Diastereoselective Formation of Trans-HC(O)SH through Hydrogenation of OCS on Interstellar Dust Grains

With the presence of evermore complex S-bearing molecules being detected lately, studies of their chemical formation routes need to keep up the pace to rationalize observations, suggest new candidates for detection, and provide input for chemical evolution models. In this paper, we theoretically characterize the hydrogenation channels of OCS on top of amorphous solid water (ASW) as an interstellar dust grain analog in molecular clouds. Our results show that the significant reaction outcome is trans-HC(O)SH, a recently detected prebiotic molecule toward G+0.693. The reaction is diastereoselective, explaining the apparent absence of the cis isomer in astronomical observations. We found that the reaction proceeds through a highly localized radical intermediate (cis-OCSH), which could be essential in the formation of other sulfur-bearing complex organic molecules due to its slow isomerization dynamics on top of ASW.

Effects of 2′-Fucosyllactose-Based Encapsulation on Probiotic Properties in Streptococcus thermophilus

Streptococcus thermophilus is widely used in dairy fermentation as a starter culture for yogurt and cheese production. Many strains are endowed with potential probiotic properties; however, since they might not survive in adequate amounts after transit through the human gastrointestinal tract, it is advisable to improve cell survivability during this passage. The present study evaluates the use of 2′-fucosyllactose, a prebiotic molecule from human milk, compared with other known molecules, such as gelatin and inulin, to form alginate-based microcapsules to fulfill these requirements. Such microcapsules, obtained by the extrusion technique, were evaluated in terms of encapsulation efficiency, storage stability, gastrointestinal condition resistance, and cell release kinetics. Results reveal that microcapsules made using 2′-fucosyllactose and those with inulin resulted in the most efficient structure to protect S. thermophilus strain TH982 under simulated gastrointestinal conditions (less than 0.45 log CFU/g decrease for both agents). In addition, a prompt and abundant release of encapsulated cells was detected after only 30 min from microcapsules made with sodium alginate plus 2′-fucosyllactose in simulated gastrointestinal fluid (more than 90% of the cells). These encouraging results represent the first report on the effects of 2′-fucosyllactose used as a co-encapsulating agent.

Acute and sub-chronic (28-day) oral toxicity profiles of newly synthesized prebiotic butyl-fructooligosaccharide in ICR mouse and Wistar rat models

B-FOS (butyl-fructooligosaccharide) is a newly synthesized prebiotic molecule, formed by the combination of FOS and butyrate by ester bonds. B-FOS has been reported to have the potential prebiotic effect of promoting intestinal flora diversity and enhancing butyrate production. The aim of this study was to investigate the potential acute and sub-chronic toxicity of B-FOS in Institute of Cancer Research (ICR) mice and Wistar rats to verify its biosafety. ICR mice were administered a single oral gavage of B-FOS at doses of 0, 500, 1000, and 2000 mg/kg body weight and observed for signs of acute toxicity for 14 days. Sub-chronic toxicity was evaluated by repeated oral administration of B-FOS at 2000 mg/kg for 28 days, in accordance with Organization for Economic Co-operation and Development (OECD) protocol test numbers 420 and 407. No mortality or abnormal clinical signs were observed during the experimental periods after B-FOS administration. Furthermore, no significant changes in body weight, organ weight, serum biochemical parameters, or tissue histology were observed after animal sacrifice. These in vivo results indicate that B-FOS does not exert any acute or sub-chronic toxicity at a dose of 2000 mg/kg, and this novel molecule can be regarded as a safe prebiotic substance for use in the food and nutraceutical industries.

Molecular Growth upon Ionization of Van Der Waals Clusters Containing HCCH and HCN is a Pathway to Prebiotic Molecules

The growth mechanisms of organic molecules in an ionizing environment such as the interstellar medium are not completely understood. Here we examine by means of ab initio molecular dynamics (AIMD) simulations and density functional theory (DFT) computations the possibility of bond formation and molecular growth upon ionization of Van der Waals clusters of pure HCN clusters, and mixed clusters of HCN and HCCH, both of which are widespread in the interstellar medium. Ionization of van der Waals clusters can potentially lead to growth in low temperature and low-density environments. Our results show, that upon ionization of the pure HCN clusters, strongly bound stable structures are formed that contain NH bonds, and growth beyond pairwise HCN molecules is seen only in a small percentage of cases. In contrast, mixed clusters, where HCCH is preferentially ionized over HCN, can grow up to 3 or 4 units long with new carbon-carbon and carbon-nitrogen covalent bonds. Moreover, cyclic molecules formed, such as the radical cation of pyridine, which is a prebiotic molecule. The results presented here are significant as they provide a feasible pathway for molecular growth of small organic molecules containing both carbon and nitrogen in cold and relatively denser environments such as in dense molecular clouds but closer to the photo-dissociation regions, and protoplanetary disks. In the mechanism we propose, first, a neutral van der Waals cluster is formed. Once the cluster is formed it can undergo photoionization which leads to chemical reactivity without any reaction barrier.

Molecular Growth upon Ionization of Van Der Waals Clusters Containing HCCH and HCN is a Pathway to Prebiotic Molecules

The growth mechanisms of organic molecules in an ionizing environment such as the interstellar medium are not completely understood. Here we examine by means of ab initio molecular dynamics (AIMD) simulations and density functional theory (DFT) computations the possibility of bond formation and molecular growth upon ionization of Van der Waals clusters of pure HCN clusters, and mixed clusters of HCN and HCCH, both of which are widespread in the interstellar medium. Ionization of van der Waals clusters can potentially lead to growth in low temperature and low-density environments. Our results show, that upon ionization of the pure HCN clusters, strongly bound stable structures are formed that contain NH bonds, and growth beyond pairwise HCN molecules is seen only in a small percentage of cases. In contrast, mixed clusters, where HCCH is preferentially ionized over HCN, can grow up to 3 or 4 units long with new carbon-carbon and carbon-nitrogen covalent bonds. Moreover, cyclic molecules formed, such as the radical cation of pyridine, which is a prebiotic molecule. The results presented here are significant as they provide a feasible pathway for molecular growth of small organic molecules containing both carbon and nitrogen in cold and relatively denser environments such as in dense molecular clouds but closer to the photo-dissociation regions, and protoplanetary disks. In the mechanism we propose, first, a neutral van der Waals cluster is formed. Once the cluster is formed it can undergo photoionization which leads to chemical reactivity without any reaction barrier.