Study of the Reaction Mechanism of Triazines and Associated Species for H2S Scavenging.

Natural gas produced worldwide contains, among other compounds, H2S and CO2. Both gases in the presence of free water can generate problems of corrosion in pipes and subtract calorific value to this gaseous hydrocarbon. Natural gas containing H2S and CO2 above the permissible limits should be treated to remove these components. Particularly, H2S is removed mainly using hexahydro-1,3,5-tris-(-2-hydroxyethyl)-s-triazine (TZ), which is the liquid scavenger of H2S leading on the market. By means of computational methods, we have studied the reaction of H2S with TZ, oxazolidine, and oxazinane to elucidate, explain, or confirm different aspects related to their proposed reaction mechanisms. Our results validate thermodynamically the production of TZ from MEA and formaldehyde, justify the presence of mixtures of TZ and oxazolidine in some commercial products, and explain why in the complexity of the H2S scavenging mechanism with TZ, tritiane is not formed and dithiazine will prefer to react by polymerization to form amorphous dithiazine and that the scavenging capacity for H2S should follow the TZ ≫ oxazinane > oxazolidine sequence.

The dengue virus non-structural protein 1 (NS1) is secreted from infected mosquito cells via a non-classical caveolin-1-dependent pathway.

Dengue virus NS1 is a glycoprotein of 46-50 kDa that is conserved among flaviviruses, associates as a dimer to cell membranes and is secreted as a hexamer to the extracellular milieu. Recent evidence showed that NS1 is secreted efficiently from infected mosquito cells. To explore the secretory route of NS1 in mosquito cells, infected cells were treated with brefeldin A (BFA) and methyl-beta-cyclodextrin (MßCD). The results showed that MßCD, but not BFA, significantly reduced the release of NS1. Moreover, silencing the expression of caveolin-1 (CAV1; a key component of the caveolar system that transports cholesterol inside the cell), but not SAR1 (a GTPase that participates in the classical secretory pathway), also results in a significant reduction of the secretion of NS1. These results indicate that NS1 is released from mosquito cells via an unconventional secretory route that bypasses the Golgi complex, with the participation of CAV1. In agreement with this notion, differences were observed in the glycosylation status between secreted NS1 and E proteins. Classical mechanics and docking simulations suggested highly favoured interactions between the caveolin-binding domain present in NS1 and the scaffolding domain of CAV1. Finally, proximity ligation assays showed direct interaction between NS1 and CAV1 in infected mosquito cells. These findings are in line with the lipoprotein nature of secreted NS1 and provide new insights into the biology of NS1.

Exploring the structure-solubility relationship of asphaltene models in toluene, heptane, and amphiphiles using a molecular dynamic atomistic methodology.

The solubility parameters, δ, of several asphaltene models were calculated by mean of an atomistic NPT ensemble. Continental and archipelago models were explored. A relationship between the solubility parameter and the molecule structure was determined. In general, increase of the fused-rings number forming the aromatic core and the numbers of heteroatoms such as oxygen, nitrogen, and sulfur produces an increase of the solubility parameter, while increases of the numbers and length of the aliphatic chains yield a systematic decrease of this parameter. Molecules with large total carbon atom number at the tails, n(c), and small aromatic ring number, n(r), exhibit the biggest values of δ, while molecules with small n(c) and large n(r) show the smallest δ values. A good polynomial correlation δ = 5.967(n(r)/n(c)) - 3.062(n(r)/n(c))(2) + 0.507(n(r)/n(c))(3) + 16.593 with R(2) = 0.965 was found. The solubilities of the asphaltene models in toluene, heptane, and amphiphiles were studied using the Scatchard-Hildebrand and the Hansen sphere methodologies. Generally, there is a large affinity between the archipelago model and amphiphiles containing large aliphatic tails and no aromatic rings, while continental models show high affinity for amphiphiles containing an aromatic ring and small aliphatic chains.