Spotlights pubs.acs.org/JPCL
Spotlights: Volume 7, Issue 17
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THE CULPRIT IS IN THE CAVE: THE CORE SITES EXPLAIN THE BINDING PROFILES OF AMYLOID-SPECIFIC TRACERS
THE FREE ENERGY OF SMALL SOLUTE PERMEATION THROUGH THE ESCHERICHIA COLI OUTER MEMBRANE HAS A DISTINCTLY ASYMMETRIC PROFILE Antibiotics have saved countless lives from bacterial infections that were once deadly; however, some of those bacteria have adapted to the drugs, making them less effective. As antibiotic resistance continues to grow, development of new antibiotics to successfully fight bacteria is both necessary and challenging. Each bacterial cell is surrounded by an outer membrane that provides a sophisticated layer of protection; to kill the bacteria, an antibiotic must either disrupt or permeate that outer membrane. Carpenter et al. (DOI: 10.1021/acs.jpclett.6b01399) studied the permeation of the outer membrane of Escherichia coli, a common bacteria that has been cited as the cause of several recent high-profile outbreaks of foodborne illness. The authors calculated the free energy of permeation of a range of compounds through a model of an E. coli membrane. Their model contained lipopolysaccharide molecules in the outer leaflet and phospholipids in the inner leaflet, and they found that the energetic barriers to permeation through the two leaflets of the membrane are distinctly asymmetric. This finding could lead to advances in the design of novel antibiotics because it helps us understand how reagents can be more effectively targeted into membranes.
Alzheimer’s disease is a devastating affliction, but early diagnosis can enable patients and their families to access resources and plan for the future. Although Alzheimer’s disease remains difficult to diagnose definitively in living subjects, advances have made it possible to follow the distribution of amyloid fibrils in the brain using positron emission tomography. Because the amyloid loads can be directly correlated to Alzheimer’s disease, the molecular tracers can be used as diagnostic agents. In an effort to gain a detailed understanding of the binding sites in amyloid targets, their number, and their binding mechanism for various tracer molecules, Murugan et al. (DOI: 10.1021/acs.jpclett.6b01586) adopted an integrated approach combining docking studies, molecular dynamics, and generalized Born-based free energy calculations to investigate site-specific interactions of different amyloid binding molecules. They found that the core sites of the amyloid beta proteins, rather than the surface sites, are responsible for the high-affinity binding of tracers to amyloid beta fibrils. This finding has promise for the design of novel diagnostic agents for amyloid imaging.
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OPERANDO NANOBEAM DIFFRACTION TO FOLLOW THE DECOMPOSITION OF INDIVIDUAL Li2O2 GRAINS IN A NONAQUEOUS Li−O2 BATTERY Electric vehicles and hybrid electric vehicles constitute a growing segment in the automotive market, and the demand for better energy storage devices capable of delivering higherenergy densities is ever increasing. The Li−air, or more accurately Li−O 2 , battery shows potential for use in automobiles because of its high theoretical specific energy density. Intense interest in this battery system over the past few years has led to a better understanding of the chemical processes involved in its functioning. However, detailed decomposition of the nanostructured Li2O2 product, held at least partially responsible for the limited reversibility and poor rate performance, is hard to measure operando under realistic electrochemical conditions. Here, Ganapathy et al. describe operando nanobeam X-ray diffraction experiments that enable monitoring of the decomposition of individual Li2O2 grains in a working Li−O2 battery (DOI: 10.1021/acs.jpclett.6b01368). The authors found asymmetric decomposition of individual Li2O2 platelets: The platelets became thinner more rapidly than they reduced in width as a function of charge time before they decomposed completely. Their findings highlight the importance of using redox mediators in solution to charge Li−O2 batteries and may be useful in the development of the next generation of batteries.
PHYSICS BEHIND WATER TRANSPORT THROUGH NANOPOROUS BORON NITRIDE AND GRAPHENE
Access to clean water is critical for human survival, but demand often exceeds available resources in many parts of the world. Although more than two-thirds of our planet is covered in water, 97% of it is seawater, which cannot be used for drinking or for irrigating crops. Desalination methods using membrane separation processes such as reverse osmosis provide an energyefficient and environmentally friendly solution for countries with direct access to seawater, but they remain expensive, in part because of the low water permeability of reverse osmosis membranes. Less expensive methods are being sought by researchers such as Garnier’s group (DOI: 10.1021/acs.jpclett.6b01365), who used molecular dynamics simulations to compare boron nitride monolayers and graphene monolayers. The authors found higher water permeability and lower surface tension in boron nitride. This lessening in surface tension was shown to result from a negative surface tension contribution due to long-range wetting of water, which also contributes to lower water permeation through a two-layer membrane with respect to permeation through a monolayer. The authors also showed that a decrease in water surface tension on a boron nitride monolayer with regards to graphene was at the origin of an increase in water permeation through boron nitride. These findings suggest that nanoporous boron nitride membranes could serve as nanofilters, enabling more efficient, lower-cost desalination of seawater. © 2016 American Chemical Society
Published: September 1, 2016 3534
DOI: 10.1021/acs.jpclett.6b01911 J. Phys. Chem. Lett. 2016, 7, 3534−3534
