The Core Histone-binding Region of the Murine Cytomegalovirus 89K Immediate Early Protein

The gene regulatory immediate early protein, pp89, of murine cytomegalovirus interacts with both DNA-associated and isolated histones in vitro. We characterized the histone-binding region of pp89 and its cellular localization during cell division to examine the possible interaction between pp89 and chromatin. pp89 expressed constitutively in cell line BALB/c 3T3 IE1 does not interact with condensed chromatin. As observed in infected cells, pp89 is localized within the nucleus of cells during interphase but spreads throughout the cell plasma following degradation of the nuclear membrane during early mitosis. In late telophase, pp89 is reorganized within the nucleus. Analysis of pp89 deletion mutants and of fragments generated by cleavage at pH 2·5 revealed that the regions responsible for association with histone are located between amino acids 71 and 415, and are not identical with the domain that shows homology to histone H2B or the highly acidic carboxy-terminal region. A potential gene-activating role of the high affinity of pp89 for isolated histones and the low affinity for DNA-associated histones is discussed

An acidic region of the 89K murine cytomegalovirus immediate early protein interacts with DNA

The product of the ie 1 gene, the regulatory immediate early protein pp89 of murine cytomegalovirus (MCMV), interacts with core histones, which can mediate the association of pp89 with DNA. We report the capacity of pp89 to interact directly with DNA in the absence of cellular proteins. After separation of proteins by SDS–PAGe, pp89 bound ds- and ssDNA, with a preference for ssDNA. Binding to specific DNA sequences in the MCMV genome was not detected. The DNA-binding region of pp89 was located to amino acids 438 to 534 by analysis of deletion mutants expressed as -galactosidase or TrpE fusion proteins. This region is identical to the highly acidic C-terminal region spanning amino acids 424 to 532. The human cytomegalovirus IE1 protein, which contains a similar extended C-terminal acidic region, does not react with DNA under the same experimental conditions

Constraints on post-depositional isotope modifications in East Antarctic firn from analysing temporal changes of isotope profiles

The isotopic composition of water in ice sheets is extensively used to infer past climate changes. In low-accumulation regions their interpretation is, however, challenged by poorly constrained effects that may influence the initial isotope signal during and after deposition of the snow. This is reflected in snow-pit isotope data from Kohnen Station, Antarctica, which exhibit a seasonal cycle but also strong interannual variations that contradict local temperature observations. These inconsistencies persist even after averaging many profiles and are thus not explained by local stratigraphic noise. Previous studies have suggested that post-depositional processes may significantly influence the isotopic composition of East Antarctic firn. Here, we investigate the importance of post-depositional processes within the open-porous firn (≳ 10 cm depth) at Kohnen Station by separating spatial from temporal variability. To this end, we analyse 22 isotope profiles obtained from two snow trenches and examine the temporal isotope modifications by comparing the new data with published trench data extracted 2 years earlier. The initial isotope profiles undergo changes over time due to downward advection, firn diffusion and densification in magnitudes consistent with independent estimates. Beyond that, we find further modifications of the original isotope record to be unlikely or small in magnitude (≪ 1 ‰ RMSD). These results show that the discrepancy between local temperatures and isotopes most likely originates from spatially coherent processes prior to or during deposition, such as precipitation intermittency or systematic isotope modifications acting on drifting or loose surface snow

The 89,000-Mr murine cytomegalovirus immediate-early protein activates gene transcription

To study trans-activation of gene expression by murine cytomegalovirus (MCMV) immediate-early (IE) proteins, the IE coding region 1 (ie1), which encodes the 89,000-Mr IE phosphoprotein (pp89), was stably introduced into L cells. A cell line was selected and characterized that efficiently expressed the authentic viral protein. The pp89 that was constitutively expressed in L cells stimulated the expression of transfected recombinant constructs containing the bacterial chloramphenicol acetyltransferase (CAT) gene under the control of viral promoters. The regulatory function of the ie1 product was confirmed by transient expression assays in which MCMV IE genes were cotransfected into L cells together with recombinant constructs of the CAT gene. For CAT activation by the ie1 product, a promoter region was required, but there was no preferential activation of a herpes simplex virus type 1 delayed-early promoter. All plasmid constructs that contained the intact coding sequences for pp89 induced gene expression in trans. The MCMV enhancer region was not essential for the expression of a functional IE gene product, and testing of the cis-regulatory activity of the MCMV enhancer revealed a low activity in L cells. Another region transcribed at IE times of infection, IE coding region 2, was unable to induce CAT expression and also did not augment the functional activity of ie1 after cotransfection

Relaxation of a dewetting contact line Part 1: A full-scale hydrodynamic calculation

The relaxation of a dewetting contact line is investigated theoretically in the so-called "Landau-Levich" geometry in which a vertical solid plate is withdrawn from a bath of partially wetting liquid. The study is performed in the framework of lubrication theory, in which the hydrodynamics is resolved at all length scales (from molecular to macroscopic). We investigate the bifurcation diagram for unperturbed contact lines, which turns out to be more complex than expected from simplified 'quasi-static' theories based upon an apparent contact angle. Linear stability analysis reveals that below the critical capillary number of entrainment, Ca_c, the contact line is linearly stable at all wavenumbers. Away from the critical point the dispersion relation has an asymptotic behaviour sigma~|q| and compares well to a quasi-static approach. Approaching Ca_c, however, a different mechanism takes over and the dispersion evolves from |q| to the more common q^2. These findings imply that contact lines can not be treated as universal objects governed by some effective law for the macroscopic contact angle, but viscous effects have to be treated explicitly.Comment: 21 pages, 9 figure

Charakterisierung hydrologischer Material-Eigenschaften mittels Multi Step Outflow (MSO) Experimenten

Die Kenntnis hydrologischer Eigenschaften ist essentiell für das Grundwassermanagement. Im Rahmen eines Projektes zur Verknüpfung mit elektrischen Eigenschaften, welche nicht-invasiv bestimmbar sind (Spektrale Induzierte Polarisation, SIP), wurden am IBG-3 (Agrosphäre; vormals ICG-IV) des Forschungszentrums Jülich hydrologische Material-Eigenschaften bestimmt mittels Multi-Step-Outflow-Experimenten (MSO). Dazu wurde ein Probenhalter entwickelt zur gemeinsamen Messung der hydraulischen und elektrischen Eigenschaften. In der MSO-Anlage wird das gesättigte Medium mittels Druckluft bzw. Saugspannung schrittweise entwässert. Unter der Probe verhindert eine poröse Keramik-Platte mit Lufteintrittswert oberhalb des angelegten Druckes die Durchströmung der Probe durch die Druckluft (was die Entsättigung beenden würde). Aus der Ausflusskurve können mittels inverser Modellierung hydrologische Kenngrößen bestimmt werden (Mualem-van-Genuchten-Ansatz, HYDRUS-Programm). HYDRUS verwendet folgende Parameter: residualer und gesättigter Wassergehalt, Porenverbindungsparameter, inverser Lufteintrittswert α, Porengrößenverteilungsindex n, van-Genuchten-Parameter m, gesättigte hydraulische Leitfähigkeit Ks. Dabei werden α und n bestimmt mittels inverser Modellierung aus Wasserhaltekurven (Wassergehalt in Abh. von angelegtem Luftdruck im Drucktopf, RetC-Programm). Ks wird bestimmt mittels falling head permeameter Experimenten (Durchfluss in Abh. vom Wasserdruck). Die ermittelten Ks-Werte in Abh. von der Korngröße folgen der Hazen-Formel. Die MSO-Daten werden ins HYDRUS-Format konvertiert (z. B. Ausfluss durch Probenhalterquerschnitt normiert, Druck [bar] oberhalb zu Saugspannung [cm] unterhalb der Säule) und mittels SHRINK-Programm systematisch reduziert. Der inverse Lufteintrittswert α aus der inversen Modellierung zeigt eine generelle Zunahme mit der Korngröße, wie wegen der inversen Beziehung beider Größen mit dem Lufteintrittswert erwartet. Mit zunehmender Korngröße wird auch zunehmender Porengrößenverteilungsindex n beobachtet. Mit α, n, m und Ks wird die Leitfähigkeit in Abhängigkeit von Wassergehalt θ bzw. Sättigung 0≤S≤1 oder Druckhöhe h berechnet, ebenso Wasserhaltekurven (θ abh. von Matrixpotential oder h), effektive Poren- und daraus Korn-Größenverteilungen, welche zu den Korngrößen passen, wie sie durch Siebung eingegrenzt wurden. Der nächste Schritt ist die Korrelation der Sättigungs-abhängigen hydraulischen Leitfähigkeiten mit den Ergebnissen der elektrischen Messungen.poste

Osmotically driven pipe flows and their relation to sugar transport in plants

In plants, osmotically driven flows are believed to be responsible for translocation of sugar in the pipe-like phloem cell network, spanning the entire length of the plant. In this paper, we present an experimental and theoretical study of transient osmotically driven flows through pipes with semipermeable walls. We extend the experimental work of Eschrich, Evert and Young \cite[]{Eschrich:1972} by providing a more accurate version of their experiment allowing for better comparison with theory. In the experiments we measure the dynamics and structure of a "sugar front", i.e. the transport and decay of a sudden loading of sugar in a pipe which is closed in both ends. We include measurements of pressure inside the membrane tube allowing us to compare the experiments directly with theory and, in particular, to confirm quantitatively the exponential decay of the front in a closed tube.In a novel setup we are able to measure the entire concentration profile as the sugar front moves. In contrast to previous studies we find very good agreement between experiment and theory. In the limit of low axial resistance (valid in our experiments as well as in many cases in plants) we show that the equations can be solved exactly by the method of characteristics yielding, in general, an implicit solution. Further we show that under more general conditions the equations of motion can be rewritten as a single integro-differential equation, which can be readily solved numerically. The applicability of our results to plants is discussed and it is shown that it is probable that the pressure-flow hypothesis can account for short distance transport of sugar in plants.Comment: 34 pages, Submitted to Journal of Fluid Mechanics on May 28, 200

Preliminary report on infrared radiometric measurements from the Mariner 9 spacecraft

Preliminary 10- and 20-μm brightness temperatures of Mars are presented. More than 35% of the Martian surface was observed with a resolution better than 100 km. On the whole, the results confirm the thermal properties derived from the Mariner 6 and 7 radiometers, although the temperatures, on the average, were cooler and shifted with respect to the Martian day during the dust storm. Thermal inertias and radiometric albedos were derived for many areas; no clear correlation exists between these properties. Thermal structure again was found at the spatial limit of the radiometer; no cases were found in which it was necessary to invoke internal heat sources