Chemical Science Blog

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

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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