化学最新文献

We present an integrated multiscale framework that combines the Density Matrix Renormalization Group (DMRG) with a polarizable fluctuating-charge (FQ) force field for the simulation of electronic excited states in solution. The method exploits the capabilities of DMRG to accurately describe systems with strong static correlation, while the FQ model provides a self-consistent and physically grounded representation of solvent polarization within a QM/MM embedding. The DMRG/FQ approach is applied to representative solvated systems, using extensive molecular dynamics sampling. The method yields reliable excitation energies, solvatochromic shifts, and a close agreement with available experimental data. The results highlight the importance of mutual polarization for capturing specific solute-solvent interactions, particularly in systems where hydrogen bonding or directional interactions play a dominant role.

Uranium, being chemo-radiotoxic, requires confinement within a safe environment to prevent severe health consequences. Chelation therapy, utilizing multidentate ligands, is a widely accepted approach for developing effective uranium decorporation treatments. In this study, a systematic investigation of uranium complexation by pyrazine-2-amidoxime (PAM) was undertaken for the first time, employing chemical speciation, in vitro studies, and computational calculations. Potentiometric and spectrophotometric titrations, corroborated by electrospray ionization mass spectrometry (ESI-MS), revealed that PAM forms 1:1 (ML) and 1:2 (ML₂) complexes with the uranyl ion (UO₂²⁺). PAM acts as a bidentate chelator, coordinating via the oxygen and nitrogen atoms of amidoxime, with high stability constants (log β) of 8.54 ± 0.04 for ML and 16.33 ± 0.07 for ML₂ complexes. Density functional theory (DFT) calculations further elucidated the preferred coordination mode, donor-site contributions, and electronic factors governing the stability of the PAM-uranyl complexes. Ex vivo experiments with human erythrocytes (RBCs) confirmed that PAM is cytocompatible and significantly enhanced uranium decorporation from human RBCs, facilitating removal of 25-40% of uranium at 100-200 μM compared to uranium-treated controls. Additionally, PAM effectively reduced uranium content by 10-20% from physiologically relevant proteins such as human serum albumin and from native human blood plasma.

The development of technologies for CO₂ sequestration and its conversion into value-added chemicals has received considerable and growing attention. However, achieving high conversion efficiency and product selectivity under mild conditions remains a major challenge. This study investigates the photocatalytic CO₂ reduction activity of Zr-based porphyrinic MOF-545 derivatives synthesized by varying the percentages of two porphyrin linkers: tetrakis(4-carboxyphenyl)porphyrin (TCPP) and its β-pyrrolic chlorinated analogue (TCPPCl₈). A comprehensive set of spectroscopic and analytical techniques was employed to characterize the materials, revealing the impact of linker chlorination on the optical band gap, particle size and crystallinity. The incorporation of chlorine-substituted linkers significantly enhanced the photocatalytic activity. Notably, under visible light irradiation and using triethanolamine (TEOA) as a sacrificial electron donor, the MOF-545 derivative containing 50% TCPPCl₈ achieved the highest formate production, with a rate 2.6 times greater than that of pristine MOF-545, with a production rate of 625 μmol g^-1 h^-1 after 2 h. Density Functional Theory (DFT) calculations were also performed to gain insight into the electronic properties of the chlorinated porphyrinic materials. These calculations showed the stabilization of both the HOMO and LUMO energy levels upon chlorination of the porphyrin linkers, with a more pronounced stabilisation of the LUMO, leading to a smaller band gap, in line with optical measurements. Additionally, the stabilisation of the HOMO level is expected to increase the oxidizing power of the photogenerated holes, thus facilitating TEOA oxidation and enhancing the overall photocatalytic activity, and this rationalizes the experimental observations.

Dehydroamino acids are valuable building blocks for the construction of artificially designed functional peptides. However, effective approaches for the preparation of dehydroselenocysteine derivatives remain largely unexplored. Herein, we disclose a concise and direct method for the synthesis of dehydroselenocysteine derivatives from cysteine derivatives using diphenyl diselenide.

The multiscale model combining the multiconfigurational self-consistent field (MCSCF) method with the fully atomistic polarizable Fluctuating Charges (FQ) force field (Sepali, C.; et al. J. Chem. Theory Comput. 2024, 20, 9954-9967) is here extended to the calculation of analytical nuclear gradients. The gradients are derived from first-principles, implemented in the OpenMolcas package, and validated against numerical references. The resulting MCSCF/FQ nuclear gradients are employed to simulate vibronic absorption spectra of aromatic molecules in aqueous solution, namely benzene and phenol. By integrating this approach with molecular dynamics simulations, both solute conformational flexibility and the dynamical aspects of solvation are properly captured. The computed spectra reproduce experimental profiles and relative band intensities with remarkable accuracy, demonstrating the capability of the MCSCF/FQ model to simultaneously describe the multireference character of the solute and its interaction with the solvent environment.

We benchmark exchange-correlation functionals for the calculation of fundamental band gaps of inorganic nitrides. These include conventional functionals such as the local density approximation (LDA), the generalized-gradient (Perdew-Burke-Ernzerhof) approximation (PBE), simple Slater exchange functionals (SLOC), specialized LDA/GGA-derived high local exchange (HLE16) and Armiento-Kümmel semilocal (AK13) functionals, meta-GGA functionals including TASK, the modified Becke-Johnson functional (mBJ), and Heyd-Scuseria-Ernzerhof (HSE06) hybrid functional, as well as quasiparticle GW theory. Since inorganic nitrides remain strongly under-represented in previous extensive benchmark studies, the current subdatabase contributes towards building a future large-scale balanced materials compilation of band gaps to benchmark theory. From a literature survey, we carefully collect 25 binary and 11 ternary nitrides with a focus on semiconductors spanning the periodic table, including ionic Li₃N, antibixbyite-structured X₃N₂ (X = Be, Mg, Ca), early transition metals and lanthanides (e.g., ScN, YN, and LaN), ultrahard Th₃P₄-type structured M₃N₄ (M = Zr, Hf) compounds, promising photocatalysts Ta₃N₅, different polymorphs of III-V reference covalent nitrides (BN, AlN, GaN), and many M₃N₄ polymorphs (M = C, Si, and Ge) such as spinel-structured phases. Consistent with previous extensive benchmark tests, conventional LDA/PBE unsystematically largely underestimate band gaps with mean absolute errors (MAE) of >1.0 eV and mean absolute percentage errors (MAPE) of about 50%. Simple Slater exchange functional, SLOC, the GGA-derived AK13LDA and HLE16 functionals show improvement over LDA/PBE with MAE of 0.5-0.6 eV (MAPE ∼ 20-25%) with mBJ and HSE06 being the most accurate, with MAE = 0.30 and 0.28 eV (MAPE 12.1% and 11.1%), respectively. Strategies for the development of machine learning and the choice of appropriate exchange-correlation functionals for high-throughput large-scale material screening are discussed in light of these results.

Photothermal effect using mild light irradiation has emerged as an interesting strategy in modern synthetic chemistry due to its rapid reaction with high selectivity and spatiotemporal control over conventional heating. However, applying photothermal conversion to carry out organic reactions efficiently using carbon nanomaterials remained largely uncharted. To address this, herein, we report for the first time, graphene oxide (GO) as the photothermal agent to perform ring-closing metathesis (RCM) under 940 nm NIR LED light, as well as solar simulator and natural sunlight, using Grubbs-II catalyst to rapidly synthesize dihydro-pyrroles in high yield with excellent GO recyclability. Theoretical calculation unveiled that this photothermal RCM efficiency originated from the cumulative synergy between substrate-GO absorption energy, activation barrier, and nonradiative relaxation rate which emerged as the predominant contributor for the overall reaction outcome. The RCM product can be further functionalized through Pd-catalyzed Heck coupling to forge various fluorophores for efficient imaging of endoplasmic reticulum (ER), mitochondria, and Golgi apparatus (GA) in HCT-116 colon cancer cells. This GO-mediated photothermal RCM can open a new direction toward synthesizing complex organic molecules with ease and high yield for biomedical applications.

Accurate and convenient detection of epinephrine (Ep) is critical for diagnosing neurological disorders and monitoring emergency medications. In this study, a ratiometric fluorescent platform was developed for Ep detection by integrating cysteine-functionalized carbon dots with gold ions (Cys-CDs/Au³⁺). The platform relied on Au³⁺-mediated oxidation of epinephrine to generate a fluorescence response, which is further enhanced by boric acid. Two detection modes were established: fluorescence assay and smartphone-assisted RGB analysis, demonstrating limits of detection (LOD) of 0.12 μM and 0.85 μM, respectively. The platform enabled accurate quantification of Ep in injections and artificial cerebrospinal fluid (aCSF). Furthermore, principal component analysis (PCA) facilitated discrimination among multiple catecholamines by reducing the dimensionality of fluorescence spectral data. This work provides a versatile platform for Ep detection and catecholamine discrimination.

Context: Elucidating the role of the hydrophobic groove in mineralocorticoid receptor (MR)-spironolactone interactions is important for structure-based drug design, receptor modulation, and the development of more selective MR antagonists. Despite the clinical importance of spironolactone, the contribution of the hydrophobic groove, particularly residues M807, F829, M845, C849, and M852, remains underexplored. Here, we demonstrate through molecular dynamic simulations that these hydrophobic residues, together with polar residue N770, stabilize the thioacetyl moiety of spironolactone. Binding free energy calculations of the hydrophobic groove, both with the complete binding site and with the groove alone, demonstrate the impact of the groove's hydrophobicity along with the polar residues N770, Q776, and R817. Simulation results, supported by statistical analysis, highlight the groove's structural and energetic significance. Site-directed mutagenesis targeting residues F829, M845, and C849 further clarifies their role in the binding mechanism, offering insights for rational drug design and biomarker development.

Methods: The crystal structure of the MR-spironolactone complex (PDB ID: 3VHU) was retrieved and mutated using COOT. Mutant complexes were constructed and subjected to 1 μs molecular dynamics simulations using GROMACS. Binding free energies were calculated via MM/PBSA. Residue-ligand interactions were analyzed from MD trajectories using LigPlot + and GROMACS tools. Statistical significance of residue contributions was assessed using ANOVA, comparing polar and hydrophobic residue mutations across simulated complexes.