Carbohydrates as ligands: coordination equilibria and structure of the metal complexes

Quantification of Distributions of Local Proton Concentrations in Heterogeneous Soft Matter and Non-Anfinsen Biomacromolecules

A new method to quantitatively analyze heterogeneous distributions of local proton densities around paramagnetic centers in unstructured and weakly structured biomacromolecules and soft matter is introduced, and its feasibility is demonstrated on aqueous solutions of stochastically spin-labeled polysaccharides. This method is based on the pulse EPR experiment ih-RIDME (intermolecular hyperfine relaxation-induced dipolar modulation enhancement). Global analysis of a series of RIDME traces allows for a mathematically stable transformation of the time-domain data to the distribution of local proton concentrations. Two pulse sequences are proposed and tested, which combine the ih-RIDME block and the double-electron-electron resonance (DEER) experiment. Such experiments can be potentially used to correlate the local proton concentration with the macromolecular chain conformation. We anticipate an application of this approach in studies of intrinsically disordered proteins, biomolecular aggregates, and biomolecular condensates.

Characterization of the surface-active exopolysaccharide produced by Halomonas sp TGOS-10: Understanding its role in the formation of marine oil snow

In this study, we characterize the exopolymer produced by Halomonas sp. strain TGOS-10 -one of the organisms found enriched in sea surface oil slicks during the Deepwater Horizon oil spill. The polymer was produced during the early stationary phase of growth in Zobell's 2216 marine medium amended with glucose. Chemical and proton NMR analysis showed it to be a relatively monodisperse, high-molecular-mass (6,440,000 g/mol) glycoprotein composed largely of protein (46.6% of total dry weight of polymer). The monosaccharide composition of the polymer is typical to that of other marine bacterial exopolymers which are generally rich in hexoses, with the notable exception that it contained mannose (commonly found in yeast) as a major monosaccharide. The polymer was found to act as an oil dispersant based on its ability to effectively emulsify pure and complex oils into stable oil emulsions-a function we suspect to be conferred by the high protein content and high ratio of total hydrophobic nonpolar to polar amino acids (52.7:11.2) of the polymer. The polymer's chemical composition, which is akin to that of other marine exopolymers also having a high protein-to-carbohydrate (P/C) content, and which have been shown to effect the rapid and non-ionic aggregation of marine gels, appears indicative of effecting marine oil snow (MOS) formation. We previously reported the strain capable of utilising aromatic hydrocarbons when supplied as single carbon sources. However, here we did not detect biodegradation of these chemicals within a complex (surrogate Macondo) oil, suggesting that the observed enrichment of this organism during the Deepwater Horizon spill may be explained by factors related to substrate availability and competition within the complex and dynamic microbial communities that were continuously evolving during that spill.

Metal-Assisted Carbohydrate Assembly

The sequence-controlled assembly of nucleic acids and amino acids into well-defined superstructures constitutes one of the most revolutionary technologies in modern science. The elaboration of such superstructures from carbohydrates, however, remains elusive and largely unexplored on account of their intrinsic constitutional and configurational complexity, not to mention their inherent conformational flexibility. Here, we report the bottom-up assembly of two classes of hierarchical superstructures that are formed from a highly flexible cyclo-oligosaccharide─namely, cyclofructan-6 (CF-6). The formation of coordinative bonds between the oxygen atoms of CF-6 and alkali metal cations (i) locks a myriad of flexible conformations of CF-6 into a few rigid conformations, (ii) bridges adjacent CF-6 ligands, and (iii) gives rise to the multiple-level assembly of three extended frameworks. The hierarchical superstructures present in these frameworks have been shown to modulate their nanomechanical properties. This research highlights the unique opportunities of constructing convoluted superstructures from carbohydrates and should encourage future endeavors in this underinvestigated field of science.

How tobacco (Nicotiana tabacum) BY-2 cells cope with Eu(III) - a microspectroscopic study

The extensive use of lanthanides in science, industry and high-technology products is accompanied by an anthropogenic input of rare earth elements into the environment. Knowledge of a metal's environmental fate is essential for reasonable risk assessment and remediation approaches. In the present study, Eu(III) was representatively used as a luminescent probe to study the chemical environment and to elucidate the molecular interactions of lanthanides with a suspension cell culture of Nicotiana tabacum BY-2. Biochemical methods were combined with luminescence spectroscopy, two-dimensional microspectroscopic mappings, and data deconvolution methods to resolve the bioassociation behavior and spatial distribution of Eu(III) in plant cells. BY-2 cells were found to gradually take up the metal after exposure to 100 μM Eu(III) without significant loss of viability. Time-resolved luminescence measurements were used to specify the occurrence of Eu(III) species as a function of time, revealing the transformation of an initial Eu(III) species into another after 24 h exposure. Chemical microscopy and subsequent iterative factor analysis reveal the presence of four distinct Eu(III) species located at different cellular compartments, e.g., the cell nucleus, nucleolus and cell walls, which could be assigned to intracellular binding motifs. In addition, a special type of bioaccumulation occurs through the formation of a Eu(III)-containing oxalate biomineral, which is already formed within the first 24 hours after metal exposure. Oxalate crystals were also obtained in analogous experiments with Gd and Sm. These results indicate that tobacco BY-2 cells induce the precipitation of metal oxalate biominerals for detoxification of lanthanides, although they also bind to other cellular ligands at the same time.

Interaction between Hexametaphosphate, Other Active Ingredients of Toothpastes, and Erosion-Abrasion in Enamel in vitro

Sodium hexametaphosphate (HMP) as toothpaste additive is claimed to reduce erosive tooth wear and to stabilize stannous ions. However, little is known about the impact of concentration and its interactions with fluoride (F) or stannous+fluoride ions (F/Sn) on enamel erosion and erosion-abrasion. In a 10 day cyclic in vitro erosion-abrasion model, 320 flat human enamel specimens were divided into ten groups (n = 32 each) and daily subjected to six erosive challenges (0.5% citric acid, 2 min) and two toothpaste suspension applications (2 min, 1:3 F-free toothpaste:mineral-salt solution, 0.23% sodium gluconate). Half of specimens per group were additionally brushed twice/day (200 g, 15 s) during suspension immersion. Nine suspensions contained HMP (0.25%, 1.75%, 3.25%), either on its own or combined with F (373 ppm F-) or F/Sn (800 ppm Sn2+, 373 ppm F-). One suspension contained sodium gluconate only (NegContr). After 10 days, specimens' surfaces were analysed with profilometry, energy dispersive X-ray spectroscopy, and scanning electron microscopy. Tissue loss (µm, mean ± standard deviation) in NegContr was 10.9 ± 2.0 (erosion), 22.2 ± 1.6 (erosion-abrasion). Under erosive conditions, only 0.25% HMP in any combination and 1.75% HMP with F/Sn reduced loss significantly (-28% to -54%); 3.25% HMP without F and F/Sn increased loss significantly (+35%). With additional abrasion, no suspension reduced loss significantly compared to NegContr, instead, in groups without F and F/Sn or with 3.25% HMP loss was increased (+15% to +30%). Conclusively, at higher concentrations, HMP increased erosive tooth wear and seemed to reduce anti-erosive effects of fluoride and stannous ions.

A study across scales to unveil microstructural regimes in the multivalent metal driven self-assembly of cellulose nanocrystals

Understanding the behaviour of self-assembled systems, from nanoscale building blocks to bulk materials, is a central theme for the rational design of high-performance materials. Herein, we revealed, at different length scales, how the self-assembly of TEMPO-oxidised cellulose nanocrystals (TOCNCs) into rod fractal gels is directed by the complexation of Fe3+ ions on the surface of colloidal particles. Different specificities in Fe3+ binding on the TOCNC surface and conformational changes of the nanocellulose chain were unveiled by paramagnetic NMR spectroscopy. The macroscopic properties of systems presenting different concentrations of TOCNCs and Fe3+ ions were investigated by rheology and microscopy, demonstrating the tunability of the self-assembly of cellulose nanorods driven by Fe3+ complexation. Near-atomistic coarse-grained molecular dynamics simulations were developed to gain microscopic insight into the behaviour of this colloidal system. We found that the formation of different self-assembled architectures is driven by metal-nanocellulose complexation combined with the attenuation of electrostatic repulsion and water structuration around cellulose, leading to different microstructural regimes, from isolated nanorods to disconnected rod fractal clusters and rod fractal gels. These findings lay the foundation to unlock the full potential of cellulose nanocrystals as sustainable building blocks to develop self-assembled materials with defined structural control for a range of advanced applications.

Metal/metal oxide-carbohydrate polymers framework for industrial and biological applications: Current advancements and future directions

Recently, the development and consumption of metal/metal oxide carbohydrate polymer nanocomposites (M/MOCPNs) are withdrawing significant attention because of their numerous salient features. Metal/metal oxide carbohydrate polymer nanocomposites are being used as environmentally friendly alternatives for traditional metal/metal oxide carbohydrate polymer nanocomposites exhibit variable properties that make them excellent prospects for a variety of biological and industrial uses. In metal/metal oxide carbohydrate polymer nanocomposites, carbohydrate polymers bind with metallic atoms and ions using coordination bonding in which heteroatoms of polar functional groups behave as adsorption centers. Metal/metal oxide carbohydrate polymer nanocomposites are widely used in woundhealing, additional biological uses and drug delivery, heavy ions removal or metal decontamination, and dye removal. The present review article features the collection of some major biological and industrial applications of metal/metal oxide carbohydrate polymer nanocomposites. The binding affinity of carbohydrate polymers with metal atoms and ions in metal/metal oxide carbohydrate polymer nanocomposites has also been described.

Advances on novel iron saccharide-iron (III) complexes as nutritional supplements

Iron deficiency is prevalent worldwide, and iron supplementation is a promising strategy to address iron needs of the body. However, traditional oral supplements such as ferrous sulfate, ferrous succinate, and ferrous gluconate are absorbed in the form of ferrous ions, leading to lipid peroxidation and side effects due to other reasons. In recent years, saccharide-iron (III) complexes (SICs) as novel iron supplements have aroused attention for the high iron absorption rate and no gastrointestinal irritation at oral doses. In addition, research on the biological activities of SICs revealed that they also exhibited good abilities in treating anemia, eliminating free radicals, and regulating the immune response. This review focused on the preparation, structural characterization, and bioactivities of these new iron supplements, as promising candidates for the prevention and treatment of iron deficiency.

Evaluating the Effect of Iron(III) in the Preparation of a Conductive Porous Composite Using a Biomass Waste-Based Starch Template

In this work, the effect of iron(III) in the preparation of a conductive porous composite using a biomass waste-based starch template was evaluated. Biopolymers are obtained from natural sources, for instance, starch from potato waste, and its conversion into value-added products is highly significant in a circular economy. The biomass starch-based conductive cryogel was polymerized via chemical oxidation of 3,4-ethylenedioxythiophene (EDOT) using iron(III) p-toluenesulfonate as a strategy to functionalize porous biopolymers. Thermal, spectrophotometric, physical, and chemical properties of the starch template, starch/iron(III), and the conductive polymer composites were evaluated. The impedance data of the conductive polymer deposited onto the starch template confirmed that at a longer soaking time, the electrical performance of the composite was improved, slightly modifying its microstructure. The functionalization of porous cryogels and aerogels using polysaccharides as raw materials is of great interest for applications in electronic, environmental, and biological fields.

Synthesis and Characterization of a New Alginate/Carrageenan Crosslinked Biopolymer and Study of the Antibacterial, Antioxidant, and Anticancer Performance of Its Mn(II), Fe(III), Ni(II), and Cu(II) Polymeric Complexes

Natural polysaccharides are essential to a wide range of fields, including medicine, food, and cosmetics, for their various physiochemical and biological properties. However, they still have adverse effects limiting their further applications. Consequently, possible structural modifications should be carried out on the polysaccharides for their valorization. Recently, polysaccharides complexed with metal ions have been reported to enhance their bioactivities. In this paper, we synthesized a new crosslinked biopolymer based on sodium alginate (AG) and carrageenan (CAR) polysaccharides. The biopolymer was then exploited to form complexes with different metal salts including MnCl₂·4H₂O, FeCl₃·6H₂O, NiCl₂·6H₂O, and CuCl₂·2H₂O. The four polymeric complexes were characterized by Fourier-transform infrared spectroscopy (FT-IR), elemental analysis, ultraviolet-visible spectroscopy (UV-Vis), magnetic susceptibility, molar conductivity methods, and thermogravimetric analysis. The X-ray crystal structure of the Mn(II) complex is tetrahedral and belongs to the monoclinic crystal system with the space group P121/n1. The Fe(III) complex is octahedral and crystal data fit with the cubic crystal system with the space group Pm-3m. The Ni(II) complex is tetrahedral and crystal data correspond to the cubic crystal arrangement with the space group Pm-3m. The data estimated for the Cu(II) polymeric complex revealed that it is tetrahedral and belongs to the cubic system with the space group Fm-3m. The antibacterial study showed significant activity of all the complexes against both Gram-positive bacteria (Staphylococcus aureus and Micrococcus luteus) and Gram-negative (Escherichia coli and Salmonella typhimurium) pathogenic strains. Similarly, the various complexes revealed an antifungal activity against Candida albicans. The Cu(II) polymeric complex recorded a higher antimicrobial activity with an inhibitory zone reaching 4.5 cm against Staphylococcus aureus bacteria and the best antifungal effect of 4 cm. Furthermore, higher antioxidant values of the four complexes were obtained with DPPH scavenging activity varying from 73 to 94%. The two more biologically effective complexes were then selected for the viability cell assessments and in vitro anticancer assays. The polymeric complexes revealed excellent cytocompatibility with normal human breast epithelial cells (MCF10A) and a high anticancer potential with human breast cancer cells (MCF-7) which increase significantly in a dose-dependent manner.

Metabolomic and cultivation insights into the tolerance of the spacecraft-associated Acinetobacter toward Kleenol 30, a cleanroom floor detergent

Introduction

Stringent cleaning procedures during spacecraft assembly are critical to maintaining the integrity of life-detection missions. To ensure cleanliness, NASA spacecraft are assembled in cleanroom facilities, where floors are routinely cleansed with Kleenol 30 (K30), an alkaline detergent.

Methods

Through metabolomic and cultivation approaches, we show that cultures of spacecraft-associated Acinetobacter tolerate up to 1% v/v K30 and are fully inhibited at ≥2%; in comparison, NASA cleanrooms are cleansed with ~0.8-1.6% K30.

Results

For A. johnsonii 2P08AA (isolated from a cleanroom floor), cultivations with 0.1% v/v K30 yield (1) no changes in cell density at late-log phase, (2) modest decreases in growth rate (~17%), (3) negligible lag phase times, (4) limited changes in the intracellular metabolome, and (5) increases in extracellular sugar acids, monosaccharides, organic acids, and fatty acids. For A. radioresistens 50v1 (isolated from a spacecraft surface), cultivations yield (1) ~50% survivals, (2) no changes in growth rate, (3) ~70% decreases in the lag phase time, (4) differential changes in intracellular amino acids, compatible solutes, nucleotide-related metabolites, dicarboxylic acids, and saturated fatty acids, and (5) substantial yet differential impacts to extracellular sugar acids, monosaccharides, and organic acids.

Discussion

These combined results suggest that (1) K30 manifests strain-dependent impacts on the intracellular metabolomes, cultivation kinetics, and survivals, (2) K30 influences extracellular trace element acquisition in both strains, and (3) K30 is better tolerated by the floor-associated strain. Hence, this work lends support towards the hypothesis that repeated cleansing during spacecraft assembly serve as selective pressures that promote tolerances towards the cleaning conditions.

A first-principles exploration of the conformational space of sodiated pyranose assisted by neural network potentials

Sampling the conformational space of monosaccharides using the first-principles methods is important and as a database of local minima provides a solid base for interpreting experimental measurements such as infrared photo-dissociation (IRPD) spectroscopy or collision-induced dissociation (CID). IRPD emphasizes low-energy conformers and CID can distinguish conformers with distinct reaction pathways. A typical computational approach is to engage empirical or semi-empirical methods to sample the conformational space first, and only selected minima are reoptimized at first-principles levels. In this work, we propose a computational scheme to explore the configurational space of 12 types of sodiated pyranoses with the assistance of a neural network potential (NNP). We demonstrated that it is possible to train an NNP based on the density functional calculations extracted from a previous study on sodiated glucose (Glc), galactose (Gal), and mannose (Man). This NNP yields a better description of the other five types of aldohexoses than the four types of ketohexoses. We further show that such a discrepancy in the accuracy of NNP can be resolved by an active learning scheme where the NNP model is engaged in generating the data and has itself updated. Through this iterative process, we can locate more than 17 000 distinct local minima at the B3LYP/6-311+G(d,p) level and an NNP with an accuracy of 1 kJ mol^-1 was created, which can be used for further studies.

Role of Metal Cations of Copper, Iron, and Aluminum and Multifunctional Ligands in Alzheimer's Disease: Experimental and Computational Insights

Alzheimer's disease (AD) is the most common form of dementia, affecting millions of people around the world. Even though the causes of AD are not completely understood due to its multifactorial nature, some neuropathological hallmarks of its development have been related to the high concentration of some metal cations. These roles include the participation of these metal cations in the production of reactive oxygen species, which have been involved in neuronal damage. In order to avoid the increment in the oxidative stress, multifunctional ligands used to coordinate these metal cations have been proposed as a possible treatment to AD. In this review, we present the recent advances in experimental and computational works aiming to understand the role of two redox active and essential transition-metal cations (Cu and Fe) and one nonbiological metal (Al) and the recent proposals on the development of multifunctional ligands to stop or revert the damaging effects promoted by these metal cations.

Pumpkin Skin Polysaccharide–Zn(II) Complex: Preparation, Characterization, and Suppression of Inflammation in Zebrafish

In this study, pumpkin (Cucurbita moschata) skin polysaccharide–zinc(II) (PSP−Zn) complex was successfully prepared. The structure and physicochemical properties of PSP and PSP−Zn were analyzed. The anti-inflammatory activity of PSP and PSP−Zn was investigated in zebrafish larvae induced by copper sulphate. PSP and PSP−Zn consisted of rhamnose, arabinose, galactose, glucose, and galacturonic acid. The molecular weight (Mw) of PSP and PSP−Zn were 3.034 × 10⁶ and 3.222 × 10⁶ Da, respectively. Fourier transform infrared spectrum (FT-IR) and circular dichroism (CD) analysis results suggested that the chemical modification of zinc might occur through hydroxyl groups of PSP. The PSP−Zn complex had lamellar texture, smooth surface morphology, and larger particle size. X-ray Diffraction (XRD) analysis revealed that both PSP and PSP−Zn were semi-crystalline substances. PSP−Zn solution showed superior stability in a weak acid and alkaline environment, especially at pH = 6.0. Moreover, PSP and PSP−Zn showed a good inhibitory effect on inflammation cells in zebrafish. Real-time quantitative polymerase chain reaction (RT-PCR) result suggested that the anti-inflammatory mechanism of PSP and PSP−Zn were through downregulation of the expression of nitric oxide synthase 2b (nos2b), inducible nitric oxide synthase (iNOS), interleukin-6 (IL-6), and nuclear factor-kappa B2 (NF-κB2). The present study indicated that PSP−Zn is expected to be a safe and efficient novel zinc supplement with anti-inflammatory activity.

The Maillard reaction in traditional method sparkling wine

The Maillard reaction between sugars and amino acids, peptides, or proteins generates a myriad of aroma compounds through complex and multi-step reaction pathways. While the Maillard has been primarily studied in the context of thermally processed foods, Maillard-associated products including thiazoles, furans, and pyrazines have been identified in aged sparkling wines, with associated bready, roasted, and caramel aromas. Sparkling wines produced in the bottle-fermented traditional method (Méthode Champenoise) have been the primary focus of studies related to Maillard-associated compounds in sparkling wine, and these wines undergo two sequential fermentations, with the second taking place in the final wine bottle. Due to the low temperature (15 ± 3°C) and low pH (pH 3-4) conditions during production and aging, we conclude that Maillard interactions may not proceed past intermediate stages. Physicochemical factors that affect the Maillard reaction are considered in the context of sparkling wine, particularly related to pH-dependent reaction pathways and existing literature pertaining to low temperature and/or low pH Maillard activity. A focus on the origins and composition of precursor species (amino acids and sugars) in sparkling wines is presented, as well as the potential role of metal ions in accelerating the Maillard reaction. Understanding the contributions of individual physicochemical factors to the Maillard reaction in sparkling wine enables a clearer understanding of reaction pathways and sensory outcomes. Advancements in analytical techniques for monitoring the Maillard reaction are also described, and important areas of future research on this topic are identified.

Metal adduction in mass spectrometric analyses of carbohydrates and glycoconjugates

Glycans, carbohydrates, and glycoconjugates are involved in many crucial biological processes, such as disease development, immune responses, and cell-cell recognition. Glycans and carbohydrates are known for the large number of isomeric features associated with their structures, making analysis challenging compared with other biomolecules. Mass spectrometry has become the primary method of structural characterization for carbohydrates, glycans, and glycoconjugates. Metal adduction is especially important for the mass spectrometric analysis of carbohydrates and glycans. Metal-ion adduction to carbohydrates and glycoconjugates affects ion formation and the three-dimensional, gas-phase structures. Herein, we discuss how metal-ion adduction impacts ionization, ion mobility, ion activation and dissociation, and hydrogen/deuterium exchange for carbohydrates and glycoconjugates. We also compare the use of different metals for these various techniques and highlight the value in using metals as charge carriers for these analyses. Finally, we provide recommendations for selecting a metal for analysis of carbohydrate adducts and describe areas for continued research.

Erbium ion implantation into LiNbO3, Al2O3, ZnO and diamond - measurement and modelling - an overview

The presented overview deals with the study of the luminescence properties of lanthanide ions incorporated into different dielectric crystalline materials for use in photonics and optoelectronics. From the crystalline materials, non-centrosymmetric hexagonal crystals of LiNbO₃, Al₂O₃ and ZnO, together with the centrosymmetric cubic crystal of diamond, were chosen. The above-mentioned materials represent a certain cross-section through various crystal structure geometries with different internal bonding of atoms which represent different crystal vicinity for the incorporated Er ions. During more than ten years of our research, each of the crystals was doped with erbium ions and the resulting structural and luminescence properties were studied in detail and compared between the mentioned crystalline materials to find similar behaviour for erbium ions in the different crystalline materials. To better understand the incorporation of erbium in the studied crystalline materials, theoretical simulations of different erbium-doped crystal models were carried out. In the calculations, cohesive energies of the structures and erbium defect-formation energies were compared in order to find the most favourable erbium positions in the crystals. Also, from the geometry optimization calculations, the optimal geometry arrangements in the vicinity of erbium ions in different crystals were studied and visualized. The results of the theoretical simulations confirmed the experimental results - i.e., from all the theoretical erbium-doped crystal models, the most stable structures contained erbium in the substitutional positions with octahedral oxygen coordination.

Deprotonation from an OH on myo-Inositol Promoted by μ2-Bridges with Possible Regioselectivity/Chiral Selectivity

Single-crystal structures of myo-inositol complexes with erbium ([Er₂(C₆H₁₁O₆)₂(H₂O)₅Cl₂]Cl₂(H₂O)₄, denoted ErI hereafter) and strontium (Sr(C₆H₁₂O₆)₂(H₂O)₂Cl₂, denoted SrI hereafter) are described. In ErI, deprotonation occurs on an OH of myo-inositol, although the complex is synthesized in an acidic solution, and the pK_a values of all of the OHs in myo-inositol are larger than 12. The deprotonated OH is involved in a μ₂-bridge. The polarization from two Er³⁺ ions activates the chemically relatively inert OH and promotes deprotonation. In the stable conformation of myo-inositol, there are five equatorial OHs and one axial OH. The deprotonation occurs on the only axial OH, suggesting that the deprotonation possesses characteristics of regioselectivity/chiral selectivity. Two Er³⁺ ions in the μ₂-bridge are stabilized by five-membered rings formed by chelating Er³⁺ with an O-C-C-O moiety. As revealed by the X-ray crystallography study, the absolute values of the O-C-C-O torsion angles decrease from ∼60 to ∼45° upon chelating. Since the O-C-C-O moiety is within a six-membered ring, the variation of the torsion angle may exert distortion of the chair conformation. Quantum chemistry calculation results indicate that an axial OH flanked by two equatorial OHs (double ax-eq motif) is favorable for the formation of a μ₂-bridge, accounting for the selectivity. The double ax-eq motif may be used in a rational design of high-performance catalysts where deprotonation with high regioselectivity/chiral selectivity is carried out.

Insoluble hyaluronan films obtained by heterogeneous crosslinking with iron(III) as resorbable implants

We present water-insoluble hyaluronan films crosslinked by trivalent iron developed as potential resorbable implants. The films were crosslinked by sorption of ferric salt into solid HA films in water/2-propanol bath. These heterogeneously crosslinked films (het-FeHA) remained tough and dimensionally stable when rehydrated in saline. In contrast, films prepared by drying the well-known homogeneous ferric hyaluronate gels (hom-FeHA) softened upon rehydration and expanded rapidly. Differences between hom-FeHA and het-FeHA result from polymer network topology (dominant inter- or intra-molecular crosslink, respectively). Moreover, Mössbauer spectroscopy of het-FeHA revealed diiron complexes, while iron in the hom-FeHA was present exclusively as γ-FeOOH nanoparticles or amorphous FeOOH. The biocompatibility tests of het-FeHA did not show any adverse effect and the sample disintegrated within one day when implanted in mice peritoneum. In conclusion, we developed implantable hyaluronan-based free-standing film with minimal swelling that can be resorbed quickly enough to avoid induction of foreign-body reaction.

Investigating Structural Property Relationships to Enable Repurposing of Pharmaceuticals as Zinc Ionophores

The importance of zinc in biology has gained greater recognition in recent years due to its essential contributions to the function of many endogenous enzymes. Disruption of zinc homeostasis may be useful in treating pathological conditions, such as Alzheimer's, and for antiviral purposes. Despite the growth of knowledge and increased interest in zinc, little is known about the structure and function of zinc ionophores. In this study we analyse the Cambridge Structural Database and solution complexation studies found in the literature to identify key functional groups which may confer zinc ionophorism. Pharmaceuticals, nutraceuticals and amino acids with these functionalities were selected to enable us to explore the translatability of ionophoric activity from in vitro assays to cellular systems. We find that although certain species may complex to zinc in the solid and solution states, and may carry ions across simple membrane systems, this does not necessarily translate into ionophoric activity. We propose that the CSD can help refine key functionalities but that ionophoric activity must be confirmed in cellular systems.

Interaction of Carrier Protein with Potential Metallic Drug Candidate N-Glycoside 'GATPT': Validation by Multi-Spectroscopic and Molecular Docking Approaches

Lysozyme is often used as a model protein to study interaction with drug molecules and to understand biological processes which help in illuminating the therapeutic effectiveness of the drug. In the present work, in vitro interaction studies of 1-{(2-hydroxyethyl)amino}-2-amino-1,2-dideoxy-d-glucose triphenyl tin (IV) (GATPT) complex with lysozyme were carried out by employing various biophysical methods such as absorption, fluorescence, and circular dichroism (CD) spectroscopies. The experimental results revealed efficient binding affinity of GATPT with lysozyme with intrinsic binding (Kb) and binding constant (K) values in the order of 105 M-1. The number of binding sites and thermodynamic parameters ΔG, ΔH, and ΔS at four different temperatures were also calculated and the interaction of GATPT with lysozyme was found to be enthalpy and entropy driven. The CD spectra revealed alterations in the population of α-helical content within the secondary structure of lysozyme in presence of GATPT complex. The morphological analysis of the complex with lysozyme and lysozyme-DNA condensates was carried out by employing confocal and SEM studies. Furthermore, the molecular docking studies confirmed the interaction of GATPT within the larger hydrophobic pocket of the lysozyme via several non-covalent interactions.

Order from a Mess: The Growth of 5-Armchair Graphene Nanoribbons

The advent of on-surface chemistry under vacuum has vastly increased our capabilities to synthesize carbon nanomaterials with atomic precision. Among the types of target structures that have been synthesized by these means, graphene nanoribbons (GNRs) have probably attracted the most attention. In this context, the vast majority of GNRs have been synthesized from the same chemical reaction: Ullmann coupling followed by cyclodehydrogenation. Here, we provide a detailed study of the growth process of five-atom-wide armchair GNRs starting from dibromoperylene. Combining scanning probe microscopy with temperature-dependent XPS measurements and theoretical calculations, we show that the GNR growth departs from the conventional reaction scenario. Instead, precursor molecules couple by means of a concerted mechanism whereby two covalent bonds are formed simultaneously, along with a concomitant dehydrogenation. Indeed, this alternative reaction path is responsible for the straight GNR growth in spite of the initial mixture of reactant isomers with irregular metal-organic intermediates that we find. The provided insight will not only help understanding the reaction mechanisms of other reactants but also serve as a guide for the design of other precursor molecules.

Opening the Egg Box: NMR spectroscopic analysis of the interactions between s-block cations and kelp monosaccharides

The best-known theory accounting for metal-alginate complexation is the so-called "Egg Box" model. In order to gain greater insight into the metal-saccharide interactions that underpin this model, the coordination chemistry of the corresponding monomeric units of alginate, L-guluronate (GulA) and D-mannuronate (ManA) have been studied herein. GulA and ManA were exposed to solutions of different s-block cations and then analysed by ¹H and ¹³C NMR spectroscopy. It was found that the α/β ratio of the pyranose anomeric equilibria of GulA showed large pertubations from the starting value (α/β = 0.21 ± 0.01) upon contact with 1.0 M Ca²⁺, Sr²⁺, and Ba²⁺ (α/β = 1.50 ± 0.03, 1.20 ± 0.02, and 0.58 ± 0.02, respectively) at pD 7.9, but remained almost constant in the presence of Na⁺, K⁺, and Mg²⁺ (α/β = 0.24 ± 0.01, 0.19 ± 0.01, and 0.26 ± 0.01, respectively). By comparison, no significant changes were observed in the α/β ratios of ManA and related mono-uronates D-glucuronate (GlcA) and D-galacturonate (GalA) in the presence of all of the metal ions surveyed. Analysis of the ¹H and ¹³C coordination chemical shift patterns indicate that the affinity of α-GulA for larger divalent cations is a consequence of the unique ax-eq-ax arrangement of hydroxyl groups found for this uronate anomer.

Structure and Thermodynamics of Eu(III) and Cm(III) Complexes with Glucuronic Acid

Complexation by small organic ligands controls the bioavailability of contaminants and influences their mobility in the geosphere. We have studied the interactions of Cm³⁺, as a representative of the trivalent actinides, and Eu³⁺, as an inactive homologue, with glucuronic acid (GlcA) a simple sugar acid. Time-resolved laser-induced luminescence spectroscopy (TRLFS) shows that complexation at pH 5.0 occurs only at high ligand to metal ratios in the form of 1:1 complexes with standard formation constants log β⁰ = 1.84 ± 0.22 for Eu³⁺ and log β⁰ = 2.39 ± 0.19 for Cm³⁺. A combination of NMR, QMMM, and TRLFS reveals the structure of the complex to be a half-sandwich structure wherein the ligand binds through its carboxylic group, the ring oxygen, and a hydroxyl group in addition to five to six water molecules. Surprisingly, Y³⁺, which was used as a diamagnetic reference in NMR, prefers a different coordination geometry with bonding through at least two hydroxyl groups on the opposite side of a distorted GlcA molecule. QMMM simulations indicate that the differences in stability among Cm, Eu, and Y are related to ring strain induced by smaller cations. At higher pH a stronger complex was detected, most likely due to deprotonation of a coordinating OH group.

Implications of the Mn:ligand ratio for Mn uptake by Glycine max L. plants fertilized with heptagluconate and gluconate complexes

BACKGROUND

The environmental risk of the application of synthetic chelates has furthered the implementation of biodegradable complexes to correct manganese (Mn)-deficient plants. This study used the biodegradable ligands of heptagluconate (G7) and gluconate (G6) to test the influence of the Mn2+ :ligand ratio on their fertilizers' capacity to provide Mn to plants. The efficacy of these complexes to correct Mn-deficient soybean was evaluated in hydroponics and calcareous soil conditions and compared with the synthetic chelate EDTA (ethylenediaminetetraacetic acid).

RESULTS

This study demonstrated that G7 was a biodegradable alternative to EDTA for supplying Mn, maintaining an adequate nutritional balance compared with G6, which reduced iron (Fe) uptake by the plants. The efficacy of the Mn complexes depended on both the ligand and the Mn:ligand ratio, with the 1:1 and 1:2 molar ratios of Mn2+ :G7 being the most effective complexes in the short term on the basis of their chemical structure and stability.

CONCLUSION

The Mn2+ :G7 (1:1 and 1:2) complexes were found to be effective Mn sources for plant nutrition due to their chemical structures providing adequate stability in alkaline solution and their fast-action effect. © 2021 Society of Chemical Industry.

Multitherapy magnetic theranostic: Synthesis, characterization and in vitro evaluation of their performance

It is well known that iron oxide magnetic nanoparticles (IONPs) have many potential utilities in biomedicine due to their unique physicochemical properties. With the aim to obtain multifunctional nanoparticles with potential uses for therapy and diagnosis (nanotheranostics), IONPs were synthesized by hydrothermal synthesis assisted by mannose. Two synthetic pathways were evaluated in order to obtain IONPs with suitable properties for biomedical applications. The formulation Mag@Man/H1 presented the best characteristics in terms of size and stability. Mag@Man/H1 was evaluated as: a) drug carrier, b) antioxidant activity, c) magnetic hyperthermia, d) contrast agent for MRI. To evaluate the point a), morin, a natural flavonoid with several pharmaceutical activities, was loaded on the nanoparticles. A high percentage of drug loading was achieved. In point b) it was determined that the carrier itself possess a high activity which increased in morin loaded nanoparticles. Point c) magnetocalorimetric evaluation were carried out at several field conditions. A specific absorption rate value of 121.4 W/gFe was achieved at 52.4 kA/m and 260 kHz and 8.8 W/gFe at 4 kA/m and 100 kHz. Regarding contrast capacity (point d), the r1 value found was close to some contrast agent based on manganese. Although the measured r2 value was quite smaller than other iron oxides, the achieved effect was strong enough to produce negative contrast. From these studies, it was concluded that Mag@Man/H1 could act as a multifunctional nanoplatform for oncological diseases treatments.

Probing the glycopolymer–ion interaction via specific ion effects

Specific ion effects were used to probe the interactions between thermoresponsive glycopolymers and different ions.

Metal complexes of 4,6-O-ethylidene-β-d-glucopyranosylamine derivatives and their application in organic synthesis

Glycosylamine derivatives of 4,6-O-ethylidene-d-glucose have been used for complexing the alkali, alkaline earth and transition metal ions. Three different series of ligands have been reported where N-(o-carboxyphenyl)-4,6-O-ethylidene-β-d-glucopyranosylamine has been used for complexing the diamagnetic (Li⁺, Na⁺, K⁺, Mg²⁺, Ca²⁺, Ba²⁺, Zn²⁺, Cd²⁺, Hg²⁺) metal ions. N-(2-Hydroxybenzoyl)-L-alanyl-4,6-O-ethylidene-β-d-glucopyranosylamine selectively interacts with molecular cupric acetate and the adduct acts as a catalyst in selective oxidation of primary and secondary alcohols into their corresponding carbonyl compounds. Salicylidene derivatives of 4,6-O-ethylidene-β-d-glucopyranosylamine have been used in complexing Ni²⁺, Cu²⁺, Zn²⁺, VO²⁺, MoO₂²⁺ and UO₂²⁺ metal ions, where Cu(II) and Mo(VI) complexes have been further used in the organic synthesis. Dinuclear copper complex exhibited catecholase like activity and also catalyzed the oxidation of primary and secondary alcohols selectively into their corresponding carbonyl compounds. Trinuclear copper complex has been reported to activate the C-Cl bond of solvent chloroform in the presence of mild organic bases below room temperature. Mo(VI) complex has been used as a catalyst for epoxidation, organic sulfide oxidation and synthesis of bis(indolyl)methanes.

Diffusion and Relaxometry to Study Carbohydrates Dissolved in Ionic Liquids

Solutions of xylan and xylose in 1-ethyl-3-methylimidazolium acetate [C2mim] [OAc], a room temperature ionic liquid, were examined across a range of temperatures (20°C–70 °C) using: NMR spectroscopy; diffusion; low-field (20 MHz) spin–lattice and spin–spin relaxation times; and rheological measurements through the zero shear rate viscosity. The addition of xylose and xylan affect the mobility of the ions, with a decrease occurring when the carbohydrate concentration is increased. The ratio of the diffusion coefficients for the anion to the cation remained constant upon the addition of both xylan and xylose, showing that the anion and cation were equally affected by the presence of the carbohydrate. The translational diffusion motion of the ions in the xylose solutions were similar in value to published results for cellobiose, which we explain in terms of the number of available carbohydrate OH groups that the ions are interacting with. We observe from the various NMR results that the dissolving mechanism of xylan in [C2mim] [OAc] is similar to that for cellulose.

The Iron Biology Status of Peritoneal Dialysis Patients May Be a Risk Factor for Development of Infectious Peritonitis

Background:Infectious peritonitis is a clinically important condition contributing to the significant mortality and morbidity rates observed in peritoneal dialysis (PD) patients. Although some of the socioeconomic risk factors for PD-associated peritonitis have been identified, it is still unclear why certain patients are more susceptible than others to infection.Methods:We examined the molecular components of human peritoneal dialysate (HPD) in an attempt to identify factors that might increase patient susceptibility to infection. Characterization studies were performed on initial and follow-up dialysate samples collected from 9 renal failure patients on PD.Results:Our in vitro data showed that peritonitis-causing bacteria grew differently in the patient dialysates. Proteomic analysis identified an association between transferrin presence and infection risk, as peritoneal transferrin was discovered to be iron-saturated, which was in marked contrast to transferrin in blood. Further, use of radioactive iron-labeled transferrin showed peritoneal transferrin could act as a direct iron source for the growth of peritonitis-causing bacteria. We also found catecholamine stress hormones noradrenaline and adrenaline were present in the dialysates and were apparently involved in enhancing the growth of the bacteria via transferrin iron provision. This suggests the iron biology status of the PD patient may be a risk factor for development of infectious peritonitisConclusions:Collectively, our study suggests transferrin and catecholamines within peritoneal dialysate may be indicators of the potential for bacterial growth in HPD and, as infection risk factors, represent possible future targets for therapeutic manipulation.

Spatially Controlled Occlusion of Polymer-Stabilized Gold Nanoparticles within ZnO

In principle, incorporating nanoparticles into growing crystals offers an attractive and highly convenient route for the production of a wide range of novel nanocomposites. Herein we describe an efficient aqueous route that enables the spatially controlled occlusion of gold nanoparticles (AuNPs) within ZnO crystals at up to 20 % by mass. Depending on the precise synthesis protocol, these AuNPs can be (i) solely located within a central region, (ii) uniformly distributed throughout the ZnO host crystal or (iii) confined to a surface layer. Remarkably, such efficient occlusion is mediated by a non-ionic water-soluble polymer, poly(glycerol monomethacrylate)₇₀ (G₇₀ ), which is chemically grafted to the AuNPs; pendent cis-diol side groups on this steric stabilizer bind Zn²⁺ cations, which promotes nanoparticle interaction with the growing ZnO crystals. Finally, uniform occlusion of G₇₀ -AuNPs within this inorganic host leads to faster UV-induced photodegradation of a model dye.

Aquatic organic matter: Classification and interaction with organic microcontaminants

Organic matter (OM) in aquatic system is originated from autochthonous and allochthonous natural sources as well as anthropogenic inputs, and can be found in dissolved, particulate or colloidal form. According to the type/composition, OM can be divided in non-humic substances (NHS) or humic substances (HS). The present review focuses on the main groups that constitute the NHS (carbohydrates, proteins, lipids, and lignin) and their role as chemical biomarkers, as well as the main characteristics of HS are presented. HS functions, properties and mechanisms are discussed, in addition to their association to the fate, bioavailability, and toxicity of organic microcontaminants in the aquatic systems. Despite the growing diversity and potential impacts of organic microcontaminants to the aquatic environment, limited information is available about their association with OM. A protective effect is, however, normally seen since the presence of OM (HS mainly) may reduce bioavailability and, consequently, the concentration of organic microcontaminants within the organism. It may also affect the toxicity by either absorbing ultraviolet radiation incidence and, then, reducing the formation of phototoxic compounds, or by increasing the oxygen reactive species and, thus, affecting the decomposition of natural and anthropogenic organic compounds. In addition, the outcome data is hard to compare since each study follows unique experimental protocols. The often use of commercial humic acid (Aldrich) as a generic source of OM in studies can also hinder comparisons since differences in composition makes this type of OM not representative of any aquatic environment. Thus, the current challenge is find out how this clear fragmentation can be overcome.

Probing the chirality of oxidovanadium(v) centers in complexes with tridentate sugar Schiff-base ligands: solid-state and solution behavior

Configurations of oxidovanadium centers in diastereomeric complexes with chiral sugar ligands are assigned and in the solid state triggered by the coordination number at the vanadium center through the steric requirements of the chelate ligand.

Selectivity for La3+ ion by synthesized 4-((5-methylfuran-2-yl)methylene)hydrazono)methyl)phenol receptor and its spectral analysis

The functionalized molecules with specific molecular sites appear to be a promising approach for detection of cation in UV-visible and fluorescence spectroscopy. The synthesized receptor 4-((5-methylfuran-2-yl)methylene)hydrazono)methyl)phenol MFMHMP was found selective for La³⁺ among Ag⁺, K⁺, Na⁺, Be²⁺, Mg²⁺, Ca²⁺, Eu³⁺, Al³⁺, La³⁺, Zr⁴⁺, Th⁴⁺, UO₂²⁺, Fe³⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Zn²⁺, Cd²⁺ and Hg²⁺ metal ions used as their nitrates by UV-visible spectroscopy and fluorescence spectroscopy. The binding nature of MFMHMP with La³⁺ ion was analyzed by UV-visible, fluorescence, IR, mass spectroscopy and cyclic voltammetric studies. The stoichiometry was established to be 1:1 by Benesi-Hildebrand, mole-ratio method and method of continuous variation (Job's method) with good association affinity K = 6.245 × 10⁴ M^-1. Computational studies and Density functional theory (DFT) calculation gives the proof of electron transfer during excitation and emission. Binding energy of complex through Density Function Theory -62.387 kcal/mol has also indication of strong binding. The electron transfer energy of Higher occupied molecular orbital (HOMO) to Lower unoccupied molecular orbital (LUMO) is about 4.662 eV for MFMHMP+La³⁺ Complex. Among that all transitions HOMO → LUMO + 8 and HOMO → LUMO + 9 play a key role for the blue shift transition during complexation.