Modification of Protein by Disulfide S-Monoxide and Disulfide S-Dioxide: Distinctive Effects on PKC

Reaction of low-molecular-mass organoselenium compounds (and their sulphur analogues) with inflammation-associated oxidants

Selenium is an essential trace element in mammals, with the majority specifically encoded as seleno-L-cysteine into a range of selenoproteins. Many of these proteins play a key role in modulating oxidative stress, via either direct detoxification of biological oxidants, or repair of oxidised residues. Both selenium- and sulphur-containing residues react readily with the wide range of oxidants (including hydrogen peroxide, radicals, singlet oxygen and hypochlorous, hypobromous, hypothiocyanous and peroxynitrous acids) that are produced during inflammation and have been implicated in the development of a range of inflammatory diseases. Whilst selenium has similar properties to sulphur, it typically exhibits greater reactivity with most oxidants, and there are considerable differences in the subsequent reactivity and ease of repair of the oxidised species that are formed. This review discusses the chemistry of low-molecular-mass organoselenium compounds (e.g. selenoethers, diselenides and selenols) with inflammatory oxidants, with a particular focus on the reaction kinetics and product studies, with the differences in reactivity between selenium and sulphur analogues described in the selected examples. These data provide insight into the therapeutic potential of low-molecular-mass selenium-containing compounds to modulate the activity of both radical and molecular oxidants and provide protection against inflammation-induced damage. Progress in their therapeutic development (including modulation of potential selenium toxicity by strategic design) is demonstrated by a brief summary of some recent studies where novel organoselenium compounds have been used as wound healing or radioprotection agents and in the prevention of cardiovascular disease.

Captopril and its dimer captopril disulfide: photodegradation, aerobic biodegradation and identification of transformation products by HPLC-UV and LC-ion trap-MS(n)

In some countries effluents from hospitals and households are directly emitted into open ditches without any further treatment and with very little dilution. Under such circumstances photo- and biodegradation in the environment can occur. However, these processes do not necessarily end up with the complete mineralization of a chemical. Therefore, the biodegradability of photoproduct(s) by environmental bacteria is of interest. Cardiovascular diseases are the number one cause of death globally. Captopril (CP) is used in this study as it is widely used in Egypt and stated as one of the essential drugs in Egypt for hypertension. Three tests from the OECD series were used for biodegradation testing: Closed Bottle test (CBT; OECD 301 D), Manometric Respirometry test (MRT; OECD 301 F) and the modified Zahn-Wellens test (ZWT; OECD 302 B). Photodegradation (150 W medium-pressure Hg-lamp) of CP was studied. Also CBT was performed for captopril disulfide (CPDS) and samples received after 64 min and 512 min of photolysis. The primary elimination of CP and CPDS was monitored by LC-UV at 210 nm and structures of photoproducts were assessed by LC-UV-MS/MS (ion trap). Analysis of photodegradation samples by LC-MS/MS revealed CP sulfonic acid as the major photodegradation product of CP. No biodegradation was observed for CP, CPDS and of the mixture resulting from photo-treatment after 64 min in CBT. Partial biodegradation in the CBT and MRT was observed in samples taken after 512 min photolysis and for CP itself in MRT. Complete biodegradation and mineralization of CP occurred in the ZWT.

Synthesis of thiophenylalanine-containing peptides via Cu(I)-mediated cross-coupling

Aryl thiolates have unique reactive, redox, electronic, and spectroscopic properties. A practical approach to synthesize peptides containing thiophenylalanine has been developed via a novel Cu(I)-mediated cross-coupling reaction between thiolacetic acid and iodophenylalanine-containing peptides in the solid phase. This approach is compatible with all canonical proteinogenic functional groups, providing general access to aryl thiolates in peptides. Peptides containing thiophenylalanine (pK(a) 6.4) were readily elaborated to contain methyl, allyl, and nitrobenzyl thioethers, disulfides, sulfoxides, sulfones, or sulfonates.

Reactive sulfur species act as prooxidants in liposomal and skeletal muscle model systems

Reactive sulfur species (RSS) are redox-active sulfur compounds formed under conditions of oxidative stress that may be capable of initiating oxidation reactions. The objective of this research was to determine if two RSS, sulfite radicals and disulfide S-oxides (DSSO), induce oxidation in n-3 liposomes and muscle homogenates. Sulfite radicals and DSSO caused an increase in secondary oxidation products compared to the unoxidized control within 5 min of addition to liposomes. In muscle homogenates, DSSO caused immediate oxidation of sulfhydryls, whereas sulfite radicals caused a slow and linear oxidation of sulfhydryls and lipid. These results suggest that if conditions exist in muscle foods that promote the formation of RSS, they could be a factor in the course of lipid oxidation by either weakening antioxidant defenses or directly oxidizing lipid molecules.