Biosynthesis of Gold Nanoparticles by Essential Oil of Diplotaxis Acris Characterization and Antimicrobial Activities

The present work reports a green biosynthesis of gold nano particles (EO-AuNPs) using an essential oil (EO) as a reducing agent of the Au(III) in HAuCl4. The EO was extracted by hydro-distillation from Diplotaxis acris flowers. A total of 16 compounds were detected from the EO oil by using GC–MS and 5-methylsulfanylpentanenitrile was identified as the major component (73.60 %). The biosynthesized EO-AuNPs were characterized performing UV–Vis, IR,XRD and TEM analyses.The UV-Vis revealed the typical features of surface plasmon resonance (SPR) of AuNPs at ~526 nm. The FT-IR spectrum of the biosynthesized nano particles exhibited the features of the nitrile (-C≡N) functional group indicating that the -C≡N-bearing EO components are likely acting as reducing and stabilizing agents for the formation of EO-AuNPs. The plausible scheme of EO-AuNPsformation was proposed.The TEM analysis showed that the EO- AuNPs were almost spherical in shape with an average particle size of 12.7 nm. In addition, the antimicrobial activity was carried out by diffusion of agar wells method. The results proved that the EO-AuNPs displayed a potential antimicrobial against gram negative strains, with a maximum zone of inhibition of 16 mm for E. coli at a concentration of 100 µg / ml.

Relief of autoinhibition by conformational switch explains enzyme activation by a catalytically dead paralog

Catalytically inactive enzyme paralogs occur in many genomes. Some regulate their active counterparts but the structural principles of this regulation remain largely unknown. We report X-ray structures of Trypanosoma brucei S-adenosylmethionine decarboxylase alone and in functional complex with its catalytically dead paralogous partner, prozyme. We show monomeric TbAdoMetDC is inactive because of autoinhibition by its N-terminal sequence. Heterodimerization with prozyme displaces this sequence from the active site through a complex mechanism involving a cis-to-trans proline isomerization, reorganization of a β-sheet, and insertion of the N-terminal α-helix into the heterodimer interface, leading to enzyme activation. We propose that the evolution of this intricate regulatory mechanism was facilitated by the acquisition of the dimerization domain, a single step that can in principle account for the divergence of regulatory schemes in the AdoMetDC enzyme family. These studies elucidate an allosteric mechanism in an enzyme and a plausible scheme by which such complex cooperativity evolved.

The Metabolism of Baicalin in Rat and the Biological Activities of the Metabolites

Baicalin is one of the major bioactive constituents of Scutellariae Radix, but the biotransformation of it is poorly understood. In this paper, the metabolism of baicalin in rat was studied. Nine metabolites including one new compound were isolated and identified structurally. The plausible scheme for the biotransformation pathways of baicalin in the rats was deduced. And the main metabolites were evaluated for their antioxidation and anti-inflammation biological activities for the first time.

MODEL OF THE DYNAMICS OF A BRANCHING SYSTEM OF THE GLIAL CELL LINEAGESIN VITRO

A genealogical model describing the dynamics of a binary branching system of astrocytes and microglia which takes into account a developmental hierarchy, is proposed. The model consists of a scheme of developmental pathways interconnecting the elements at various stages of development from a common progenitor to a nonproliferating end stage. To the elements at each stage are attributed probabilities of division, differentiation and quiescence. The pathway of any particular element at the end of each cycle is determined by a random-number generator according to the predetermined probabilities. The model is applied to colony formation in vitro. The development of each colony is followed for several cycles of division and theoretical results are compared to experimental values. Comparison of values obtained from several variants of the theoretical model with experimental data is then used to derive the most plausible scheme of branching pathways under given experimental conditions. The model is defined as follows: a common unlabeled progenitor with a high self-renewal potential differentiates into unlabeled monopotential precursors which further develop into astrocytes and microglia, identified experimentally as GFAP-positive cells and CR3-positive cells, respectively. Both the monopotential unlabeled cells and the identifiable progeny also have the capability of self-renewal.

Evolutionary conservation and ontogenetic emergence of neural algorithms

Neural algorithms are conserved during evolution. Neurons with different shapes and using different molecular mechanisms can perform the same computation. However, evolutionary conservation of neural algorithms is not sufficient for claiming the realization of an algorithm for a specific computational problem. A plausible scheme for ontogenetic emergence of the structure of the algorithm must also be provided.