Reconstitution and Membrane Topology of Mistic from Bacillus subtilis

Cells and organelles are enclosed by membranes that consist of a lipid bilayer harboring highly diverse membrane proteins (MPs). These carry out vital functions, and α-helical MPs, in particular, are of outstanding pharmacological importance, as they comprise more than half of all drug targets. However, knowledge from MP research is limited, as MPs require membranemimetic environments to retain their native structures and functions and, thus, are not readily amenable to in vitro studies. To gain insight into vectorial functions, as in the case of channels and transporters, and into topology, which describes MP conformation and orientation in the context of a membrane, purified MPs need to be reconstituted, that is, transferred from detergent micelles into a lipid-bilayer system. The ultimate goal of this thesis was to elucidate the membrane topology of Mistic, which is an essential regulator of biofilm formation in Bacillus subtilis consisting of four α-helices. The conformational stability of Mistic has been shown to depend on the presence of a hydrophobic environment. However, Mistic is characterized by an uncommonly hydrophilic surface, and its helices are significantly shorter than transmembrane helices of canonical integral MPs. Therefore, the means by which its association with the hydrophobic interior of a lipid bilayer is accomplished is a subject of much debate. To tackle this issue, Mistic was produced and purified, reconstituted, and subjected to topological studies. Reconstitution of Mistic in the presence of lipids was performed by lowering the detergent concentration to subsolubilizing concentrations via addition of cyclodextrin. To fully exploit the advantages offered by cyclodextrin-mediated detergent removal, a quantitative model was established that describes the supramolecular state of the reconstitution mixture and allows for the prediction of reconstitution trajectories and their cross points with phase boundaries. Automated titrations enabled spectroscopic monitoring of Mistic reconstitutions in real time. On the basis of the established reconstitution protocol, the membrane topology of Mistic was investigated with the aid of fluorescence quenching experiments and oriented circular dichroism spectroscopy. The results of these experiments reveal that Mistic appears to be an exception from the commonly observed transmembrane orientation of α-helical MPs, since it exhibits a highly unusual in-plane topology, which goes in line with recent coarse-grained molecular dynamics simulations

Das Wissen von der Adoption: einige praxisbezogene Hinweise auf dem Hintergrund des gegenwärtigen Forschungsstandes

Vor dem Hintergrund des gegenwärtigen Forschungsstandes gibt der Autor des vorliegenden Beitrages Hinweise darauf, welche Bedeutung die Aufklärung von Adoptivkindern über ihren Status hat. Er stellt fest, daß trotz der Erkenntnis, daß diese Kinder so früh wie möglich erfahren sollten, daß sie adoptiert sind, Adoptiveltern sich bewußt machen müssen, daß die Kinder erst im zweiten Lebensjahrzehnt die Adoption mit allen Implikationen begreifen. (SH

Identification and quantification of dust aerosol emission over the Sahara from Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) observations

Dust aerosols are an important component of the climate system and a challenge to incorporate into weather and climate models. Information on the location and magnitude of dust emission remains a key information gap to inform model development. Inadequate surface observations ensure that satellite data remain the primary source of this information over extensive and remote desert regions. Here, we develop estimates of the relative magnitude of active dust emission over the Sahara desert based on data from the Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP). Utilising the unique vertical profile of aerosol characteristics provided by CALIOP our algorithm identifies emission from aerosol extinction and lidar backscatter in the near surface layers. From the long-term CALIOP archive of day and night-time orbits over 2006–13 we construct coarse resolution maps of a new dust emission index (DEI) for the Sahara desert during the peak summer dust season (June to September). The spatial structure of DEI indicates highest emission over a broad zone focused on the border regions of Southern Algeria, Northern Mali and northwest Niger, displaced substantially (∼7°) to the east of the mean maximum in satellite-derived aerosol optical depth. In this region night-time emission exceeds that during the day. The DEI maps substantially corroborate recently derived dust source frequency count maps based on back-tracking plumes in high temporal resolution SEVIRI imagery. As such, a convergence of evidence from multiple satellite data sources using independent methods provides an increasingly robust picture of Saharan dust emission sources. Various caveats are considered. As such, quantitative estimates of dust emission may require a synergistic combined multi-sensor analysis

Investigation of the first and second aerosol indirect effects using data from the May 2003 Intensive Operational Period at the Southern Great Plains

Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/95668/1/jgrd12974.pd

Surface ocean iron fertilization: the role of subduction zone and hotspot volcanic ash and fluxes into the Pacific Ocean

Surface ocean iron (Fe) fertilization can affect the marine primary productivity (MPP), thereby impacting on CO2 exchanges at the atmosphere-ocean interface and eventually on climate. Mineral (aeolian or desert) dust is known to be a major atmospheric source for the surface ocean biogeochemical iron cycle, but the significance of volcanic ash is poorly constrained. We present the results of geochemical experiments aimed at determining the rapid release of Fe upon contact of pristine volcanic ash with seawater, mimicking their dry deposition into the surface ocean. Our data show that volcanic ash from both subduction zone and hot spot volcanoes (n = 44 samples) rapidly mobilized significant amounts of soluble Fe into seawater (35–340 nmol/g ash), with a suggested global mean of 200 ± 50 nmol Fe/g ash. These values are comparable to the range for desert dust in experiments at seawater pH (10–125 nmol Fe/g dust) presented in the literature (Guieu et al., 1996; Spokes et al., 1996). Combining our new Fe release data with the calculated ash flux from a selected major eruption into the ocean as a case study demonstrates that single volcanic eruptions have the potential to significantly increase the surface ocean Fe concentration within an ash fallout area. We also constrain the long-term (millennial-scale) airborne volcanic ash and mineral dust Fe flux into the Pacific Ocean by merging the Fe release data with geological flux estimates. These show that the input of volcanic ash into the Pacific Ocean (128–221 × 1015 g/ka) is within the same order of magnitude as the mineral dust input (39–519 × 1015 g/ka) (Mahowald et al., 2005). From the similarity in both Fe release and particle flux follows that the flux of soluble Fe related to the dry deposition of volcanic ash (3–75 × 109 mol/ka) is comparable to that of mineral dust (1–65 × 109 mol/ka). Our study therefore suggests that airborne volcanic ash is an important but hitherto underestimated atmospheric source for the Pacific surface ocean biogeochemical iron cycle

A Systems Biology Approach Identifies a R2R3 MYB Gene Subfamily with Distinct and Overlapping Functions in Regulation of Aliphatic Glucosinolates

BACKGROUND: Glucosinolates are natural metabolites in the order Brassicales that defend plants against both herbivores and pathogens and can attract specialized insects. Knowledge about the genes controlling glucosinolate regulation is limited. Here, we identify three R2R3 MYB transcription factors regulating aliphatic glucosinolate biosynthesis in Arabidopsis by combining several systems biology tools. METHODOLOGY/PRINCIPAL FINDINGS: MYB28 was identified as a candidate regulator of aliphatic glucosinolates based on its co-localization within a genomic region controlling variation both in aliphatic glucosinolate content (metabolite QTL) and in transcript level for genes involved in the biosynthesis of aliphatic glucosinolates (expression QTL), as well as its co-expression with genes in aliphatic glucosinolate biosynthesis. A phylogenetic analysis with the R2R3 motif of MYB28 showed that it and two homologues, MYB29 and MYB76, were members of an Arabidopsis-specific clade that included three characterized regulators of indole glucosinolates. Over-expression of the individual MYB genes showed that they all had the capacity to increase the production of aliphatic glucosinolates in leaves and seeds and induce gene expression of aliphatic biosynthetic genes within leaves. Analysis of leaves and seeds of single knockout mutants showed that mutants of MYB29 and MYB76 have reductions in only short-chained aliphatic glucosinolates whereas a mutant in MYB28 has reductions in both short- and long-chained aliphatic glucosinolates. Furthermore, analysis of a double knockout in MYB28 and MYB29 identified an emergent property of the system since the absence of aliphatic glucosinolates in these plants could not be predicted by the chemotype of the single knockouts. CONCLUSIONS/SIGNIFICANCE: It seems that these cruciferous-specific MYB regulatory genes have evolved both overlapping and specific regulatory capacities. This provides a unique system within which to study the evolution of MYB regulatory factors and their downstream targets

Effect of changes in climate and emissions on future sulfate-nitrate-ammonium aerosol levels in the United States

Global simulations of sulfate, nitrate, and ammonium aerosols are performed for the present day and 2050 using the chemical transport model GEOS-Chem. Changes in climate and emissions projected by the IPCC A1B scenario are imposed separately and together, with the primary focus of the work on future inorganic aerosol levels over the United States. Climate change alone is predicted to lead to decreases in levels of sulfate and ammonium in the southeast U.S. but increases in the Midwest and northeast U.S. Nitrate concentrations are projected to decrease across the U.S. as a result of climate change alone. In the U.S., climate change alone can cause changes in annually averaged sulfate-nitrate-ammonium of up to 0.61 μg/m^3, with seasonal changes often being much larger in magnitude. When changes in anthropogenic emissions are considered (with or without changes in climate), domestic sulfate concentrations are projected to decrease because of sulfur dioxide emission reductions, and nitrate concentrations are predicted to generally increase because of higher ammonia emissions combined with decreases in sulfate despite reductions in emissions of nitrogen oxides. The ammonium burden is projected to increase from 0.24 to 0.36 Tg, and the sulfate burden to increase from 0.28 to 0.40 Tg S as a result of globally higher ammonia and sulfate emissions in the future. The global nitrate burden is predicted to remain essentially constant at 0.35 Tg, with changes in both emissions and climate as a result of the competing effects of higher precursor emissions and increased temperature

The Efficiency of the Human CD8+ T Cell Response: How Should We Quantify It, What Determines It, and Does It Matter?

Multidisciplinary techniques, in particular the combination of theoretical and experimental immunology, can address questions about human immunity that cannot be answered by other means. From the turnover of virus-infected cells in vivo, to rates of thymic production and HLA class I epitope prediction, theoretical techniques provide a unique insight to supplement experimental approaches. Here we present our opinion, with examples, of some of the ways in which mathematics has contributed in our field of interest: the efficiency of the human CD8+ T cell response to persistent viruses

Diglossia and identity in Northeast Thailand: Linguistic, social, and political hierarchy

The paper explores diglossic relations between Central Thai and phasa isan, a variety officially known as a dialect of Thai, but linguistically close to Lao. Phasa isan is spoken by almost one-third of Thailand's population but its speakers in the Northeast are often stigmatized as uneducated and backward. We conducted field research mainly among university students in Ubon Ratchathani, a northeastern border province, by drawing upon data from survey questionnaires, reflective essays, interviews, and field observations. The findings suggest a transitional diglossic relationship in which Central Thai is the High and phasa isan the Low variety. These relationships are discussed in terms of nationalism, social hierarchy, and language maintenance and shift