Mechanistic Elucidations of Highly Dispersed Metalloporphyrin Metal-Organic Framework Catalysts for CO2 Electroreduction

Immobilization of porphyrin complexes into crystalline metal–organic frameworks (MOFs) enables high exposure of porphyrin active sites for CO₂ electroreduction. Herein, well-dispersed iron-porphyrin-based MOF (PCN-222(Fe)) on carbon-based electrodes revealed optimal turnover frequencies for CO₂ electroreduction to CO at 1 wt.% catalyst loading, beyond which the intrinsic catalyst activity declined due to CO₂ mass transport limitations. In situ Raman suggested that PCN-222(Fe) maintained its structure under electrochemical bias, permitting mechanistic investigations. These revealed a stepwise electron transfer-proton transfer mechanism for CO₂ electroreduction on PCN-222(Fe) electrodes, which followed a shift from a rate-limiting electron transfer to CO₂ mass transfer as the potential increased from −0.6 V to −1.0 V vs. RHE. Our results demonstrate how intrinsic catalytic investigations and in situ spectroscopy are needed to elucidate CO₂ electroreduction mechanisms on PCN-222(Fe) MOFs.     

Characterization and adsorption capacity of Brazilian kaolin

Journal of Radioanalytical and Nuclear Chemistry - This study has evaluated chemical, radiological composition and determined the cation exchange capacity (CEC) for three commercially available...     

Compatibility study of tobramycin and pharmaceutical excipients using differential scanning calorimetry,FTIR, DRX,and HPLC

Differential scanning calorimetry (DSC), isothermal stress testing–Fourier transform infrared spectroscopy (IST–FTIR), isothermal stress testing–high-performance liquid chromatography, and powder X-ray diffraction (PDRX) were used as screening techniques for assessing the compatibility of tobramycin with some currently employed ophthalmic excipients. In the first phase of the study, DSC was used as a tool to detect any interaction. The absolute value of the difference between the enthalpy of the pure tobramycin melting peak and that of its melting peak in the different analyzed mixtures was chosen as a parameter of the drug–excipient interaction degree. DSC results demonstrated that benzalkonium chloride, monobasic sodium phosphate, boric acid, edetate disodium, sodium metabisulfite, thimerosal, and potassium sorbate interact with tobramycin. Taking into account these results, it could be suggested that some of the changes observed in the IST–FTIR spectra of binary blends of tobramycin and some of the excipients would account for a possible interaction between the mixture component. In this study, PDRX did not provide much information, since only tobramycin–thimerosal interactions could be detected. DSC and IST–FTIR are suitable and simple methods for the detection of potential incompatibilities between active pharmaceutical ingredient (API) and excipients.

     

Theoretical Study of Aerosol Filtration by Nucleopore Filters: The Intermediate Crossover Regime of Brownian Diffusion and Direct Interception

We study the problem of aerosol filtration by formulating a unified approach that incorporates the dominant mechanisms of particle capture in cylindrical pores. The theoretical approach presented here takes into account the effects of flow slip at the pore wall and predicts an enhanced efficiency in the intermediate crossover regime between Brownian diffusion and direct interception. We also suggest how the results obtained for cylindrical pores can be used to estimate the efficiency of granular ceramic filters in the region of the most penetrating particle size, where the enhanced efficiency effects are strongly amplified by the large number of pores, or more generally unit bed elements, acting in series. Copyright 2001 Academic Press.     

trans‐[N,N′‐Bis­(salicyl­idene)­cyclo­hexane‐1,2‐diaminato]­nickel(II)–chloro­form (1/1)

In the title complex, trans‐{2,2′‐[cyclo­hexane‐1,2‐diyl­bis­(ni­t­rilo­methyl­idyne)]­di­phenol­ato‐κ⁴O,N,N′,O′}­nickel(II)–chloro­form (1/1), [Ni(C₂₀H₂₀N₂O₂)]·CHCl₃, the Ni atom has a square‐planar geometry, slightly tetrahedrally distorted. The Ni—N and Ni—O bonding distances are within the expected ranges for Ni–Schiff base derivatives. The di­imine bridge has a gauche conformation with the cyclo­hexyl ring almost coplanar with the NiN₂O₂ plane. The complex mol­ecules pack in dimers with an Ni?Ni distance of 3.59 (1) Å and form a three‐dimensional structure displaying a herring‐bone configuration. Channels are occupied by solvent mol­ecules, which are involved in C—H?O hydrogen bonds with the ligand O atoms.     

Physical properties (thermal,thermomechanical, magnetic,and adhesive) of some smart orthodontic wires

Thermal, thermomechanical, and caloric properties of commercial orthodontic wires (produced by Natural Orthodontics Corp., USA) with cylindrical and rectangular geometry were studied. Depending on the applied forces, there were identified the range of elasticity, the elasticity–viscoelasticity coexistence domain and the domain in which a maximum force of 18 N is applied, for the orthodontic wires. When increasing the thickness of orthodontic wires, deformation decreases. The Controlled Force Module, in the tension mode, was used for the determination of the orthodontic wires elongation at application of the stretching forces from 0 to 13 N, at 35 °C, maintaining each static force value for 3 min. The increase in the cross-sectional area of the orthodontic wires disfavors the process of elongation of the sample, at the same applied static force. Using the Multi-Frequency–Strain–Stress modulus, in the tension mode, DMA cyclic heating–cooling measurements were performed. The measured physical quantities for orthodontic wires were Storage Modulus, Loss Modulus, Tanδ and Stiffness, at heating and cooling. Thus, the characteristic temperatures of the phase transitions (A_s, A_f, M_s, M_f), of all the studied orthodontic wires were identified. Also, the values of the elasticity modulus (Young’s Modulus) of the orthodontic wires were calculated at 35 °C. With the DSC Q200 device, using temperature-modulated differential scanning calorimetry method, a multi-step temperature variation program, was applied to a rectangular wire, in three stages (cooling–heating–cooling). Through the interpretation of heat fluxes (reversible, irreversible and total), the phase transitions in the formation of martensite, austenite, but also of the rombohedral phase (R-phase), were identified. Formations of austenite and martensite were also evidenced by the classical DSC method, but the classical DSC method also enabled the R-phase identification. The adherence of some food dyes on the orthodontic wires, as well as the modification of the surface roughness of the orthodontic wire after the deposition of the food dye, was also studied. By magnetic measurements, it was established that the orthodontic wires had paramagnetic properties at room temperature, and nitinol was a mixture of 49.2% austenite and 50.8% martensite.

     

Antiproliferative factor (APF) binds specifically to sites within the cytoskeleton-associated protein 4 (CKAP4) extracellular domain

Background

Antiproliferative factor (APF) is a sialoglycopeptide elevated in the urine of patients with interstitial cystitis—a chronic, painful bladder disease. APF inhibits the proliferation of normal bladder epithelial cells and cancer cells in vitro, presumably by binding to its cellular receptor, cytoskeleton associated-protein 4 (CKAP4); however, the biophysical interaction of APF with CKAP4 has not been characterized previously. In this study, we used surface plasmon resonance (SPR) to explore the binding kinetics of the interaction of APF and as-APF (a desialylated APF analogue with full activity) to CKAP4.

Results

We immobilized non-glycosylated APF (TVPAAVVVA) to the Fc1 channel as the control and as-APF to Fc2 channel as the ligand in order to measure the binding of CKAP4 recombinant proteins encompassing only the extracellular domain (Aa 127–602) or the extracellular domain plus the transmembrane domain (Aa 106–602). Positive binding was detected to both CKAP4_126–602 and CKAP4_106–602, suggesting that as-APF can bind specifically to CKAP4 and that the potential binding site(s) are located within the extracellular domain. To identify the primary APF binding site(s) within the CKAP4 extracellular domain, deletion mutants were designed according to structural predictions, and the purified recombinant proteins were immobilized on a CM5 chip through amine-coupling to measure as-APF binding activity. Importantly, both CKAP4_127–360 and CKAP4_361–524 exhibited a fast association rate (k _on ) and a slow dissociation rate (k _off ), thus generating high binding affinity and suggesting that both regions contribute relatively equally to overall as-APF binding. Therefore, two or more as-APF binding sites may exist within the Aa 127–524 region of the CKAP4 extracellular domain.

Conclusions

We determined that the CKAP4_127–360 and CKAP4_361–524 mutants exhibit improved binding activity to as-APF as compared to the full-length extracellular domain, making it possible to detect low concentrations of as-APF in urine, thereby establishing a foundation for a non-invasive diagnostic assay for IC. Further, these data have revealed novel APF binding site(s) suggesting that targeting this region of CKAP4 to inhibit APF binding may be a useful strategy for treating IC-related bladder pathology.