Characterization of galactooligosaccharides derived from lactulose

Galactooligosaccharides are non-digestible carbohydrates with potential ability to modulate selectively the intestinal microbiota. In this work, a detailed characterization of oligosaccharides obtained by transgalactosylation reactions of the prebiotic lactulose, by using β-galactosidases of different fungal origin (Aspergillus oryzae, Aspergillus aculeatus and Kluveromyces lactis), is reported. Oligosaccharides of degree of polymerization (DP) up to 6 were detected and quantified by HPLC-ESI MS from a complex mixture produced by transgalactosylation reaction with A. oryzae (GOSLuAo), whereas only carbohydrates up to DP4 and DP5 were found for those obtained from the reaction with β-galactosidases from K. lactis (GOSLuKl) and A. aculeatus (GOSLuAa), respectively. Disaccharides (galactosyl-galactoses and galactosyl-fructoses) and trisaccharides were characterised in the three mixtures by GC-MS as their trimethylsilyl oximes. Galactosyl- and digalactosyl-glycerols were produced during the transgalactosylation reaction of lactulose with β-galactosidases from A. aculeatus and K. lactis, due to the presence of glycerol as enzyme stabiliser.     

The microwave spectrum of cyanoformamide

The spectrum of cyanoformamide, NCCONH₂, has been measured between 18 and 40 GHz using a Hewlett-Packard spectrometer with Stark modulation. The molecule is somewhat unstable and could most conveniently be measured in a flow system. The quadrupole hyperfine structure due to the two nitrogen nuclei has been analyzed for the ground state, and quadrupole coupling constants, rotational constants, and centrifugal distortion constants have been determined for the ground state. A rough determination of the components of the electric dipole moment was possible from the Stark shifts of suitable transitions.     

Impact of ultrasound on galactooligosaccharides and gluconic acid production throughout a multienzymatic system

Galactooligosaccharides (GOS), recognised prebiotic, can be industrially produced from lactose and commercial β-galactosidase (β-gal) from Kluyveromyces lactis. Residual lactose and glucose limit GOS applications. To handle this problem, a multienzymatic system, with β-gal and glucose oxidase (Gox), was proposed to reduce glucose content in reaction media through its oxidation to gluconic acid (GA). Besides, ultrasound (US) probe effect over the multienzymatic system to produce GOS and GA has been evaluated. A production around 40% of GOS was found in all treatments after the first hour of reaction. However, glucose consumption and GA production was significantly higher (P < 0.05) for sequential reaction assisted by US, obtaining the best production of GOS (49%) and GA (28%) after 2 h of reaction. The conformational and residual activity changes of enzymes under US conditions were also evaluated, Gox being positively affected whereas in β-gal hardly any change was found.     

Effects of ultrasound on the degradation kinetics,physicochemical properties and prebiotic activity of Flammulina velutipes polysaccharide

The controllable ultrasonic modification was hindered due to the uncertainty of the relationship between ultrasonic parameters and polysaccharide quality. In this study, the ultrasonic degradation process was established with kinetics. The physicochemical properties and prebiotic activity of ultrasonic degraded Flammulina velutipes polysaccharides (U-FVPs) were investigated. The results showed that the ultrasonic degradation kinetic models were fitted to 1/M_t-1/M₀ = kt. When the ultrasonic intensity increased from 531 to 3185 W/cm², the degradation proceeded faster. The decrease of polysaccharide concentration contributed to the degradation of FVP, and the fastest degradation rate was at 60 °C. Ultrasound changed the solution conformation of FVP, and partially destroyed the stability of the triple helix structure of FVP. Additionally, the viscosity and gel strength of FVP decreased, but its thermal stability was improved by ultrasound. Higher ultrasonic intensity led to larger variations in physicochemical properties. Compared with FVP, U-FVPs could be more easily utilized by gut microbiota. U-FVPs displayed better prebiotic activity by promoting the growth of Bifidobacterium and Brautella and inhibiting the growth of harmful bacteria. Ultrasound could be effectively applied to the degradation of FVP to improve its physicochemical properties and bioactivities.     

低能离子与腺苷酸组分水溶液作用合成腺苷酸

利用自行设计的实验装置将低能离子引入水溶液以诱发水溶液中的化学反应,模拟原始地球条件研究核苷酸的前生物合成.以低能N＋注入含D 核糖、磷酸二氢铵的腺嘌呤过饱和溶液,用高效液相色谱、核磁共振等方法对反应产物进行分析,证明有5′ 腺苷酸生成.给出了产物的产额时间曲线,并对反应机理作了初步探讨.     

Light within small particles

We calculate the energy density distribution in the ultraviolet within small spheres containing concentric cavities, aimed at simulating interstellar dust grains. We explore the dependence on chemical composition by progressively changing, in an arbitrary way, the refractive index of the sphere material. We conclude that a significant fraction of the energy of the impinging radiation is trapped throughout the particle interior.     

HCN、H2S、PH3、N2-NH3与CH4-H2O气体混合物的前生物分子合成

原始大气反应生成的HCN部分按Strecker反应合成氨基酸,其余随降雨进入水体.由于气液平衡,HCN可重返大气层参与由放电与太阳辐射引发的化学过程.气相中分子扩散迅速、无笼效应,故生物分子的合成较液相中更有效.本文验证了这一过程,并研究了CH₄、H₂S、HCN等在合成生命分子中的作用.     

Spatio-temporal dynamics in simple asymmetric hypercycles under weak parasitic coupling

Hypercycles represent an example of cooperation at the molecular level suggested to be involved in the evolution of the first autonomous, self-reproducing molecular living-like systems. However, they are vulnerable to parasites: an established hypercycle may decay if a selfish replicator appears i.e. one that receives catalytic help but does not reciprocate catalysis. In this work we study the dynamics of a two-member hypercycle with an attached, weak parasite. We are using a mean field model and a stochastic cellular automaton (CA) focusing on the role of the kinetic properties of both hypercycle replicators, exploited by the parasite. Both approaches show three possible, parameter-dependent outcomes: (i) hypercycle stability and parasite extinction; (ii) extinction of the entire system; and (iii) coexistence between the hypercycle and the parasite. Scenario (iii) is shown to be structurally unstable in the mean field model but the addition of space allows a wider coexistence phase. Moreover the CA model also indicates that the degree of hypercycle’s asymmetry may be relevant in the survival of the catalytic replicators, being also responsible for qualitatively different dynamics e.g. if the parasite is attached to the fittest hypercycle unit, low-dimensional chaos arises. The coexistence phase is characterized by the emergence of hypercyclic aggregates with a broad distribution of cluster sizes and mixed patterns of replicators able to provide the hypercycle with resistance against the parasites. Nevertheless the resistance to the parasite is shown to reduce with increase of diffusion. The role of the kinetic properties of the hypercycle and of diffusion in the survival of the hypercycle is discussed in the context of prebiotic evolution.     

Prebiological evolution and the physics of the origin of life

The basic tenet of the heterotrophic theory of the origin of life is that the maintenance and reproduction of the first living systems depended primarily on prebiotically synthesized organic molecules. It is unlikely that any single mechanism can account for the wide range of organic compounds that may have accumulated on the primitive Earth, suggesting that the prebiotic soup was formed by contributions from endogenous syntheses in reducing environments, metal sulphide-mediated synthesis in deep-sea vents, and exogenous sources such as comets, meteorites and interplanetary dust. The wide range of experimental conditions under which amino acids and nucleobases can be synthesized suggests that the abiotic syntheses of these monomers did not take place under a narrow range defined by highly selective reaction conditions, but rather under a wide variety of settings. The robustness of this type of chemistry is supported by the occurrence of most of these biochemical compounds in the Murchison meteorite. These results lend strong credence to the hypothesis that the emergence of life was the outcome of a long, but not necessarily slow, evolutionary processes. The origin of life may be best understood in terms of the dynamics and evolution of sets of chemical replicating entities. Whether such entities were enclosed within membranes is not yet clear, but given the prebiotic availability of amphiphilic compounds this may have well been the case. This scheme is not at odds with the theoretical models of self-organized emerging systems, but what is known of biology suggest that the essential traits of living systems could have not emerged in the absence of genetic material able to store, express and, upon replication, transmit to its progeny information capable of undergoing evolutionary change. How such genetic polymer first evolved is a central issue in origin-of-life studies.