Spotlights Cite This: J. Am. Chem. Soc. 2017, 139, 16433-16433
pubs.acs.org/JACS
Spotlights on Recent JACS Publications
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PROGRESS TOWARD “LIFE-LIKE” SYNTHETIC MATERIALS In living systems, self-assembled proteins undergo changes in their degree of polymerization to perform numerous functions, such as cell division and cell mobility. The driving force behind many of these transformations is the molecule adenosine triphosphate (ATP), which is commonly known as the energy currency of the cell. In an effort to mimic the fuel-driven functioning of natural systems, researchers have explored the creation of materials that allow spatiotemporal control over their organization and function. In a new report, Subi George and colleagues describe the fueldependent helical assembly and disassembly of a supramolecular polymer (DOI: 10.1021/jacs.7b07469). On the route to disassembly, the helical supramolecular polymer adopts multiple different nonequilibrium conformational states. The transformations are mediated by enzymes in tandem and programmed by adenosine phosphates, which serve as the chemical fuel. This enables researchers to exert temporal control over the transformations. This highly modular system is expected to be adaptive toward different enzymes, and may lead to the development of future life-like materials with active and autonomous behavior. Christine Herman, Ph.D.
interactions can be short-lived and weak. For example, histone deacetylases help regulate the interactions of proteins with DNA and other proteins, as well as chromatin structure. But scientists have not been able to figure out all the substrates these enzymes interact with, or the widespread effects of those interactions. Brent Martin, Carol Fierke, and colleagues introduce a new way to catch some of these substrates in action, by replacing several residues in the active site of one histone deacetylase with a light-reactive synthetic amino acid, p-benzoyl-L-phenylalanine (DOI: 10.1021/jacs.7b07603). They then incubate mammalian cell lysates with the protein, expose them to ultraviolet light to promote cross-linking, and obtain the resulting substrates using immunoprecipitation and mass spectrometry. This photo-crosslinking technique allows the researchers to identify and study more than 100 proteins that may be substrates for the enzyme HDAC8. Some of these substrates are involved in cellular roles that had not been previously linked with the enzyme. This approach is expected to provide a new method for better understanding of enzyme−substrate interactions. Deirdre Lockwood, Ph.D.
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VANADIUM COMPLEX RAPIDLY MEASURES ENANTIOMERIC EXCESS Enantiomeric excess (ee) determination is crucial to many aspect of chemistry, especially in the control of organic asymmetric reactions. To quickly quantify ee following a reaction that generates chiral molecules, researchers spike the products with a chiral molecule that rapidly converts between its enantiomers. This dynamic probe interacts with the chiral analyte, shift itself toward one of the enantiomeric forms, thus enhancing its signal in circular dichroism (CD). Accurate measurements, however, require knowing the precise concentrations of both the probe and the analyte, which limits the practical applications. Giulia Licini, Cristiano Zonta, and colleagues report a concentrationindependent CD probe for the fast and reliable measurement of ee for a wide range of substrates (DOI: 10.1021/jacs.7b09469). The researchers synthesize a vanadium complex with propeller-like aminotriphenolate (TPA) ligands as the probe for enantioenriched molecules. When complexed to an analyte, the probe absorbs light at wavelengths unobstructed by other organic molecules. The probe’s absorbance, combined with the change in dichroic signal in the presence of an analyte, provides a way to determine ee without knowing the concentrations of either species. This new approach of developing dynamic chiroptical probes based on simple coordination process could be useful for high-throughput screening techniques in modern CD spectrometers. Melissae Fellet, Ph.D.
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CONVERTING LIGHT TO SOUND TO DIVE DEEPER By combining DNA aptamer-based probes with photoacoustic imaging, Yi Lu, Jefferson Chan, and co-workers show that they can visualize target molecules deep into tissues of live animals, without invasive techniques (DOI: 10.1021/jacs.7b07913). Due to the limited depth that fluorescent signals can penetrate, molecular imaging is typically constrained to skin and superficial tissues, or requires invasive surgical procedures to expose the tissue, or collection of tissue samples. Being able to detect and measure specific targets in tissues previously inaccessible to optical techniques, in a noninvasive manner, could be a real game changer for biomedical discovery and diagnostics. Toward this goal, the researchers couple a DNA aptamer complex to a nearinfrared fluorophore/quencher pair. Once this probe binds its target, the DNA complex disassembles, separating the nearinfrared dye from the quencher and changing the photoacoustic signal. The activatable property of this probe, by its target, enables quantitation of the target molecule. This strategy may be generalized to make new DNA-aptamer-based probes for the sensing of a wide range of targets in vivo. Researchers would be able to monitor biological processes including development, disease progression, and responses to treatment in intact animals. Sue Min Liu, Ph.D.
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CATCH (SUBSTRATES) AS PHOTO-CROSS-LINKER CAN Identifying the many different substrates of biologically important enzymes is challenging because some of these © 2017 American Chemical Society
Published: November 22, 2017 16433
DOI: 10.1021/jacs.7b12041 J. Am. Chem. Soc. 2017, 139, 16433−16433
