Release of prostaglandin D2 by murine mast cells: importance of metabolite formation for antiproliferative activity.

Prostaglandin (PG) D2, PGJ2 and delta12-PGJ2 are antiproliferative eicosanoids. We investigated the production of PGD2 by murine bone marrow-derived mast cells (BMMC) taking into consideration metabolism of PGD2 to PGD2 and delta12-PGJ2. PG-metabolites were quantified by high performance liquid chromatography (HPLC) combined with radioimmunoassay (RIA). Stimulated with calcium ionophore A23187 BMMC released eight-fold more PGJ2 and delta12-PGJ2 than PGD2. Conversion of endogenously produced PGD2 to PGJ2 and delta12-PGJ2 proceeded rapidly in contrast to metabolism of exogenously added PGD2. The antiproliferative potency of these prostaglandins is demonstrated in vitro. We conclude that determination of PGD2 production by mast cells must take into consideration rapid conversion to active derivatives, which may play a significant role in growth regulation

The whole and its parts : why and how to disentangle plant communities and synusiae in vegetation classification

Most plant communities consist of different structural and ecological subsets, ranging from cryptogams to different tree layers. The completeness and approach with which these subsets are sampled have implications for vegetation classification. Non‐vascular plants are often omitted or sometimes treated separately, referring to their assemblages as “synusiae” (e.g. epiphytes on bark, saxicolous species on rocks). The distinction of complete plant communities (phytocoenoses or holocoenoses) from their parts (synusiae or merocoenoses) is crucial to avoid logical problems and inconsistencies of the resulting classification systems. We here describe theoretical differences between the phytocoenosis as a whole and its parts, and outline consequences of this distinction for practise and terminology in vegetation classification. To implement a clearer separation, we call for modifications of the International Code of Phytosociological Nomenclature and the EuroVegChecklist. We believe that these steps will make vegetation classification systems better applicable and raise the recognition of the importance of non‐vascular plants in the vegetation as well as their interplay with vascular plants

The crystal structure of mycobacterial epoxide hydrolase A

The human pathogen Mycobacterium tuberculosis is the causative agent of tuberculosis resulting in over 1 million fatalities every year, despite decades of research into the development of new anti-TB compounds. Unlike most other organisms M. tuberculosis has six putative genes for epoxide hydrolases (EH) of the α/β-hydrolase family with little known about their individual substrates, suggesting functional significance for these genes to the organism. Due to their role in detoxification, M. tuberculosis EH’s have been identified as potential drug targets. Here, we demonstrate epoxide hydrolase activity of M. thermoresistibile epoxide hydrolase A (Mth-EphA) and report its crystal structure in complex with the inhibitor 1,3-diphenylurea at 2.0 Å resolution. Mth-EphA displays high sequence similarity to its orthologue from M. tuberculosis and generally high structural similarity to α/β-hydrolase EHs. The structure of the inhibitor bound complex reveals the geometry of the catalytic residues and the conformation of the inhibitor. Comparison to other EHs from mycobacteria allows insight into the active site plasticity with respect to substrate specificity. We speculate that mycobacterial EHs may have a narrow substrate specificity providing a potential explanation for the genetic repertoire of epoxide hydrolase genes in M. tuberculosis

Millisecond cryo-trapping by the spitrobot crystal plunger simplifies time-resolved crystallography

We introduce the spitrobot, a protein crystal plunger, enabling reaction quenching via cryo-trapping with millisecond time-resolution. Canonical micromesh loops are mounted on an electropneumatic piston, reactions are initiated via the liquid application method (LAMA), and finally intermediate states are cryo-trapped in liquid nitrogen. We demonstrate binding of several ligands in microcrystals of three enzymes, and trapping of reaction intermediates and conformational changes in macroscopic crystals of tryptophan synthase