Cysteine-390 is the binding site of luminous substance with symplectin, a photoprotein from Okinawan squid, Symplectoteuthis oualaniensis

Symplectin is a photoprotein from a luminous squid, Symplectoteuthis oualaniensis. It has a luminous substrate, dehydrocoelenterazine (DCZ), linked through a thioether bond with a cysteine residue. We have proven the binding site of luminous substrate in symplectin by using an artificial analogue of DCZ, ortho-fluoro-DCZ (F-DCZ). F-DCZ-symplectin emitting strong blue light was reconstituted from apo-symplectin and F-DCZ. Proteolytic digestion of the reconstituted F-DCZ-symplectin afforded peptides including C(390)GLK-F-DCZ (amide), which was detected with a house assembled nano-LC-ESI-Q-TOF-MS. The chromo-peptide derived from the F-DCZ-symplectin after luminescence showed the lower molecular mass than that before the luminescence by 12 mass units, corresponding to the loss of one carbon atom upon emitting light. Thus, we have concluded that F-DCZ analogue binds to Cys390 in symplectin so as to emit light.     

Intermolecular Interaction of Tetrabutylammonium and Tetrabutylphosphonium Salt Hydrates by Low-Frequency Raman Observation

Semi-clathrate hydrates are attractive heat storage materials because the equilibrium temperatures, located above 0 °C in most cases, can be changed by selecting guest cations and anions. The equilibrium temperatures are influenced by the size and hydrophilicity of guest ions, hydration number, crystal structure, and so on. This indicates that intermolecular and/or interionic interaction in the semi-clathrate hydrates may be related to the variation of the equilibrium temperatures. Therefore, intermolecular and/or interionic interaction in semi-clathrate hydrates with quaternary onium salts was directly observed using low-frequency Raman spectroscopy, a type of terahertz spectroscopy. The results show that Raman peak positions were mostly correlated with the equilibrium temperatures: in the semi-clathrate hydrates with higher equilibrium temperatures, Raman peaks around 65 cm⁻¹ appeared at a higher wavenumber and the other Raman peaks at around 200 cm⁻¹ appeared at a lower wavenumber. Low-frequency Raman observation is a valuable tool with which to study the equilibrium temperatures in semi-clathrate hydrates.     

Selenium-Based Catalytic Scavengers for Concurrent Scavenging of H2S and Reactive Oxygen Species

Hydrogen sulfide (H₂S) is an endogenous gasotransmitter that plays important roles in redox signaling. H₂S overproduction has been linked to a variety of disease states and therefore, H₂S-depleting agents, such as scavengers, are needed to understand the significance of H₂S-based therapy. It is known that elevated H₂S can induce oxidative stress with elevated reactive oxygen species (ROS) formation, such as in H₂S acute intoxication. We explored the possibility of developing catalytic scavengers to simultaneously remove H₂S and ROS. Herein, we studied a series of selenium-based molecules as catalytic H₂S/H₂O₂ scavengers. Inspired by the high reactivity of selenoxide compounds towards H₂S, 14 diselenide/monoselenide compounds were tested. Several promising candidates such as S6 were identified. Their activities in buffers, as well as in plasma- and cell lysate-containing solutions were evaluated. We also studied the reaction mechanism of this scavenging process. Finally, the combination of the diselenide catalyst and photosensitizers was used to achieve light-induced H₂S removal. These Se-based scavengers can be useful tools for understanding H₂S/ROS regulations.     

A Sulfur Monoxide Surrogate Designed for the Synthesis of Sulfoxides and Sulfinamides**

Sulfur monoxide (SO) is a highly reactive species that cannot be isolated in bulk. However, SO can play a pivotal role as a fundamental building block in organic synthesis. Reported herein is the design and application of a sulfinylhydrazine reagent as an easily prepared sulfur monoxide surrogate. We show facile thermal SO transfer from this reagent to dienes where a reaction using a mechanistic probe suggests the generation of singlet SO. Combined with Grignard reagents and appropriate carbon or nitrogen electrophiles, the reagent serves as an effective “SO” donor to enable the one-pot, three-component synthesis of sulfoxides and sulfinamides.