Crystal structure of nucleotide-free dynamin

Dynamin is a mechanochemical GTPase that oligomerizes around the neck of clathrin-coated pits and catalyses vesicle scission in a GTP-hydrolysis-dependent manner. The molecular details of oligomerization and the mechanism of the mechanochemical coupling are currently unknown. Here we present the crystal structure of human dynamin 1 in the nucleotide-free state with a four-domain architecture comprising the GTPase domain, the bundle signalling element, the stalk and the pleckstrin homology domain. Dynamin 1 oligomerized in the crystals via the stalks, which assemble in a criss-cross fashion. The stalks further interact via conserved surfaces with the pleckstrin homology domain and the bundle signalling element of the neighbouring dynamin molecule. This intricate domain interaction rationalizes a number of disease-related mutations in dynamin 2 and suggests a structural model for the mechanochemical coupling that reconciles previous models of dynamin function

Glycan labeling strategies and their use in identification and quantification

Most methods for the analysis of oligosaccharides from biological sources require a glycan derivatization step: glycans may be derivatized to introduce a chromophore or fluorophore, facilitating detection after chromatographic or electrophoretic separation. Derivatization can also be applied to link charged or hydrophobic groups at the reducing end to enhance glycan separation and mass-spectrometric detection. Moreover, derivatization steps such as permethylation aim at stabilizing sialic acid residues, enhancing mass-spectrometric sensitivity, and supporting detailed structural characterization by (tandem) mass spectrometry. Finally, many glycan labels serve as a linker for oligosaccharide attachment to surfaces or carrier proteins, thereby allowing interaction studies with carbohydrate-binding proteins. In this review, various aspects of glycan labeling, separation, and detection strategies are discussed

Long-term record of H2O2 in polar ice cores

At Dye 3 and Camp Century, Greenland, and at Byrd Station, West-Antarctica, ice cores were drilled to bedrock. They offer an archive of solid precipitation over the last 50.000 to 100,OOO years. H2O2 has been found to be one of the dominant trace components in the ice. We present a survey of the H2O2 levels in the three deep cores. In the Greenland ice cores the H2O2 level decreases with increasing depth and is extremely low during the last glaciation. In the Byrd core an H2O2 concentration spike is observed in the time period 6000 to 12,000 years before present. Possible explanations for the decreasing trend with age and depth and the drop during the Ice Age are discussed

Measurements of hydrogen peroxide in polar ice samples

Hydrogen peroxide, a powerful oxidant, is believed to be a key component in the oxidation of SO2 to H2SO4 in clouds1. The first quantitative H2O2 measurements in snow, rain, hoarfrost and fog were reported in 1874 (ref. 2), however, systematic investigations of H2O2 concentrations in precipitation and hydrometeors began only a few years ago3,4. We report here measurements of hydrogen peroxide in polar ice samples. To our knowledge, chemically-reactive species have not been previously analysed in ice core samples. Our measurements show that H2O2 is a dominant trace compound present in clouds over remote and clean areas

Transcriptional response of the model planctomycete Rhodopirellula baltica SH1T to changing environmental conditions

Background The marine model organism Rhodopirellula baltica SH1T was the first Planctomycete to have its genome completely sequenced. The genome analysis predicted a complex lifestyle and a variety of genetic opportunities to adapt to the marine environment. Its adaptation to environmental stressors was studied by transcriptional profiling using a whole genome microarray. Results Stress responses to salinity and temperature shifts were monitored in time series experiments. Chemostat cultures grown in mineral medium at 28°C were compared to cultures that were shifted to either elevated (37°C) or reduced (6°C) temperatures as well as high salinity (59.5‰) and observed over 300 min. Heat shock showed the induction of several known chaperone genes. Cold shock altered the expression of genes in lipid metabolism and stress proteins. High salinity resulted in the modulation of genes coding for compatible solutes, ion transporters and morphology. In summary, over 3000 of the 7325 genes were affected by temperature and/or salinity changes. Conclusion Transcriptional profiling confirmed that R. baltica is highly responsive to its environment. The distinct responses identified here have provided new insights into the complex adaptation machinery of this environmentally relevant marine bacterium. Our transcriptome study and previous proteome data suggest a set of genes of unknown functions that are most probably involved in the global stress response. This work lays the foundation for further bioinformatic and genetic studies which will lead to a comprehensive understanding of the biology of a marine Planctomycete