Amycolamicin: A Novel Broad‐Spectrum Antibiotic Inhibiting Bacterial Topoisomerase

The abuse of antibacterial drugs imposes a selection pressure on bacteria that has driven the evolution of multidrug resistance in many pathogens. Our efforts to discover novel classes of antibiotics to combat these pathogens resulted in the discovery of amycolamicin (AMM). The absolute structure of AMM was determined by NMR spectroscopy, X‐ray analysis, chemical degradation, and modification of its functional groups. AMM consists of trans‐decalin, tetramic acid, two unusual sugars (amycolose and amykitanose), and dichloropyrrole carboxylic acid. The pyranose ring named as amykitanose undergoes anomerization in methanol. AMM is a potent and broad‐spectrum antibiotic against Gram‐positive pathogenic bacteria by inhibiting DNA gyrase and bacterial topoisomerase IV. The target of AMM has been proved to be the DNA gyrase B subunit and its binding mode to DNA gyrase is different from those of novobiocin and coumermycin, the known DNA gyrase inhibitors.     

Visible‐Light Photochemical Activity of Nanoporous Carbons under Monochromatic Light

By using monochromatic light the ability of semiconductor‐free nanoporous carbons to convert the low‐energy photons from the visible spectrum into chemical reactions (i.e. phenol photooxidation) is demonstrated. Data shows that the onset wavelength of the photochemical activity can be tuned by surface functionalization, with enhanced visible‐light conversion upon introducing N‐containing groups.     

Nucleic Acid‐Barcoding Technologies: Converting DNA Sequencing into a Broad‐Spectrum Molecular Counter

The emergence of high‐throughput DNA sequencing technologies sparked a revolution in the field of genomics that has rippled into many branches of the life and physical sciences. The remarkable sensitivity, specificity, throughput, and multiplexing capacity that are inherent to parallel DNA sequencing have since motivated its use as a broad‐spectrum molecular counter. A key aspect of extrapolating DNA sequencing to non‐traditional applications is the need to append nucleic‐acid barcodes to entities of interest. In this review, we describe the chemical and biochemical approaches that have enabled nucleic‐acid barcoding of proteinaceous and non‐proteinaceous materials and provide examples of downstream technologies that have been made possible by DNA‐encoded molecules. As commercially available high‐throughput sequencers were first released less than 15 years ago, we believe related applications will continue to mature and close by proposing new frontiers to support this assertion.     

Broad‐Spectrum Catalysts for the Ambient Temperature Anti‐Markovnikov Hydration of Alkynes

Anti‐Markovnikov alkyne hydration provides a valuable route to aldehydes. Half‐sandwich ruthenium complexes ligated by 5,5′‐bis(trifluoromethyl)‐2,2′‐bipyridine are remarkably active for this transformation. In the presence of 2 mol % metal, a wide range of functionalized aliphatic and aromatic alkynes are hydrated in high yield at ambient temperature.     

Broad‐Spectrum Liquid‐ and Gas‐Phase Decontamination of Chemical Warfare Agents by One‐Dimensional Heteropolyniobates

A wide range of chemical warfare agents and their simulants are catalytically decontaminated by a new one‐dimensional polymeric polyniobate (P‐PONb), K₁₂[Ti₂O₂][GeNb₁₂O₄₀]?19 H₂O ( KGeNb ) under mild conditions and in the dark. Uniquely, KGeNb facilitates hydrolysis of nerve agents Sarin (GB) and Soman (GD) (and their less reactive simulants, dimethyl methylphosphonate (DMMP)) as well as mustard (HD) in both liquid and gas phases at ambient temperature and in the absence of neutralizing bases or illumination. Three lines of evidence establish that KGeNb removes DMMP, and thus likely GB/GD, by general base catalysis: a) the k(H₂O)/k(D₂O) solvent isotope effect is 1.4; b) the rate law (hydrolysis at the same pH depends on the amount of P‐PONb present); and c) hydroxide is far less active against the above simulants at the same pH than the P‐PONbs themselves, a critical control experiment.     

Two‐Photon Absorption and the Design of Two‐Photon Dyes

Two photons are better than one : This principle applies to a wide range of applications, ranging from engineering to physiology. Recent advances in our understanding of the phenomenon of two‐photon absorption (see picture) and in the design of two‐photon dyes are rapidly increasing the scope of this field.

     

Solving Blue Light Riddles: New Lessons from Flavin‐binding LOV Photoreceptors

Detection of blue light (BL) via flavin‐binding photoreceptors (Fl‐Blues) has evolved throughout all three domains of life. Although the main BL players, that is light, oxygen and voltage (LOV), blue light sensing using flavins (BLUF) and Cry (cryptochrome) proteins, have been characterized in great detail with respect to structure and function, still several unresolved issues at different levels of complexity remain and novel unexpected findings were reported. Here, we review the most prevailing riddles of LOV‐based photoreceptors, for example: the relevance of water and/or small metabolites for the dynamics of the photocycle; molecular details of light‐to‐signal transduction events; the interplay of BL sensing by LOV domains with other environmental stimuli, such as BL plus oxygen‐mediating photodamage and its impact on microbial lifestyles; the importance of the cell or chromophore redox state in determining the fate of BL‐driven reactions; the evolutionary pathways of LOV‐based BL sensing and associated functions through the diverse phyla. We will discuss major novelties emerged during the last few years on these intriguing aspects of LOV proteins by presenting paradigmatic examples from prokaryotic photosensors that exhibit the largest complexity and richness in associated functions.     

Blue Light Emitting Defective Nanocrystals Composed of Earth‐Abundant Elements

Copper‐based ternary (I–III–VI) chalcogenide nanocrystals (NCs) are compositionally‐flexible semiconductors that do not contain lead (Pb) or cadmium (Cd). Cu‐In‐S NCs are the dominantly studied member of this important materials class and have been reported to contain optically‐active defect states. However, there are minimal reports of In‐free compositions that exhibit efficient photoluminescence (PL). Here, we report a novel solution‐phase synthesis of ≈4 nm defective nanocrystals (DNCs) composed of copper, aluminum, zinc, and sulfur with ≈20 % quantum yield and an attractive PL maximum of 450 nm. Extensive spectroscopic characterization suggests the presence of highly localized electronic states resulting in reasonably fast PL decays (≈1 ns), large vibrational energy spacing, small Stokes shift, and temperature‐independent PL linewidth and PL lifetime (between room temperature and ≈5 K). Furthermore, density functional theory (DFT) calculations suggest PL transitions arise from defects within a CuAl₅S₈ crystal lattice, which supports the experimental observation of highly‐localized states. The results reported here provide a new material with unique optoelectronic characteristics that is an important analog to well‐explored Cu‐In‐S NCs.     

Photoreception and Phototropism in Phycomyces: Antagonistic Interactions between Far-UV, Blue, and Red Light

Abstract— Phototropism of the sporangiophore of the fungus Phycomyces is mediated by UV and blue light. Classical phototropism action spectra with maxima near 280, 370 and 450 nm indicate a flavin-like photoreceptor. Blue light mediates positive phototropism while far-UV light mediates negative phototropism. To better understand the mode of interaction of far-UV with blue light we performed phototropism experiments in which sporangio-phores were placed for 4 h between sources of 280 and 454 nm light coming from opposite directions. The fluence rates of the far-UV were chosen such that unilateral light alone elicited 90° of negative bending. For blue light, moderate fluence rates were applied that elicited about 40° bending. Under conditions of bilateral irradiation the blue light substantially reduced the far-UV elicited phototropism. In the presence of tonic red light the antagonism between far-UV and blue light was greatly reduced. Red light, which by itself is phototropically ineffective, also reduced phototropic bending elicited by either far-UV or blue light. These observations are taken as indications for the existence of a red light-absorbing intermediate of the blue-light receptor. Because the far-UV/ blue-light antagonism disappeared almost completely in the presence of tonic red light, the antagonism may occur at the level of this receptor intermediate.     

Discovery of Key TIPS‐Naphthalene for Efficient Visible‐to‐UV Photon Upconversion under Sunlight and Room Light**

While many studies have been done on triplet–triplet annihilation‐based photon upconversion (TTA‐UC) to produce visible light with high efficiency, the efficient TTA‐UC from visible to UV light, despite its importance for a variety of solar and indoor applications, remains a challenging task. Here, we report the highest visible‐to‐UV TTA‐UC efficiency of 20.5 % based on the discovery of an excellent UV emitter, 1,4‐bis((triisopropylsilyl)ethynyl)naphthalene (TIPS‐Nph). TIPS‐Nph is an acceptor with desirable features of high fluorescence quantum yield and high singlet generation efficiency by TTA. TIPS‐Nph has a low enough triplet energy level to be sensitized by Ir(C6)₂(acac), a superior donor that does not quench UV emission. The combination of TIPS‐Nph and Ir(C6)₂(acac) realizes the efficient UV light production even with weak light sources such as an AM 1.5 solar simulator and room LEDs.