An introduction to thiol redox proteins in the endoplasmic reticulum and a review of current electrochemical methods of detection of thiols

Smartphone-assisted colorimetric detection of glutathione in food and pharmaceutical samples using MIL-88A(Fe)

Metal-organic frameworks (MOFs) have risen to prominence due to their unique structural features, including high porosity and tunable surface chemistry. As nanozymes, the MOFs replicate the catalytic activity of natural enzymes, thereby offering stability under diverse conditions and heightened efficiency. Glutathione (GSH) is a vital intracellular antioxidant and disease biomarker for cancer and neurodegenerative disorders. In this study, the intrinsic-oxidase activity of MIL-88A(Fe) was explored to develop a naked-eye-based colorimetric sensor for the detection of GSH. The 3,3',5,5',-tetramethyl benzidine (TMB) substrate was oxidized by MIL-88A(Fe), leading to the formation ofblue-colored oxidized TMB. The addition of GSH resultsin the reduction of oxidized TMB, causing the blue color to fade and a decrease in absorbance at 652 nm. Under optimal conditions, the developed sensor has a good linear relationship with GSH concentrations ranging from 0-40 μM with a detection limit of 150 nM. The developed methodwas successfully used to determine GSH accurately in real food and pharmaceutical samples. Further, the sensor demonstrated satisfactory performance for smartphone-based GSH detection on a paper-based assay. This work demonstrates the rapid, inexpensive, and ultrasensitive detection of GSH, opening new avenues for additional food quality and pharmaceuticalmonitoring.

A near-infrared Nile red fluorescent probe for the discrimination of biothiols by dual-channel response and its bioimaging applications in living cells and animals

Biothiols, including cysteine (Cys), homocysteine (Hcy), glutathione (GSH) and H₂S, play important roles in human physiological processes.

A Fluorescent Coumarin-Based Probe for the Fast Detection of Cysteine with Live Cell Application

A new coumarin-based fluorescent probe, containing an allylic esters group, has been designed and synthesized for sensing cysteine in physiological pH. In this fluorescent probe, the coumarin was applied as the fluorophore and an allylic esters group was combined as both a fluorescence quencher and a recognition unit. The probe can selectively and sensitively detect cysteine (Cys) over homocysteine, glutathione, and other amino acids, and has a rapid response time of 30 min and a low detection limit of 47.7 nM. In addition, the probe could be applied for cell imaging with low cytotoxicity.

Spectral mapping of 3D multi-cellular tumor spheroids: time-resolved confocal microscopy

The tumor micro-environment of 3D multicellular spheroids and their interaction with a drug molecule are studied using time resolved confocal microscopy.

Chemical etching of bovine serum albumin-protected Au25 nanoclusters for label-free and separation-free detection of cysteamine

This study describes a novel Au nanocluster-based fluorescent sensor for label-free, separation-free and selective detection of cysteamine (CSH). The sensing mechanism is based on CSH etching-induced fluorescence quenching of the bovine serum albumin-protected Au25 nanoclusters (BSAGNCs). A series of characterizations is carried out towards a better understanding of the CSH-induced fluorescence quenching of the BSAGNCs. It is found that CSH can etch the Au25 nanoclusters, exhibiting the potent etching activity. Other thiol-containing compounds such as glutathione and cysteine and other 19 natural amino acids do not interfere with such CSH-induced etching process. The decreases in fluorescence intensity of the BSAGNCs allow sensitive detection of free CSH in the range of 500-10,000nM. The detection limit for CSH is 150nM (S/N=3). The spiked human serum samples can be analyzed with satisfactory results.

Determination of aminothiols by liquid chromatography with amperometric detection at a silver electrode: application to white wines

Liquid chromatography coupled to a silver electrode based flow-through amperometric detector (LC-EC-Ag) was developed for the determination of aminothiols in white wines. The C18 reversed phase LC system operated in the isocratic mode at 0.7 mL min(-1) and used an acidic mobile phase composed of formic acid, EDTA, sodium nitrate, sodium hydroxide, and methanol 1% (v/v) at pH 4.5. The working electrode operated at 0.08 V vs Ag/AgCl, 3M KCl and its manual cleaning was realized once a month by smoothing on a polishing cloth. The analyzed aminothiols were resolved and eluted within 4 min, and all standard curves were linear in the range 2×10(-7)-2×10(-5) M. The analyzed wine samples needed no preparation other than dilution with the mobile phase. The concentration of cysteine (CYS), homocysteine (HCYS), glutathione (GSH) and N-acetylcysteine (NAC) in bottled white wines, determined by the method of standard addition, was found to be in the low μM range (0.2-2 mg L(-1)) depending on the wine type and its age.

Quantification of thiols and disulfides

BACKGROUND

Disulfide bond formation is a key posttranslational modification, with implications for structure, function and stability of numerous proteins. While disulfide bond formation is a necessary and essential process for many proteins, it is deleterious and disruptive for others. Cells go to great lengths to regulate thiol-disulfide bond homeostasis, typically with several, apparently redundant, systems working in parallel. Dissecting the extent of oxidation and reduction of disulfides is an ongoing challenge due, in part, to the facility of thiol/disulfide exchange reactions.

SCOPE OF REVIEW

In the present account, we briefly survey the toolbox available to the experimentalist for the chemical determination of thiols and disulfides. We have chosen to focus on the key chemical aspects of current methodology, together with identifying potential difficulties inherent in their experimental implementation.

MAJOR CONCLUSIONS

While many reagents have been described for the measurement and manipulation of the redox status of thiols and disulfides, a number of these methods remain underutilized. The ability to effectively quantify changes in redox conditions in living cells presents a continuing challenge.

GENERAL SIGNIFICANCE

Many unresolved questions in the metabolic interconversion of thiols and disulfides remain. For example, while pool sizes of redox pairs and their intracellular distribution are being uncovered, very little is known about the flux in thiol-disulfide exchange pathways. New tools are needed to address this important aspect of cellular metabolism. This article is part of a Special Issue entitled Current methods to study reactive oxygen species - pros and cons and biophysics of membrane proteins. Guest Editor: Christine Winterbourn.

Fabrication and characterization of molybdenum(VI)complex-TiO2 nanoparticles modified electrode for the electrocatalytic determination of L-cysteine

A novel voltammetric sensor for the determination of L-cysteine (L-Cys) was fabricated based on a TiO2 nanoparticles/bis [bis(salicylidene-1,4-phenylenediamine)-molybdenum(VI)] carbon paste electrode. The electrochemical behavior of the sensor was investigated in detail by cyclic voltammetry. The apparent electron transfer rate constant (ks) and charge transfer coefficient (?) of the TiO2 nanoparticles / molybdenum(VI) complex/CPE were also determined by cyclic voltammetry and found to be about 4.53 s?1 and 0.54, respectively. The sensor displayed good electrocatalytic activity towards the oxidation of LCys. The peak potential for the oxidation of L-Cys was lowered by at least 130 mV compared with that obtained at an unmodified CPE. Under optimal conditions, the linear range spans L-Cys concentrations from 1.5?10?6 M to 1.2?10?3 M and the detection limit was 0.70 ? 0.01 ?M at a signal-to-noise ratio of 2. In addition, the sensor showed good stability and reproducibility.

Thioredoxin and related molecules--from biology to health and disease

Thioredoxin and glutaredoxin systems in mammalian cells utilize thiol and selenol groups to maintain a reducing intracellular redox state acting as antioxidants and reducing agents in redox signaling with oxidizing reactive oxygen species. During the last decade, the functional roles of thioredoxin in particular have continued to expand, also including novel functions such as a secreted growth factor or a chemokine for immune cells. The role of thioredoxin and glutaredoxin in antioxidant defense and the role of thioredoxin in controlling recruitment of inflammatory cells offer potential use in clinical therapy. The fundamental differences between bacterial and mammalian thioredoxin reductases offer new principles for treatment of infections. Clinical drugs already in use target the active site selenol in thioredoxin reductases, inducing cell death in tumor cells. Thioredoxin and binding proteins (ASK1 and TBP2) appear to control apoptosis or metabolic states such as carbohydrate and lipid metabolism related to diseases such as diabetes and atherosclerosis.