Amorphous Co(OH)2 nanocages achieving efficient photo-induced charge transfer for significant SERS activity

Boosting substrate-molecule interactions, especially the strong vibronic coupling and efficient photo-induced charge transfer (PICT) transitions, are critical issues to improve surface-enhanced Raman scattering (SERS) sensitivity of non-metal substrates. Here, by...

Application of SNAP-Tag in Expansion Super-Resolution Microscopy Using DNA Oligostrands

Expansion super-resolution technology is a new technology developed in recent years. It anchors the dye on the hydrogel and the dye expands with the expansion of the hydrogel so that a super-resolution map can be obtained under an ordinary microscope. However, by labeling the target protein with a first antibody and secondary antibody, the distance between the fluorescent group and the actual target protein is greatly increased. Although fluorescent proteins can also be used for expansion super-resolution to reduce this effect, the fluorescent protein is often destroyed during sample preparation. To solve this problem, we developed a novel label system for expansion microscopy, based on a DNA oligostrand linked with a fluorescent dye, acrylamide group (linker), and benzoylguanine (BG, a small substrate molecule for SNAP-tag). This protocol greatly reduced the error between the position of fluorescent group and the actual target protein, and also reduced loss of the fluorescent group during sample preparation.

The Charge Transfer Effect on SERS in a Gold-decorated Surface Defect Anatase Nanosheet/ Methylene Blue (MB) system

Revealing substrate−molecule vibronic coupling enhancement, especially photoinduced charge transfer (CT) process, is hugely important for understanding Surface-enhanced Raman spectroscopy (SERS) enhancement mechanism. In this work, oxygen atoms were extracted from...

Evidence from Mutational Analysis for a Single Transmembrane Substrate Binding Site in the Histidine ATP-Binding Cassette Transporter ofSalmonella entericaSerovar Typhimurium

ABSTRACTThe histidine ATP-binding cassette (ABC) transporter ofSalmonella entericaserovar Typhimurium is among the best-studied type I ABC import systems. The transporter consists of two transmembrane subunits, HisQ and HisM, and a homodimer of the nucleotide-binding subunit, HisP. Substrates are delivered by two periplasmic solute binding proteins, HisJ and LAO, with preferences for histidine and for lysine, arginine, and ornithine, respectively. A homology model was built by using the arginine-bound crystal structure of the closely related Art(QN)2transporter ofThermoanaerobacter tengcongensisas the template. In the homodimeric Art(QN)2, one substrate molecule is bound to each of the ArtQ subunits, whereas the structural model and sequence alignments predict only one substrate molecule in contact with HisM. To address the question whether one or two binding sites exist in heterodimeric HisQM, we have studied the functional consequences of mutations by monitoring (i) the complementation of growth ond-histidine of auxotrophic tester strains, (ii) the growth of tester strains on arginine as a nitrogen source, and (iii) ATPase activity of purified variants in a lipid environment. Our results demonstrate that two negatively charged residues, namely, HisM-E166 and HisQ-D61, are indispensable for function. Furthermore, the complete reconstruction of an ArtQ-like binding site in HisQ resulted in an inactive transporter. Likewise, switching the positions of both negatively charged residues between HisQ and HisM caused transport-deficient phenotypes. Thus, we propose that one substrate molecule is primarily liganded by residues of HisM while HisQ-D61 forms a crucial salt bridge with the α-amino group of the substrate.IMPORTANCECanonical ATP-binding cassette (ABC) importers are major players in the translocation of numerous nutrients, vitamins, and growth factors to the cytoplasm of prokaryotes. Moreover, some ABC importers have been identified as virulence factors in bacterial pathogenesis. Thus, a full understanding of their mode of action is considered a prerequisite, among others, for the development of novel antibacterial drugs. However, mainly owing to the lack of structural information, the knowledge of the chemical nature and number of substrate binding sites formed by the transmembrane subunits of ABC importers is scarce. Here, we provide evidence from mutational analyses that, in contrast to homologous homodimeric systems, the heterodimeric histidine transporter ofSalmonella entericaserovar Typhimurium is liganding only one substrate molecule between its transmembrane subunits, HisM and HisQ.

Influence of Lewis acid strength on hydride transfer to unsaturated substrates

Coordination of a Lewis acid to a substrate molecule increases its ability to accept a hydride between 20 and 70 kcal mol−1.

From Cell Death to Metabolism: Holin-Antiholin Homologues with New Functions

ABSTRACT Programmed cell death in bacteria is generally triggered by membrane proteins with functions analogous to those of bacteriophage holins: they disrupt the membrane potential, whereas antiholins antagonize this process. The holin-like class of proteins is present in all three domains of life, but their functions can be different, depending on the species. Using a series of biochemical and genetic approaches, in a recent article in mBio, Charbonnier et al. (mBio 8:e00976-17, 2017, https://doi.org/10.1128/mBio.00976-17 !) demonstrate that the antiholin homologue in Bacillus subtilis transports pyruvate and is regulated in an unconventional way by its substrate molecule. Here, we discuss the connection between cell death and metabolism in various bacteria carrying genes encoding these holin-antiholin analogues and place the recent study by Charbonnier et al. in an evolutionary context.

On the critical role of the substrate: the adsorption behaviour of tetrabenzoporphyrins on different metal surfaces

2HTPTBPs assemble into different supramolecular structures on different metal surfaces due to different molecule–substrate (molecule) interactions.