Archive for the ‘News’ Category

A rotaxane-based mimic of biological springs

Scientists in China have made a molecular spring that mimics stretchable systems in living systems, for example titin (a protein found in cardiac and skeletal muscles). 

Although molecular springs based on rotaxane are known, they can only change their length stepwise. This new rotaxane-based spring changes its length continuously as solvent polarity varies and so is a better mimic of biological springs.

A solvent-driven molecular spring

 

Link to journal article
A solvent-driven molecular spring

Z Zhang et al
Chem. Sci.,
2012, DOI: 10.1039/c2sc20728a

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Hydrogen and methane storage MOF with the highest uptake capacities to date

A new metal-organic framework (MOF) with the highest hydrogen uptake at 298K of all the MOFs that have been examined to date has been made by US scientists. The MOF exhibits exceptionally high hydrogen (58mg/g-1 and 39g/L-1 at 52 bar and 77K) and methane (276mg/g-1 and 189g/L-1 at 80 bar and 298K) uptake capacities, they say.

The team attributes the exceptionally high gas uptake capacity to the highly branched, aromatic-rich nature of the bridging ligand, optimal pore size and the open metal sites in the trizinc secondary building units.

 

The work highlights the potential of designing MOFs with even higher gas uptake capacities by further optimising their structural, chemical and topological characteristics. 

Hydrogen and methane storage MOF with the highest uptake capacities to date

 

Link to journal article
A High Connectivity Metal-Organic Framework with Exceptional Hydrogen and Methane Uptake Capacities

D Liu et al
Chem. Sci.,
2012, DOI: 10.1039/c2sc20601c

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First use of carbene to dissociate homonuclear bonds

The first example of using an isolable carbene to dissociate homonuclear bonds (e.g. S-S, Br-Br) has been reported by researchers in the US.

The conditions are mild and metal-free – a surprisingly straightforward way to activate a variety of substrates. The dissociation of homonuclear bonds is critical to chemical reactions that range from the rearrangement of disulfide linkages in proteins to the synthesis of small molecules.

Link to journal article
Homonuclear Bond Activation Using A Stable N,N’-Diamidocarbene
K M Wiggins et al
Chem. Sci., 2012, DOI: 10.1039/c2sc20639k

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What is inside the intermediate black box during metallation reactions?

Metallation is an entry point to constructing compounds, and by converting inert C-H bonds to reactive C-metal bonds, it opens up bond forming opportunities. Mixed metal reagents are widely used; combining an alkali metal with a softer, less reactive metal charges the softer metal component with super-reactivity, which, combined with good selectivity and functional group tolerances, makes the reagents superior to organolithium reagents. But how do they work? 

To remove the mystery surrounding these mixed-metal reagents, scientists in the UK have studied one such reagent in detail. They discover (surprisingly) that LiCd(TMP)3 is unlikely to be an ate as previously thought, instead consisting of two independent homometallic amides. Rather than a synergistic metallation of the substrate, the metallation is a two step process: ortholithiation followed by transmetallation to cadmium.

What is inside the intermediate black box during metallation reactions?

 

Link to journal article
Opening the black box of mixed-metal TMP metallating reagents: direct cadmation or lithium-cadmium transmetallation

D R Armstrong et al
Chem. Sci.
, 2012, DOI: 10.1039/c2sc20392h

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Monitoring levels of hydrogen sulfide – possible cause of Alzheimer’s and Down’s Syndrome

Hydrogen sulfide is a gas best known for its rotten egg smell. Although generally considered toxic, our bodies produce it in small amounts. It is thought to help keep our heart and other organs healthy and may be involved in signalling. Altered levels of H2S have been implicated in a number of diseases, including Alzheimer’s and Down’s Syndrome. 

Scientists in China have reported a fluorescent probe for detecting H2S in blood and brain tissue. Although other probes are known, this one has the advantage of being fast in addition to selective and sensitive. The team used it to test H2S levels in mice blood and brain tissue. They say it is the first probe that could allow parallel measurements of H2S concentrations in both blood and tissues.

Monitoring levels of hydrogen sulfide

 

Link to journal article
A Fluorescent Probe for Rapid Detection of Hydrogen Sulfide in Blood Plasma and Brain Tissues in Mice

Y Qian et al
Chem. Sci.,
2012, DOI: 10.1039/c2sc20537h

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Protein power: An interview with Tom Muir

One of my highlights from Challenges in Organic Chemistry and Chemical Biology (ISACS7) was Tom Muir’s talk on protein ligation. His work is truly inspiring so I caught up with him to find out how a boy from bonnie Scotland became a world leader in protein engineering.

Here is an excerpt from that interview; the full interview is published in Chemistry World.

Protein Power

Tom Muir, professor of chemistry and molecular biology, Princeton University, US, is an expert in protein engineering and its application to studying cellular signalling networks. His lab has developed a suite of chemistry-driven tools for studying the structure and function of proteins in the test tube and in live cells. In addition, his laboratory employs cutting edge methods in protein engineering (computational protein design and directed evolution), structural biology (NMR spectroscopy and x-ray crystallograghy) and cell biology (imaging).

Tom Muir is Chemical Sciences new Associate Editor for Chemical Biology. Find out more >

What led you to a career in science? Were you interested in science from an early age?

I would be lying if I said I was deeply passionate about it when I was in high school, but I could always do it and it was the path of least resistance into university. It was when I got to university that I first realised that I was lucky enough to have chosen a major that I really liked. I made some great friends and we collectively discovered the subject together. I loved the logic of chemistry. 

You studied for your undergraduate degree and PhD in Edinburgh. How did you find the move to the US? What do you think are the main differences between practising science in the US and the UK? 

I knew within weeks of arriving in the US that I was never coming back. I loved it! I moved to Southern California and, as someone coming from the west of Scotland, I found it quite agreeable. I was at The Scripps Research Institute in La Jolla when I was a post doc and the sense of anything’s possible in science there was pervasive and infectious; the penny truly dropped in terms of what it means to be a research scientist. The ‘can do’ attitude that I experienced knocked me out. Sitting on the beach didn’t hurt either!

You started out as an organic chemist, but your work now combines chemistry with biochemistry and cell biology. How did you make the transition into this interdisciplinary research area?  

The move to chemical biology wasn’t part of a grand plan. I have always felt like I am on a boat being blown in different directions on a lake. Mainly, I’ve been very lucky in the people that I have interacted with, both mentors and collaborators.

I have to thank particularly my PhD supervisor at Edinburgh, Bob Ramage, who is an amazing organic chemist and whose approach to the subject was rigorous and forward looking. He appreciated just how much more chemistry had to offer biologists, molecular biologists specifically, and he set up the post doc position for me in San Diego. I worked with Stephen Kent, who was also an amazing mentor, and I was fortunate to be in his lab during a critical period in the development of modern protein chemistry. As I learned more about biology, I absolutely bought into the importance of chemistry in solving much more complicated biological problems.

Then I moved to Rockefeller as an assistant professor. Rockefeller has many amazing biologists, probably unequalled. I had the opportunity to talk to all these luminaries and they introduced me to problems that I hadn’t even thought about. They once again highlighted the huge role that chemistry has to play, opening new doors for me.

Your research revolves around proteins and how they work. What is it about this particular type of biomolecule that fascinates you?

I am staggered by how byzantine they are. They are incredibly complicated machines. It is almost like peeling back layers of an onion: you think you understand one layer and you peel it back and there is a whole other layer of complexity underneath. With each layer, you get closer and closer to physics. It always amazes me how complicated their regulation is, how many different ways they can be controlled and how many different types of chemistry they have evolved to catalyse reactions and to recognise other types of biological molecules. But I’ve always thought of them as big organic molecules and therefore it seems natural to me that organic chemists should be studying them.

Have you never found their complexity daunting? 

I always find it daunting, but I think tackling daunting tasks is exactly what academics should be doing. It is easier, because it is safe, to work on problems that are in a sense crumbs off the big table. But chemists should have a chip on this table, we should be working on problems that make us throw our hands in the air and shout ‘I’ll never figure this out!’ We have to try. At some point, everything was daunting until someone figured it out. I am not saying that I am going to be the one to figure out say epigenetics, but if nobody tries, it will forever remain a mystery. Yes, I feel daunted but that inspires, rather than scares, me.

Read more in Chemistry World >

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New route for activating carbon dioxide using MOFs

Hybridising metal nodes in metal-organic frameworks (MOFs) could open up a new route for activating CO2 so it can be converted into useful chemicals, claim Chinese scientists. 

Using theoretical methods, they calculated the properties of a copper-based MOF into which they hybridised tungsten ions. They found that the asymmetric W-Cu centres in the MOF have unique catalytic reactivity towards CO2 conversion that W-W or Cu-Cu centres don’t possess.

New route for activating CO2 using MOFs

 Link to journal article
Catalyzed Activation of CO2 by a Lewis Base Site in W-Cu-BTC Hybrid Metal Organic Frameworks

Q Zhang et al
Chem. Sci.,
2012, DOI: 10.1039/c2sc20521a

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In the spotlight: Catalysis

Graphical abstract: Experimental and quantum chemical characterization of the water oxidation cycle catalysed by [RuII(damp)(bpy)(H2O)]2+Catalysis is all around us, from the enzymatic reactions in our body to the synthesis of fuels and medicines. Quite rightly, it forms an important part of Chemical Science too.  

We’ve gathered together some recent catalysis Edge articles and reviews for your perusal. If you enjoy these, sign up for the Chemical Science e-alert to be notified when the next issue is out.  

Synergistic catalysis: A powerful synthetic strategy for new reaction development
Anna E. Allen and David W. C. MacMillan
Chem. Sci., 2012, 3, 633-658  (free to access until 11th July)

Rh(I)-catalyzed enantioselective intramolecular hydroarylation of unactivated ketones with aryl pinacolboronic esters
Gary M. Gallego and Richmond Sarpong
Chem. Sci., 2012, 3, 1338-1342

Catalytic intermolecular hydroacylation of C–C π-bonds in the absence of chelation assistance
Joyce C. Leung and Michael J. Krische
Chem. Sci., 2012, 3, 2202-2209 (free to access until 11th July)

Hindered biaryls by C–H coupling: bisoxazoline-Pd catalysis leading to enantioselective C–H coupling
Kazuya Yamaguchi, Junichiro Yamaguchi, Armido Studer and Kenichiro Itami
Chem. Sci., 2012, 3, 2165-2169

Cavity-induced enantioselectivity reversal in a chiral metal–organic framework Brønsted acid catalyst
Min Zheng, Yan Liu, Cheng Wang, Shubin Liu and Wenbin Lin
Chem. Sci., 2012, DOI: 10.1039/C2SC20379K

Artificial chirogenesis: a gateway to new opportunities in material science and catalysis
Martha V. Escárcega-Bobadilla and Arjan W. Kleij
Chem. Sci., 2012, DOI: 10.1039/C2SC20381B (free to access until 11th July)

Selective liquid phase oxidation with supported metal nanoparticles
Nikolaos Dimitratos, Jose A. Lopez-Sanchez and Graham J. Hutchings
Chem. Sci., 2012, 3, 20-44 (free to access until 11th July)

Enhanced photocatalytic activity of hybrid Fe2O3–Pd nanoparticulate catalysts
Yanhu Wei, Shuangbing Han, David A. Walker, Scott C. Warren and Bartosz A. Grzybowski
Chem. Sci., 2012, 3, 1090-1094

Active phase evolution in single Ni/Al2O3 methanation catalyst bodies studied in real time using combined μ-XRD-CT and μ-absorption-CT
Matthew G. O’Brien, Simon D. M. Jacques, Marco Di Michiel, Paul Barnes, Bert M. Weckhuysen and Andrew M. Beale
Chem. Sci., 2012, 3, 509-523

Lanthanide ions as required cofactors for DNA catalysts
Victor Dokukin and Scott K. Silverman
Chem. Sci., 2012, 3, 1707-1714

Molecular scaffolds with remote directing groups for selective palladium-catalyzed C–H bond functionalizations
Erin E. Stache, Curtis A. Seizert and Eric M. Ferreira
Chem. Sci., 2012, 3, 1623-1628

Experimental and quantum chemical characterization of the water oxidation cycle catalysed by [RuII(damp)(bpy)(H2O)]2+
Laura Vigara, Mehmed Z. Ertem, Nora Planas, Fernando Bozoglian, Nils Leidel, Holger Dau, Michael Haumann, Laura Gagliardi, Christopher J. Cramer and Antoni Llobet
Chem. Sci., 2012, DOI: 10.1039/C2SC20399E

Hydrogenases and oxygen
Martin Tillmann Stiebritz and Markus Reiher
Chem. Sci., 2012, 3, 1739-1751 (free to access until 11th July)

Also of interest: Outstanding organocatalysis: an article collection

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Chemical Science celebrates its first Impact Factor – 7.525

SunflowerAt Chemical Science, our focus is quality. We are committed to publishing only the most exceptional research.

That’s why we are delighted by our first Impact Factor* – an impressive 7.525. This is a tremendous result for a new journal and it firmly places Chemical Science in the top tier of general chemistry journals. Thank you to all who have made this possible – our authors, referees, readers and Editorial and Advisory Boards.

Our unique combination of high quality articles, outstanding Associate Editors, free colour and flexible format makes it clear why so many leading scientists have already chosen to publish in Chemical Science.

Join them – submit your exceptional research today to be seen with the best.

Find out how other RSC journals are ranked in the latest Impact Factor release >

*The Impact Factor provides an indication of the average number of citations per paper. Produced annually, Impact Factors are calculated by dividing the number of citations in a year, by the number of citeable articles published in the preceding two years. Data based on 2011 Journal Citation Reports®, (Thomson Reuters, 2012).

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Enzyme responsive nanoparticles

US scientists have made nanoparticles that undergo enzyme-induced changes in structure which are detectable in complex environments.

Enzymes have previously been used to manipulate nanoscale structures, with methods such as electron microscopy used to analyse the morphology changes. But, says Nathan Gianneschi at University of California, San Diego, changes in nanoscale architecture will only be detectable in vivo if the enzyme’s action results in an output signal unique to the nanoscale assembly, such as a spectrophotometric response.

So Gianneschi and colleagues developed enzyme-responsive fluorogenic micellar nanoparticles made from peptide–polymer amphiphiles labelled with fluorescent dyes. They showed they could use Förster Resonance Energy Transfer (FRET) signals to sensitively monitor the nanoparticles’ response to enzymes.

The results are a step towards the use of enzyme-programmed materials for molecular diagnostics and drugs.

Link to journal article

Fluorogenic Enzyme-Responsive Micellar Nanoparticles

M-P Chien et al
Chem. Sci.,
2012, DOI: 10.1039/c2sc20165h

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