Search

The catalytic conversion of biomass into high‐value chemicals is an increasing field of research. This study uniquely investigates the use of various Keggin‐type heteropoly salts (HPS) for the chemical conversion of sugars into lactic acid under mild conditions of 160 °C and 20 bar N2. In the first phase, Nb– and V–substituted HPSs were employed to synthesize lactic acid from dihydroxyacetone, an intermediate in the conversion of sugars to lactic acid. Results indicated that increasing the Nb content within the Keggin structure enhances the yield of lactic acid while reducing the formation of the byproduct acetaldehyde. A correlation was established between the redox activity of the HPS and the catalytic performance. The most active catalyst, Na5[PNb2Mo10O40], (NaNb2) achieved a lactic acid yield of 20.9 % after 1 h of reaction. In the second phase of the study, NaNb2 was applied for the conversion of different sugars including glucose, fructose, mannose, sucrose, xylose, and cellobiose. It was demonstrated that the catalyst remains active for complex hexoses, achieving lactic acid yields of up to 12 %. Post‐mortem analysis using infrared (IR) and Raman spectroscopy, nuclear magnetic resonance (NMR), and inductively coupled plasma optical emission spectrometry (ICP‐OES) confirmed the stability of NaNb2. [ABSTRACT FROM AUTHOR]

The aqueous glucose‐to‐fructose isomerization is controlled by thermodynamics to an equilibrium limit of ~50 % fructose yield. However, here we report an in situ fructose removal strategy enabled by an interfacial local photothermal effect in combination with relay catalysis of geminal and isolated potassium single atoms (K SAs) on graphene‐type carbon (Ksg/GT) to effectively bypass the equilibrium limit and markedly speed up glucose‐to‐fructose isomerization. At 25 °C, an unprecedented fructose yield of 68.2 % was obtained over Ksg/GT in an aqueous solution without any additives under 30‐min solar‐like irradiation. Mechanistic studies expounded that the interfacial thermoconvection caused by the local photothermal effect of the graphene‐type carbon and preferable glucose adsorption on single‐atom K could facilitate the release of in situ formed fructose. The geminal K SAs were prone to form a stable metal‐glucose complex via bidentate coordination, and could significantly reduce the C−H bond electron density by light‐driven electron transfer toward K. This facilitated the hydride shift rate‐determining step and expedited glucose isomerization. In addition, isolated K SAs favored the subsequent protonation and ring‐closure process to furnish fructose. The integration of the interfacial thermoconvection‐enhanced in situ removal protocol and tailored atomic catalysis opens a prospective avenue for boosting equilibrium‐limited reactions under mild conditions. [ABSTRACT FROM AUTHOR]

Utilization of lignocellulosic biomass as a renewable resource to produce liquid fuels/fuel additives and commodity chemicals offer solutions to minimize the exhaustion of nonrenewable carbon‐based fossil resources and mitigate environmental problems. Cellulose and hemicellulose derived from lignocellulose can be converted into several important platform molecules like glucose, fructose, xylose, 5‐hydroxymethylfurfural, furfural, levulinic acid, etc. which subsequently can be transformed into fuels/fuel additives and value‐added chemicals using heterogeneous catalytic processes. Aluminophosphates (AlPO‐n) are zeotype materials with tunable physicochemical properties like acidity and porosity, and this have promoted their wide use as versatile catalysts for several acid‐catalyzed reactions, including hydrolysis, dehydration, isomerization, transfer hydrogenation, reductive etherification, acetalization and aldol condensation. This review summarizes the design and synthetic advances of AlPO‐n catalysts as well as their application in the valorization of lignocellulose and derivatives to platform chemicals and fuel compounds. Perspectives for future design strategies are finally outlined. [ABSTRACT FROM AUTHOR]

Cationic‐shell core‐crosslinked micelles (CCM−C) with rhodium nanoparticles (RhNPs) anchored to core‐linked triphenylphosphine oxide (TPPO) ligands were synthesized by a facile one‐pot approach by the reduction of [Rh(COD)(μ‐Cl)]2/toluene in the presence of an aqueous TPPO@CCM−C latex. The resulting RhNP‐TPPO@CCM−C latex showed to be performant for the aqueous biphasic hydrogenation of styrene with an average corrected turnover frequency (cTOF) up to 23600 h−1 based on the RhNP surface atoms. The catalyst system also proved reusable in multiple catalytic runs without any visible RhNP loss during the recycling process as well as applicable to the hydrogenation of other selected alkenes, alkynes and carbonyl substrates (average cTOF of 1000–3200 h−1), thus demonstrating a high versatility. [ABSTRACT FROM AUTHOR]

Electrical membrane properties of skeletal muscle fibers have been thoroughly studied over the last five to six decades. This has shown that muscle fibers from a wide range of species, including fish, amphibians, reptiles, birds, and mammals, are all characterized by high resting membrane permeability for Cl(-) ions. Thus, in resting human muscle, ClC-1 Cl(-) ion channels account for ∼80% of the membrane conductance, and because active Cl(-) transport is limited in muscle fibers, the equilibrium potential for Cl(-) lies close to the resting membrane potential. These conditions-high membrane conductance and passive distribution-enable ClC-1 to conduct membrane current that inhibits muscle excitability. This depressing effect of ClC-1 current on muscle excitability has mostly been associated with skeletal muscle hyperexcitability in myotonia congenita, which arises from loss-of-function mutations in the CLCN1 gene. However, given that ClC-1 must be drastically inhibited (∼80%) before myotonia develops, more recent studies have explored whether acute and more subtle ClC-1 regulation contributes to controlling the excitability of working muscle. Methods were developed to measure ClC-1 function with subsecond temporal resolution in action potential firing muscle fibers. These and other techniques have revealed that ClC-1 function is controlled by multiple cellular signals during muscle activity. Thus, onset of muscle activity triggers ClC-1 inhibition via protein kinase C, intracellular acidosis, and lactate ions. This inhibition is important for preserving excitability of working muscle in the face of activity-induced elevation of extracellular K(+) and accumulating inactivation of voltage-gated sodium channels. Furthermore, during prolonged activity, a marked ClC-1 activation can develop that compromises muscle excitability. Data from ClC-1 expression systems suggest that this ClC-1 activation may arise from loss of regulation by adenosine nucleotides and/or oxidation. The present review summarizes the current knowledge of the physiological factors that control ClC-1 function in active muscle.

Myasthenia gravis (MG) is a neuromuscular disease that results in compromised transmission of electrical signals at the neuromuscular junction (NMJ) from motor neurons to skeletal muscle fibers. As a result, patients with MG have reduced skeletal muscle function and present with symptoms of severe muscle weakness and fatigue. ClC-1 is a skeletal muscle specific chloride (Cl−) ion channel that plays important roles in regulating neuromuscular transmission and muscle fiber excitability during intense exercise. Here, we show that partial inhibition of ClC-1 with an orally bioavailable small molecule (NMD670) can restore muscle function in rat models of MG and in patients with MG. In severely affected MG rats, ClC-1 inhibition enhanced neuromuscular transmission, restored muscle function, and improved mobility after both single and prolonged administrations of NMD670. On this basis, NMD670 was progressed through nonclinical safety pharmacology and toxicology studies, leading to approval for testing in clinical studies. After successfully completing phase 1 single ascending dose in healthy volunteers, NMD670 was tested in patients with MG in a randomized, placebo-controlled, single-dose, three-way crossover clinical trial. The clinical trial evaluated safety, pharmacokinetics, and pharmacodynamics of NMD670 in 12 patients with mild MG. NMD670 had a favorable safety profile and led to clinically relevant improvements in the quantitative myasthenia gravis (QMG) total score. This translational study spanning from single muscle fiber recordings to patients provides proof of mechanism for ClC-1 inhibition as a potential therapeutic approach in MG and supports further development of NMD670. Editor's summary: Myasthenia gravis (MG) is caused by an autoimmune response against postsynaptic components of the neuromuscular junction, leading to impaired communication between motor neurons and muscle fibers. Here, Skov et al. show that inhibition of the ClC-1 chloride channel with an orally bioavailable small molecule (NMD670) augmented muscle excitability in response to motor commands and thereby improved muscle function in rat models of MG. Data from a small randomized clinical trial demonstrate that treatment with NMD670 was well tolerated in patients with MG and improved a quantitative disease severity score. These findings support further clinical development of ClC-1 inhibitors for MG. —Daniela Neuhofer [ABSTRACT FROM AUTHOR]

Zirconia-supported vanadium–copper catalysts (VCux:yZr) were used for the oxidative depolymerization of softwood LignoBoost Kraft lignin (LB). Various VCux:yZr catalysts were prepared (x:y = 0:1, 1:4, 1:2, 3:4, 1:1, and 1:0) by incipient wetness impregnation, and reactions were performed in alkaline water at 150 °C under an O2 pressure of 5 bar for 10 min. 1H–13C HSQC NMR spectroscopy was used for product identification and quantification. The most promising catalyst was VCu1:2Zr, giving a total monomer yield of 9 wt% and the highest selectivity for vanillin (59%). This catalyst was characterized before and after use by N2 physisorption, XRD, TGA, SEM-EDS, and XPS. Cleavage of the main interunit linkages in LB, including the β-O-4 bonds and recalcitrant C–C bonds, was also observed. The findings of this study demonstrate the potential of the V–Cu/ZrO2 catalyst system in the production of value-added aromatics from technical lignin under relatively mild conditions. This would contribute to the more sustainable use of an underutilized side-stream in forest-based industries, provided catalyst reuse can be successfully demonstrated. [ABSTRACT FROM AUTHOR]