The quest for planar sp2-hybridized carbon
allotropes other than graphene, such as graphenylene and biphenylene
networks, has stimulated substantial research efforts because of the
materials’ predicted mechanical, electronic, and transport properties.
However, their syntheses remain challenging given the lack of reliable
protocols for generating nonhexagonal rings during the in-plane tiling of
carbon atoms. We report the bottom-up growth of an ultraflat biphenylene
network with periodically arranged four-, six-, and eight-membered rings of
sp2-hybridized carbon atoms through an on-surface
interpolymer dehydrofluorination (HF-zipping) reaction. The characterization
of this biphenylene network by scanning probe methods reveals that it is
metallic rather than a dielectric. We expect the interpolymer HF-zipping
method to complement the toolbox for the synthesis of other nonbenzenoid
carbon allotropes.
The surface charge as well as the electrochemical properties and ligand binding abilities of the Gram‐positive cell wall is controlled by the d‐alanylation of the lipoteichoic acid. The incorporation of d‐Ala into lipoteichoic acid requires the d‐alanine:d‐alanyl carrier protein ligase (DltA) and the carrier protein (DltC). We have heterologously expressed, purified, and assayed the substrate selectivity of the recombinant proteins DltA with its substrate DltC. We found that apo‐DltC is recognized by both endogenous 4′‐phosphopantetheinyl transferases AcpS and Sfp. After the biochemical characterization of DltA and DltC, we designed an inhibitor (d‐alanylacyl‐sulfamoyl‐adenosine), which is able to block the d‐Ala adenylation by DltA at a Ki value of 232 nmin vitro. We also performed in vivo studies and determined a significant inhibition of growth for different Bacillus subtilis strains when the inhibitor is used in combination with vancomycin.
The adsorption of diethyl ether (Et 2 O) on Si(001) was studied by means of scanning tunneling microscopy (STM) and photoelectron spectroscopy. Et 2 O reacts on Si(001) via a datively bonded intermediate, which was isolated at surface temperatures below 100 K. At higher surface temperature, Et 2 O converts dissociatively into the final state by cleaving one O−C bond; the resulting −O−C 2 H 5 and −C 2 H 5 fragments are found to attach on two Si dimers of neighboring dimer rows. Tipinduced hopping of the −C 2 H 5 fragment on one dimer was observed at positive sample bias. The results are discussed in the context of recent experiments on the reaction of tetrahydrofuran (THF) on Si(001) (Mette et al. ChemPhysChem 2014, 15, 3725) and allow a more general description of the reaction of ethers on Si(001).
Surface-enhanced Raman scattering (SERS) spectroscopy can be used for the determination and quantification of biologically representative atomic ions. In this work, the detection and quantification of chloride is demonstrated by monitoring the vibrational changes occurring at a specific interface (a Cl-sensitive dye) supported on a silver-coated silica microbead. The engineered particles play a key role in the detection, as they offer a stable substrate to support the dye, with a dense collection of SERS hot spots. These results open a new avenue toward the generation of microsensors for fast ultradetection and quantification of relevant ions inside living organisms such as cells. Additionally, the use of discrete particles rather than rough films, or other conventional SERS supports, will also enable a safe remote interrogation of highly toxic sources in environmental problems or biological fluids.
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