Recent advances in probe design to detect reactive sulfur species and in the chemical reactions employed for fluorescence switching

Quantitative profiling of supersulfides naturally occurring in dietary meats and beans

Sulfur is essential in the inception of life and crucial for maintaining human health. This mineral is primarily supplied through the intake of proteins and is used for synthesizing various sulfur-containing biomolecules. Recent research has highlighted the biological significance of endogenous supersulfides, which include reactive persulfide species and sulfur catenated residues in thiol and proteins. Ingestion of exogenous sulfur compounds is essential for endogenous supersulfide production. However, the content and composition of supersulfides in foods remain unclear. This study investigated the supersulfide profiles of protein-rich foods, including edible animal meat and beans. Quantification of the supersulfide content revealed that natto, chicken liver, and bean sprouts contained abundant supersulfides. In general, the supersulfide content in beans and their derivatives was higher than that in animal meat. The highest proportion (2.15 %) was detected in natto, a traditional Japanese fermented soybean dish. These results suggest that the abundance of supersulfides, especially in foods like natto and bean sprouts, may contribute to their health-promoting properties. Our findings may have significant biological implications and warrant developing novel dietary intervention for the human health-promoting effects of dietary supersulfides abundantly present in protein-rich foods such as natto and bean sprouts.

An ICT-FRET-based ratiometric fluorescent probe for hydrogen polysulfide based on a coumarin-naphthalimide derivative

Hydrogen polysulfide (H2Sn, n > 1), as one of the important members of reactive sulfur species (RSS), plays a vital part in the processes of both their physiology and pathology. In this work, a ratiometric fluorescent probe for H2Sn had been designed and prepared based on the combination mechanism of intramolecular charge transfer (ICT) and fluorescence resonance energy transfer (FRET). The probe chose a coumarin derivative as the energy donor, a naphthalimide derivative as the energy acceptor and 2-fluoro-5-nitrobenzoate as the H2Sn recognition group. When H2Sn was not present in the system, the ICT process of the naphthalimide acceptor was inhibited and the FRET process from the coumarin donor to the naphthalimide acceptor was turned off. When H2Sn was added, both ICT and FRET occurred due to the nucleophilic substitution-cyclization reactions between the probe and hydrogen polysulfide. In addition, the ratio value of the emission intensities at 550 nm and 473 nm (I550 nm/I473 nm) of this probe had a good linear relationship with H2Sn concentration in the range of 6.0 × 10-7-5.0 × 10-5 mol·L-1, and a detection limit of 1.8 × 10-7 mol·L-1 was obtained. The developed probe had high selectivity and sensitivity, as well as good biocompatibility. Additionally, the probe had been used to successfully image both indigenous and exogenous hydrogen polysulfide in A549 cells using confocal microscope.

Fluorescent probes for the detection of disease-associated biomarkers

Fluorescent probes have emerged as indispensable chemical tools to the field of chemical biology and medicine. The ability to detect intracellular species and monitor physiological processes has not only advanced our knowledge in biology but has provided new approaches towards disease diagnosis. In this review, we detail the design criteria and strategies for some recently reported fluorescent probes that can detect a wide range of biologically important species in cells and in vivo. In doing so, we highlight the importance of each biological species and their role in biological systems and for disease progression. We then discuss the current problems and challenges of existing technologies and provide our perspective on the future directions of the research area. Overall, we hope this review will provide inspiration for researchers and prove as useful guide for the development of the next generation of fluorescent probes.

Gut microbiota reinforce host antioxidant capacity via the generation of reactive sulfur species

Gut microbiota act beyond the gastrointestinal tract to regulate the physiology of the host. However, their contribution to the antioxidant capacity of the host remains largely understudied. In this study, we observe that gut bacteria increase the steady-state plasma levels of high-antioxidant molecules, reactive sulfur species (RSS), such as hydrogen sulfide and cysteine persulfide (CysSSH), in the host. Moreover, gut bacteria utilize cystine as a substrate to enzymatically produce CysSSH. Administration of cystine to mice increases their plasma levels of RSS and suppresses the concanavalin-A-induced oxidative stress and liver damage in a gut-microbiota-dependent manner. We find that gut bacteria belonging to the Lachnospiraceae and Ruminococcaceae families have a high capacity to produce RSS, requiring pyridoxal 5'-phosphate for their enzymatic reactions. Collectively, our data demonstrate that gut microbiota enhance the antioxidant capacity of the host through the generation of RSS.

The Modus Operandi of Hydrogen Sulfide(H2S)-Dependent Protein Persulfidation in Higher Plants

Protein persulfidation is a post-translational modification (PTM) mediated by hydrogen sulfide (H₂S), which affects the thiol group of cysteine residues from target proteins and can have a positive, negative or zero impact on protein function. Due to advances in proteomic techniques, the number of potential protein targets identified in higher plants, which are affected by this PTM, has increased considerably. However, its precise impact on biological function needs to be evaluated at the experimental level in purified proteins in order to identify the specific cysteine(s) residue(s) affected. It also needs to be evaluated at the cellular redox level given the potential interactions among different oxidative post-translational modifications (oxiPTMs), such as S-nitrosation, glutathionylation, sulfenylation, S-cyanylation and S-acylation, which also affect thiol groups. This review aims to provide an updated and comprehensive overview of the important physiological role exerted by persulfidation in higher plants, which acts as a cellular mechanism of protein protection against irreversible oxidation.