Chemical Science Blog

Covalent organic frameworks (COFs) are an emerging class of porous materials with potential for gas storage and organic photovoltaics. Their development has been hampered because the building blocks most commonly used to make them are poorly soluble and prone to oxidation.

Now US chemists have developed a general strategy for making COFs from stable, soluble starting materials. They also gained insight into the transformation’s mechanism, which should help scientists predict crystallisation conditions and prepare materials with improved properties.

Find out more in A mechanistic study of Lewis acid-catalyzed covalent organic framework formation by William Dichtel and colleagues.

UK scientists have worked out how ionic liquids solubilise cellulose, an important step in biomass processing.

The precise mechanism for the dissolution of cellulose by ionic liquids is hotly debated, with some researchers insisting that the ionic liquid cation forms a hydrogen bond to the sugar’s OH groups, without data to back it up.

Now researchers have proved conclusively with experimental data that there are no hydrogen bonding interactions between the cation and the sugars.

Read Christopher Hardacre’s Chemical Science Edge article to find out more.

Also of interest:
How polar are ionic liquids? Solutions of charge-transfer salts in ionic liquids reveal a dual nature of solvent polarity and an absence of ion pairing

UK scientists have reported a novel, more general method for inserting a useful ‘tag’ into proteins, enabling easier protein modification.

Dehydroalanine is an amino acid residue and useful precursor to a range of post-translational modifications. Several chemical and biochemical methods for incorporating dehydroalanine into peptides and proteins have been reported but each strategy has its limitations, says Ben Davis, from the University of Oxford.

Davis’ team assessed the merits and drawbacks of these methods and came up with a more general method – the bis-alkylation-elimination of cysteine to dehydroalanine using a stable, easy to prepare dibromide compound.

To demonstrate the scope and utility of the method, they used it to incorporate the tag into an antibody, then glycosylated it.

To find out more about Professor Davis’ research, download his Chemical Science Edge article. You can also see him speak at Challenges in Chemical Biology (ISACS5) in Manchester in July – registration deadline 24th June 2011.

US scientists have demonstrated for the first time that a metal–carbon multiple bond complex can activate methane. The work could open the way for efficiently converting methane into useful hydrocarbons including ethylene, one of the fundamental building blocks of the chemical industry.

Methane is the principal component of natural gas and a major contributor to global warming. It is therefore desirable to find cleaner and cheaper ways of using it as a resource by converting it into more useful chemicals. However, such reactions pose significant challenges because of methane’s low reactivity and strong tetrahedral C–H bonds, which are not readily accessible for chemical attack and activation.

The research could ultimately enable scientists to use methane as a feedstock for C–C bond formation, important for the production of chemicals including pharmaceuticals and plastics, say Daniel Mindiola (Indiana University) and colleagues.

Download Mindiola’s Edge article to find out more.

Teams from Germany, the US and Finland have re-investigated the structure of a famous gold-phosphine-halide compound.

The ‘‘Schmid Au55’’ cluster, originally formulated as Au₅₅(PPh₃)₁₂Cl₆, is one of the first and probably most utilised gold nanoparticles. However, the team found that the most energetically favourable anion is
[Au₆₉(PR₃)₂₀Cl₁₂]^-1. It is energetically and chemically superior to the standard models based on Au₅₅(PR₃)₁₂X₆.

Download the Chemical Science Edge article to find out more.

Cell membranes are made up of a mixture of different lipids and proteins. Membrane lipids aren’t randomly distributed but instead form raft-like microdomains. These are thought to provide platforms for protein interaction allowing protein trafficking and cell signalling.

Scientists have found it difficult to study these microdomains because their reported size is smaller than the resolution of light microscopy. Now a team of scientists from Japan and Belgium have circumvented this limitation by designing probes for cholesterol and sphingolipid-enriched microdomains for use in superresolution microscopy.

They visualised clustering of lipid molecules in nanodomains with a spatial resolution one order of magnitude better than the diffraction limit and were able to resolve the detailed structure of the domains.

Read more:
Fluorescent probes for superresolution imaging of lipid domains on the plasma membrane
Hideaki Mizuno, Mitsuhiro Abe, Peter Dedecker, Asami Makino, Susana Rocha, Yoshiko Ohno-Iwashita, Johan Hofkens, Toshihide Kobayashi and Atsushi Miyawaki, Chem. Sci., 2011, DOI: 10.1039/C1SC00169H

Johan Hofkens, one of the authors of this manuscript, is a plenary speaker at the forthcoming Challenges in Chemical Biology (ISACS5) meeting. Register by 24th June to hear him speak.

A team of scientist from the US and India have developed a simple and sensitive way to detect ricin in liquid foods, such as orange juice and milk.

Ricin is a protein toxin naturally present in the castor bean plant (Ricinus communis); it is classified as a ‘select’ bioterror agent and was involved in a recent bioterrorism attack plot targeting US hotels and restaurants at multiple locations, as reported by the Department of Homeland Security officials in December 2010.

 Theodore Labuza, at the University of Minnesota, and colleagues developed a two-step assay, in which the ricin was first captured out of food matrices by aptamer-conjugated silver dendrites and then the Raman spectrum was directly read on the silver dendrites. The measurement is based on the Raman ‘‘finger-print’’ of the target itself. Combined with the specific capture agent, Labuza says false positive results are extremely unlikely.

The assay shows great promise as a rapid (<40min), sensitive, and simple ‘‘Yes/No’’ method to detect bio-weapons, say the researchers.

Find out more for free by downloading Labuza’s Chemical Science Edge article.

Also of interest
ChemComm Surface Enhanced Raman Spectroscopy web themed issue