Stoichiometry Of Complexes Research Articles

Probing Host‐Guest Inclusion Complex of DHP with β‐CD in Augmenting Bioavailability to Boost Biochemical Applications Optimized by Physicochemical and Molecular Docking

AbstractThis research aims to develop the inclusion complex of 2, 4‐diamino‐6‐hydroxypyrimidine (DHP) with β‐cyclodextrin (β‐CD) using an inclusion process, and to investigate the effect of inclusion on the photo stability and bioactivity of DHP. The formation of DHP‐β‐CD inclusion complex has been examined by means of physicochemical as well as spectroscopic techniques (1H NMR, FT‐IR, PXRD and SEM) suggesting the successful inclusion of the DHP molecule into the β‐CD cavity. The 1 : 1 stoichiometry of the inclusion complex was validated through Job's plot. β‐CD displayed a fairly strong affinity (Ka =889.67 M−1) for DHP, indicating that the binding process is thermodynamically feasible. A molecular docking study speculated the most preferred orientation of DHP molecule within the binding pocket of β‐CD cavity. The photostability of DHP was found to improve on complexation with β‐CD. In vitro antibacterial activity test demonstrated that the DHP‐β‐CD inclusion complex displayed better activity than pure DHP. DHP‐β‐CD inclusion complex (IC50 =240.04 μM) also exhibited relatively significant in vitro cytotoxic activity than pure DHP towards the human kidney cancer cell line (ACHN). These results reveals that the inclusion of DHP using β‐CD could lead to stabilization of DHP and efficient display of its bioactivity.

Dyeing behaviour of iron(III)-gallic acid complexes on wool as function of pH-dependent iron(III)-complex stoichiometry

Iron complexes with polyphenolics e.g. gallotannins and flavonoids have been used since ancient times for coloration of textiles, painting and preparation of inks. The composition of iron gall inks on historical artefacts has been investigated with modern instrumental methods. However the dyeing behaviour of iron-complexes with polyphenols still bases on empirical knowledge. In this study Fe(III)-complexes with gallic acid were used as model system to elucidate their pH dependent sorption and dyeing behaviour on wool. At dyebath pH 3 high sorption of Fe(III)-gallic acid complexes was observed, however darker dyeings were obtained at dyebath pH 4. Model calculations for the complex species present in the dyebath indicated the presence of the binary complex [Fe(III)(GA2−)]+ as main species at pH 3, while at pH 4 the ternary species [Fe(III)(GA2−)2]- prevails. The dye sorption bases on Van-der-Waals forces, while ionic interactions between Fe(III)-complex and keratin are of minor relevance. The elaborated theoretical model also explains the influence of dyebath pH in dyeing with gallotannins, polyphenols and flavonoids in presence of iron salts and thus is of particular relevance for improved utilisation of these natural colorants.

Deciphering Pathways and Thermodynamics of Protein Assembly Using Native Mass Spectrometry.

Protein oligomerization regulates many critical physiological processes, and its dysregulation can contribute to dysfunction and diseases. Elucidating the assembly pathways and quantifying their underlying thermodynamic and kinetic parameters are crucial for a comprehensive understanding of biological processes and for advancing therapeutics targeting abnormal protein oligomerization. Established binding assays, with limited mass precision, often rely on simplified models for data interpretation. In contrast, high-resolution native mass spectrometry (nMS) can directly determine the stoichiometry of biomolecular complexes in vitro. However, quantification is hindered by the fact that the relative abundances of gas-phase ions generally do not reflect solution concentrations due to nonuniform response factors. Recently, slow mixing mode (SLOMO)-nMS, which can quantify the relative response factors of interacting species, has been demonstrated to reliably measure the affinity (Kd) of binary biomolecular complexes. Here, we introduce an extended form of SLOMO-nMS that enables simultaneous quantification of the thermodynamics in multistep association reactions. Application of this method to homo-oligomerization of concanavalin A and insulin confirmed the reliability of the assay and uncovered details about the assembly processes that had previously resisted elucidation. Results acquired using SLOMO-nMS implemented with charge detection shed new light on the binding of recombinant human angiotensin-converting enzyme 2 and the SARS-CoV-2 spike protein. Importantly, new assembly pathways were uncovered, and the affinities of these interactions, which regulate host cell infection, were quantified. Together, these findings highlight the tremendous potential of SLOMO-nMS to accelerate the characterization of protein assembly pathways and thermodynamics and, in so doing, enhance fundamental biological understanding and facilitate therapeutic development. https://orcid.org/0000-0002-3389-7112.

Novel Co(II), Cu(II) and Zn(II) complexes derived from thiazole containing Schiff base ligands: Green synthesis, antimicrobial and anti-cancer studies

Six novel metal complexes of Co(II), Cu(II), and Zn(II) were synthesized using a microwave-assisted method. These complexes were derived from Schiff base ligands prepared through the condensation of 4-(p-fluorophenyl)-5-methyl-2-aminothiazole with 3-methoxysalicyldehyde (L1) and 2-hydroxynaphthaldehyde (L2). Characterization techniques, including UV–vis, IR, NMR, and HR-MS confirm the tridentate nature of Co(II), Zn(II), and bidentate nature of Cu(II) complexes. Elemental and thermogravimetric analysis showed 1:2 (M: L) stoichiometry in metal complexes. Meanwhile, magnetic susceptibility and powder X-ray diffraction express the geometry and crystal systems of complexes. The antimicrobial analysis of the synthesized compounds indicates Cu(II) complexes have greater potency against gram-positive bacterial and fungal strains while Zn(II) complexes show a greater zone of inhibition against gram-negative bacterial strains. Moreover, MIC values of the most potent complexes [Cu(L2)2] and [Zn(L2)2] range from 190-375 µg/mL. Furthermore, ligands and their complexes have been tested for anticancer potential against MDA-MB 231 and A549 cell lines by MTT assay. [Zn(L1)2] and [Zn(L2)2] complexes were found to have potent activity with IC50 values of 16.7 µM, 24.1 µM, and 8.7 µM, 13.4 µM respectively on MDA-MB-231 and A549 cell lines compared to other complexes and parent ligands. Molecular docking study performed using the PyRx 0.8 (with RF-Score V2 scoring function) program against EGFR (PDB: 5XGM) showed strong binding interactions which supports the experimental results.

Novel Schiff base decorated cyclotriphosphazene chemosensors for Fe and Cu ions detection

In this study, new 2-aminobenzothiazole derivative Schiff base decorated cyclotriphosphazene compounds (SBCTP 1 and 2), which are likely to have chemical sensor properties, were designed and synthesized successfully. The compounds were structurally characterized by mass analysis and NMR (1H, 13C and 31P) spectroscopies. Photophysical and chemosensory properties of SBCTP 1 and 2 against some analytes were examined by UV–vis and Fluorescence spectrophotometry. While a significant increase was observed in the UV–vis absorption signals observed at 350 nm with the addition of Fe3+ and Fe2+ ions and a new absorption band was observed at 290 nm with the addition of Cu2+. In addition, according to Job's plot obtained from UV–vis absorption titrations, the complex stoichiometries of SBCTP 1 and 2 with selective analytes were determined as 1:1 (L/M) and 1:2 (L/M), respectively. The selective interaction of donor atoms on SBCTP 1 and 2 with Cu2+, Fe2+ and Fe3+ ions give these compounds chemosensory properties. This study showed that the synthesized Schiff base decorated cyclotriphosphazene compounds (SBCTP 1 and 2) could be new chemosensors with high selective and immediate sensitivity for the detection of iron and copper ions.

Synthesis of 2‐Pyridyl Based N(1)‐Substituted Thiosemicarbazonates of Nickel(II) as Bioactive Materials against MRSA, S. aureus, S. typhimurium 2, and K. pneumonia

AbstractIn this investigation, the bio‐activity and biosafe potential of thiosemicarbazonates of nickel(II) as well as that of ligands are described. Reactions of nickel(II) acetate with a series of thiosemicarbazones, {R1(py)C2=N3‐N2(H)‐C1(=S)‐NHR; R1=py, Me, H and Ph; R=H, Me, Et, Ph}, led to the loss of acidic hydrazinic N2(H) protons, and resulted in the formation of six‐coordinated complexes of stoichiometry, [Ni(N,N,S−L)2], where anionic N,N,S−L=py2tsc‐NHR, 1–4; apytsc‐NHR, 5–8; pytsc‐NHR, 9–12 and bpytsc‐NHR, 13–16. All these complexes have been characterized using analytical data, IR and UV‐visible spectroscopy and ESI‐mass spectrometry. The single crystal X‐ray crystal structure of several complexes {2(Me), 7(Et), 11(Et), 12(Ph), 13(H),14(Me) and 15(Et)} were also determined. Thio‐ligands coordinate to nickel(II) through pyridyl nitrogen‐N4, azomethine nitrogen‐N3 and thiolato sulfur atoms, resulting in the formation of homoleptic complexes with octahedral structures. Complexes 1–16 and uncoordinated thiosemicarbzones, were evaluated for their antimicrobial activity, in terms of ZOI, MIC, time kill assay and in vitro percent cell viability MTT assay, against clinical isolate methicillin‐resistant Staphylococcus aureus (MRSA), Staphylococcus aureus (MTCC740), Klebsiella pneumonia (MTCC109), Salmonella typhimurium (MTCC1251), and Candida albicans (MTCC227), a yeast. Both the ligands and their metal complexes exhibited moderate to high bioactivity, and were found to be biosafe with high cell viability, 88–92 %, in several cases.

Metformin hydrolase is a recently evolved nickel-dependent heteromeric ureohydrolase

The anti-diabetic drug metformin is one of the most widely prescribed medicines in the world. Together with its degradation product guanylurea, it is a major pharmaceutical pollutant in wastewater treatment plants and surface waters. An operon comprising two genes of the ureohydrolase family in Pseudomonas and Aminobacter species has recently been implicated in metformin degradation. However, the corresponding proteins have not been characterized. Here we show that these genes encode a Ni2+-dependent enzyme that efficiently and specifically hydrolyzes metformin to guanylurea and dimethylamine. The active enzyme is a heteromeric complex of α- and β- subunits in which only the α-subunits contain the conserved His and Asp residues for the coordination of two Ni2+ ions in the active site. A crystal structure of metformin hydrolase reveals an α2β4 stoichiometry of the hexameric complex, which is unprecedented in the ureohydrolase family. By studying a closely related but more widely distributed enzyme, we find that the putative predecessor specifically hydrolyzes dimethylguanidine instead of metformin. Our findings establish the molecular basis for metformin hydrolysis to guanylurea as the primary pathway for metformin biodegradation and provide insight into the recent evolution of ureohydrolase family proteins in response to an anthropogenic compound.

Density functional modeling of ternary Am(III) hydroxo complexes with Ca or Mg counterions. Do Mg stabilized species exist?

We carried out density functional computations to investigate experimentally suggested ternary Ca–Am(III)–OH and possible Mg–Am(III)–OH complexes in water. We confirmed the experimental stoichiometry for the Ca complexes and their relative stability. For the Mg complexes, we find comparable or weaker complexation. This finding is in agreement with experimental observations. We demonstrate that explicit solvation of counterions is important when comparing Ca and Mg species. For the Ca complexes this has a minimal effect on their relative stability. Contrariwise, Mg complexes exhibit a lower stability and are highly sensitive to explicit short-range solvation effects. Explicit Mg2+ solvation significantly altered both absolute and relative formation energies compared to a simpler model. These findings highlight the crucial role of incorporating explicit short-range solvation effects in accurate computational modeling when small and highly charged ions are treated.

Engineering Supramolecular Hydrogels via Reversible Photoswitching of Cucurbit[8]uril-Spiropyran Complexation Stoichiometry.

The integration of photoswitchable supramolecular units into hydrogels allows for spatiotemporal control over their nanoscale topological network and macroscale properties using light. Nevertheless, the current availability of photoswitchable supramolecular interactions for the development of such materials remains limited. Here, the molecular design of a novel photoswitchable cucurbit[8]uril-spiropyran host-guest complex exhibiting fast and reversible switching of binding ratios between 1:2 and 1:1 is reported. Photoswitchable complexation stoichiometries are rationally exploited as (de)crosslinking units in multiple polymers for the design of supramolecular hydrogels displaying highly dynamic and switchable features that are spatiotemporally controlled by light. The hydrogels exhibit rapid reversible mechanical softening-hardening upon alternating irradiation with blue and UV light, which is used to significantly accelerate and improve the efficiency of self-healing and shape-remolding of hydrogels. Furthermore, spiropyran endows such materials with unique reversible photochromic properties for reproducible patterning/erasing and information storage. Using a dual-light-assisted extrusion process, meter-scale hydrogel fibers with enhanced structural integrity and photoswitchable ionic conductivity are constructed and woven into various slidable knots and fluorescent shapes. This work represents an innovative molecular design strategy for advancing the development of spatiotemporally engineered supramolecular hydrogels using light and opens avenues for their prospective applications in dynamic materials and adaptive systems.

Structural basis for lipid transfer by the ATG2A-ATG9A complex.

Autophagy is characterized by the formation of double-membrane vesicles called autophagosomes. Autophagy-related proteins (ATGs) 2A and 9A have an essential role in autophagy by mediating lipid transfer and re-equilibration between membranes for autophagosome formation. Here we report the cryo-electron microscopy structures of human ATG2A in complex with WD-repeat protein interacting with phosphoinositides 4 (WIPI4) at 3.2 Å and the ATG2A-WIPI4-ATG9A complex at 7 Å global resolution. On the basis of molecular dynamics simulations, we propose a mechanism of lipid extraction from the donor membranes. Our analysis revealed 3:1 stoichiometry of the ATG9A-ATG2A complex, directly aligning the ATG9A lateral pore with ATG2A lipid transfer cavity, and an interaction of the ATG9A trimer with both the N-terminal and the C-terminal tip of rod-shaped ATG2A. Cryo-electron tomography of ATG2A liposome-binding states showed that ATG2A tethers lipid vesicles at different orientations. In summary, this study provides a molecular basis for the growth of the phagophore membrane and lends structural insights into spatially coupled lipid transport and re-equilibration during autophagosome formation.

Impact of mineral and non-mineral sources of iron and sulfur on the metalloproteome of Methanosarcina barkeri.

Methanogens often inhabit sulfidic environments that favor the precipitation of transition metals such as iron (Fe) as metal sulfides, including mackinawite (FeS) and pyrite (FeS2). These metal sulfides have historically been considered biologically unavailable. Nonetheless, methanogens are commonly cultivated with sulfide (HS-) as a sulfur source, a condition that would be expected to favor metal precipitation and thus limit metal availability. Recent studies have shown that methanogens can access Fe and sulfur (S) from FeS and FeS2 to sustain growth. As such, medium supplied with FeS2 should lead to higher availability of transition metals when compared to medium supplied with HS-. Here, we examined how transition metal availability under sulfidic (i.e., cells provided with HS- as sole S source) versus non-sulfidic (cells provided with FeS2 as sole S source) conditions impact the metalloproteome of Methanosarcina barkeri Fusaro. To achieve this, we employed size exclusion chromatography coupled with inductively coupled plasma mass spectrometry and shotgun proteomics. Significant changes were observed in the composition and abundance of iron, cobalt, nickel, zinc, and molybdenum proteins. Among the differences were alterations in the stoichiometry and abundance of multisubunit protein complexes involved in methanogenesis and electron transport chains. Our data suggest that M. barkeri utilizes the minimal iron-sulfur cluster complex and canonical cysteine biosynthesis proteins when grown on FeS2 but uses the canonical Suf pathway in conjunction with the tRNA-Sep cysteine pathway for iron-sulfur cluster and cysteine biosynthesis under sulfidic growth conditions.IMPORTANCEProteins that catalyze biochemical reactions often require transition metals that can have a high affinity for sulfur, another required element for life. Thus, the availability of metals and sulfur are intertwined and can have large impacts on an organismismal biochemistry. Methanogens often occupy anoxic, sulfide-rich (euxinic) environments that favor the precipitation of transition metals as metal sulfides, thereby creating presumed metal limitation. Recently, several methanogens have been shown to acquire iron and sulfur from pyrite, an abundant iron-sulfide mineral that was traditionally considered to be unavailable to biology. The work presented here provides new insights into the distribution of metalloproteins, and metal uptake of Methanosarcina barkeri Fusaro grown under euxinic or pyritic growth conditions. Thorough characterizations of this methanogen under different metal and sulfur conditions increase our understanding of the influence of metal availability on methanogens, and presumably other anaerobes, that inhabit euxinic environments.

Inclusion complexes of α-cyclodextrin with p-aminobenzoic acid and nicotinic acid: Crystal structure, DSC and IR spectroscopy analysis in solid state and 1H NMR and ITC calorimetric studies of complexation in solutions

In this work, inclusion complexes of α-cyclodextrin with p-aminobenzoic acid (PABA) and nicotinic acid (NIK) were studied. Solid-state complexes were obtained and studied with single-crystal X-ray diffraction, powder X-ray diffraction, differential scanning calorimetry, and FT-IR spectroscopy. Additionally, the formation of complexes was studied in aqueous solutions with isothermal titration calorimetry and 1H NMR spectroscopy in DMSO‑d6 solutions. Single crystal studies, FT-IR spectroscopy and powder diffraction confirmed the inclusion of PABA and NIK inside the cyclodextrin cavity. From the results of the isothermal titration calorimetry, the stoichiometry (n) and standard thermodynamic functions (ΔH, ΔG, ΔS) of complexation, as well as binding constants (K) for the formed complexes were calculated. The obtained results confirmed the thermodynamically spontaneous formation of complexes in exothermic reactions. Furthermore, the results obtained were compared for complexes of PABA/NIK acids with β-cyclodextrin. A database survey of α-cyclodextrin complexes with different benzoic acids available in the CSD database was performed.

Effect of cyclodextrin modification on complexation thermodynamics with hexadecyltrimethylammonium cation with emphasis on subsequent surfactant micellization

Surfactant-cyclodextrin based complexes, are ideal guest-hosts for fundamental studies since both surfactant hydrophobic region with head group, and cyclodextrin cavity can be systematically varied. This allows, better understanding of the contributions that different chemical entities do to the stabilization of the complex and subsequent surfactant micellization. We studied systematically the interaction of hexadecyltrimethylammonium bromide (▪) with native α-, β- and γ-CDs, 2-hydroxypropylated and methylated α- and β-CDs, using isothermal titration calorimetry (ITC), measuring below critical micellization concentration (CMC) at least at three temperatures in the range (288.15 to 318.15) K. Data were treated simultaneously allowing the estimation of thermodynamically consistent temperature dependences of the equilibrium constant, the enthalpy and heat capacity for the inclusion complex formation. The data for cation/CD interaction were analysed mostly by the sequential binding model with 1:1 and 1:2 (cation:CD) stoichiometries, while some cation-CD combinations were examined using only 1:1, or more complicated 1:1, 2:1 and 2:2 stoichiometries. Thermodynamic quantities for complexation are discussed in terms of structural features, their temperature dependence with previous literature being examined. The shift of the CMC in presence of CDs was calculated founding large discrepancies with data in the literature. An extended mass-action chemical equilibrium model is proposed including free surfactant, free CD, complexes of the above mention stoichiometries, also including micelle, surfactant-cyclodextrin complexes of higher order stoichiometry, similar to that found for sodium dodecylsulfate-CDs systems. The new model provides a qualitative match with our own calorimetric titration curves measured above CMC for all studied ▪/CD combinations, and matches quantitatively with literature CMC values.

2-hydroxy-1- Naphthaldehyde Based Colorimetric Probe for the Simultaneous Detection of Bivalent Copper and Nickel with High Sensitivity and Selectivity.

A neoteric colorimetric probe based on 2-hydroxy-1-naphthaldehyde (PMB3) was designed and synthesized for the real-time as well as on-site naked-eye detection of Cu2+/Ni2+ ions. Various physicochemical methods were employed to characterize the probe, and its colorimetric response to different metal ions was meticulously investigated. The probe, PMB3, exhibited a sensitive colorimetric response to Cu2+/Ni2+ ions among other competing metal ions, culminating in a prominent colour change from colourless to yellow. The stoichiometry of the ligand metal complexes was ascertained to be in a 1:1 ratio using Job's plot analysis, which was further corroborated by ESI-MS data. With detection limits of 4.56µM for Cu2+ and 2.68µM for Ni2+, the method was effectively extended to real sample analysis, ensuring propitious results that closely aligned with the actual values.

Spectrophotometric analysis and mechanistic insights investigation of a developed CT complex as colorimetric real-time sensing performance towards Fe2+ in aqueous medium

A newly developed charge transfer complex (CTC) is explored for colorimetric real-time sensing behavior towards the Fe2+ ion, as a highly selective real-time colorimetric chemosensor material. The synthesized and characterized CTC / P1, [(2HP)+(SA)−] is cheap, remarkably distinctive, and simple to manufacture. Beyond the exposure limitations, iron is also the most common cofactor in enzyme reactions, which is, therefore a crucial part of life. However, too much or not enough iron leads to anemia, liver damage, cancer, Alzheimer's disease, and Parkinson's disease. In this report, unusual sensing capacity has been reported with a relatively low detection limit of 1.247 ppb for Fe2+ ions in aqueous medium, which was lowest at 1.267 ppb in previous reports of CTC sensors. By using a static quenching process, the incredible sensing behavior of this material as a chemosensor was determined. Colorimetric sensing behavior in real-time has also been observed. The complex has been described using a variety of methods, including UV-visible and FTIR spectroscopy. In FTIR spectra, the CTC (P1) showed a change in wavenumber when compared to its reactants. Furthermore, the complex's stoichiometry was measured using UV-visible spectroscopy by taking mixture with an equimolar ratio using the straight-line approach known as the Benesi-Hildebrand equation, which was found to be 1:1. Oscillator strength (f), transition dipole moment (μEN), molar extinction coefficient (εCT), energy of interaction (ECT), and stability constant (KCT) were among the thermodynamic and physical characteristics studied. Van't Hoff's equation was used to compute other parameters such as Gibbs free energy (G°), absorptivity coefficient (ε), Resonance energy (RN), etc. [O+—H……O−] hydrogen bonding was used to depict the interaction between reactants (salicylic acid and 2-hydroxypyridine). The stability of the P1 as a function of temperature is demonstrated through TG/DTA analysis.

Influence of chitosanon on the ability of LPS to interact with cells of the immune system

Complexes of lipopolysaccharide (LPS) from the bacterium Escherichia coli and chitosan (CN) with a molecular weight of 5 kDa were obtained and their supramolecular organization was studied. Using atomic force microscopy, it was shown that during the formation of complexes there is a transition from the micellar structure of the original LPS to linear network structures uniformly distributed over the surface of mica. The stability of LPS-CN complexes of various stoichiometries in biological media in the presence of serum proteins was investigated. It was shown that complexes with an LPS:CN ratio of 1:1 in the presence of serum proteins lost their surface charge and tended to aggregate; while complexes with maximum saturation of CN (1:5) did not aggregate under these conditions and maintained their surface charge. The effect of CNs of different molecular weights on the ability of LPS to interact with neutrophils in human whole blood was studied. It was observed that LPS-CN complexes were capable of binding to neutrophils and entering the cell, and this ability was enhanced in the presence of serum proteins. Chitosan exhibited the ability to suppress the synthesis of the proinflammatory cytokine TNF-α, induced by LPS, not only as part of the complex but also when cells were pretreated with a polycation.

Experimental and computational perspectives on the interaction of nerve agent VX metabolite ethyl methylphosphonic acid with human serum albumin

This study employed electrochemical methods to investigate the interaction between ethyl methylphosphonic acid (EMPA), the primary hydrolysis product of the nerve agent VX, and human serum albumin (HSA). Utilizing cyclic voltammetry (CV) and differential pulse voltammetry (DPV) on the surface of a glassy carbon electrode (GCE). The interaction was analyzed based on changes in the electrochemical behavior of the K3Fe(CN)6/K4Fe(CN)6 redox species under physiological pH conditions. Electrochemical parameters of the redox probe in the presence of HSA, EMPA, and the EMPA-HSA complex were measured. The alteration of the redox couple responses indicates the formation of an electro-inactive complex between the protein and EMPA. The binding parameters of the EMPA-HSA interaction, including the binding constant and complex stoichiometry, were determined, revealing the formation of EMPA-HSA complex with a binding constant of 1.03 × 104M−1 and a binding number of 0.624, suggesting a 1:1 stoichiometry. Molecular modeling was also conducted to further investigate the binding mode of EMPA with HSA, where the binding energy of EMPA to HSA was calculated as −4.78 kcal/mol with hydrogen bonding and hydrophobic contacts being the main interactions behind the complex formation. This research offers valuable insights into the albumin-EMPA interaction, with implications for toxicology, pharmacokinetics, and environmental impact.

Design, Characterization, and DFT exploration of new mononuclear Fe(III) and Co(II) complexes based on Isatin-hydrazone derivative: Anti-inflammatory profiling and molecular docking insights

This research focuses on the synthesis and detailed analysis of novel compounds encompassing Fe(III) (C1) and Co(II) (C2) ions, featuring 4-(2-oxo-1,2-dihydro-3H-indol-3-ylidene)hydrazono]methylphenyl 4-methylbenzenesulfonate ligand. The structural elucidation of these freshly prepared compounds was meticulously pursued employing a battery of spectroscopic techniques including NMR, UV–vis, IR, mass spectroscopy, magnetic susceptibility, conductivity, and thermal analysis (TG, DTA). Furthermore, the determination of complex stoichiometry and identification of their octahedral structural configuration were facilitated through the application of Job's techniques and molar ratio analysis. Complementing the experimental analyses, computational investigations via Density Functional Theory (DFT) were conducted to garner deeper insights into the structural, orbital, and electronic attributes of the compounds. Moreover, the anti-inflammatory properties of these synthetic compounds were scrutinized through in vitro assays, notably highlighting the superior efficacy of the C1 complex among the examined compounds. To validate their therapeutic potential, a comparative assessment was made against established anti-inflammatory agents. The hierarchy of anti-inflammatory activity among the metal complexes is established as follows: C1 > C2 > L, with the C1 exhibiting the highest potency. Additionally, a molecular docking study was executed to elucidate the compounds' interaction with the cyclooxygenase-2 (COX-2) enzyme (PDB ID: 5IKT), further corroborating their potential pharmacological relevance.

Stoichiometry and architecture of the human pyruvate dehydrogenase complex.

The pyruvate dehydrogenase complex (PDHc) is a key megaenzyme linking glycolysis with the citric acid cycle. In mammalian PDHc, dihydrolipoamide acetyltransferase (E2) and the dihydrolipoamide dehydrogenase-binding protein (E3BP) form a 60-subunit core that associates with the peripheral subunits pyruvate dehydrogenase (E1) and dihydrolipoamide dehydrogenase (E3). The structure and stoichiometry of the fully assembled, mammalian PDHc or its core remained elusive. Here, we demonstrate that the human PDHc core is formed by 48 E2 copies that bind 48 E1 heterotetramers and 12 E3BP copies that bind 12 E3 homodimers. Cryo-electron microscopy, together with native and cross-linking mass spectrometry, confirmed a core model in which 8 E2 homotrimers and 12 E2-E2-E3BP heterotrimers assemble into a pseudoicosahedral particle such that the 12 E3BP molecules form six E3BP-E3BP intertrimer interfaces distributed tetrahedrally within the 60-subunit core. The even distribution of E3 subunits in the peripheral shell of PDHc guarantees maximum enzymatic activity of the megaenzyme.

Mitochondrial DNA mutations attenuate Bleomycin-induced dermal fibrosis by inhibiting differentiation into myofibroblasts

Post-mitotic, non-proliferative dermal fibroblasts have crucial functions in maintenance and restoration of tissue homeostasis. They are involved in essential processes such as wound healing, pigmentation and hair growth, but also tumor development and aging-associated diseases. These processes are energetically highly demanding and error prone when mitochondrial damage occurs. However, mitochondrial function in fibroblasts and the influence of mitochondrial dysfunction on fibroblast-specific demands are still unclear. To address these questions, we created a mouse model in which accelerated cell-specific mitochondrial DNA (mtDNA) damage accumulates. We crossed mice carrying a dominant-negative mutant of the mitochondrial replicative helicase Twinkle (RosaSTOP system) with mice that express fibroblast-specific Cre Recombinase (Collagen1A2 CreERT) which can be activated by Tamoxifen (TwinkleFIBRO). Thus, we are able to induce mtDNA deletions and duplications in specific cells, a process which resembles the physiological aging process in humans, where this damage accumulates in all tissues. Upon proliferation in vitro, Tamoxifen induced Twinkle fibroblasts deplete most of their mitochondrial DNA which, although not disturbing the stoichiometry of the respiratory chain complexes, leads to reduced ROS production and mitochondrial membrane potential as well as an anti-inflammatory and anti-fibrotic profile of the cells. In Sodium Azide treated wildtype fibroblasts, without a functioning respiratory chain, we observe the opposite, a rather pro-inflammatory and pro-fibrotic signature. Upon accumulation of mitochondrial DNA mutations in vivo the TwinkleFIBRO mice are protected from fibrosis development induced by intradermal Bleomycin injections. This is due to dampened differentiation of the dermal fibroblasts into α−smooth-muscle-actin positive myofibroblasts in TwinkleFIBRO mice. We thus provide evidence for striking differences of the impact that mtDNA mutations have in contrast to blunted mitochondrial function in dermal fibroblasts and skin homeostasis. These data contribute to improved understanding of mitochondrial function and dysfunction in skin and provide mechanistic insight into potential targets to treat skin fibrosis in the future.