Chemical Science Blog

All of the referee-recommended articles below are free to access until 21st July:

A full-adder based on reconfigurable DNA-hairpin inputs and DNAzyme computing modules
Ron Orbach, Fuan Wang, Oleg Lioubashevski, R. D. Levine, Francoise Remacle and Itamar Willner  
Chem. Sci., 2014, Advance Article
DOI: 10.1039/C4SC00914B, Edge Article

Millisecond lifetime imaging with europium complex using a commercial confocal microscope under one or two-photon excitations
Olivier Maury, Alexandre Haefele, Simon Pascal, Chantal Andraud, Alexei Grichine, Alain DUPERRAY and Richard MICHEL  
Chem. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4SC00473F, Edge Article

Supramolecular chemistry with ureido-benzoic acids
E W Meijer, Anja R. A. Palmans, Wilco Appel, Bas FM de Waal, Marko Nieuwenhuizen and Martin Lutz  
Chem. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4SC00871E, Edge Article

Synthesis and Chemoselective Ligations of MIDA Acylboronates with O-Me Hydroxylamines
Hidetoshi Noda and Jeffrey W Bode  
Chem. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4SC00971A, Edge Article

In nature, many cellular processes are controlled by structures that are only assembled when they are needed, in response to a chemical energy input. The structure (and hence the action of the structure) is maintained so long as the chemical energy input, or ‘fuel’ for the process is present. For example, microtubules can ‘grow’ or ‘shrink’ depending on the presence of guanosine triphosphate (GTP), and hence GTP serves as a ‘fuel’ for the function of the microtubules.

Inspired by this principle, Tom Fyles and his team from University of Victoria, Canada have used thiol–thioester exchange chemistry to assemble a metastable ion channel that disassembles over time in the absence of a chemical fuel.

In the scheme below, thiol 4 is not an active ion channel, but the addition of thioester 5 causes the formation of 3 by thiol-thioester exchange. 3 forms an active ion channel, but is metastable and therefore over time it disassembles into 4 + 6 which stops the ion transport. Adding more 5 (the fuel) will temporarily regenerate the ion transport as more C is formed.

While this system functions exactly as planned, its design was not without complications, says Fyles: “One setback was that these compounds do not work in vesicles so we had to develop reaction monitoring techniques using the bilayer clamp experiment.  That gives us exquisite sensitivity, but also allows us to detect very minor amounts of impurities.  So another setback was the observation that an oxidation impurity was vastly more active than the compounds we wanted to see.  This problem was easy enough to solve, but it took some time to recognize what was going on.”

This work also opens up exciting new avenues of investigation for the future for Fyles and his team. “The more general insight is that this system depends entirely on kinetic factors.  As chemists we are used to thinking about rates in terms of the reaction order and uniform reactant concentrations in the bulk.  Our system additionally shows the importance of local concentrations as opposed to the bulk concentration.  This introduces additional kinetic components related to diffusion.  The functioning of our system recorded using the bilayer clamp is largely controlled by diffusion processes, rather than the reaction kinetics we control in the design of the system.  This suggests that we might be able to make other systems that deliberately exploit non-uniform concentrations – yet another feature we can see in nature. Stay tuned.”

To download the full article for free*, click the link below:

Dissipative Assembly of a Membrane Transport System
A. K. Dambenieks, P. H. Q. Vu and T. M. Fyles
DOI: 10.1039/C4SC01258E

*Access is free untill the 17.07.14 through a registered RSC account – click here to register

Dye sensitized solar cells (DSSCs) are photovoltaic devices which use a sensitizer in combination with a photosensitive material and a wide band gap semiconductor to produce an electric current. Thin-film DSSCs can offer packaging and application opportunites, have potential as functional coatings, and exhibit high power conversion efficiencies (PCE) of up to 12-13%.

Current state-of-the-art dye sensitized solar cells are usually solid phase systems, removing any issues surrounding leakage of components or the corrosive nature of some electrolytes. In such configurations a constituent known as a hole transport material (HTM) is now commonly used instead of a liquid electrolyte.

In this Chemical Science Edge article, authors from the Energy Research Institute, Nanyang, and the Nanyang Technological University, Singapore, give details of a group of triptycene based molecules which, they claim, perform on a comparable level with the current best in class HTM, (spiro-OMeTAD). The materials described were prepared from a starting tri-iodotryptycene material which was derivatised using a variety of transformations including Stille and Suzuki coupling reactions. The materials contain diphenylamine moieties separated from the triptycene core by aromatic spacers, enabling charge transfer.

These materials were fabricated in a complex process into a typical DSSC, containing fluorine doped tin oxide, semiconducting titanium dioxide and lead iodide perovskite dye sensitizer material. Power conversion efficiencies are comparable to devices comprimising the best performing HTMs. For the T102 andT103 derivatives, PCEs were reported as 12.24 and 12.38%, comparable to devices fabricated with spiro-OMeTAD (12.78%). Without a HTM present the number falls to less than 5%.

This article presents details of promising HTM materials which may give rise to significant economic advantages for the production and commercialisation of solid state DSSCs, with current best in class performance levels.

Read this HOT Chemical Science Edge Article for free* today:

Novel hole transporting materials based on triptycene core for high efficiency mesoscopic perovskite solar cells

Anurag Krishna, Dharani Sabba, Hairong Li, Jun Yin, Pablo P. Boix, Cesare Soci, Subodh G. Mhaisalkar and  Andrew C. Grimsdale
DOI: 10.1039/C4SC00814F

About the webwriter

Kevin Murnaghan is a guest web-writer for Chemical Communications. He is currently a Research Chemist in the Adhesive Technologies Business Sector of Henkel AG & Co. KGaA, based in Düsseldorf, Germany. His research interests focus primarily on enabling chemistries and technologies for next generation adhesives and surface treatments. Any views expressed here are his personal ones and not those of Henkel AG & Co. KGaA.

*Access is free untill the 11.07.14 through a registered RSC account – click here to register

Photosensitiser–water oxidation catalysts in heterogeneous (top), membrane-bound (middle) and homogeneous (bottom) systems

For the first time, a water oxidation catalyst and photosensitiser have been co-embedded into a membrane to make an artificial water photooxidation system. The arrangement can generate oxygen from water at far lower catalyst concentrations than ever before.

Chemical systems to turn solar energy into fuel are of paramount importance in the quest for sustainable green energy. Mimicking natural photosynthesis, the aim is to achieve sunlight-driven conversion of water and carbon dioxide into carbohydrates and oxygen. One branch of the process involves photocatalytic water splitting, comprising oxidative and reductive half reactions. The more complex photoxidation step involves a four-electron transfer reaction and very reactive oxygen intermediates. In nature, this extremely endothermic reaction is performed by Photosystem II (PSII), using membrane bound chromophores and catalytic units.

Read the full article in Chemistry World»

Read the original journal article in Chemical Science – it’s free to download until 30th June:
Photocatalytic water oxidation at soft interfaces
Malte Hansen, Fei Li, Licheng Sun and Burkhard König
Chem. Sci., 2014, Advance Article
DOI: 10.1039/C4SC01018C, Edge Article

Chinese scientists are developing a new approach to create “universal” blood: red blood cells (RBCs) that can be transfused into any patient, regardless of the patient or recipient blood group.

Blood groups are characterised by the presence (or absence) of various proteins known as antigens on the surface of RBCs, the most well-known of which form the ABO system and the Rhesus D (RhD) system. One consequence of the existence of these groups is that blood mismatching can occur when an incompatible blood group is used for transfusion. The recipient’s antibodies recognise the antigens on the donor RBCs as being foreign and attack the cells – with potentially fatal results.

Antigenic epitopes on RBCs are sheltered by polydopamine

Read the full article in Chemistry World»

Read the original journal article in Chemical Science – it’s free to access until 1st July:
Antigenic-sheltering universal red blood cells by polydopamine-based cell superficial-engineering
Ben Wang, Guangchuan Wang, Binjie Zhao, Jiajun Chen, Xueyun Zhang and Ruikang Tang  
Chem. Sci., 2014, Accepted Manuscript, DOI: 10.1039/C4SC01120A, Edge Article

Regan Thomson’s group from Northwestern University, Illinois, present the first total synthesis of propolisbenzofuran B. The synthesis has been completed in 17 steps, starting from the phenolic aldehyde, vanillin.

In the natural world propolis is a resin made by bees and used in their hives to preserve a sterile environment. It encases waste and carcasses to prevent the decomposition of proteins and therefore decay.

The beneficial health effects of honeybee products have been hypothesised since ancient Roman times. More recently it has been determined that propolis has many biological and pharmacological properties including antibacterial, antibiotic, anti-oxidant, anti-fungal, anti-cancer and anti-inflammatory activities.

Propolisbenzofuran B is a natural product found in Brazilian propolis, first isolated in 2000 by Banskota and co-workers. Initial biological testing determined that the compound had a cytotoxic effect on murine colon 26-L5 carcinoma and human HT-1080 fibrosarcoma cells.

It was not only the promising range of biological activity which drew the authors’ attention to this particular compound; propolisbenzofuran B has a unique core with an unusual ring-system. The development of an efficient synthesis for this core opens the door to further biological evaluation and possible modifications to the compound.

Highlights of the synthesis include a silicon-tether controlled oxidative ketone-ketone cross-coupling as well as a novel and efficient benzofuran cascade. The cascade was discovered to be induced rapidly with the addition of trimethylsilyl triflate to the 1,4-diketone precursor. The authors believe this methodology will be useful in the synthesis of other complex molecules containing benzofuran groups.

To download the full article for free* click the link below:

Total synthesis of propolisbenzofuran B
Brian T. Jones, Christopher T. Avetta and Regan J. Thomson
DOI: 10.1039/c4sc00356j

*Access is free untill 13.06.14 through a registered RSC account – click here to register

Scientists in China have designed a velcro-like material held together by non-covalent interactions that can be unfastened by electrical means and refastened again under pressure.

The velcro is ‘stuck’ together by compressing a flexible, conductive poly(ionic liquid) membrane (PIL) functionalised with ferrocene (Fc) with a PIL functionalised with β-cyclodextrin (β-CD). The strong binding of the Fc groups within the β-CD cavities causes the layers to adhere together tightly. Oxidation of the Fc moieties to ferrocenium ions (Fc⁺) by chemical or electrochemical means causes the layers to come unstuck, as the charged Fc⁺ is not bound inside the hydrophobic β-CD cavity. A reducing potential and further pressing reassembles the material.

A hook-and-loop strategy fastens the layers together but these links can be unfastened by an electric current

Read the full article in Chemistry World»

Read the original journal article in Chemical Science – it’s free to download until 19th June:
Flexible and Voltage-Switchable Polymer Velcro Constructed by Host−Guest Recognition Between Poly(ionic liquid) Strips
Jiangna Guo, Chao Yuan, Mingyu Guo, Lei Wang and Feng Yan  
Chem. Sci., 2014, Accepted Manuscript
DOI: 10.1039/C4SC00864B, Edge Article