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Humins, (side-)products of the acid-catalysed dehydration of carbohydrates, will be produced in substantial quantities with the development of industrial biorefining processes. Most structural knowledge about such humins is based on synthetic model humins prepared at lab-scale from typical carbohydrate(-derived) compounds. Here, we report the first extensive characterisation study of an industrial humin. The soluble humin was generated from pilot plant-scale methanolic cyclodehydration of D-fructose to 5-methoxymethyl-2-furfural (MMF), as part of the Avantium YXY® process to produce FDCA. Purification of the industrial humin followed by fractionation allowed isolation of a water-insoluble, high molecular weight fraction (WIPIH) and a water-soluble, low-to-middle molecular weight soluble fraction (WES). Characterisation by elemental analysis, thermogravimetry, IR and NMR spectroscopy and size exclusion chromatography provided a detailed picture of the humin structure in both fractions. Aided by a comprehensive NMR spectral library of furanic model compounds, we identified the main furanic building blocks and inter-unit linkages and propose a structure for this industrial humin sample. The WIPIH and WES fractions were found to be composed of furanic rings interconnected by short aliphatic chains containing a wide range of functionalities including alcohols, ethers, carboxylic acids, esters, aldehydes and ketones. The low level of crosslinking and high functional group content of the industrial humin differ from the more extensively studied, (highly over-)condensed synthetic model humins, towards which they can be considered intermediates. The structural and compositional insights into the nature of an actual industrial humin open up a broad spectrum of valorisation opportunities. [ABSTRACT FROM AUTHOR]

The average and the local structure of phosphorus-treated HZSM-5 zeolites were investigated by means of atom probe tomography, powder X-ray diffraction (at ambient and cryogenic temperatures) and 1H, 29Si, 27Al, and 31P magic angle spinning (MAS) solid state nuclear magnetic resonance (NMR) spectroscopy. Phosphatation to yield a product with P/Al ≤ 1 followed by thermal treatment leads to breaking of the Si–OH–Al bridging groups, and subsequent partial dealumination of the zeolite framework, as shown by the contraction of the orthorhombic unit-cell volume and by the loss of tetrahedral framework Al, as observed in the 27Al Multiple Quantum (MQ) MAS NMR spectrum. Most of the framework Al is present in an electronic environment distorted by the presence of phosphorus and appears not to be involved in classic Si–OH–Al Brønsted acid sites. The 31P MAS NMR signals indicate that phosphorus interacts with the zeolitic framework to locally form silico-aluminophosphate (SAPO) domains and the presence of a new kind of acidic site was confirmed by the resonance at ∼8.6 ppm in the 1H MAS NMR spectra, attributed to P–OH groups. Increasing the phosphorus loading (P/Al > 1) promotes further dealumination of the framework and cross-dehydroxylation between P–OH and Si–OH species, leading to the formation of a crystalline silicon orthophosphate phase. With decreasing Al content, the monoclinic HZSM-5 structure becomes preferred, especially at 85 K where the strain relaxation is higher. However, the presence of a higher amount of silicophosphate impurities hinders the low-temperature strain release of the framework, indicating that some of these species are localized in the zeolite pores and contribute to the strain build up. [ABSTRACT FROM AUTHOR]

The properties of the zeolite ZSM-5 have been optimised for the production and deoxygenation of the bio-oil* (bio-oil on water-free basis) fraction by lignocellulose catalytic pyrolysis. Two ZSM-5 supports possessing high mesopore/external surface area, and therefore enhanced accessibility, have been employed to promote the conversion of the bulky compounds formed in the primary cracking of lignocellulose. These supports are a nanocrystalline material (n-ZSM-5) and a hierarchical sample (h-ZSM-5) of different Si/Al ratios and acid site concentrations. Acidic features of both zeolites have been modified and adjusted by incorporation of ZrO2, which has a significant effect on the concentration and distribution of both Brønsted and Lewis acid sites. These materials have been tested in the catalytic pyrolysis of acid-washed wheat straw (WS-ac) using a two-step (thermal/catalytic) reaction system at different catalyst/biomass ratios. The results obtained have been assessed in terms of oxygen content, energy yield and composition of the produced bio-oil*, taking also into account the selectivity towards the different deoxygenation pathways. The ZrO2/n-ZSM-5 sample showed remarkable performance in the biomass catalytic pyrolysis, as a result of the appropriate combination of accessibility and acidic properties. In particular, modification of the zeolitic support acidity by incorporation of highly dispersed ZrO2 effectively decreased the extent of secondary reactions, such as severe cracking and coke formation, as well as promoted the conversion of the oligomers formed initially by lignocellulose pyrolysis, thus sharply decreasing the proportion of the components not detected by GC-MS in the upgraded bio-oil*. [ABSTRACT FROM AUTHOR]

Abstract: After a prolonged effort over many years, the route for the formation of a direct carbon−carbon (C−C) bond during the methanol‐to‐hydrocarbon (MTH) process has very recently been unveiled. However, the relevance of the “direct mechanism”‐derived molecules (that is, methyl acetate) during MTH, and subsequent transformation routes to the conventional hydrocarbon pool (HCP) species, are yet to be established. This important piece of the MTH chemistry puzzle is not only essential from a fundamental perspective, but is also important to maximize catalytic performance. The MTH process was probed over a commercially relevant H‐SAPO‐34 catalyst, using a combination of advanced solid‐state NMR spectroscopy and operando UV/Vis diffuse reflectance spectroscopy coupled to an on‐line mass spectrometer. Spectroscopic evidence is provided for the formation of (olefinic and aromatic) HCP species, which are indeed derived exclusively from the direct C−C bond‐containing acetyl group of methyl acetate. New mechanistic insights have been obtained from the MTH process, including the identification of hydrocarbon‐based co‐catalytic organic reaction centers. [ABSTRACT FROM AUTHOR]

Abstract: After a prolonged effort over many years, the route for the formation of a direct carbon−carbon (C−C) bond during the methanol‐to‐hydrocarbon (MTH) process has very recently been unveiled. However, the relevance of the “direct mechanism”‐derived molecules (that is, methyl acetate) during MTH, and subsequent transformation routes to the conventional hydrocarbon pool (HCP) species, are yet to be established. This important piece of the MTH chemistry puzzle is not only essential from a fundamental perspective, but is also important to maximize catalytic performance. The MTH process was probed over a commercially relevant H‐SAPO‐34 catalyst, using a combination of advanced solid‐state NMR spectroscopy and operando UV/Vis diffuse reflectance spectroscopy coupled to an on‐line mass spectrometer. Spectroscopic evidence is provided for the formation of (olefinic and aromatic) HCP species, which are indeed derived exclusively from the direct C−C bond‐containing acetyl group of methyl acetate. New mechanistic insights have been obtained from the MTH process, including the identification of hydrocarbon‐based co‐catalytic organic reaction centers. [ABSTRACT FROM AUTHOR]

Abstract: Chromatin function depends on a dense network of interactions between nucleosomes and a wide range of proteins. A detailed description of these protein–nucleosome interactions is required to reach a full molecular understanding of chromatin function in both genetics and epigenetics. Herein, we show that the structure, dynamics, and interactions of nucleosomes can be interrogated in a residue‐specific manner by using state‐of‐the‐art solid‐state NMR spectroscopy. Using sedimented nucleosomes, high‐resolution spectra were obtained for both flexible histone tails and the non‐mobile histone core. Through co‐sedimentation of a nucleosome‐binding peptide, we demonstrate that protein‐binding sites on the nucleosome surface can be determined. We believe that this approach holds great promise as it is generally applicable, extendable to include the structure and dynamics of the bound proteins, and scalable to interactions of proteins with higher‐order chromatin structures, including isolated and cellular chromatin. [ABSTRACT FROM AUTHOR]

Abstract: Chromatin function depends on a dense network of interactions between nucleosomes and a wide range of proteins. A detailed description of these protein–nucleosome interactions is required to reach a full molecular understanding of chromatin function in both genetics and epigenetics. Herein, we show that the structure, dynamics, and interactions of nucleosomes can be interrogated in a residue‐specific manner by using state‐of‐the‐art solid‐state NMR spectroscopy. Using sedimented nucleosomes, high‐resolution spectra were obtained for both flexible histone tails and the non‐mobile histone core. Through co‐sedimentation of a nucleosome‐binding peptide, we demonstrate that protein‐binding sites on the nucleosome surface can be determined. We believe that this approach holds great promise as it is generally applicable, extendable to include the structure and dynamics of the bound proteins, and scalable to interactions of proteins with higher‐order chromatin structures, including isolated and cellular chromatin. [ABSTRACT FROM AUTHOR]

Methanol-to-olefin (MTO) catalysis is a very active field of research because there is a wide variety of sometimes conflicting mechanistic proposals. An example is the ongoing discussion on the initial C−C bond formation from methanol during the induction period of the MTO process. By employing a combination of solid-state NMR spectroscopy with UV/Vis diffuse reflectance spectroscopy and mass spectrometry on an active H-SAPO-34 catalyst, we provide spectroscopic evidence for the formation of surface acetate and methyl acetate, as well as dimethoxymethane during the MTO process. As a consequence, new insights in the formation of the first C−C bond are provided, suggesting a direct mechanism may be operative, at least in the early stages of the MTO reaction. [ABSTRACT FROM AUTHOR]

Methanol-to-olefin (MTO) catalysis is a very active field of research because there is a wide variety of sometimes conflicting mechanistic proposals. An example is the ongoing discussion on the initial C−C bond formation from methanol during the induction period of the MTO process. By employing a combination of solid-state NMR spectroscopy with UV/Vis diffuse reflectance spectroscopy and mass spectrometry on an active H-SAPO-34 catalyst, we provide spectroscopic evidence for the formation of surface acetate and methyl acetate, as well as dimethoxymethane during the MTO process. As a consequence, new insights in the formation of the first C−C bond are provided, suggesting a direct mechanism may be operative, at least in the early stages of the MTO reaction. [ABSTRACT FROM AUTHOR]

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1H detection can significantly improve solid-state NMR spectral sensitivity and thereby allows studying more complex proteins. However, the common prerequisite for 1H detection is the introduction of exchangeable protons in otherwise deuterated proteins, which has thus far significantly hampered studies of partly water-inaccessible proteins, such as membrane proteins. Herein, we present an approach that enables high-resolution 1H-detected solid-state NMR (ssNMR) studies of water-inaccessible proteins, and that even works in highly complex environments such as cellular surfaces. In particular, the method was applied to study the K+ channel KcsA in liposomes and in situ in native bacterial cell membranes. We used our data for a dynamic analysis, and we show that the selectivity filter, which is responsible for ion conduction and highly conserved in K+ channels, undergoes pronounced molecular motion. We expect this approach to open new avenues for biomolecular ssNMR. [ABSTRACT FROM AUTHOR]

Incorporation of Ca in ZSM-5 results in a twofold increase of propylene selectivity (53 %), a total light-olefin selectivity of 90 %, and a nine times longer catalyst lifetime (throughput 792 gMeOH gcatalyst−1) in the methanol-to-olefins (MTO) reaction. Analysis of the product distribution and theoretical calculations reveal that post-synthetic modification with Ca2+ leads to the formation of CaOCaOH+ that strongly weaken the acid strength of the zeolite. As a result, the rate of hydride transfer and oligomerization reactions on these sites is greatly reduced, resulting in the suppression of the aromatic cycle. Our results further highlight the importance of acid strength on product selectivity and zeolite lifetime in MTO chemistry. [ABSTRACT FROM AUTHOR]

1H-detection can greatly improve spectral sensitivity in biological solid-state NMR (ssNMR), thus allowing the study of larger and more complex proteins. However, the general requirement to perdeuterate proteins critically curtails the potential of 1H-detection by the loss of aliphatic side-chain protons, which are important probes for protein structure and function. Introduced herein is a labelling scheme for 1H-detected ssNMR, and it gives high quality spectra for both side-chain and backbone protons, and allows quantitative assignments and aids in probing interresidual contacts. Excellent 1H resolution in membrane proteins is obtained, the topology and dynamics of an ion channel were studied. This labelling scheme will open new avenues for the study of challenging proteins by ssNMR. [ABSTRACT FROM AUTHOR]

¹H-detection can greatly improve spectral sensitivity in biological solid-state NMR (ssNMR), thus allowing the study of larger and more complex proteins. However, the general requirement to perdeuterate proteins critically curtails the potential of ¹H-detection by the loss of aliphatic side-chain protons, which are important probes for protein structure and function. Introduced herein is a labelling scheme for ¹H-detected ssNMR, and it gives high quality spectra for both side-chain and backbone protons, and allows quantitative assignments and aids in probing interresidual contacts. Excellent ¹H resolution in membrane proteins is obtained, the topology and dynamics of an ion channel were studied. This labelling scheme will open new avenues for the study of challenging proteins by ssNMR. [ABSTRACT FROM AUTHOR]

The β-barrel assembly machinery (BAM) is involved in folding and insertion of outer membrane proteins in Gram-negative bacteria, a process that is still poorly understood. With its 790 residues, BamA presents a challenge to current NMR methods. We utilized a 'divide and conquer' approach in which we first obtained resonance assignments for BamA's periplasmic POTRA domains 4 and 5 by solution NMR. Comparison of these assignments to solid-state NMR (ssNMR) data obtained on two BamA constructs including the transmembrane domain and one or two soluble POTRA domains suggested that the fold of POTRA domain 5 critically depends on the interface with POTRA 4. Using specific labeling schemes we furthermore obtained ssNMR resonance assignments for residues in the extracellular loop 6 that is known to be crucial for BamA-mediated substrate folding and insertion. Taken together, our data provide novel insights into the conformational stability of membrane-embedded, non-crystalline BamA. [ABSTRACT FROM AUTHOR]

A method to measure 13C-13C cross-relaxation rates in a fully 13C labeled protein has been developed that can give information about the mobility of side chains in proteins. The method makes use of the (H)CCH-NOESY pulse sequence and includes a suppression scheme for zero-quantum (ZQ) coherences that allows the extraction of initial rates from NOE buildup curves. The method has been used to measure 13C-13C cross-relaxation rates in the 269-residue serine-protease PB92. We focused on Cα-Cβ cross-relaxation rates, which could be extracted for 64% of all residues, discarding serine residues because of imperfect ZQ suppression, and methyl 13C-13C cross-relaxation rates, which could be extracted for 47% of the methyl containing C-C pairs. The Cα-Cβ cross-relaxation rates are on average larger in secondary structure elements as compared to loop regions, in agreement with the expected higher rigidity in these elements. The cross-relaxation rates for methyl containing C-C pairs show a general decrease of rates further into the side chain, indicating more flexibility with increasing separation from the main chain. In the case of leucine residues also long-range Cβ-Cδ cross-peaks are observed. Surprisingly, for most of the leucines a cross-peak with only one of the methyl Cδ carbons is observed, which correlates well with the χ2 torsion-angle and can be explained by a difference in mobility for the two methyl groups due to an anisotropic side chain motion. [ABSTRACT FROM AUTHOR]

The possibility of generating protein folds at the stage of backbone assignment using structural restraints derived from experimentally measured cross-hydrogen bond scalar couplings and secondary chemical shift information is investigated using as a test case the small α/β protein chymotrypsin inhibitor 2. Dihedral angle restraints for the φ and ψ angles of 32 out of 64 residues could be obtained from secondary chemical shift analysis with the TALOS program (Corneliscu et al., 1999a). This information was supplemented by 18 hydrogen-bond restraints derived from experimentally measured cross-hydrogen bond 3hbJNC′ coupling constants. These experimental data were sufficient to generate structures that are as close as 1.0 Å backbone rmsd from the crystal structure. The fold is, however, not uniquely defined and several solutions are generated that cannot be distinguished on the basis of violations or energetic considerations. Correct folds could be identified by combining clustering methods with knowledge-based potentials derived from structural databases. [ABSTRACT FROM AUTHOR]

Der Reaktionsmechanismus der industriell wichtigen Umwandlung von Methanol in Olefine über Zeolithkatalysatoren wurde untersucht. In der Zuschrift auf S. 16072 ff. zeigen M. Baldus, B. M. Weckhuysen et al. einen effektiven, auf Festkörper‐NMR‐Spektroskopie und Operando‐UV/Vis‐Spektroskopie basierenden Ansatz, um den Beweis für einen direkten Mechanismus bei der Bildung der ersten Kohlenstoff‐Kohlenstoff‐Bindung während der Anfangsphase der Reaktion zu liefern. [ABSTRACT FROM AUTHOR]

The inside back cover of the December 2016 issue of the journal "Angewandte Chemie International Edition" is presented.

The front cover artwork for Issue 19/2016 is provided by researchers from the Catalysis Engineering group at TU Delft (The Netherlands). The image shows that after impregnation with Ca, ZSM-5 becomes a 'super-catalyst', which is able to suppress formation of aromatics thus increasing selectivity to the desired propylene in MTO reaction. See the Full Paper itself at . [ABSTRACT FROM AUTHOR]

The Front Cover shows Ca‐ZSM‐5 as a “super‐catalyst” fighting coke – the evil of MTO world.In their Full Paper, I. Yarulina et al. investigated the mechanism of methanol to olefins (MTO) reaction, which is characterized by the presence of two competing cycles – olefinic and aromatic. The latter is responsible for catalyst deactivation since aromatic species act as coke precursors. It was shown that post‐synthetic incorporation of calcium in ZSM‐5 by different methods leads to transformation of Brønsted acid sites to Lewis ones. After this modification, ZSM‐5 becomes a “super‐catalyst”, which is able to suppress formation of aromatics not only prolonging catalyst lifetime but also increasing selectivity to the desired propylene through fighting coke – the evil of MTO world. More information can be found in the Full Paper by I. Yarulina et al. on page 3057 in Issue 19, 2016 (DOI: 10.1002/cctc.201600650). [ABSTRACT FROM AUTHOR]