Thiomelin

2-Mercaptosuccinic acid (MS) is an important and versatile substance for diverse fields of applications of which the most significant are surveyed in this article. Biological, chemical, and physical properties of MS as well as the knowledge of its synthesis and microbial degradation are illustrated. In addition, exemplary structural analogs of the organic sulfur compound are commented. The key application of MS in nanotechnology is discussed in detail with particular emphasis on quantum dots (nanocrystals) and self-assembled monolayers in combination with gold or silver. Furthermore, some medical and pharmaceutical applications are given, inter alia in bioimaging, as a nanocarrier, and with regard to the antimicrobial activity of MS-silver and MS-gold nanoparticles. Moreover, biological and chemical applications of MS are exemplified: the thiol compound can serve as an inhibitor for glutathione peroxidase, or the toxicity of substances can be increased due to the presence of MS in the respective cells or tissues. In the field of cosmetics, MS is widely utilized as a reducing agent for numerous products as explained in this article. Additionally, the microbial utilization of MS as a carbon and energy source for growth is elucidated in-depth, providing insight into different catabolic mechanisms.

The self-assembly of thiomalic acid (TMA) on Au(111) and on preformed Au nanoparticles (AuNPs) protected by weak ligands has been studied by X-ray photoelectron spectroscopy (XPS) and electrochemical techniques. Results show that TMA is adsorbed on the Au(111) surface as thiolate species with a small amount of atomic sulfur (~10%) and a surface coverage lower than that found for alkanethiols due to steric factors. The amount of atomic sulfur markedly increases when the TMA is adsorbed on AuNPs by the ligand exchange method. We propose that the atomic sulfur is produced as a consequence of C-S bond cleavage, a process that is more favorable at defective sites of the AuNPs surface. The bond scission is also assisted by the presence of the electron-withdrawing carboxy moiety in the α-position relative to the C-S bond. Moreover, the high local concentration of positively charged species increases the stability of the negatively charged leaving group, leading to a higher amount of coadsorbed atomic sulfur. Our results demonstrate that the terminal functionalities of thiols are conditioning factors in the final structure and composition of the adlayers.

Crosslinked polyesters with Young's moduli similar to that of certain soft biological tissues were prepared via bulk polycondensation of thiomalic acid and 1,8-octanediol alone, and with citric or maleic acid. The copolymers were converted to nitric oxide (NO)-releasing S-nitrosothiol (RSNO) analogues by reaction with tert-butyl nitrite. Additional conjugation steps were avoided by inclusion of the thiolated monomer during the polycondensation to permit thiol conversion to RSNOs. NO release at physiological pH and temperature (pH 7.4, 37 °C) was determined by chemiluminescence-based NO detection. The average total NO content for poly(thiomalic-co-maleic acid-co-1,8-octanediol), poly(thiomalic-co-citric acid-co-1,8-octanediol), and poly(thiomalic acid-co-1,8-octanediol) was 130 ± 39 μmol g-1, 200 ± 35 μmol g-1, and 130 ± 11 μmol g-1, respectively. The antibacterial properties of the S-nitrosated analogues were confirmed against Escherichia coli and Staphylococcus aureus. The hydrolytic degradation products were analyzed by time-of-flight mass spectrometry after a 10-week study to investigate their composition. Tensile mechanical tests were performed on the non-nitrosated polymers as well as their S-nitrosated derivatives and suggested that the materials have appropriate Young's moduli and elongation values for biomedical applications.