Ivana Škugor Rončević

Real-time monitoring of “self-oxidation” of cysteine in presence of Cu2+ : Novel findings in the oxidation mechanism

A novel approach for investigation of a mechanism and rate of “self-oxidation” of cysteine in the presence of Cu2+ is presented. Continuous monitoring was performed using simple, low-cost, and widely available commercial ion-selective electrode for Cu2+. Presented procedure provides a complete real-time picture of overall oxidation process and has revealed a sequentially organized process, with the domination of certain reactions in each stage. A plausible mechanism, in the light of the previously reported explanation, has been proposed to account for the experimental results together with an adequate scheme of the overall process. The dependence of both the pH (measurements were performed at pH 5, 7, 8) and the concentration of the initially present Cu2+ is presented and discussed. Additionally, information into the process was collected by experiments performed in oxygen-free atmosphere and changes in the mechanism of oxidation, at weakly alkaline pH values, were observed. Information presented in this study can be utilized in advanced biochemical monitoring systems, when considering the importance of the position of cysteine and cysteine containing peptides in metabolic processes.Graphical abstract

Surface Modifications of the Mg Alloy by Self-Assembled Monolayers of Fatty Acids

As biocompatible, osteoconductive, and degradable materials magnesium and its alloys are promising candidates for temporary implants. The main limitation of their use in the clinical application is the fast degradation inhysiological environments. Several possibilities exist to tailor the degradation rate of magnesium by using alloying elements and protective coatings. In the present study the native and anodically formed oxide films on the Mg-alloy (AZ91D) were modified with the self assembling monolayers (SAMs) of a long-chain carboxylic acid to protect the alloy degradation in a physiological solution. Fourier transform infrared spectroscopy (FTIR), electrochemical impedance spectroscopy (EIS) and voltammetry methods were used to examine the surface layers ; their structural properties and corrosion resistance in the Hanks′ solution.