Electrochemistry and spectroelectrochemistry of bioactive hydroxyquinolines: a mechanistic study

The oxidation mechanism of selected hydroxyquinoline carboxylic acids such as 8-hydroxyquinoline-7-carboxylic acid (1), the two positional isomers 2-methyl-8-hydroxyquinoline-7-carboxylic acid (3) and 2-methyl-5-hydroxyquinoline-6-carboxylic acid (4), as well as other hydroxyquinolines were studied in aprotic environment using cyclic voltammetry, controlled potential electrolysis, in situ UV vis and IR spectroelectrochemistry, and HPLC-MS/MS techniques. IR spectroelectrochemistry showed that oxidation unexpectedly proceeds together with protonation of the starting compound. We proved that the nitrogen atom in the heterocycle of hydroxyquinolines is protonated during the apparent 0.7 electron oxidation process. This was rationalized by the autodeprotonation reaction by another two starting molecules of hydroxyquinoline, so that the overall oxidation mechanism involves two electrons and three starting molecules. Both the electrochemical and spectroelectrochemical results showed that the oxidation mechanism is not influenced by the presence of the carboxylic group in the chemical structure of hydroxyquinolines, as results from oxidation of 2,7-dimethyl-S-hydroxyquinoline (6). In the presence of a strong proton acceptor such as pyridine, the oxidation ECEC process involves two electrons and two protons per one molecule of the hydroxyquinoline derivative. The electron transfer efficiency of hydroxyquinolines in biosystems may be related to protonation of biocompounds containing nitrogen bases. Molecular orbital calculations support the experimental findings

A voltammetric pH sensor for food and biological matrices

Measurement of pH is of fundamental importance in a wide range of environmental, biological and industrial applications. Glass electrode and litmus paper are widely used for this, but the former is difficult to miniaturize, prone to drift and fragile, the latter is inaccurate. This paper describes a pH sensor based on an indoaniline-derivative (4-((4-aminophenyl)imino)-2,6-dimethoxycyclohexa-2,5-dien-1-one), which exploits alternating current voltammetry to measure pH in the range between 2 and 12. The synthetized indoaniline-derivative was not genotoxic (A. cepa assay), and the sensor reliably measured pH in milk, tea, orange juice, blood, urine and saliva. Results were comparable with those obtained with a glass electrode calibrated with certified solutions (maximum relative standard deviation of 3 % and accuracy less than 0.2 pH unit). The sensor had negligible hysteresis, an almost Nernstian sensitivity (56 mV/pH) and was fully functional after a two-month storage. Sensor response showed a limited dependence on temperature (0.14 mV per pH unit and °C) and limited sensitivity to possible interferents such as lithium and sodium ions; its response to these was similar to that of a glass electrode, and was absent for ascorbic acid

Hlasy z ticha? Úvahy o „coming outu“ v socialistickém Československu

Region střední a východní Evropy ssse na zákaldě svých despotickýh sociálních podmínek v bývalé socialistické společnosti staly symboly nemožnosti formulovat ne-heterosexuální identity. Tato studie analyzuje data z 19 hloubkových rozhovorů s lidmi staršími než 50 let žijícími v České republice, kteří se identifikují jako lesbičky, homosexuálové nebo bisexuálové. Zaměřuje se na způsoby, kterými jejich vynucené mlčení a neschopnost mluvit o svých sexuálních touhách rezonovaly v jejich životopisných příbězích.The region of Central and Eastern Europe and oppressive social conditions in former socialist society often became symbols of the impossibility to articulate non-heterosexual identities under the conditions of a totalitarian regime. This study analyzes data from 19 in-depth interviews with people older than 50 living in the Czech Republic who identify themselves as lesbian, gay, or bisexual. It focuses on the ways in which their forced silence and inability to speak about their sexual desires resonated throughout their biographical narratives. The first part of this paper focuses on themes surrounding the absence of representations of non-heterosexual identities in socialist Czechoslovakia’s public sphere and the impact of this absence on participants’ perceptions of their own life experiences. The second part of the paper analyzes the ways in which participants relate to their own coming out and their reflections on their previous lives in relation to newfound opportunities to live outside of heterosexual norms. The paper strives to problematize the concept of “silence” as one of the defining features of this generation, in contrast with the concept of coming out as a sign of emancipation in younger generations