Trapped ion mobility spectrometry and PASEF enable in-depth lipidomics from minimal sample amounts

A comprehensive characterization of the lipidome from limited starting material remains very challenging. Here we report a high-sensitivity lipidomics workflow based on nanoflow liquid chromatography and trapped ion mobility spectrometry (TIMS). Taking advantage of parallel accumulation-serial fragmentation (PASEF), we fragment on average 15 precursors in each of 100 ms TIMS scans, while maintaining the full mobility resolution of co-eluting isomers. The acquisition speed of over 100 Hz allows us to obtain MS/MS spectra of the vast majority of isotope patterns. Analyzing 1 mu L of human plasma, PASEF increases the number of identified lipids more than three times over standard TIMS-MS/MS, achieving attomole sensitivity. Building on high intra- and inter-laboratory precision and accuracy of TIMS collisional cross sections (CCS), we compile 1856 lipid CCS values from plasma, liver and cancer cells. Our study establishes PASEF in lipid analysis and paves the way for sensitive, ion mobility-enhanced lipidomics in four dimensions

Rubber friction on wet and dry road surfaces: the sealing effect

Rubber friction on wet rough substrates at low velocities is typically 20-30% smaller than for the corresponding dry surfaces. We show that this cannot be due to hydrodynamics and propose a novel explanation based on a sealing effect exerted by rubber on substrate "pools" filled with water. Water effectively smoothens the substrate, reducing the major friction contribution due to induced viscoelastic deformations of the rubber by surface asperities. The theory is illustrated with applications related to tire-road friction.Comment: Format Revtex 4; 8 pages, 11 figures (no color); Published on Phys. Rev. B (http://link.aps.org/abstract/PRB/v71/e035428); previous work on the same topic: cond-mat/041204

Enzymkinetiken steuern den initialen Streuabbau in Gründlandflächen unterschiedlicher Nutzungsintensität

Extrazelluläre hydrolytische Enzyme (EHEs), die überwiegend von Bodenmikroorganismen produziert werden, übernehmen eine wichtige Rolle beim Umsatz der organischen Substanz im Boden. Die Zusammenhänge zwischen Enzymkinetiken und Abbauraten organischer Substanz sind allerdings kaum untersucht. Als Kenngrößen des katalytischen Verhaltens von EHEs können die limitierende Umsatzrate (Vmax) sowie die apparente Substrataffinität (Km) mittels der Michaelis-Menten-Gleichung angenähert werden. Am Abbau von Cellulose z.B. sind Enzyme aus drei verschiedenen Klassen beteiligt. So katalysieren Cellotriosidasen (CTH), die Abspaltung von drei Glucose-Molekülen und Cellobiohydrolasen (CBH) die Umsetzung zu Cellobiose. beta-Glucosidasen (BG) nutzen Cellobiose und zerlegen dieses Substrat in einzelne Glucose-Moleküle. Somit liegt die Vermutung nahe, dass z.B. maximale Umsatzraten (Vmax) von BG durch die Km-Werte von CBH und CTH reguliert werden. Um den Einfluss unterschiedlicher Streuqualität auf solche Interaktionen zwischen verschiedenen Enzymen zu testen wurden Teebeutel mit grünem Tee (C/N Verhältnis 12) und Teebeutel mit Rooibos-Tee (C/N Verhältnis 43) in Anlehnung an Keuskamp et al. (2013) für drei Monate auf je 25 unterschiedlich intensiv bewirtschafteten Grünlandflächen der Biodiversitätsexploratorien (Hainich, Schorfheide) eingebracht. In den ausgebrachten, 3-monatig-exponierten, Teeproben wurden die katalytischen Eigenschaften der oben genannten EHEs sowie die Enzymaktivitäten von Phenol- und Peroxidasen gemessen. Die bisher ermittelten kinetischen Parameter der EHEs die am Abbau von Zellulose beteiligt sind weisen deutlich auf die unterschiedlichen Abbaumuster der beiden Teesorten hin. In den Rooibostee-Proben sind die vermuteten Beziehungen zwischen den Vmax-Werten von BG und den Km-Werten der anderen Cellulasen nachzuweisen und stehen in Beziehung zur Abbaurate. In den Grüntee-Proben dagegen bestehen Beziehungen zwischen den Vmax-Werten aller drei Cellulose abbauenden Enzyme

Impact experiments in support of “Lithopanspermia”: The route from Mars to Earth

Shock recovery experiments on a Martian analogue rock (gabbro) loaded with three types of microorganisms reveal that these organisms survive the impact and ejection phase on Mars at shock pressures up to about 50 GPa with exponentially decreasing survival rates

Projective quantum spaces

Associated to the standard $SU_{q}(n)$ R-matrices, we introduce quantum spheres $S_{q}^{2n-1}$, projective quantum spaces $CP_{q}^{n-1}$, and quantum Grassmann manifolds $G_{k}(C_{q}^{n})$. These algebras are shown to be homogeneous quantum spaces of standard quantum groups and are also quantum principle bundles in the sense of T Brzezinski and S. Majid (Comm. Math. Phys. 157,591 (1993)).Comment: 8 page

An Incoherent α−Ω\alpha-\Omega Dynamo in Accretion Disks

We use the mean-field dynamo equations to show that an incoherent alpha effect in mirror-symmetric turbulence in a shearing flow can generate a large scale, coherent magnetic field. We illustrate this effect with simulations of a few simple systems. In accretion disks, this process can lead to axisymmetric magnetic domains whose radial and vertical dimensions will be comparable to the disk height. This process may be responsible for observations of dynamo activity seen in simulations of dynamo-generated turbulence involving, for example, the Balbus-Hawley instability. In this case the magnetic field strength will saturate at $\sim (h/r)^2$ times the ambient pressure in real accretion disks. The resultant dimensionless viscosity will be of the same order. In numerical simulations the azimuthal extent of the simulated annulus should be substituted for $r$. We compare the predictions of this model to numerical simulations previously reported by Brandenburg et al. (1995). In a radiation pressure dominated environment this estimate for viscosity should be reduced by a factor of $(P_{gas}/P_{radiation})^6$ due to magnetic buoyancy.Comment: 23 pages, uses aaste

Toy Model for Pion Production in Nucleon-Nucleon Collisions

We develop a toy model of pion production in nucleon-nucleon collisions that reproduces some of the features of the chiral Lagrangian calculations. We calculate the production amplitude and examine some common approximations.Comment: 9 pages, 3 figure

Dissolved organic matter characteristics of deciduous and coniferous forests with variable management: different at the source, aligned in the soil

This dataset contains the data to the article: "Dissolved organic matter characteristics of deciduous and coniferous forests with variable management: different at the source, aligned in the soil" published in BiogeosciencesDFG/108154260/Elementkreisläufe in Grünland- und Waldökosystemen der Biodiversitätsexploratorien in Abhängigkeit von Landnutzungsintensität und damit verknüpfter Biodiversität/BECycle

Bulk spectral function sum rule in QCD-like theories with a holographic dual

We derive the sum rule for the spectral function of the stress-energy tensor in the bulk (uniform dilatation) channel in a general class of strongly coupled field theories. This class includes theories holographically dual to a theory of gravity coupled to a single scalar field, representing the operator of the scale anomaly. In the limit when the operator becomes marginal, the sum rule coincides with that in QCD. Using the holographic model, we verify explicitly the cancellation between large and small frequency contributions to the spectral integral required to satisfy the sum rule in such QCD-like theories.Comment: 16 pages, 2 figure

Extended Classical Over-Barrier Model for Collisions of Highly Charged Ions with Conducting and Insulating Surfaces

We have extended the classical over-barrier model to simulate the neutralization dynamics of highly charged ions interacting under grazing incidence with conducting and insulating surfaces. Our calculations are based on simple model rates for resonant and Auger transitions. We include effects caused by the dielectric response of the target and, for insulators, localized surface charges. Characteristic deviations regarding the charge transfer processes from conducting and insulating targets to the ion are discussed. We find good agreement with previously published experimental data for the image energy gain of a variety of highly charged ions impinging on Au, Al, LiF and KI crystals.Comment: 32 pages http://pikp28.uni-muenster.de/~ducree