Jamal Ouazzani

In situ localisation and quantification of surfactins in a Bacillus subtilis swarming community by imaging mass spectrometry

Surfactins are a family of heptacyclopeptides in which the C‐terminal carbonyl is linked with the β‐hydroxy group of a fatty acid acylating the N‐terminal function of a glutamic acid residue. The fatty acyl chain is 12–16 carbon atoms long. These compounds, which are secreted by the Gram‐positive bacterium Bacillus subtilis in stationary phase in liquid cultures, play an important role in swarming communities on the surface of agar media in the formation of dendritic patterns. TOF secondary ion MS (TOF‐SIMS) imaging was used to map surfactins within 16–17 h swarming patterns, with a 2 μm spatial resolution. Surfactins were mainly located in the central mother colony (the site of initial inoculation), in a ‘ring’ surrounding the pattern and along the edges of the dendrites. In the mother colony and the interior of the dendrites, surfactins with shorter chain lengths are present, whereas in the ring surrounding the swarm community and between dendrites, surfactins with longer fatty acyl chain lengths were found. A quantitative analysis by MALDI‐TOF MS showed a concentration gradient of surfactin from the mother colony to the periphery. The concentration of surfactin was ∼400 pmol/mL in the mother colony and ∼10 pmol/mL at the base of the dendrites, decreasing to 2 pmol/mL at their tips.

Study of the mechanisms of the photodegradation of atrazine in the presence of two photocatalysts: TiO2 and Na4W10O32

The mechanisms of the photodegradation of atrazine under direct photolysis and in the presence of two different photocatalysts, TiO2 and Na4W10O32, are investigated by the means of GC/MS, total radioactivity counting, HPLC and TLC analysis on 14C ring-labelled atrazine solutions. Integration of photo- and biodegradation processes is studied.

Photocatalytic degradation of 5-nitro-1,2,4-triazol-3-one NTO in aqueous suspention of TiO2. Comparison with Fenton oxidation.

5-nitro-1,2,4-triazol-3-one (NTO) is a powerful insensitive explosive, present in industrial waste waters. A remediation method based on photochemical decomposition and Fenton oxidation of NTO has been evaluated by monitoring the mineralization of 14C-labelled NTO. The TiO2-catalyzed photodegradation (lambda > 290 nm, TiO2 0.4 g/l, NTO 150 mg/l)) leads to the complete mineralization of NTO in 3 hours. This degradation involves a simultaneous denitrification and ring scission of NTO leading to nitrites, nitrates and carbon dioxide. No significant photo-degradation of NTO was detected in the absence of the catalyst. Long term irradiation over one week, leads to a complete degradation of concentrated NTO (5 g/l), suggesting that this method could be useful to clean-up NTO wastes. Fenton oxidation offers an efficient cost-effective method for NTO remediation. This reaction is faster that the TiO2 catalyzed photolysis and find application on the mineralization of high concentrations of NTO (15 g/l). Fenton oxidation provokes ring cleavage and subsequent elimination of the two carbon atoms of NTO as CO2. During this reaction, the nitro group is completely transformed into nitrates.

Chemobiological transformations of octalone and hydrindenone derivatives

Abstract Examples are given for allylic hydroxylations with Rhizopus arrhizus ATCC 11145. Chemical allylic hydroxylations are compared with microbiological

Strong Inhibition of Neuronal Nitric Oxide Synthase by the Calmodulin Antagonist and Anti-Estrogen Drug Tamoxifen

The anti-estrogen drug tamoxifen (TMX) was found to act as a strong inhibitor of purified neuronal nitric oxide synthase (nNOS) (IC50 = 2 +/- 0.5 microM), whereas it was inactive toward inducible macrophage NOS (IC50 > 100 microM). TMX affected the activation of NOS by calmodulin, as it not only inhibited L-arginine oxidation to nitric oxide and L-citrulline but also NADPH oxidation and calmodulin-dependent cytochrome c reduction catalyzed by nNOS. These results suggest that TMX could exert some of its biological effects by interfering with constitutive NOS-dependent formation of nitric oxide and/or superoxide ion in various tissues.

Natural hydrazine-containing compounds: Biosynthesis, isolation, biological activities and synthesis.

Hydrazine, hydrazone and hydrazide derivatives are nitrogen-nitrogen bond containing compounds. Such molecules are relatively scarce in nature and have been isolated from plants, marine organisms and microorganisms. These compounds exhibit remarkable structural diversity and relevant biological activities. The enzymes involved in the formation of the N-N bond are still unknown, but many lines of evidence support the involvement of N-nitrosation and N-hydroxylation activating steps. Beside the challenging N-N bond, N-acylases catalyzing the C-N bond formation contribute to the chemical diversity of N-N-containing natural products (N2NP). This review examines the state of knowledge regarding the biosynthesis of N2NP, for which only two biosynthetic gene clusters have been investigated. Biological properties and chemical synthesis of hydrazines, hydrazones and hydrazides are also reported.

A Practical Synthesis of (2S,3R,4S)-4-Hydroxyisoleucine, A Potent Insulinotropic α-Amino Acid from Fenugreek

An efficient eight-step synthesis of optically pure (2S,3R,4S)-4-hydroxyisoleucine (1), a potent insulinotropic α-amino acid found in the seeds of fenugreek (Trigonella foenum-graecum L.), is achieved in 39% overall yield. The method is suitable for large-scale production of the title compound. The key steps involve the biotransformation of ethyl 2-methylacetoacetate to ethyl (2S,3S)-2-methyl-3-hydroxybutanoate (2) with Geotrichum candidum and an asymmetric Strecker synthesis. (© Wiley-VCH Verlag GmbH, 69451 Weinheim, Germany, 2002)

Chemoenzymatic synthesis of enantiomerically pure 4-fluoro-3-nitro and 3-fluoro-4-nitro phenylalanine

Enantiomerically pure L- and D-4-fluoro-3-nitrophenylalanines and L- and D-3-fluoro-4-nitrophenylalanines were obtained from their corresponding racemates via enzymic resoln. [on SciFinder (R)]

Bicyclic and tetracyclic diterpenes from a Trichoderma symbiont of Taxus baccata.

Trichoderma atroviridae UB-LMA is an endophytic fungus isolated from Taxus baccata trees. Liquid-state fermentation coupled to in situ solid phase extraction (SPE) was applied, and four compounds were discovered. Compounds 2-4 belong to the harziane tetracyclic diterpene family. Bicylic compound 1 may represent the biosynthetic precursor of this scarce family of compounds.

NADH oxidase activity of Bacillus subtilis nitroreductase NfrA1: Insight into its biological role

MINT‐7990140: nfrA1 (uniprotkb:P39605) and nfrA1 (uniprotkb:P39605) bind (MI:0407) by X‐ray crystallography (MI:0114)