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In this episode of the Chemistry Literature Feature, we celebrate chemistry at the University of Michigan! Keep scrolling to learn about chemical reactions happening high in the clouds, how to teach a bad catalyst to keep itself together for longer, and new developments in small molecule cancer treatments. But first, check out the Chem Lit Feature's newest addition: CLFPic!
Analytical - Aqueous Processing of Atmospheric Organic Particles in Cloud Water Collected via Aircraft Sampling [link]
Chemical reactions happening in water droplets and clouds high in the atmosphere affect conditions down at the surface. Models exist to describe how various chemicals get incorporated into atmospheric water and how they change once they've been dissolved or once they form particles, but the models fall short in some key areas. The authors of this study, published in Environmental Science and Technology (ACS) flew an airplane through different cloud regions to collect samples of both particle aerosols and water droplets containing dissolved chemicals. They examined differences in the compositions of the particles versus the water droplets in an effort to determine whether and how organic compounds react when dissolved in atmospheric water. Their findings suggest that some organic molecules, particularly organosulfates, react in water to form nitrogen-containing compounds. The result shows a relatively unexplored pathway by which volatile organics can change composition once they become part of the atmosphere.
University of Michigan research from Dr. Kerri Pratt's group, first author Eric Boone.
Chemical Biology - Electron Microscopic Visualization of Protein Assemblies on Flattened DNA Origami [link]
DNA is a very attractive platform for tailored biomaterials due to its well-characterized and predictable structure. Those features allow chemists to purposefully synthesize artificial DNA that assembles itself in a particular way, macromolecularly speaking. In "DNA origami," strands of DNA assemble themselves into two-dimensional sheets. The authors of this paper in ACS Nano demonstrate a new method for preparing flat DNA origami sheets. They then decorate the sheets with three proteins in order to demonstrate the ability to create precisely controlled arrays of proteins on DNA origami. The proteins can be reliably placed within the same nanometer-sized window across a thousand measured sheets. Discoveries like this pave the way for new advances in biocompatible materials for things like sensing.
University of Michigan research from Dr. Nils Walter's group, first author Leena Mallik.
Inorganic - A Proton-Switchable Bifunctional Ruthenium Complex That Catalyzes Nitrile Hydroboration [link]
Chemists are always looking for easier and energetically cheaper ways of making molecules. Using catalysts instead of stoichiometric reagents, for example, saves material, thereby saving the energy that goes into making it. The authors of this open-access publication in the Journal of the American Chemical Society have created a pincer catalyst that reduces nitriles and ketones while adding boron functional groups, a process known as hydroboration. The ruthenium-based catalyst uses its second coordination sphere to promote reactivity. Lewis acidic groups attached to the complex that point towards the metal center promote the reduction reaction by shuffling electrons around and pinning the molecule in place. A wealth of crystallographic and synthetic data supports the conclusion that this catalyst can hydroborate 13 different nitriles, which can then be easily converted to amines.
University of Michigan research from Dr. Nate Szymczak's group, first author Jacob Geri
Fans of chemical biology might also like the Organic paper.
Materials - Improving the stability and selectivity for the oxygen-evolution reaction on semiconducting WO3 photoelectrodes with a solid-state FeOOH catalyst [link]
Storing solar energy economically in the form of a fuel is one of the most challenging ideas facing today's chemists. There just has not been a single material discovered that does the reaction for long enough or with enough selectivity to be industrially viable. The authors of this paper, published in the Journal of Materials Chemistry A (RSC), are one of many who have turned to two-phase materials that mix and match attractive aspects. By taking tungsten oxide, which quickly dissolves when performing water splitting, and adding a solid layer of a cheap iron oxide catalyst, the authors were able to create a new catalyst that performs for much longer than the original material. They also showed that the material oxidizes water almost exclusively, shutting down side reactions that reduce lifetime and efficiency.
University of Michigan research from Dr. Bart Bartlett's group, first author Charles Lhermitte.
Organic - Synthesis and biological evaluation of pharbinilic acid and derivatives as NF-κB pathway inhibitors [link]
The authors of this communication in Chemical Communications (RSC) are interested in the ability of a naturally occurring compound, pharbinilic acid, to kill cancer cells. Pharbinilic acid is found in morning glory seeds, but the process used to extract them isn't very efficient. So, the authors took a commercially available starting material, gibberic acid, and developed an efficient method of creating pharbinilic acid and derivatives. They then tested the drugs with an in vitro assay designed to report how well cells can keep the NF-κB pathway going. NF-κB is an important series of processes for all living cells but is particularly important in cancer cells; in some kinds of cancer, when NF-κB shuts down, the cancer cells die. The initial results in this paper show that pharbinilic acid derivatives are promising candidates for further research on cancer cell inhibition.
University of Michigan research from Dr. Corinna Schindler's group, first author James Annand.
Physical - Dynamics of Rhenium Photocatalysts Revealed through Ultrafast Multidimensional Spectroscopy [link]
Ultrafast spectroscopy is an exciting field of measurement because it allows scientists to see processes that are on the timescale of molecular motion and usually much faster than chemical reactions. The authors of this paper in Accounts of Chemical Research (ACS) are concerned with using ultrafast two-dimensional infrared spectroscopy (2DIR) to understand how a well-researched rhenium carbonyl complex catalyzes the reduction of carbon dioxide to carbon monoxide. The paper discusses differences in 2DIR measurements across many different versions of the catalyst in three different solvents. Critically, the paper highlights differences between the 2DIR results when the catalyst is illuminated and when it is not. The authors discuss their findings in the context of a broad field of literature and make suggestions about how 2DIR can be used to understand catalytic processes in the future.
University of Michigan research from Dr. Kevin Kubarych's group, first author Laura Kiefer.
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ACS - American Chemical Society
GDCh - Gesellschaft Deutscher Chemiker (German Chemical Society)
RSC - Royal Society of Chemistry