Suppressing Dormant Ru States in the Presence of Conventional Metal Oxides Promotes the Ru-MACHO-BH-Catalyzed Integration of CO₂ Capture and Hydrogenation to Methanol

Integrated CO2 capture and hydrogenation to methanol may replace fossil resources for production of clean fuels, chemicals, and materials. As opposed to the classic concept of lowering the transition state barriers in the rate determination step, here we demonstrate that suppression of a resting state species can also be a viable approach to accomplish catalytic improvement. As a promising NH/M bifunctional molecular catalyst for integrated CO2 capture and conversion to methanol, Ru-MACHO-BH in the presence of amine additives was evaluated in the presence of a second catalyst, preferably ZnO. The latter is capable of suppressing the Ru-formate resting state intermediate by accelerating formate to formamide formation. This strategy is capable of advancing methanol formation and CO2 conversion, adding up to 100 and 294 turnover numbers, respectively, under mild operational conditions. Operando high-pressure ATR-IR spectroscopy evidenced the existence of such Ru-formate resting state species in the presence of amine additives and its disappearance upon addition of ZnO under catalytic conditions. Given that metal oxide enhances the amide bond formation rate, but has insignificant activity in catalytic hydrogenation of CO2 and the formamide intermediate, its promoting effect can be fully ascribed to an increased availability of the active Ru-dihydride species upon suppressing the dormant Ru-formate catalyst intermediate

Improved Method for Counting DNA Molecules on Biofunctionalized Nanoparticles

In order to accurately determine low numbers (1−100) of immobilized ssDNA molecules at a single, silica 250 nm nanoparticle surface, we hereby propose an integrated approach combining classic single molecule confocal microscopy (SMCM), that is, stepwise photobleaching of labeled ssDNA, with modified total internal reflection fluorescence microscopy (mTIRF). We postulate that SMCM alone is unable to exactly account for all labeled ssDNA because of inherent laser polarization effects; that is, perpendicularly oriented molecules to the sample surface are not (or are only slightly) susceptible to laser excitation and thus are invisible in a classic photobleaching experiment. The SMCM method accounts for at best two-thirds (68%) of the present ssDNA molecules. The principle of the mTIRF technique, which relies on the creation of highly inclined illumination combined with part of the laser remaining in normal Köhler illumination, enables accurate counting of SMCM invisble molecules. The combined approach proposed here circumvents the polarization issue and allows a complete single molecule counting on individual nanoparticles, fully in line with bulk measurements, as will be demonstrated

Synthesis of Novel Renewable Polyesters and Polyamides with Olefin Metathesis

Unsaturated and hydroxyl-functionalized C6-dicarboxylic acids were successfully synthesized via olefin metathesis from methyl vinyl glycolate (MVG), a renewable α-hydroxy C4-ester product from Lewis-acid carbohydrate conversion. Addition of a second-generation Hoveyda–Grubbs catalyst to neat MVG leads to a near quantitative yield of dimethyl-2,5-dihydroxy-3-hexene­dioate (DMDHHD). Additional hydrolysis and hydrogenation steps form interesting polymer building blocks like 2,5-dihydroxy-3-hexenedioic acid (DHHDA) and 2,5-dihydroxy­adipic acid (DHAA). Their use in polyester and polyamide synthesis is demonstrated after determination of their physical and spectroscopic characteristics. Copolymerization of DHHDA with l-lactic acid for instance produces a cross-linked poly­(l-lactic acid-co-DHHDA) polyester. Proof of cross-links is ascertained by NMR and FTIR. Substantial impact on the melting, thermal, and polar properties of PLA are observed already at low amounts of DHHDA (0.1 mol %) in accord with the presence of cross-links in the polymer. Biobased polyamides were also synthesized by equimolar reaction of DHHDA with hexamethylenediamine, producing a renewable polyamide analogue of the petroleum-based nylon-6,6. Interestingly, the as-synthesized polyamide (α-bishydroxylated unsaturated polyamide, HUPA) possesses similar thermal stability as nylon-6,6 but shows different chemical properties as a result of the double bond and α-hydroxy functionality

Determination and Optimization of the Luminescence External Quantum Efficiency of Silver-Clusters Zeolite Composites

We have measured for the first time the external quantum efficiency (EQE) of silver clusters containing zeolites (henceforth referred to as silver-clusters zeolite composites). These materials, fabricated by silver cation exchange followed by a thermal autoreduction process, have EQEs up to 69%. Because of their unique spectral features such as large Stokes shift and high EQE, these materials could be potentially used as phosphors for the fabrication of fluorescent lamps and as wavelength convertors in solar cells. An EQE comparison between less pure commercial silver-loaded zeolites and self-synthesized silver-zeolites showed the importance of the chemical and optical purity of the starting host material. Besides this, the zeolite topology and silver content play an important role on the luminescent performance of such materials. The ability to reliably measure the EQE enabled us to further optimize the synthesis of silver-zeolite composites. A new reduction–oxidation cycle is demonstrated not only to improve the luminescent performance of the silver-zeolite composites but also to enhance their water stability

Data_Sheet_1_Engineering Curcumin Biosynthesis in Poplar Affects Lignification and Biomass Yield.docx

Lignocellulosic biomass is recalcitrant toward deconstruction into simple sugars mainly due to the presence of lignin. By engineering plants to partially replace traditional lignin monomers with alternative ones, lignin degradability and extractability can be enhanced. Previously, the alternative monomer curcumin has been successfully produced and incorporated into lignified cell walls of Arabidopsis by the heterologous expression of DIKETIDE-CoA SYNTHASE (DCS) and CURCUMIN SYNTHASE2 (CURS2). The resulting transgenic plants did not suffer from yield penalties and had an increased saccharification yield after alkaline pretreatment. Here, we translated this strategy into the bio-energy crop poplar. Via the heterologous expression of DCS and CURS2 under the control of the secondary cell wall CELLULOSE SYNTHASE A8-B promoter (ProCesA8-B), curcumin was also produced and incorporated into the lignified cell walls of poplar. ProCesA8-B:DCS_CURS2 transgenic poplars, however, suffered from shoot-tip necrosis and yield penalties. Compared to that of the wild-type (WT), the wood of transgenic poplars had 21% less cellulose, 28% more matrix polysaccharides, 23% more lignin and a significantly altered lignin composition. More specifically, ProCesA8-B:DCS_CURS2 lignin had a reduced syringyl/guaiacyl unit (S/G) ratio, an increased frequency of p-hydroxyphenyl (H) units, a decreased frequency of p-hydroxybenzoates and a higher fraction of phenylcoumaran units. Without, or with alkaline or hot water pretreatment, the saccharification efficiency of the transgenic lines was equal to that of the WT. These differences in (growth) phenotype illustrate that translational research in crops is essential to assess the value of an engineering strategy for applications. Further fine-tuning of this research strategy (e.g., by using more specific promoters or by translating this strategy to other crops such as maize) might lead to transgenic bio-energy crops with cell walls more amenable to deconstruction without settling in yield.</p

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