Binderupfarrell3124

KGaA, Weinheim.Anion-π catalysis functions by stabilizing anionic transition states on aromatic π surfaces, thus providing a new approach to molecular transformation. The delocalized nature of anion-π interactions suggests that they serve best in stabilizing long-distance charge displacements. Aiming therefore for an anionic cascade reaction that is as charismatic as the steroid cyclization is for conventional cation-π biocatalysis, reported here is the anion-π-catalyzed epoxide-opening ether cyclizations of oligomers. Only on π-acidic aromatic surfaces having a positive quadrupole moment, such as hexafluorobenzene to naphthalenediimides, do these polyether cascade cyclizations proceed with exceptionally high autocatalysis (rate enhancements kauto /kcat >104  m-1 ). This distinctive characteristic adds complexity to reaction mechanisms (Goldilocks-type substrate concentration dependence, entropy-centered substrate destabilization) and opens intriguing perspectives for future developments. © 2020 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.Nanoceria (CeO 2 NPs) is an extensively studied nanozyme with interesting oxidase-mimicking activity. Since it can work in the absence of toxic and unstable H 2 O 2 , CeO 2 NPs has been widely used in biosensing. CeO 2 NPs often encounters phosphate containing molecules that may affect its catalytic activity and various reports exist in the literature showing both promoted and inhibited activity. In this work, we systematically studied five types of phosphates including orthophosphate, pyrophosphate, triphosphate, a polyphosphate with 25 phosphate units (Pi 25 ), and also DNA oligonucleotides of various lengths and sequences. DNA was included since they contain a phosphate backbone that can strongly adsorb on nanoceria. We observed inhibited activity by a high concentration of DNA in both acetate and phosphate buffer, however, we only observed obvious increase activity by relatively low concentration of DNA in phosphate buffer. These discoveries provide an important understanding for further use of CeO 2 NPs in biosensor development, materials science, and nanotechnology. © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.About one-third of orchid species are thought to offer no floral reward and therefore to attract pollinators through deception. Statements of this idea are common in the botanical literature, but the empirical basis of the estimate is rarely mentioned. We traced citation pathways for the one-third estimate in a sample of the literature and found that the paths lead to empirical foundations that are surprisingly narrow. Moreover, recent measurements have detected minute quantities of sugar available to insect visitors in some orchids thought to be rewardless, raising the possibility of a pollination strategy that is largely deceitful but different to absolute rewardlessness. The orchids are a well studied group and there is no doubt that rewardlessness is common in the family. However, greater empirical effort is needed to verify rewardlessness in orchids and to explore geographic and environmental variation in the proportion of rewardless species. This article is protected by copyright. All rights reserved.Enzyme-mediated proton transport across biological membranes is critical for many vital cellular processes. pH-sensitive fluorescent dyes are an indispensable tool for investigating the molecular mechanism of proton-translocating enzymes. Here, we present a novel strategy to entrap pH-sensitive probes into the lumen of liposomes that has several advantages over soluble or lipid-coupled probes. In our approach, the pH sensor is linked to a DNA oligomer with a sequence complementary to a second oligomer modified with a lipophilic moiety that anchors the DNA conjugate to the inner and outer leaflet of the lipid bilayer. The use of DNA as a scaffold allows subsequent selective enzymatic removal of the probe in the outer bilayer. The method shows a high yield of insertion and is compatible with reconstitution of membrane proteins via different methods. Using two large membrane protein complexes the usefulness of the conjugate for time-resolved proton pumping measurements is demonstrated. © 2020 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.High-grade periodate is relatively expensive, but is required for many sensitive applications such as the synthesis of active pharmaceutical ingredients (APIs). These high costs originate from using lead dioxide anodes in contemporary electrochemical methods and from expensive starting materials employed. A direct and cost-efficient electrochemical synthesis of periodate from iodide as less costly and easily available starting material is reported. The oxidation is conducted at boron-doped diamond anodes, which are durable, metal-free and non-toxic. The avoidance of lead dioxide ultimately diminishes the costs for purification and quality assurance. The electrolytic process was optimized by statistical methods and was scaled-up in an electrolysis flow cell that enhanced the space-time yields by a cyclization protocol. An LC-PDA analytical protocol was established enabling simple quantification of iodide, iodate, and periodate simultaneously in a remarkable precision. © 2020 WILEY-VCH Verlag GmbH & Co. https://www.selleckchem.com/products/lc-2.html KGaA, Weinheim.Chirality is ubiquitous in nature and occurs at all length scales. The development of applications for chiral nanostructures is rising rapidly. With the recent achievements of atomically precise nanochemistry, total structures of ligand-protected Au and other metal nanoclusters (NCs) are successfully obtained, and the origins of chirality are discovered to be associated with different parts of the cluster, including the surface ligands (e.g., swirl patterns), the organic-inorganic interface (e.g., helical stripes), and the kernel. Herein, a unified picture of metal-ligand surface bonding-induced chirality for the nanoclusters is proposed. The different bonding modes of M-X (where M = metal and X = the binding atom of ligand) lead to different surface structures on nanoclusters, which in turn give rise to various characteristic features of chirality. A comparison of Au-thiolate NCs with Au-phosphine ones further reveals the important roles of surface bonding. Compared to the Au-thiolate NCs, the Ag/Cu/Cd-thiolate systems exhibit different coordination modes between the metal and the thiolate.