small clusters (i.e. the seeds), the number of the seeds and the total concentration of the added metal precursors control the resulting MOF crystal size (Figure 1).

 

Figure 1. A schematic illustration of the growth of MOF crystals via a typical conventional method (top) and the reported decoupling method (down).

Using this method, the authors prepared a series of Pt@ZIF-8 MOF crystals (with sizes ranging from 45 nm to 440 nm) and investigated their ability to catalyze the reaction of 1-hexene hydrogenation. The catalytic activity of different sized crystals was quantified, with a linear correlation observed between the size and the activity (Figure 2).

Figure 2. The linear relationship between the Pt@ZIF-8 MOF size (r) and the hydrogenation reaction rate (D). r0 and D0 represent the size and the reaction rate of the smallest MOF (45 nm).

This reported approach is expected to be applicable for synthesizing MOF crystals other than Pt@ZIF-8. The availability of size-tunable MOFs will facilitate mechanistic studies in determining the optimal crystal size for different applications.

To find out more please read:

A General and Facile Strategy for Precisely Controlling the Crystal Size of Monodispersed Metal-Organic Frameworks via Separating the Nucleation and Growth

Xiaocheng Lan, Ning Huang, Jinfu Wang and Tiefeng Wang

Chem. Commun. 2017, DOI: 10.1039/c7cc08244d

About the blogger:

Tianyu Liu obtained his Ph.D. (2017) in Physical Chemistry from University of California, Santa Cruz in United States. He is passionate about scientific communication to introduce cutting-edge research to both the general public and scientists with diverse research expertise. He is an online blog writer for Chem. Commun. and Chem. Sci. More information about him can be found at http://liutianyuresearch.weebly.com/.

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Suzuki–Miyaura–hydrogenation targets 3D drugs

Scientists in the UK have unveiled a way to make pharmaceutical molecules with increased 3D characteristics. The single pot Suzuki–Miyaura–hydrogenation reaction results in sp2–sp3 linked pharmaceutically relevant molecules.

Source: Royal Society of Chemistry
A single pot Suzuki–Miyaura-hydrogenation can be used to furnish lead and fragment-like products in good to excellent yields

The number of tetrahedral carbon atoms, or how 3D a molecule is, is one factor that determines the success of a molecule in clinical drug trials. Molecules with a high sp3 fraction are in demand, however current methods to make them suffer drawbacks. The Suzuki–Miyaura reaction is common for the cross-coupling of sp2–sp3 systems, but alkyl boron or alkyl halides are prone to β-elimination and other side reactions, producing mixtures of products.

Read the full story by Suzanne Howson on Chemistry World.

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