Tandem Organocatalysis and Photocatalysis: An Anthraquinone‐Catalyzed Indole‐C3‐Alkylation/Photooxidation/1,2‐Shift Sequence

Quinones exhibit orthogonal ground‐ and excited‐state reactivities and are therefore highly suitable organocatalysts for the development of sequential catalytic processes. Herein, the discovery of an anthraquinone‐catalyzed thermal indole‐C3‐alkylation with benzylamines is described, which can be combined sequentially with a new visible‐light‐driven catalytic photooxidation/1,2‐shift reaction. The one‐flask tandem process converts indoles into 3‐benzylindole intermediates, which are further transformed into new fluorescent 2,2‐disubstituted indoline‐3‐one derivatives.     

The Effect of Water on the 2-Propanol Oxidation Activity of Co-Substituted LaFe1−xCoxO3 Perovskites

Perovskites are interesting oxidation catalysts due to their chemical flexibility enabling the tuning of several properties. In this work, we synthesized LaFe_1−xCo_xO₃ catalysts by co-precipitation and thermal decomposition, characterized them thoroughly and studied their 2-propanol oxidation activity under dry and wet conditions to bridge the knowledge gap between gas and liquid phase reactions. Transient tests showed a highly active, unstable low-temperature (LT) reaction channel in conversion profiles and a stable, less-active high-temperature (HT) channel. Cobalt incorporation had a positive effect on the activity. The effect of water was negative on the LT channel, whereas the HT channel activity was boosted for x>0.15. The boost may originate from a slower deactivation rate of the Co³⁺ sites under wet conditions and a higher amount of hydroxide species on the surface comparing wet to dry feeds. Water addition resulted in a slower deactivation for Co-rich catalysts and higher activity in the HT channel state.     

Peptide Conjugated Dihydroazulene/Vinylheptafulvene Photoswitches in Aqueous Environment

Light-responsive molecules have seen a major advance in modulating biological functions in recent years. Especially photoswitches are highly attractive building blocks due to the reversible nature of their light-mediated reactivity. They are frequently used to affect both the properties of small bioactive compounds and biomacromolecules if incorporated suitably. Despite their success in a plethora of applications, only a limited set of photochromic core structures is routinely employed and a large number of photochromic couples are under-investigated in biological context. Broadening the toolbox of photoswitches available to modulate biological activity would open new avenues and unlock the full potential of photoswitchable molecules for biological studies. In this work, we explore the photochemical and thermal properties of the dihydroazulene/vinylheptafulvene photochromic couple as peptide conjugates in aqueous environment.     

Experimental validation of a new integrated simulated moving bed process for the production of single enantiomers

A new integrated 3-zone simulated moving bed (SMB) concept with internal racemization reaction was suggested recently for the production of single enantiomers from racemic mixtures [1,2]. The process utilizes an internal gradient to trigger the racemization within a single zone. It can deliver the pure enantiomer and outperforms conventional technologies. In this contribution, the concept is validated experimentally for the separation of a model system compound. The results demonstrate that the new concept is capable of producing a single enantiomer with purity, yield and conversion of 100%.     

Synergistic Effects of Co and Fe on the Oxygen Evolution Reaction Activity of LaCoxFe1−xO3

In a combined experimental and theoretical study we assess the role of Co incorporation on the OER activity of LaCo_xFe_1−xO₃. Phase pure perovskites were synthesized up to in 0.025/0.050 steps. HAADF STEM and EDX analysis points towards FeO₂-terminated (001)-facets in LaFeO₃, in accordance with the stability diagram obtained from density functional theory calculations with a Hubbard U term (DFT+U). Linear sweep voltammetry conducted in a rotating disk electrode setup shows a reduction of the OER overpotential and a nonmonotonic trend with x, with double layer capacitance measurements indicating an intrinsic nature of activity. This is supported by DFT+U results that show reduced overpotentials for both Fe and Co reaction sites with the latter reaching values of 0.32–0.40 V, ∼0.3 V lower than for Fe. This correlates with a stronger reduction of the binding energy difference of the *O and *OH intermediates towards an optimum value of 1.6 eV for , the OH deprotonation being the potential limiting step in most cases. Significant variations of the magnetic moments of both surface and subsurface Co and Fe during OER demonstrate that the beneficial effect is a result of a concerted action involving many surrounding ions, which extends the concept of the active site.     

A Photoclick-Based High-Throughput Screening for the Directed Evolution of Decarboxylase OleT

Enzymatic oxidative decarboxylation is an up-and-coming reaction yet lacking efficient screening methods for the directed evolution of decarboxylases. Here, we describe a simple photoclick assay for the detection of decarboxylation products and its application in a proof-of-principle directed evolution study on the decarboxylase OleT. The assay was compatible with two frequently used OleT operation modes (directly using hydrogen peroxide as the enzyme's co-substrate or using a reductase partner) and the screening of saturation mutagenesis libraries identified two enzyme variants shifting the enzyme's substrate preference from long chain fatty acids toward styrene derivatives. Overall, this photoclick assay holds promise to speed-up the directed evolution of OleT and other decarboxylases.     

Pseudopotentials for H to Kr optimized for gradient-corrected exchange-correlation functionals

Pseudopotential parameter sets for the elements from H to Kr using the relativistic, norm-conserving, separable, dual-space Gaussian-type pseudopotentials of Goedecker, Teter, and Hutter (GTH) are presented as optimized for the gradient-corrected exchange-correlation functionals of Becke, Lee, Yang, and Parr (BLYP), Becke and Perdew (BP), and Perdew, Burke, and Ernzerhof (PBE). The accuracy and reliability of the GTH pseudopotentials is shown by calculations for a series of small molecules. Contribution to Karl Jug Honorary Issue     

Stable isotopes in river waters in the Tajik Pamirs: regional and temporal characteristics

The Gunt River catchment in the Central Pamirs is a representative of the headwater catchments of the Aral Sea Basin. It covers 14,000 km², spanning altitudes between 2000 and 6700 m a.s.l. In a monitoring network, water samples were taken at 30 sampling points every month and analysed for the stable water isotopes (¹⁸O and ²H). Our first results show δ²H values in the range from?131.2 to?94.9 ‰ and δ¹⁸O values from?18.0 to?14.0 ‰. The stable isotope patterns in the catchment seem to follow a systematic way, dominated by an altitude effect with a mean Δ δ²H=?3.6 ‰/100 m. The observed seasonal variations can be explained by geographical aspects such as the influence of different wind systems as well as melting processes.     

A method for nonlinear modal analysis and synthesis: Application to harmonically forced and self-excited mechanical systems

The recently developed generalized Fourier–Galerkin method is complemented by a numerical continuation with respect to the kinetic energy, which extends the framework to the investigation of modal interactions resulting in folds of the nonlinear modes. In order to enhance the practicability regarding the investigation of complex large-scale systems, it is proposed to provide analytical gradients and exploit sparsity of the nonlinear part of the governing algebraic equations.