Strength and Character of R–X···π Interactions Involving Aromatic Amino Acid Sidechains in Protein-Ligand Complexes Derived from Crystal Structures in the Protein Data Bank

Unraveling the mechanism of iodate adsorption by anthocyanin-rich fruit waste as green adsorbents for Applications of radioactive iodine remediation in water environment

In aquatic settings, radioactive iodine from nuclear waste can exist as iodate (IO3-). This study explored the efficiency and mechanism of IO3- adsorption by minimally modified anthocyanin-based adsorbents. Pomegranate peels and mangosteen pericarps were selected from an initial screening test and could remove over 70% of 10 mg/L IO3-. The adsorbents yielded adsorption capacity (q) of 9.59 mg/g and 2.31 mg/g, respectively, at room temperature. At 5 °C, q values increased to 14.5 and 5.13 mg/g, respectively. Pomegranate peels showed superior performance, with approximately 4 times the anthocyanin content of mangosteen pericarps. Both adsorbents took 120 min to reach adsorption equilibrium, and no desorption was observed after 8 days (I-131 half-time). Confirmation of physisorption was indicated by the fit of the pseudo-first-order reaction model, negative entropy (exothermic), and negative activation energy (Arrhenius equation). IO3- inclusion was confirmed through adsorbent surface modifications in scanning electron microscope images, the increased iodine content post-adsorption in energy-dispersive X-ray spectroscopy analysis, and alterations in peaks corresponding to anthocyanin-related functional groups in Fourier transform infrared spectroscopy analysis. X-ray absorption near-edge spectroscopy at 4564.54 eV showed that iodine was retained in the form of IO3-. Through the computational analysis, electrostatic forces, hydrogen bonds, and π-halogen interactions were deduced as mechanisms of IO3- adsorption by anthocyanin-based adsorbents. Anthocyanin-rich fruit wastes emerged as sustainable materials for eliminating IO3- from water.

Synthesis and structure-activity relationships of pyrazole-based inhibitors of meprin α and β

Targeting metalloproteinases has been in the focus of drug design for a long time. However, meprin α and β emerged as potential drug targets just recently and are linked to several diseases with different pathological background. Nevertheless, the validation of meprins as suitable drug targets still requires highly potent and selective inhibitors as chemical probes to elucidate their role in pathophysiology. Albeit highly selective inhibitors of meprin β have already been reported, only inhibitors of meprin α with modest activity or selectivity are known. Starting from recently reported heteroaromatic scaffolds, the aim of this study was the optimisation of meprin α and/or meprin β inhibition while keeping the favourable off-target inhibition profile over other metalloproteases. We report potent pan-meprin inhibitors as well as highly active inhibitors of meprin α with superior selectivity over meprin β. The latter are suitable to serve as chemical probes and enable further target validation.

Studying the Mechanism of Interaction of Doxofylline with Human Lysozyme: A Biophysical and In Silico Approach

In this study, multiple spectroscopic and computational methods were utilized to investigate the binding mechanism of doxofylline with lysozyme. The in vitro methods were used to obtain the binding kinetics and thermodynamics. UV-vis spectroscopy indicated the formation of complex between doxofylline and lysozyme. The Gibb's free energy and binding constant from UV-vis data was obtained as -7.20 kcal M^-1 and 1.929 × 10⁵ M^-1, respectively. Doxofylline successfully quenched the fluorescence of lysozyme, confirming the formation of complex. The k_q and K_sv values for the quenching of lysozyme's fluorescence by doxofylline were 5.74 × 10¹¹ M^-1 s^-1 and 3.32 × 10³ M^-1, respectively. These values signified a moderate binding affinity between doxofylline and lysozyme. In synchronous spectroscopy, red shifts were observed for indicating the changes in microenvironment of lysozyme following the binding of doxofylline. The secondary structural analysis was determined using circular dichroism (CD) which revealed an increase in % α-helical as a result of doxofylline interaction. The binding affinity and flexibility of lysozyme upon complexation have been revealed via molecular docking and molecular dynamic (MD) simulations, respectively. According to the many parameters of the MD simulation, the lysozyme-doxofylline complex was stable under physiological conditions. All during the simulation time, hydrogen bonds were continuously present. The MM-PBSA binding energy for lysozyme and doxofylline binding was found to be -30.55 kcal mol^-1.

New O- and N-N-Bridging Complexes of Tc(V), the Role of the Nitrogen Atom Position in Aromatic Rings: Reaction Mechanism, Spectroscopy, DTA, XRD and Hirshfeld Surface Analysis

In this work, O- and N-N-bridging complexes of technetium (V), previously known only for rhenium, were obtained for the first time. Tc(V) complexes with pyridazine (pyd), 1,2,4-triazole (trz), 3,5-dimethylpyrazole (dmpz) and pyrimidine (pyr) were obtained. In three complexes [{TcOCl₂}₂(μ-O)(μ-pyd)₂], [{TcOCl₂}₂(μ-O)(μ-trz)₂]·Htrz·Cl and [{TcO(dmpz)₄}(μ-O)(TcOCl₄)] two technetium atoms are linked by a Tc-O-Tc bond, and in the first two, Tc atoms are additionally linked by a Tc-N-N-Tc bond through the nitrogen atoms of the aromatic rings. We determined the role of nitrogen atom position in the aromatic ring and the presence of substituents on the formation of such complexes. For the first time, a reaction mechanism for the formation of such complexes was proposed. This article details the crystal structures of four new compounds. The work describes in detail the coordination of Tc atoms in the obtained structures and the regularities of the formation of crystal packings. The spectroscopic properties of the obtained compounds and their mother solutions were studied. The decomposition temperatures of the described complexes were determined. An assumption was made about the oligomerization of three-bridged complexes based on the results of mass spectrometry. Through the analysis of non-valent interactions in the structures, π-stacking, halogen-π and CH-π interactions were found. An analysis of the Hirshfeld surface for [{TcOCl₂}₂(μ-O)(μ-pyd)₂], [{TcOCl2}2(μ-O)(μ-trz)₂] and their rhenium analogues showed that the main contribution to the crystalline packing is made by interactions of the type Hal···H/H···Hal (45.4-48.9%), H···H (10.2-15.8%), and O···H/H···O (9.4-16.5%).

Design and Synthesis of Coumarin Derivatives as Cytotoxic Agents through PI3K/AKT Signaling Pathway Inhibition in HL60 and HepG2 Cancer Cells

In this study, a series of coumarin derivatives, either alone or as hybrids with cinnamic acid, were synthesized and evaluated for their cytotoxicity against a panel of cancer cells using the MTT assay. Then, the most active compounds were inspected for their mechanism of cytotoxicity by cell-cycle analysis, RT-PCR, DNA fragmentation, and Western blotting techniques. Cytotoxic results showed that compound (4) had a significant cytotoxic effect against HL60 cells (IC₅₀ = 8.09 µM), while compound (8b) had a noticeable activity against HepG2 cells (IC₅₀ = 13.14 µM). Compounds (4) and (8b) mediated their cytotoxicity via PI3K/AKT pathway inhibition. These results were assured by molecular docking studies. These results support further exploratory research focusing on the therapeutic activity of coumarin derivatives as cytotoxic agents.

Direct detection of the crystal form of an active pharmaceutical ingredient in tablets by X-ray absorption fine structure spectroscopy

Different crystal forms of active pharmaceutical ingredients (APIs) may display variations in physicochemical properties. During the drug development process, the definitive purpose is to maintain homogeneous quality in a single crystalline form. Hence, it is important to evaluate and understand the properties of each crystal form of APIs in pharmaceutics. In this study, forms 0, Ⅰ, Ⅱ, III of bromhexine hydrochloride, and form S of bromhexine were characterized by the commonly used methods X-ray powder diffraction, thermogravimetry-differential thermal analysis, and single crystal structure X-ray diffraction. Additionally, X-ray absorption fine structure spectroscopy (XAFS), a seldom used method in the pharmaceutics discipline was also applied to explore the chemical environment of bromine atoms in forms 0, Ⅰ, Ⅱ and S as well as chloride ions in forms 0 to Ⅱ. The XAFS spectra of each form were different from each of the other forms which indicated the chemical environment around target elements in the crystal polymorphs were distinct. Then, we measured the commercial bromhexine hydrochloride tablets with XAFS measurement and found that XAFS could distinguish the crystal form in the tablets. Hence, we demonstrated that XAFS measurements would be applicable as one of the methods for the direct detection of APIs in the tablets.

Supramolecular architectures sustained by delocalised C–I⋯π(arene) interactions in molecular crystals and the propensity of their formation

A survey of delocalised C–I⋯π(chelate ring) interactions is presented.

Stepwise coordination isomerism of 2D networks: adsorption of diiodomethane into crystals and recognition in SCSC mode

3CH₂Cl₂·2C₂H₅OH@[CdI₂L] with a new 2D topology of {4³·6²·8} are isomerized into new single crystals of 4C₄H₈O@[CdI₂L]. Interestingly, both crystals are integral to an efficient and tolerant matrix for recognition of diiodomethane in the SCSC mode.

3-(2,5-Dichlorothiophen-3-yl)-5-(2,4-dimethoxyphenyl)-1-methyl-4,5-dihydro-1H-pyrazole

In the title compound, C16H16Cl2N2O2S, the pyrazole ring has an envelope conformation with the C atom bearing the phenyl ring being the flap. The dihedral angles between the central pyrazole ring (all atoms) and pendant thiophene and phenyl rings are 2.00 (14) and 81.49 (12)°, respectively. In the crystal, weak C—H...O, Cl...π and π–π stacking interactions link the molecules into a three-dimensional network.