Effect of an Emollient Emulsion Containing 15.0% of Caprylic/Capric Triglyceride on the Urocanic Acid of the Stratum Corneum

Natural moisturizing factor (NMF) includes several compounds in the stratum corneum (SC), among them, urocanic acid (UCA). Ultraviolet (UV) exposure turns the trans-UCA of the SC into its cis isomer. We investigated the impact of a topical emollient emulsion treatment on the UCA isomers of the SC exposed to artificial UV stress. Aliquots of emollient emulsion were applied in healthy subjects for 2 h on delimited areas of the volar forearm, then, the SC was removed by tape stripping. Tapes were irradiated in a solar simulator chamber and a high performance liquid chromatograph was used to quantify UCA isomers from stripped SC extract. The amount of both UCA isomers were almost twice higher in the SC treated with the emollient emulsion. We also observed that the UV irradiation elevated the amount of the cis/trans UCA ratio on the SC (non-treated and treated), suggesting that the emollient sample was not able to avoid the UCA isomerization. The in vivo tests corroborated with the UCA data obtained ex vivo, since we found an increase in the superficial skin hydration with respective reduction of the TEWL, probably occurring by the occlusion performed by the emollient emulsion containing 15.0% w/w of caprylic/capric triglyceride.

Characterization of LC-MS based urine metabolomics in healthy children and adults

Previous studies reported that sex and age could influence urine metabolomics, which should be considered in biomarker discovery. As a consequence, for the baseline of urine metabolomics characteristics, it becomes critical to avoid confounding effects in clinical cohort studies. In this study, we provided a comprehensive lifespan characterization of urine metabolomics in a cohort of 348 healthy children and 315 adults, aged 1 to 78 years, using liquid chromatography coupled with high resolution mass spectrometry. Our results suggest that sex-dependent urine metabolites are much greater in adults than in children. The pantothenate and CoA biosynthesis and alanine metabolism pathways were enriched in early life. Androgen and estrogen metabolism showed high activity during adolescence and youth stages. Pyrimidine metabolism was enriched in the geriatric stage. Based on the above analysis, metabolomic characteristics of each age stage were provided. This work could help us understand the baseline of urine metabolism characteristics and contribute to further studies of clinical disease biomarker discovery.

Tuning Receptor Properties of Metal-Amyloid Beta Complexes. Studies on the Interaction between Ni(II)-Aβ5-9 and Phosphates/Nucleotides

Amyloid-beta (Aβ) peptides, potentially relevant in the pathology of Alzheimer's disease, possess distinctive coordination properties, enabling an effective binding of transition-metal ions, with a preference for Cu(II). In this work, we found that a N-truncated Aβ analogue bearing a His-2 motif, Aβ5-9, forms a stable Ni(II) high-spin octahedral complex at a physiological pH of 7.4 with labile coordination sites and facilitates ternary interactions with phosphates and nucleotides. As the pH increased above 9, a spin transition from a high-spin to a low-spin square-planar Ni(II) complex was observed. Employing electrochemical techniques, we showed that interactions between the binary Ni(II)-Aβ5-9 complex and phosphate species result in significant changes in the Ni(II) oxidation signal. Thus, the Ni(II)-Aβ5-9 complex could potentially serve as a receptor in electrochemical biosensors for phosphate species. The obtained results could also be important for nickel toxicology.

“Doing More with Less”: Ni(II)@ORMOSIL, a Novel Sol-Gel Pre-Catalyst for the Reduction of Nitrobenzene

Reduction of nitrobenzene with NaBH4 using zero-valent iron nanoparticles (ZVI-NPs) and NiCl2∙6H2O incorporated in organically modified hybrid silica matrices as ZVI@ORMOSIL and Ni(II)@ORMOSIL catalysts is proposed as a remediation strategy. Ni(II)@ORMOSIL is prepared by ion-exchanging H+ of the ORMOSIL matrix with NiII. Ni(II)@ORMOSIL is a pre-catalyst that undergoes reduction by NaBH4 by an in-situ reaction and promotes nitrobenzene reduction by the unconsumed NaBH4, leading to sparing use of the catalyst. Ni(II)@ORMOSIL undergoes color change from green to black in this process, returning to a green hue after washing and drying. Nitrobenzene reductions were examined in aqueous acetonitrile solvent mixtures, and the reduction cascade produced the reaction end-products with catalytic implications. Plausible mechanisms of ZVI@ORMOSIL and Ni(II)@ORMOSIL catalyzed reductions of nitrobenzene are discussed. This work is the first to report M(II)@ORMOSIL pre-catalysts for in-situ reduction of nitrobenzene, and expands the scope of the ORMOSIL series of catalysts for the reduction of polluting compounds. This approach enables the development of catalysts that use very low concentrations of transition metal cations.

Influence of d-Electron Divalent Metal Ions in Complex Formation with L-Tartaric and L-Malic Acids

Binary complexes of α-hydroxy acids (L-Tartaric acid and L-Malic acid) with d-electron metal ions (copper, cobalt, nickel) were investigated. Potentiometric measurements have been performed in aqueous solution with computer analysis of the data for determination of the stability constants of complexes formed in the studied systems. The coordination mode of the complexes was defined using spectroscopic methods: electron paramagnetic resonance (EPR), ultraviolet-visible (UV-Vis), circular dichroism (CD), and infrared (IR). Results of the equilibrium studies have provided evidence for the formation of dimers with copper(II) ions and monomers with cobalt(II) and nickel(II) ions.

Trans-urocanic acid enhances tenofovir alafenamide stability for long-acting HIV applications

Long-acting (LA) pre-exposure prophylaxis (PrEP) for HIV prevention is poised to address non-adherence and implementation challenges by alleviating the burden of user-dependent dosing. Due to its potency, tenofovir alafenamide (TAF) is a viable candidate for LA PrEP. However, the inherent hydrolytic instability of TAF presents a challenge for application in LA systems. In this work, we examined the mechanism of TAF hydrolysis in a reservoir-based implant system and characterized TAF degradation kinetics as a function of the solution pH. We determined a pH "stability window" between pH 4.8 - 5.8 in which TAF degradation is substantially mitigated, with minimal degradation at pH 5.3. In a pursuit of a TAF formulation suitable for LA PrEP, we studied trans-urocanic acid (UA) as a buffer excipient. Here we show that UA can maintain the pH of TAF free base (TAFfb) solution inside a surrogate implant model at approximately pH 5.4. Through in vitro analysis, we demonstrated preservation of released TAF purity above 90% for over 9 months. Further, we performed an in vivo assessment of TAFfb-UA formulation in a reservoir-based nanofluidic implant inserted subcutaneously in non-human primates. Preventive levels of tenofovir diphosphate above 100 fmol/106 peripheral blood mononuclear cells were achieved in 2 days and sustained over 35 days. Fluid retrieved from implants after 60 days of implantation showed that UA preserved the aqueous phase in the implant at ~ pH 5.5, effectively counteracting the neutralizing action of interstitial fluids. Moreover, residual TAF in the implants maintained > 98% purity. Overall, TAF-UA represents a viable formulation applicable for LA HIV PrEP.

Ternary Cu(II) Complex with GHK Peptide and Cis-Urocanic Acid as a Potential Physiologically Functional Copper Chelate

The tripeptide NH₂–Gly–His–Lys–COOH (GHK), cis-urocanic acid (cis-UCA) and Cu(II) ions are physiological constituents of the human body and they co-occur (e.g., in the skin and the plasma). While GHK is known as Cu(II)-binding molecule, we found that urocanic acid also coordinates Cu(II) ions. Furthermore, both ligands create ternary Cu(II) complex being probably physiologically functional species. Regarding the natural concentrations of the studied molecules in some human tissues, together with the affinities reported here, we conclude that the ternary complex [GHK][Cu(II)][cis-urocanic acid] may be partly responsible for biological effects of GHK and urocanic acid described in the literature.

Application of Ni-Oxide@TiO₂ Core-Shell Structures to Photocatalytic Mixed Dye Degradation, CO Oxidation, and Supercapacitors

Performing diverse application tests on synthesized metal oxides is critical for identifying suitable application areas based on the material performances. In the present study, Ni-oxide@TiO₂ core-shell materials were synthesized and applied to photocatalytic mixed dye (methyl orange + rhodamine + methylene blue) degradation under ultraviolet (UV) and visible lights, CO oxidation, and supercapacitors. Their physicochemical properties were examined by field-emission scanning electron microscopy, X-ray diffraction analysis, Fourier-transform infrared spectroscopy, and UV-visible absorption spectroscopy. It was shown that their performances were highly dependent on the morphology, thermal treatment procedure, and TiO₂ overlayer coating.

Dissecting ITC data of metal ions binding to ligands and proteins

BACKGROUND

ITC is a powerful technique that can reliably assess the thermodynamic underpinnings of a wide range of binding events. When metal ions are involved, complications arise in evaluating the data due to unavoidable solution chemistry that includes metal speciation and a variety of linked equilibria.

SCOPE OF REVIEW

This paper identifies these concerns, provides recommendations to avoid common mistakes, and guides the reader through the mathematical treatment of ITC data to arrive at a set of thermodynamic state functions that describe identical chemical events and, ideally, are independent of solution conditions. Further, common metal chromophores used in biological metal sensing studies are proposed as a robust system to determine unknown solution competition.

MAJOR CONCLUSIONS

Metal ions present several complications in ITC experiments. This review presents strategies to avoid these pitfalls and proposes and experimentally validates mathematical approaches to deconvolute complex equilibria that exist in these systems.

GENERAL SIGNIFICANCE

This review discusses the wide range of complications that exists in metal-based ITC experiments. It provides a starting point for scientists new to this field and articulates concerns that will help experienced researchers troubleshoot experiments.

SEDPHAT--a platform for global ITC analysis and global multi-method analysis of molecular interactions

Isothermal titration calorimetry experiments can provide significantly more detailed information about molecular interactions when combined in global analysis. For example, global analysis can improve the precision of binding affinity and enthalpy, and of possible linkage parameters, even for simple bimolecular interactions, and greatly facilitate the study of multi-site and multi-component systems with competition or cooperativity. A pre-requisite for global analysis is the departure from the traditional binding model, including an 'n'-value describing unphysical, non-integral numbers of sites. Instead, concentration correction factors can be introduced to account for either errors in the concentration determination or for the presence of inactive fractions of material. SEDPHAT is a computer program that embeds these ideas and provides a graphical user interface for the seamless combination of biophysical experiments to be globally modeled with a large number of different binding models. It offers statistical tools for the rigorous determination of parameter errors, correlations, as well as advanced statistical functions for global ITC (gITC) and global multi-method analysis (GMMA). SEDPHAT will also take full advantage of error bars of individual titration data points determined with the unbiased integration software NITPIC. The present communication reviews principles and strategies of global analysis for ITC and its extension to GMMA in SEDPHAT. We will also introduce a new graphical tool for aiding experimental design by surveying the concentration space and generating simulated data sets, which can be subsequently statistically examined for their information content. This procedure can replace the 'c'-value as an experimental design parameter, which ceases to be helpful for multi-site systems and in the context of gITC.

Ni(ii) ions cleave and inactivate human alpha-1 antitrypsin hydrolytically, implicating nickel exposure as a contributing factor in pathologies related to antitrypsin deficiency

Ni(ii) ions cleave AAT hydrolytically, inactivating the protein.