Visualizing the Entire Range of Noncovalent Interactions in Nanocrystalline Hybrid Materials Using 3D Electron Diffraction

Protonation State Insights into the Influence of Biocatalytic Function for Acetylcholinesterase Mediated by Neonicotinoids

The catalytic efficiency of acetylcholinesterase (AChE) is likely regulated by the protonation states and conformational adaptations of its catalytic residues. While neonicotinoid insecticides are recognized for impairing AChE function through neurotoxic mechanisms, the precise molecular mechanisms governing this inhibition remain poorly characterized. This investigation elucidates how structural variations among neonicotinoids modulate the protonation equilibria of Glu-202 and His-447 in AChE's catalytic triad. Comparative analysis reveals that nitro-substituted neonicotinoids (imidacloprid, clothianidin) induce more pronounced protonation state transitions compared to their cyano-containing counterparts (thiacloprid, acetamiprid). Specifically, the strong electron-withdrawing nitro groups facilitate the conversion of Glu-202 from the deprotonation (GLU) to protonation (GLH) state and His-447 from the δ- (HID) to ε-position protonation (HIE) state through enhanced electrostatic interactions. These electronic perturbations trigger structural reorganization within the active site, evidenced by nitro group-directed residue realignment and subsequent H-bond formation. Energy decomposition analysis identifies electrostatic contributions as the primary determinant of binding affinity differences, with nitro-neonicotinoids exhibiting stronger interactions than cyano-neonicotinoids. QM/MM metadynamics reveals that substantial protonation state alterations disrupt AChE's biocatalytic function, particularly its capacity for acetylcholine hydrolysis. Finally, SH-SY5Y-based cellular assays show that imidacloprid exhibits the strongest inhibitory effect on AChE intracellular activity, while thiacloprid and acetamiprid show weaker inhibitory effects, aligning with the computational predictions. This study provides insights into the protonation-state-induced biocatalytic function for acetylcholinesterase mediated by neonicotinoids, contributing to the assessment of exogenous ligand-induced potential ecological and human health risks.

Localized Boron Sites in Large Pore Borosilicate Zeolite EMM-59 Determined by Electron Crystallography

The structure of novel large pore borosilicate zeolite EMM-59 (|C19H42N2|8[B5.2Si218.8O448]) with localized framework boron sites was determined by using three-dimensional electron diffraction (3D ED) and scanning transmission electron microscopy (STEM) imaging. EMM-59 was synthesized using 2,2-(cyclopentane-1,1-diyl)bis(N,N-diethyl-N-methylethan-1-aminium) as an organic structure-directing agent (OSDA). The framework has a three-dimensional intersecting channel system delimited by 12 × 10 × 10-ring openings and contains 28 T and 60 oxygen atoms in the asymmetric unit, making it the most complex monoclinic zeolite. The 3D ED data collected from as-made EMM-59 under cryogenic conditions revealed three symmetry-independent locations of the OSDAs, and STEM imaging showed that the OSDAs are flexible and adopt different molecular conformations in channels with identical structural environments. The framework boron atoms were exclusively found in T-sites of 4-rings, especially those shared by multiple 4-rings. The tetrahedral BO4 with the highest boron content (38.6%) was transformed into a trigonal BO3 after the OSDAs were removed upon calcination. Its location and boron content could also be identified by STEM imaging.

Locating Hydrogen Positions for COF-300 by Cryo-3D Electron Diffraction

Covalent organic frameworks (COFs) have wide-ranging applications, and their host-guest interactions play an essential role in the achievement of COF functions. To investigate these host-guest interactions, it is necessary to locate all atoms, especially hydrogen atoms. However, it is difficult to determine the hydrogen atomic positions in COFs because of the complexities in synthesizing high-quality large single crystals. Three-dimensional electron diffraction (3D ED) has unique advantages for the structural determination of nanocrystals and identification of light atoms. In this study, it was demonstrated for the first time that the hydrogen atoms of a COF, not only on the framework but also on the guest molecule, can be located by 3D ED using continuous precession electron diffraction tomography (cPEDT) under cryogenic conditions. The host-guest interactions were clarified with the location of the hydrogen atoms. These findings provide novel insights into the investigation of COFs.

Guiding Principles for the Rational Design of Hybrid Materials: Use of DFT Methodology for Evaluating Non-Covalent Interactions in a Uranyl Tetrahalide Model System

Together with the synthesis and experimental characterization of 14 hybrid materials containing [UO2 X4 ]2- (X=Cl- and Br- ) and organic cations, we report on novel methods for determining correlation trends in their formation enthalpy (ΔHf ) and observed vibrational signatures. ΔHf values were analyzed through isothermal acid calorimetry and a Density Functional Theory+Thermodynamics (DFT+T) approach with results showing good agreement between theory and experiment. Three factors (packing efficiency, cation protonation enthalpy, and hydrogen bonding energy [E H , norm total ${{E}_{H,{\rm { norm}}}^{{\rm { total}}}}$ ]) were assessed as descriptors for trends in ΔHf . Results demonstrated a strong correlation betweenE H , norm total ${E_{{\rm{H}},{\rm{norm}}}^{{\rm{total}}} }$ and ΔHf , highlighting the importance of hydrogen bonding networks in determining the relative stability of solid-state hybrid materials. Lastly, we investigate how hydrogen bonding networks affect the vibrational characteristics of uranyl solid-state materials using experimental Raman and IR spectroscopy and theoretical bond orders and find that hydrogen bonding can red-shift U≡O stretching modes. Overall, the tightly integrated experimental and theoretical studies presented here bridge the trends in macroscopic thermodynamic energies and spectroscopic features with molecular-level details of the geometry and electronic structure. This modeling framework forms a basis for exploring 3D hydrogen bonding as a tunable design feature in the pursuit of supramolecular materials by rational design.