ACS Physical Chemistry Au最新文献

In-droplet hydrogen/deuterium exchange (HDX)-mass spectrometry (MS) experiments have been conducted for peptides of highly varied conformational type. A new model is presented that combines the use of protection factors (PF) from molecular dynamics (MD) simulations with intrinsic HDX rates (k_int) to obtain a structure-to-reactivity calibration curve. Using the model, the relationship of peptide structural flexibility and HDX reactivity for different peptides is elucidated. Additionally, the model is used to describe the degree of conformational flexibility and structural bias for the disease-relevant Nt17 peptide; although highly flexible, intrinsically primed for facile conversion to α-helical conformation upon binding with molecular partners imparts significant in-droplet HDX protection for this peptide. In the future, a scale may be developed whereby HDX reactivity is predictive of the degree of structural flexibility and bias (propensity to form 2° structural elements such as α-helix, β-sheet, and β-turn) for intrinsically disordered regions (IDRs). Such structural resolution may ultimately be used for high-throughput screening of IDR structural transformation(s) upon binding of ligands such as drug candidates.

In-droplet hydrogen/deuterium exchange (HDX)-mass spectrometry (MS) experiments have been conducted for peptides of highly varied conformational type. A new model is presented that combines the use of protection factors (PF) from molecular dynamics (MD) simulations with intrinsic HDX rates (k _int) to obtain a structure-to-reactivity calibration curve. Using the model, the relationship of peptide structural flexibility and HDX reactivity for different peptides is elucidated. Additionally, the model is used to describe the degree of conformational flexibility and structural bias for the disease-relevant Nt17 peptide; although highly flexible, intrinsically primed for facile conversion to α-helical conformation upon binding with molecular partners imparts significant in-droplet HDX protection for this peptide. In the future, a scale may be developed whereby HDX reactivity is predictive of the degree of structural flexibility and bias (propensity to form 2° structural elements such as α-helix, β-sheet, and β-turn) for intrinsically disordered regions (IDRs). Such structural resolution may ultimately be used for high-throughput screening of IDR structural transformation(s) upon binding of ligands such as drug candidates.

In an effort to improve safety and cycling stability of liquid electrolytes, the use of dicarbonates has been explored. In this study, four dicarbonate structures with varying end groups and spacers are investigated. The effect of these structural differences on the physical and ion transport properties is elucidated, showing that the end group has a significant influence on ion transport. The solvation structure and ion transport in the dicarbonates are compared to those of the linear carbonates dimethyl carbonate (DMC) and diethyl carbonate (DEC). Although the carbonate coordination numbers (CN) are similar in the different systems, the CN from the anion is higher in dicarbonate electrolytes. At low salt concentrations, rapid solvent exchange is observed in the DMC- and DEC-containing systems, transitioning to a more correlated ion transport at high salt concentration. In contrast, the exchange of solvents around lithium ions (Li⁺) is limited in the dicarbonate systems regardless of the salt concentration, with only one carbonate group from each molecule participating in the coordination. In addition, according to the molecular dynamics simulations, Li⁺ mainly moves together with coordinating dicarbonate molecules and anion(s).

In an effort to improve safety and cycling stability of liquid electrolytes, the use of dicarbonates has been explored. In this study, four dicarbonate structures with varying end groups and spacers are investigated. The effect of these structural differences on the physical and ion transport properties is elucidated, showing that the end group has a significant influence on ion transport. The solvation structure and ion transport in the dicarbonates are compared to those of the linear carbonates dimethyl carbonate (DMC) and diethyl carbonate (DEC). Although the carbonate coordination numbers (CN) are similar in the different systems, the CN from the anion is higher in dicarbonate electrolytes. At low salt concentrations, rapid solvent exchange is observed in the DMC- and DEC-containing systems, transitioning to a more correlated ion transport at high salt concentration. In contrast, the exchange of solvents around lithium ions (Li⁺) is limited in the dicarbonate systems regardless of the salt concentration, with only one carbonate group from each molecule participating in the coordination. In addition, according to the molecular dynamics simulations, Li⁺ mainly moves together with coordinating dicarbonate molecules and anion(s).

The unique properties and versatile applications of natural deep eutectic solvents (NaDES) have sparked significant interest in the field of green chemistry. Comprised of natural components that form liquids at room temperature through strong noncovalent electrostatic interaction, these solvents are cost-effective, nontoxic, and versatile. Betaine chloride-based NaDES, in particular, have shown promise in biocatalysis and sugar extraction due to their excellent properties. Despite their potential, the complex nature of these solvents, characterized by intense hydrogen bonding and proton transfer processes, poses significant challenges. This study employs quantum molecular dynamics (ab initio MD-AIMD) to explore the intricate NaDES-microstructure formed from betaine chloride and amino acids (arginine, histidine, lysine). Our findings highlight the dynamic nature of proton transfers within these solvents, demonstrating rapid and extensive hydrogen bonding interactions. The Van Hove correlation functions reveal that proton transfers are highly mobile, facilitating the formation and breaking of covalent hydrogen bonds. This dynamic behavior is further corroborated by the radial distribution functions, which indicate significant proton exchange between amino acids and betaine cations. Chloride anions play a crucial role in maintaining the structural integrity of NaDES through strong interactions with proton donors. These findings advance our understanding of these eutectic solvents and their potential applications in sustainable chemical processes.

The unique properties and versatile applications of natural deep eutectic solvents (NaDES) have sparked significant interest in the field of green chemistry. Comprised of natural components that form liquids at room temperature through strong noncovalent electrostatic interaction, these solvents are cost-effective, nontoxic, and versatile. Betaine chloride-based NaDES, in particular, have shown promise in biocatalysis and sugar extraction due to their excellent properties. Despite their potential, the complex nature of these solvents, characterized by intense hydrogen bonding and proton transfer processes, poses significant challenges. This study employs quantum molecular dynamics (ab initio MD-AIMD) to explore the intricate NaDES-microstructure formed from betaine chloride and amino acids (arginine, histidine, lysine). Our findings highlight the dynamic nature of proton transfers within these solvents, demonstrating rapid and extensive hydrogen bonding interactions. The Van Hove correlation functions reveal that proton transfers are highly mobile, facilitating the formation and breaking of covalent hydrogen bonds. This dynamic behavior is further corroborated by the radial distribution functions, which indicate significant proton exchange between amino acids and betaine cations. Chloride anions play a crucial role in maintaining the structural integrity of NaDES through strong interactions with proton donors. These findings advance our understanding of these eutectic solvents and their potential applications in sustainable chemical processes.

Novel coumarin-triphenyliminophosphorane (TPIPP) fluorophores, synthesized via a nonhydrolytic Staudinger reaction, exhibit remarkable redox-responsive optical properties. Upon chemical and electrochemical oxidation, these compounds display a hypsochromic shift in absorption from 430 to 350 nm, accompanied by up to 11-fold fluorescence enhancement under 405 nm excitation. The fluorescence switching occurs at an electrochemical oxidation potential of approximately +2.0 V. This enhanced one-photon excited fluorescence is attributed to an emissive radical effect, stemming from in situ generated radical cations at the polarizable iminophosphorane (P=N) bond. The radical formation was confirmed by trapping experiments using tetracyanoquinodimethane, which produced characteristic absorption of radical anions around 850 nm, and by electron spin resonance studies using 5,5-dimethyl-1-pyrroline N-oxide as a spin trap. Conversely, two-photon excited fluorescence under 800 nm pulsed laser excitation decreases upon oxidation, likely due to reduced two-photon absorption resulting from altered π-conjugation. This work demonstrates that external redox modulation can induce significant changes in absorption profiles and enable switching between enhanced one-photon and diminished two-photon excited fluorescence, highlighting the potential of leveraging the controllable radical character of the P=N bond in designing redox-responsive fluorophores.

Novel coumarin-triphenyliminophosphorane (TPIPP) fluorophores, synthesized via a nonhydrolytic Staudinger reaction, exhibit remarkable redox-responsive optical properties. Upon chemical and electrochemical oxidation, these compounds display a hypsochromic shift in absorption from 430 to 350 nm, accompanied by up to 11-fold fluorescence enhancement under 405 nm excitation. The fluorescence switching occurs at an electrochemical oxidation potential of approximately +2.0 V. This enhanced one-photon excited fluorescence is attributed to an emissive radical effect, stemming from in situ generated radical cations at the polarizable iminophosphorane (P=N) bond. The radical formation was confirmed by trapping experiments using tetracyanoquinodimethane, which produced characteristic absorption of radical anions around 850 nm, and by electron spin resonance studies using 5,5-dimethyl-1-pyrroline N-oxide as a spin trap. Conversely, two-photon excited fluorescence under 800 nm pulsed laser excitation decreases upon oxidation, likely due to reduced two-photon absorption resulting from altered π-conjugation. This work demonstrates that external redox modulation can induce significant changes in absorption profiles and enable switching between enhanced one-photon and diminished two-photon excited fluorescence, highlighting the potential of leveraging the controllable radical character of the P=N bond in designing redox-responsive fluorophores.

Neutron-Transformer Reflectometry Advanced Computation Engine (N-TRACE), a neural network model using a transformer architecture, is introduced for neutron reflectometry data analysis. It offers fast, accurate initial parameter estimations and efficient refinements, improving efficiency and precision for real-time data analysis of lithium-mediated nitrogen reduction for electrochemical ammonia synthesis, with relevance to other chemical transformations and batteries. Despite limitations in generalizing across systems, it shows promises for the use of transformers as the basis for models that could accelerate traditional approaches to modeling reflectometry data.

Neutron-Transformer Reflectometry Advanced Computation Engine (N-TRACE), a neural network model using a transformer architecture, is introduced for neutron reflectometry data analysis. It offers fast, accurate initial parameter estimations and efficient refinements, improving efficiency and precision for real-time data analysis of lithium-mediated nitrogen reduction for electrochemical ammonia synthesis, with relevance to other chemical transformations and batteries. Despite limitations in generalizing across systems, it shows promises for the use of transformers as the basis for models that could accelerate traditional approaches to modeling reflectometry data.