Hydrogen Sulfide (H2S) and Polysulfide (H2Sn) Signaling: The First 25 Years

Since the first description of hydrogen sulfide (H2S) as a toxic gas in 1713 by Bernardino Ramazzini, most studies on H2S have concentrated on its toxicity. In 1989, Warenycia et al. demonstrated the existence of endogenous H2S in the brain, suggesting that H2S may have physiological roles. In 1996, we demonstrated that hydrogen sulfide (H2S) is a potential signaling molecule, which can be produced by cystathionine β-synthase (CBS) to modify neurotransmission in the brain. Subsequently, we showed that H2S relaxes vascular smooth muscle in synergy with nitric oxide (NO) and that cystathionine γ-lyase (CSE) is another producing enzyme. This study also opened up a new research area of a crosstalk between H2S and NO. The cytoprotective effect, anti-inflammatory activity, energy formation, and oxygen sensing by H2S have been subsequently demonstrated. Two additional pathways for the production of H2S with 3-mercaptopyruvate sulfurtransferase (3MST) from l- and d-cysteine have been identified. We also discovered that hydrogen polysulfides (H2Sn, n ≥ 2) are potential signaling molecules produced by 3MST. H2Sn regulate the activity of ion channels and enzymes, as well as even the growth of tumors. S-Sulfuration (S-sulfhydration) proposed by Snyder is the main mechanism for H2S/H2Sn underlying regulation of the activity of target proteins. This mini review focuses on the key findings on H2S/H2Sn signaling during the first 25 years.

Formation of Citrazinic Acid Ions and Their Contribution to Optical and Magnetic Features of Carbon Nanodots: A Combined Experimental and Computational Approach

The molecular model is one of the most appealing to explain the peculiar optical properties of Carbon nanodots (CNDs) and was proven to be successful for the bottom up synthesis, where a few molecules were recognized. Among the others, citrazinic acid is relevant for the synthesis of citric acid-based CNDs. Here we report a combined experimental and computational approach to discuss the formation of different protonated and deprotonated species of citrazinic acid and their contribution to vibrational and magnetic spectra. By computing the free energy formation in water solution, we selected the most favoured species and we retrieved their presence in the experimental surface enhanced Raman spectra. As well, the chemical shifts are discussed in terms of tautomers and rotamers of most favoured species. The expected formation of protonated and de-protonated citrazinic acid ions under extreme pH conditions was proven by evaluating specific interactions with H2SO4 and NaOH molecules. The reported results confirm that the presence of citrazinic acid and its ionic forms should be considered in the interpretation of the spectroscopic features of CNDs.

A DFT study of structural and electronic properties of anatase TiO2 phase with Ni and oxygen vacancies impurities

In the present work, first-principle theory using the functional density theory (DFT) was used in the ABINIT software package using the PBE pseudopotential (norm-conserving pseudopotentials). To determine the structural parameters such as lattice constant, Bulk modules, and energy formation, for the TiO2 anatase phase doped with substitutional and interstitial nickel impurity, oxygen vacancies (VO) are also included in the present work. For this study, the 2x1x1 supercells with 24 atoms and 2x2x1 with 48 atoms were used. Different types of Ni dopants and oxygen vacancies were considered for energy formation using the 2x2x1 supercell. Our results show that the values of network parameters, minimum energy, and Bulk modulus remain constant with the supercell's growth. With the inclusion of Ni in the supercell substituting the Ti-ions, the unit cell volume (V) exhibits a decrease in agreement with ionic radii mismatch between Ti and Ni atoms. However, when entry as an interstitial form a significant increase is shown. The preliminary results of the energy of formation analyzed for the Ni defects show that it is more probable for an interstitial Ni than for a substitutional Ni.

A DFT study of structural and electronic properties of anatase TiO2 phase with Ni and oxygen vacancies impurities

In the present work, first-principle theory using the functional density theory (DFT) was used in the ABINIT software package using the PBE pseudopotential (norm-conserving pseudopotentials). To determine the structural parameters such as lattice constant, Bulk modules, and energy formation, for the TiO2 anatase phase doped with substitutional and interstitial nickel impurity, oxygen vacancies (VO) are also included in the present work. For this study, the 2x1x1 supercells with 24 atoms and 2x2x1 with 48 atoms were used. Different types of Ni dopants and oxygen vacancies were considered for energy formation using the 2x2x1 supercell. Our results show that the values of network parameters, minimum energy, and Bulk modulus remain constant with the supercell's growth. With the inclusion of Ni in the supercell substituting the Ti-ions, the unit cell volume (V) exhibits a decrease in agreement with ionic radii mismatch between Ti and Ni atoms. However, when entry as an interstitial form a significant increase is shown. The preliminary results of the energy of formation analyzed for the Ni defects show that it is more probable for an interstitial Ni than for a substitutional Ni.

Investigation of Differences in the Cultivation of Nannochloropsis and Chlorella species by Fourier-transform Infrared Spectroscopy

The increasing use of energy in the world is leading to the exhaustion of fossil fuels, so novel alternative solutions have to be found to meet our needs. One solution is renewable raw materials extracted from algae. The use of microalgae is widespread, in addition to energy formation, their biomass can also be utilized as food and other valuable components of them, e.g. amino acids, vitamins and minerals can be used in drugs and cosmetics. Due to their boundless diversity and components, they have become the focus of an ever-increasing number of research areas. Different processes can induce changes in their nutritional content, so optimizing the conditions used during their cultivation is important to produce the desired product. In our study different isolates of microalgae, namely Nannochloropsis sp. and Chlorella vulgaris, were studied using Fourier-transform infrared (FT-IR) spectroscopic analysis. Variations in the spectra of a given species were studied under different cultivation conditions.

Isochronal Annealing of Electron-Irradiated Tungsten Modelled by CD Method: 1D and 3DModel of SIA Diffusivity

The evolution of the microstructure of tungsten under electron irradiation and post-irradiation annealing hasbeen modeled using a multiscale approach based on Cluster Dynamics simulations. In these simulations, bothself-interstitials atoms (SIA) and vacancies, carbon atoms isolated or in clusters, are considered. Isochronal annealing has been simulated in carbon free tungsten and tungsten with carbon, focusing on the recovery stages I and II. The carbon atom, single SIA, single vacancy and vacancy clusters with sizes up to four are treated as the mobile pieces. Their diffusivities as well as the energy formation and binding energies are based on the experimental data and ab initio predictions and some of these parameters have been slightly adjusted, without modifying the interaction character, on isochronal annealing experimental data. The both models with assumption on 1D as well as 3D dimensionality of diffusivity of SIA are treated. The advantage of the model with 1D diffusivity of SIA is found.