No abstract

Galacto-oligosaccharides (GOS) are versatile food ingredients that possess prebiotic properties. However, at present there is a lack of precise analytical methods to demonstrate specific GOS consumption by bifidobacteria. To better understand the role of GOS as prebiotics, purified GOS (pGOS) without disaccharides and monosaccharides was prepared and used in bacterial fermentation experiments. Growth curves showed that all bifidobacteria assayed utilized and grew on pGOS preparations. We used a novel mass spectrometry approach involving matrix-assisted laser desorption ionization-Fourier transform ion cyclotron resonance (MALDI-FTICR) to determine the composition of oligosaccharides in GOS syrup preparations. MALDI-FTICR analysis of spent fermentation media demonstrated that there was preferential consumption of selected pGOS species by different bifidobacteria. The approach described here demonstrates that MALDI-FTICR is a rapid-throughput tool for comprehensive profiling of oligosaccharides in GOS mixtures. In addition, the selective consumption of certain GOS species by different bifidobacteria suggests a means for targeting prebiotics to enrich select bifidobacterial species.

No abstract

aWe present a study of the reactions of the meteoritic mineral schreibersite (Fe,Ni) 3 P, focusing primarily on surface chemistry and prebiotic phosphorylation. In this work, a synthetic analogue of the mineral was synthesized by mixing stoichiometric proportions of elemental iron, nickel and phosphorus and heating in a tube furnace at 820 1C for approximately 235 hours under argon or under vacuum, a modification of the method of Skála and Drábek (2002). Once synthesized, the schreibersite was characterized to confirm the identity of the product as well as to elucidate the oxidation processes affecting the surface. In addition to characterization of the solid product, this schreibersite was reacted with water or with organic solutes in a choline chloride-urea deep eutectic mixture, to constrain potential prebiotic products. Major inorganic solutes produced by reaction of water include orthophosphate, phosphite, pyrophosphate and hypophosphate consistent with prior work on Fe 3 P corrosion. Additionally, schreibersite corrodes in water and dries down to form a deep eutectic solution, generating phosphorylated products, in this case phosphocholine, using this synthesized schreibersite.

The efficiency of HCO formation stemming from non-energetic H-atoms and CO molecules is highlighted both in the condensed phase and within a neon matrix environment, which is half-way between the condensed-phase and gas-phase. Our experiments demonstrated that HCO production within the neon-matrix needed very little or no activation energy. The efficiency of HCO formation depended only on the capability of H-atoms to diffuse in the solid and to subsequently encounter CO molecules. The novelty of the presented matrix experiment sheds light on the debated question of whether activation energy is required in order to produce HCO, because of the use of non-energetic ground state H-atoms within the neon-matrix.

No abstract

Fourier transform-infrared spectroscopy (FT-IR) and temperature programmed desorption (TPD) have been used to examine the thermal processing of three isotopes of pure formamide ice (HCONH2, DCONH2, and HCOND2) adsorbed on a SiO2 interstellar grain analogue. Pure formamide ice on SiO2 nanoparticles displays at least three different phases that we interpret as a porous phase from ∼70-145 K, a compacted polycrystalline phase from ∼145-210 K, and a third slow diffusion and sublimation phase from ∼210-380 K. Possible dimerization is also discussed. Formamide desorption from the SiO2 grain surface is characterized by TPD of pure HCONH2 and mixed H2O:HCONH2 ices. Water desorbs at 160 K, and formamide has a TPD peak maximum at ∼228 K. A mean Eact of ∼14.7 kcal/mol (0.64 eV) was obtained using Redhead analysis, indicating strong intermolecular forces within formamide ice. The mixed H2O:HCONH2 ice TPD data suggests possible formamide accumulation if the grains are exposed to temperature cycles <180 K.

The successive hydrogenation of CO has been investigated by two methods. The first is hydrogenation of a CO surface. The second is co-injection of CO molecules and H atoms. Both methods have been performed at 3 and 10 K. In the first method, the interaction of H atoms with solid CO at 10 K shows that CO is consumed to form H2CO and CH3OH. No trace of species such as HCO and CH3O is detected. No product was observed when the same experiment was performed at 3 K. In the second method, when H and CO are codeposited at 10 K, HCO and CH3O are observed. In fact, the yield of these intermediate species depends on the amount of the H radicals interacting with CO molecules. At 3 K, the presence of H2 in the solid screens the hydrogenation reaction. This causes a termination for the reaction in the stage of the formation of HCO and H2CO. At 10 K, H2 cannot condense, and the reaction between CO and H is total. In this case, species such as HCO, H2CO, CH3O, and CH3OH are observed.