The Structure and Properties of TiO(2)-Cu(II)-EDTA Ternary Surface Complexes

The Role of the CuCl Active Complex in the Stereoselectivity of the Salt-Induced Peptide Formation Reaction: Insights from Density Functional Theory Calculations

The salt-induced peptide formation (SIPF) reaction is a prebiotically plausible mechanism for the spontaneous polymerization of amino acids into peptides on early Earth. Experimental investigations of the SIPF reaction have found that in certain conditions, the l enantiomer is more reactive than the d enantiomer, indicating its potential role in the rise of biohomochirality. Previous work hypothesized that the distortion of the CuCl active complex toward a tetrahedral-like structure increases the central chirality on the Cu ion, which amplifies the inherent parity-violating energy differences between l- and d-amino acid enantiomers, leading to stereoselectivity. Computational evaluations of this theory have been limited to the protonated-neutral l + l forms of the CuCl active complex. Here, density functional theory methods were used to compare the energies and geometries of the homochiral (l + l and d + d) and heterochiral (l + d) CuCl-amino acid complexes for both the positive-neutral and neutral-neutral forms for alanine, valine, and proline. Significant energy differences were not observed between different chiral active complexes (i.e., d + d, l + l vs. l + d), and the distortions of active complexes between stereoselective systems and non-selective systems were not consistent, indicating that the geometry of the active complex is not the primary driver of the observed stereoselectivity of the SIPF reaction.

Transparent Copper-Based Antibacterial Coatings with Enhanced Efficacy against Pseudomonas aeruginosa

Bacterial surface contamination is a major cause of hospital-associated infections. Antibacterial coatings can play an important role in reducing bacterial transmission via inanimate surfaces in healthcare settings. In this work, transparent copper-based antibacterial coatings were fabricated on commercial poly(vinyl fluoride) and stainless steel. Acrylated quaternized chitosan and ethylenediaminetetraacetic acid were covalently grafted on the substrate for complexation with copper ions. The number of viable Staphylococcus aureus in a droplet [containing ∼10⁴ colony forming units (CFU)], deposited on the copper-containing coating decreased by ∼96% within 60 min at 25 °C. With Pseudomonas aeruginosa, one of the most virulent and hardest to kill bacteria, no CFU could be observed within the same time span (killing efficacy >99.8% based on the detection limit). An increase in copper release from the coating was observed in the presence of P. aeruginosa, which was postulated to be due to the proteolytic activity of P. aeruginosa. The higher efficacy of the coating against P. aeruginosa compared to S. aureus is thus attributed to this increased copper release from the coating, which resulted in extensive bacterial membrane damage and death. The copper-containing coating on poly(vinyl fluoride) retained its antibacterial efficacy after 100 wipes with a water-wetted cloth or isopropanol wipes, demonstrating its durability and long-term efficacy. The coating did not exhibit significant cytotoxicity toward mammalian fibroblasts, further demonstrating its potential for mitigating bacterial transmission in a clinical setting.

Structural modification of mordenite zeolite with Fe for the photo-degradation of EDTA

Fe(2+) was incorporated inside mordenite through ion exchange technique in aqueous solution. The amount of Fe loading was 25-100 wt %, using FeSO(4).7H(2)O as precursor and Na-mordenite starting material Na-M. The Fe incorporated (Fe-M) thus prepared was characterized by XRD, FTIR and N(2) adsorption measurements. It was found that Fe mordenite retained the same structure as that for Na-mordenite which may indicate that Fe well dispersed into mordenite channels. BET indicated that Fe-M samples possessed higher surface area compared to the parent Na-M. Photocatalytic degradation of EDTA was carried out in presence of the prepared Fe-M catalysts. Effects of catalyst concentration and temperature were also studied. Thermodynamic parameters calculated for 50% Fe-M showed the highest catalytic activity toward EDTA degradation.

Environmental chemistry of aminopolycarboxylate chelating agents

Aminopolycarboxylate chelating agents are under scrutiny due to their influence on metal availability and mobility and in particular due to their persistence in the environment. In this review chelate adsorption, metal-mobilization, metal-exchange, mineral dissolution, reactive transport, photodegradation, and chemical degradation are all shown to be substantially affected by the chelated metal ion. The different reactivities of the metal-complexes have to be considered when assessing the reactions of chelating agents in the environment because they occur in natural waters predominantly in the form of metal complexes. Knowing the speciation of chelating agents in natural waters is therefore crucial for predicting their environmental fate. Despite this importance, only a few speciation measurements have been reported for natural waters, and model calculations have been frequently used instead. These calculations are, however, complicated by slow metal-exchange reactions that result in a nonequilibrium speciation and by the presence of naturally occurring ligands that compete with the chelating agents for available metals. The basis for a refined risk assessment of aminocarboxylate chelates should be the actual speciation in the natural water directly determined by analytical methods. The discussion of the influence of chelates on metal availability and fate also has to include the potential presence of other aminopolycarboxylate chelating agents besides the well-known EDTA and NTA.