Spotlights on Recent JACS Publications - Journal of the American

Jul 21, 2017 - An ester-to-carboxylic acid decomposition strategy is used to increase the fluorescence of three BODIPY dyes across the visible spectru...
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Spotlights on Recent JACS Publications





METAL−ORGANIC FRAMEWORK CATALYST FOR METHANE CONVERSION TO METHANOL The North American fracking boom is making natural gas cheaper, and entrepreneurs are seeking ways to use excess methane beyond burning it. An efficient way to convert methane into methanol, a chemical intermediate, solvent, and fuel, would be valuable. Researchers have experimented with copper (Cu) catalysts over the past few years, but the pathways have required regeneration after each step, using a lot of energy, or have been slow. Now a group led by Johannes Lercher shows a promising new path that involves trapping copper oxide clusters in a metal− organic framework called NU-1000 (DOI: 10.1021/ jacs.7b02936). The researchers use atomic layer deposition to place copper oxide on zirconium nodes of the NU-1000 crystals. They examine the Cu structure, employing several types of X-ray analysis and theory, and confirm that the framework retains porosity, important for exposing the catalysts to the methane. The analysis determines also the relative fractions of Cu+ and Cu2+ along the conversion path, establishing the role of Cu in the redox process. These first-generation designed catalysts function at 150 °C and achieve 45−60% selectivity for methanol and dimethyl ether. Lucas Laursen

TRIGGERED ESTER DECOMPOSITION CREATES BODIPY BIOPROBES To visualize cellular components and molecular signals, researchers seek sensitive bioprobes that generate fluorescence only in the presence of a particular molecule or protein. The family of boron dipyrromethene (BODIPY) dyes are widely used fluorescent dyes because of their stability and excellent fluorescence at wavelengths ranging from cyan to far-red. Recently, researchers increased the fluorescence of a yellow BODIPY dye by hydrolyzing a meso-ester substituent into a carboxyl group (Chem. Eur. J., DOI: 10.1002/chem.201501127). Changhua Li and colleagues apply this ester-to-carboxylic acid fluorescent enhancement strategy to three BODIPY dyes across the visible spectrum. To make their molecules bioprobes, the researchers design the ester substituent so that a biomolecule hydrogen peroxide, hydrogen sulfide, or protease enzyme triggers the decomposition (DOI: 10.1021/jacs.7b05920). To test the dye for biological imaging, the researchers modify one of the dyes with groups that enable it to enter mitochondria; upon reacting with H2O2 inside the mitochondria, the dye glows. The versatile synthesis as well as the generality of the method to increase fluorescence means this approach could be used to customize bioprobes with different emission wavelengths to respond to various molecular triggers. Melissae Fellet, Ph.D.





EPIC IMPLICATIONS FOR EPIGENETICS Epigeneticsthe study of external influences to genomic information that affects the DNA’s functionis increasingly recognized for its importance in the regulation of gene expression and the development of disease. Epigenetics research, however, is plagued by tremendous inherent complexity. In the cell, genomic DNA lives in the nucleus as part of an intricate conglomerate of proteins and nucleic acids bundled together in structures called chromatin with varied, complicated mechanisms for controlling gene expression and cell fate. Despite impressive recent insights offered by advances in genomics and proteomics for deciphering aspects of the structure and function of chromatin, detailed understanding at the molecular level is still lacking. In their Perspective, Tom Muir and Yael David illuminate the unique opportunities this challenge presents to chemical biologists (DOI: 10.1021/jacs.7b03430). A hallmark of chromatin regulation is rooted in the over 30 structural modifications routinely and dynamically instilled in histones, the major protein component of chromatin, throughout the life cycle of the cell. These modifications, which include methylation, acetylation, and phosphorylation as well as additions of entire proteins, are well suited for interrogation and manipulation by recently developed, sophisticated chemical biological approaches. Protein engineering techniques, high-throughput screening assays, protein fusion strategies, and genome editing technologies have tremendous potential for expanding our knowledge of this intriguing field. Eva J. Gordon, Ph.D. © 2017 American Chemical Society

A MOF FOR MAINTAINING MOISTURE Effective control over indoor humidity is important not only to human comfort in climate-controlled environments but also to the longevity of building materials and the stability of perishable stored goods. The ideal humidity-managing material would swiftly adsorb water vapor when relative humidity (RH) rises above 65% and desorb water vapor when it falls to 45%, keeping RH between the range recommended by the American Society of Heating, Refrigerating, and Air-Conditioning Engineers. Mohamed Eddaoudi and co-workers report a metal−organic framework (MOF) that adsorbs moisture when RH exceeds ∼60% and desorbs it below ∼45% RH (DOI: 10.1021/ jacs.7b04132). This unusual material, Y-shp-MOF-5, changes its adsorption/desorption activity based solely on changes in RH. Tests show that this activity remains consistent after >1000 cycles, with the MOF’s crystal structure remaining intact. Further investigation suggests that the mechanism behind this capability involves water adsorbing first to open metal sites, followed by the key factor driving the moisture control, the formation of water superclusters within the MOF’s pores as humidity rises. Water then leaves the pores when humidity falls below 45%. The authors suggest that this material might find use in confined spaces where humidity control is especially important, such as space shuttles, aircraft cabins, and air-conditioned buildings. Christen Brownlee Published: July 21, 2017 10165

DOI: 10.1021/jacs.7b07502 J. Am. Chem. Soc. 2017, 139, 10165−10165