S=1/2 One‐Dimensional Random‐Exchange Ferromagnetic Zigzag Ladder,Which Exhibits Competing Interactions in a Critical Regime

The synthesis, crystal structure, and magnetic properties (from a combined experimental and First‐Principles Bottom‐Up theoretical study) of the new compound catena‐dichloro(2‐Cl‐3Mpy)copper(II), 1 , [2‐Cl‐3Mpy=2‐chloro‐3‐methylpyridine] are described and rationalized. Crystals of 1 present well isolated magnetic 1D chains (no 3D order was experimentally observed down to 1.8 K) and magnetic frustration stemming from competing ferromagnetic nearest‐neighbor (J_NN) interactions and antiferromagnetic next‐nearest neighbor (J_NNN) interactions, in which α=J_NNN/J_NN <?0.25. These magnetic interactions give rise to a unique magnetic topology: a two‐leg zigzag ladder composed of edge‐sharing up‐down triangles with antiferromagnetic interactions along the rails and ferromagnetic interactions along the zigzag chain that connects the rails. Crystals of 1 also present a random distribution of the 2‐Cl‐3Mpy groups, which are arranged in two different orientations, each with a 50 % occupancy. This translates into a random static structural disorder within each chain by virtue of which the value of the J_NN magnetic interactions can randomly take one of the following three values: 53, 36, and 16 cm^?1. The structural disorder does not affect the J_NNN value, which in all cases is approximately ?9 cm^?1. A proper statistical treatment of this disorder provides a computed magnetic susceptibility curve that reproduces the main features of the experimental data.     

Racemic and Quasi‐Racemic X‐ray Structures of Cyclic Disulfide‐Rich Peptide Drug Scaffolds

Cyclic disulfide‐rich peptides have exceptional stability and are promising frameworks for drug design. We were interested in obtaining X‐ray structures of these peptides to assist in drug design applications, but disulfide‐rich peptides can be notoriously difficult to crystallize. To overcome this limitation, we chemically synthesized the L ‐ and D ‐forms of three prototypic cyclic disulfide‐rich peptides: SFTI‐1 (14‐mer with one disulfide bond), cVc1.1 (22‐mer with two disulfide bonds), and kB1 (29‐mer with three disulfide bonds) for racemic crystallization studies. Facile crystal formation occurred from a racemic mixture of each peptide, giving structures solved at resolutions from 1.25 Å to 1.9 Å. Additionally, we obtained the quasi‐racemic structures of two mutants of kB1, [G6A]kB1, and [V25A]kB1, which were solved at a resolution of 1.25 Å and 2.3 Å, respectively. The racemic crystallography approach appears to have broad utility in the structural biology of cyclic peptides.     

Surface activity and self-aggregation ability of three cationic quaternized aminocalix[4]arenes

The self-aggregation ability of three amphiphilic cationic calix[4]arenes possessing four quaternary amino groups (aminoCAs) was investigated using a variety of methods. All of the studied compounds possess high aggregation ability. Their critical aggregation concentration (CAC) values in water are in the 0.0009–0.04 % (w/v) concentration range. Several size populations of aggregates were detected by DLS for all three CAs, and restructuring of aggregates was observed to be dependent on concentration. Particles formed above CAC were attributed to formation of vesicular structures (vesicles). The coexistence of other type of aggregates (presumably micelles) with vesicles was observed in the aqueous solution of CAs 2 and 3 from concentrations of 0.5 and 0.8 % (w/v), respectively. The filtration procedure was found to be a significant factor since the obtained data from filtered and unfiltered samples was different. The particle sizes obtained by TEM measurements were somewhat correlated with the DLS data for unfiltered CAs solutions. An analysis of the aggregate composition was undertaken by a size-exclusion method using semi-permeable cellophane membranes with different MWCO. A negative deviation from linearity of permeability flux profile starting from 0.8 % (w/v) concentration of donor phase indicated that the fraction of large aggregates at this point is significant enough that the molecules could not easily permeate through the membranes.     

Tuning Aqueous Supramolecular Polymerization by an Acid-Responsive Conformational Switch

Besides their widespread use in coordination chemistry, 2,2’-bipyridines are known for their ability to undergo cis–trans conformational changes in response to metal ions and acids, which has been primarily investigated at the molecular level. However, the exploitation of such conformational switching in self-assembly has remained unexplored. In this work, the use of 2,2’-bipyridines as acid-responsive conformational switches to tune supramolecular polymerization processes has been demonstrated. To achieve this goal, we have designed a bipyridine-based linear bolaamphiphile, 1 , that forms ordered supramolecular polymers in aqueous media through cooperative aromatic and hydrophobic interactions. Interestingly, addition of acid (TFA) induces the monoprotonation of the 2,2’-bipyridine moiety, leading to a switch in the molecular conformation from a linear (trans) to a V-shaped (cis) state. This increase in molecular distortion along with electrostatic repulsions of the positively charged bipyridine-H⁺ units attenuate the aggregation tendency and induce a transformation from long fibers to shorter thinner fibers. Our findings may contribute to opening up new directions in molecular switches and stimuli-responsive supramolecular materials.     

Sensitive Quantification of Fe(III) in Food Samples at Screen Printed Carbon Electrode Modified with Graphene and Piroxicam by Catalytic Adsorptive Voltammetry

A new disposable sensitive voltammetric sensor for the determination of Fe(III) based on a graphene (G) and piroxicam (Pir) modified screen printed carbon electrode (Pir/G/SPCE) has been developed. The developed method is based on accumulation of Fe(III) on the surface of the prepared sensor strip, formation a complex with Pir and subsequent reduction the adsorbed chelated Fe(III) at ?0.03 V (vs. Ag/AgCl) coupled with the catalytic enhancement of bromate. Characterizations of the modified electrode surface were performed by field emission scanning electron microscopy (FE‐SEM), energy dispersive X‐ray spectroscopy (EDX) and electrochemical impedance spectroscopy (EIS). Electrochemical behavior of the modified SPCEs was investigated by cyclic voltammetry (CV) and differential pulse voltammetry (DPV). Under the optimum conditions, the catalytic voltammetric method exhibited linear calibration plot in the concentration ranges of 1–100 ng mL^?1 and 100–3500 ng mL^?1 Fe(III) with a limit of detection of 0.3 ng mL^?1. The sensor strip displayed good reproducibility with 1.7 % relative standard deviation (RSD%). The developed method was successfully applied for the determination of iron in food samples such as vegetables, fruit, and cereal.     

Dendritic analogues of engineering plastics - a general one-step synthesis of dendritic polyaryl ethers

The first general single-step route to dendritic or cascade polyaryl ethers analogous to common linear polyaryl ethers is described. The sodium salts of four AB₂ monomers each containing a single phenolic hydroxyl group and two aryl fluorides activated toward nucleophilic substitution by carbonyl, sulphonyl, or tetrafluorophenyl moieties are shown to polymerize in hot N, N-dimethylacetamide. The products are high molecular weight polymers (7000 < M_n < 36000), have narrow polydispersities (1.50 < M_w/M_n < 4.50), and are highly soluble in organic solvents. The molecular weights of two of the polymers increase with monomer concentration. The polymers are thermally stable (500 °C under N₂) and have glass transition temperatures ranging from 135 to 231 °C.     

Effects of Roxadustat on Erythropoietin Production in the Rat Body

Anemia is a major complication of chronic renal failure. To treat this anemia, prolylhydroxylase domain enzyme (PHD) inhibitors as well as erythropoiesis-stimulating agents (ESAs) have been used. Although PHD inhibitors rapidly stimulate erythropoietin (Epo) production, the precise sites of Epo production following the administration of these drugs have not been identified. We developed a novel method for the detection of the Epo protein that employs deglycosylation-coupled Western blotting. With protein deglycosylation, tissue Epo contents can be quantified over an extremely wide range. Using this method, we examined the effects of the PHD inhibitor, Roxadustat (ROX), and severe hypoxia on Epo production in various tissues in rats. We observed that ROX increased Epo mRNA expression in both the kidneys and liver. However, Epo protein was detected in the kidneys but not in the liver. Epo protein was also detected in the salivary glands, spleen, epididymis and ovaries. However, both PHD inhibitors (ROX) and severe hypoxia increased the Epo protein abundance only in the kidneys. These data show that, while Epo is produced in many tissues, PHD inhibitors as well as severe hypoxia regulate Epo production only in the kidneys.     

Comparative Hydrodynamic Study on Non-Aqueous Soluble Archaeological Wood Consolidants: Butvar B-98 and PDMS-OH Siloxanes

Butvar B-98 and PDMS-OH both have a demonstrable ability as consolidants for archaeological wood. This makes them both potential treatment options for the Oseberg collection, which is one of the most important archaeological finds from the Viking era. Both Butvar B-98 and PDMS-OH are soluble in organic solvents, offering a useful alternative to aqueous-based consolidants. Extensive characterisation studies were carried out on both of these polymers, with the use of analytical ultracentrifugation and viscometry, for the benefit of conservators wanting to know more about the physical properties of these materials. Short column sedimentation equilibrium analysis using SEDFIT-MSTAR revealed a weight-average molar mass (weight-average molecular weight) M_w of (54.0 ± 1.5) kDa (kg · mol⁻¹) for Butvar B-98, while four samples of PDMS-OH siloxanes (each with a different molar mass) had an M_w of (52.5 ± 3.0) kDa, (38.8 ± 1.5) kDa, (6.2 ± 0.7) kDa and (1.6 ± 0.1) kDa. Sedimentation velocity confirmed that all polymers were heterogeneous, with a wide range of molar masses. All molecular species showed considerable conformational asymmetry from measurements of intrinsic viscosity, which would facilitate networking interactions as consolidants. It is anticipated that the accumulated data on these two consolidants will enable conservators to make a more informed decision when it comes to choosing which treatment to administer to archaeological artefacts.     

Mammalian-like Purple Acid Phosphatases in Plants

Introduction Purpleacidphosphatases(PAPs)compriseofa familyofbinuclearmetal containinghydrolases,some membersofwhichhavebeenisolatedandcharacterized fromanimal,plantandfungalsources[1].PAPsnoton lycatalyzethehydrolysesofawiderangeofphosphate estersandanhy…