Chemphyschem最新文献

Histamine is a neurotransmitter, and it is available as protonated state at the physiological conditions. We predicted theoretically the possibility of excited state intra-molecular proton transfer (ESIPT) at the excited state of N-protonated gauche-form histamine in aqueous phase. The proton transfer occurs from the ammonium unit of aliphatic chain to the nitrogen of the imidazole ring. The acidity of aliphatic amine (N14) and basicity of imidazole nitrogen (N8) increase only at the excited state, suggesting the possibility of proton transfer at the excited state. The distance between amine proton and acceptor nitrogen in the imidazole ring becomes closer at the excited state (∼3.23 Å changes to ∼1.86 Å) in aqueous phase, which facilitates proton transfer from the amine group to imidazole nitrogen at the excited state. The energy barrier calculated using the potential energy surface scans suggests the low activation energy (∼5.1 kcalmol⁻¹) facilitating faster reaction. At pre-ESIPT state, protonated histamine (gauche form) absorbs light of ∼219 nm and emits at ∼315 nm in aqueous phase, whereas at post-ESIPT state it emits at ∼407 nm, reflecting a large red-shifted emission due to ESIPT in protonated histamine. Born-Oppenheimer Molecular Dynamics studies detected the timescale of the ESIPT reaction as ∼203 fs for protonated histamine in aqueous phase, which correlates well with the experimental ESIPT time scale for other systems reported in literature.

Methanol (CH₃OH) is increasingly used as an alternative marine fuel due to its ability to reduce emissions of CO₂ and particulate matter. However, its application often leads to elevated levels of unburned methanol in the exhaust. Catalytic oxidation is widely considered an effective strategy for eliminating methanol slip. In this article, a series of Cu/SSZ-13 catalysts with different Cu loadings are prepared by the impregnation method. Methanol conversion increased markedly as the Cu loading increased from 2.5 to 10 wt%. The Cu₁₀/SSZ-13 catalyst achieved complete CH₃OH conversion at 225 °C with minimal byproduct formation throughout the tested temperature range. Further increasing the Cu loading to 12.5 wt% resulted in no significant change in either CH₃OH conversion or byproduct yields. Characterization results indicated that the Cu species predominantly existed as CuO nanoparticles dispersed on the external surface of SSZ-13, rather than as framework-incorporated isolated Cu²⁺ ions. CuO is identified as the primary active phase for CH₃OH oxidation. The superior performance of Cu₁₀/SSZ-13 is attributed to its abundant surface-adsorbed oxygen species and high density of basic sites. In situ DRIFTS measurements further revealed that methoxy and formate species are the key intermediates during methanol oxidation over the Cu₁₀/SSZ-13 catalyst.

The aim of the study was the preparation and characterization of organo-mineral fertilizers supporting sustainable development of agriculture. Materials were obtained by the drum granulation in laboratory conditions and by the pan granulation on a semi-industrial plant. On a laboratory scale, three fertilizer formulas NPK 5-10-20, NPK 4-18-23, and NPK 3-10-12 and 60 fertilizer formulations modified with three different organic materials (lignite, peat, and compost), with five levels of their content (5%, 10%, 15%, 20%, and 30%) were prepared. The effect of granulation on a semi-industrial scale was two fertilizer formulas: NPK 5-10-20 and NPK 4-18-23, with three levels of lignite content (10%, 20%, and 30%). In the obtained materials, the granulometric composition, static and dynamic strength as well as the content of macro and micronutrients were analysed. The properties of the produced fertilizing materials were also verified in microbiological experiments. Based on the experiments carried out, it was found that the only formula that met the legal and quality requirements would be the NPK 4-18-23 formula with ≈20% lignite content. It was found that the organic materials used are not a source of microorganisms in the prepared fertilizers, and these fertilizers would meet the requirements of the regulations.

The Front Cover depicts two ¹³C spins that interact over nanometer-scale distances, thus allowing the number of spins in a cluster to be counted. The thermometer displays the cryogenic temperature used, and the 25 minutes on the clock represent the mixing time needed to enable the nuclei to influence each other over this distance range. The signal was enhanced by dynamic nuclear polarization to achieve this unprecedented mixing time needed to reach nanometer distances. More information can be found in the Research Article by L. B. Andreas and co-workers (DOI: 10.1002/cphc.202500585).

The phase behavior and electrical conductivity of two ionic liquids (ILs) with the same anion (dicyanamide) and different cations (1-ethyl-3-methylimidazolium and 1-butyl-3-methylimidazolium) at different temperatures (including subzero ones) are studied in detail, and the relationship between the phase state and electrical conductivity is shown. It is found that the formation of several crystalline mesophases at temperatures below −10 °C and their successive melting in the range between −10 and 10 °C leads to a curvature of the Arrhenius plot. In this case, two linear sections and an inflection in the temperature dependence of electrical conductivity are interpreted in terms of the phase states of the IL: homogeneous (solid and liquid) and a heterogeneous (mixed) phases, and the activating energy of conductivity E_a(κ) of the solid IL is significantly higher than that of the molten one. The obtained results may be useful in the designing of new electrolytes based on IL used in a wide range of temperatures.

The copper-catalyzed azide–alkyne cycloaddition (CuAAC) reaction is a foundational transformation in synthetic chemistry, owing to its high efficiency and selectivity. In this work, state-of-the-art quantum chemical methods are applied to elucidate the preference for the dinuclear CuAAC mechanism, involving two copper centers, over the mononuclear analog, involving one copper center. Activation strain and Kohn–Sham molecular orbital analyses reveal that the enhanced reactivity of the dinuclear CuAAC mechanism arises not from alleviation of strain in the copper acetylide upon formation of the six-membered metallacycle, as previously proposed, but rather from reduced steric Pauli repulsion between the copper acetylide and the azide. These results provide mechanistic insight into the origin of dinuclear catalysis in the CuAAC reaction.

Sulerythrins (SulE) are ferritin-like proteins from obligate aerobes such as Sulfolobus tokodaii, forming a domain-swapped dimer with a four-helix-bundle scaffold and a heterobimetallic Fe–Zn center. The diFe-SulE variant resembles diiron carboxylate proteins and contains two bimetallic active sites coordinated by histidines, glutamates, and bridging oxo ligands. High-resolution crystallography revealed slight differences in Fe–Fe distances and mixed-valence states, but the precise chemical nature of the oxo species remains unclear. To clarify the electronic and structural properties of diFe-SulE, we performed hybrid quantum mechanical/molecular mechanics (QM/MM) calculations on models varying in protonation, dioxo ligands, and iron redox states of the active site. Our results reveal at least three electronic states for diFe-SulE: (i) a diferrous center with an end-on di-μ-hydroperoxo ligand; (ii) a diferric center with hydroxo ligands interacting with protonated Glu95; and (iii) a diferrous center bridged by a di-μ-peroxo ligand, also interacting with protonated Glu95. These states are consistent with the structural heterogeneity observed experimentally. Overall, the hybrid QM/MM approach refines the crystallographic models and offers subatomic-level insight into the electronic structure and reactivity of the SulE diiron center, deepening our understanding of nonheme diiron enzymes.

By stabilizing weak and transient protein–protein interactions (PPIs), molecular glues address the challenge of targeting proteins previously considered undruggable. Rapamycin and WDB002 are molecular glues that bind to FK506-binding protein (FKBP12) and target the FKBP12-rapamycin-associated protein (FRAP) and the centrosomal protein 250 (CEP250), respectively. Herein, molecular dynamics simulations were used to gain insights into the effects of molecular glues on protein conformation and PPIs. The molecular glues modulated protein flexibility, leading to less flexibility in some regions, and changed the pattern and stability of water-mediated hydrogen bonds between the proteins. In the FKBP12-FRAP-rapamycin complex, two out of three water-mediated hydrogen bonds present in the crystallographic structure are more stable in the presence of the molecular glue, while in the FKBP12-CEP250-WDB002 complex, more water-mediated hydrogen bonds are present in the presence of the molecular glue, and they displayed higher stability. The findings highlight the importance of considering water-mediated hydrogen bonds in developing strategies for the rational design of molecular glues.

In this study, constant potential molecular dynamics simulations have been employed to investigate the impact of sodium fluorosulfonyl(trifluoromethylsulfonyl)amide (NaFTA) salt on the interfacial properties of 1-methyl-1-propylpyrrolidinium fluorosulfonyl(trifluoromethylsulfonyl)amide (Pyrr_1,3FTA) ionic liquid (IL) confined between two graphite electrodes at different applied potential differences. For the pure IL, it is observed that at higher negative voltages, the FTA⁻ anions are completely replaced by Pyrr_1,3⁺ cations, resulting in an unsolvated cation near the negative electrode. In the salt–IL solutions, at 0.1 mole fraction of the salt, most of the Na⁺ ions are found to interact with the FTA⁻ near the positive electrode, and a moderate presence of Na⁺ ions is observed closer to the negative electrode. Interestingly, accumulation of Na⁺ ions near both the electrodes is observed in the solution having highest mole fraction of the salt (x^NaFTA = 0.3). A nonmonotonous change in the intensity of the peaks in the number density profile of the Na⁺ ions is observed near the positive electrode surface. Analysis of the average orientational order parameter for the Pyrr_1,3⁺ cations reveals a parallel arrangement of their ring closer to the negative electrode, which is minimally affected by the presence of NaFTA salt. The distribution of the C-S-S-F improper dihedral angle of the FTA⁻ ions near the positive electrode (+2.5 V) interfacial region shows that the probability of finding their $$ conformation increases up to 0.2 mole fraction of the salt.

Exciton coupling model provides one of the most intuitive and powerful frameworks to directly connect molecular structure with chiroptical responses. This review focuses on rigid architectures with C₂ symmetry, in which conformational rigidity, symmetry constraints, and independent chromophores allow for direct correlations among molecular geometry, Davydov splitting, and electronic circular dichroism intensity. After introducing the theoretical basis of exciton coupling and its crucial role in absolute configuration assignment, we analyze how molecular design strategies control the conformational space, as well as how the electron transition dipole moments of interacting chromophores enable the modulation of dissymmetry factors (g-factors). Next, we expand these principles from isolated molecules to supramolecular assemblies, thin films, and polymers, where cooperative effects and new structural constraints can come into play to amplify or distort excitonic signatures. Overall, this review compiles transferable design principles to guide the development of next-generation chiroptical materials with broad relevance for sensing, optoelectronic, and spintronic applications.