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Oxidative transformation of cysteine thiol groups into different functional groups is considered a significant posttranslational modification of great importance in pathological and physiological processes. A cysteine sulfenic acid (SA) residue is the transient state for thiol group oxidation and it can react with free thiols to form disulfide bonds or can be further oxidized with reactive oxygen/reactive nitrogen species (ROS/RNS) to form sulfinic and sulfonic acids. The increase in ROS/RNS concentrations is correlated to age-related diseases such as cancer and Alzheimer's disease. Since the formation of SA represents a transient state of oxidation of thiols, its formation can be considered a redox-sensitive sensor for the presence of ROS/RNS. Thereby, the detection of the short-lived SA will provide greater insight into the redox-mediated events that alter the structure and function of peptides and proteins. The aim of this study is to provide a new strategy for the highly sensitive and specific detection of SA in peptides as a proof of concept. For this aim, SA was firstly generated in model peptides on oxidation with HO and then captured by the linear alkyne β-ketoester (KE) previously linked to a lanthanide (Ln)-containing chelator (Ln-DOTA, where DOTA is 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid). The linking of the KE to DOTA was performed by click chemistry, resulting in a new reagent (Ln-DOTA-KE) that permits highly sensitive elemental (inductively coupled plasma) and molecular (electrospray) mass spectrometric detection. The new reagent (Ln-DOTA-KE) reacts specifically with SA, offering improved reactivity at physiological pH, facile derivatization and a cell-membrane-permeable compound that has promising future applications. Graphical Abstract A new derivatizing reagent for specific detection of sulphenic acid (SA) generated in model peptides by oxidation of cysteine groups is presented in this work.

Formation of cysteine sulfenic acid (SA) is considered a transient state of thiol oxidation in living organisms that can be either reduced back or continue to result in the formation of sulfinic and sulfonic acids. As any disturbance in oxidation is correlated to age-related diseases such as cancer and Alzheimer's disease, the detection of SA transient state formed a sensor for such redox-mediated events. Thus, detection of low amounts of SA is critical in order to prevent further oxidative damage of cells and tissues and for this aim specific strategies have to be developed. In this work, detection and quantification of induced SA in human serum albumin is reported by specific capture using alkyne bketoester (KE) previously linked to a lanthanide (Ln)-containing chelator (Ln-DOTA, where DOTA is 1,4,7,10-tetraazacyclododecane-1,4,7,10-tetraacetic acid). SA formation was induced by hydrogen peroxide to mimic oxidative conditions produced in living cells by ROS and was detected using molecular and elemental mass spectrometric (MS) techniques. The developed strategy has been further applied to the determination of SA-induced formation in human serum by using affinity chromatography for purification of albumin followed by inductively coupled plasma mass spectrometry (ICP-MS) to monitor the formed SA linked to Ln-DOTA-KE in combination with isotope dilution analysis (IDA) for absolute quantification. Quantitative results showed levels of oxidative damage regarding SA formation in up to 40% of the albumin present.

This study investigated the nematicidal and fungicidal activities of the two immiscible camphor and orange oils formulated in Janus emulsion (JE). JE was prepared from camphor and orange oils by a single-step emulsification with different concentrations chosen from an established phase diagram. Camphor oil nematicidal activity was studied against the root knot nematode Meloidogyne incognita, while orange oil fungicidal activity was studied against the wilt fungus Fusarium oxysporum f. sp. lycopersici (Fol). For a comparison study, different concentrations of JE and double emulsions were prepared. Results showed that JE had a significant mortality effect on the secondstage juveniles (J2s) M. incognita with 81% mortality and was able to delay the growth of Fol four and seven days after exposure, while changes in the efficiency of DE were recorded. Prepared JEs were shown to maintain the efficiency and to have slow release profiles for encapsulated oils.ARTICLE HISTORY

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