Tethered bimolecular lipid membranes—A novel model membrane platform

This contribution summarizes some of our efforts in designing, synthesizing, assembling, and characterizing functional tethered bimolecular lipid membranes (tBLMs) as a novel platform for biophysical studies of and with artificial membranes or for sensor development employing, e.g., membrane integral receptor proteins. Chemical coupling schemes based on thiol groups for Au substrates or silanes used in the case of oxide surfaces allow for the covalent and, hence, chemically and mechanically robust attachment of anchor lipids to the solid support, stabilizing the proximal layer of a tethered membrane on the transducer surface. Surface plasmon optics, the quartz crystal microbalance, fluorescence- and IR spectroscopies, and electrochemical techniques are used to characterize the build-up of these complex supramolecular interfacial architectures. We demonstrate, in particular, that bilayers with a specific electrical resistance of better than 10 MΩ cm² can be achieved routinely with this approach.The functionalization of the lipid membranes by the incorporation of peptides is demonstrated for the carrier valinomycin which shows in our tBLMs the expected discrimination by four orders of magnitude between the translocation of K⁺- and Na⁺-ions across the hydrophobic barrier. For the synthetic channel-forming peptide M2 the high electrical resistance of the bilayer with the correspondingly low background current allows for the recording of even single channel current fluctuations.From the many membrane proteins that we reconstituted so far we describe results obtained with the redox-protein cytochrome c oxidase. Here, we also use a genetically modified mutant with a His-tag at either the C- or the N-terminus for the oriented attachment of the protein via the NTA/Ni²⁺ approach. With this strategy, we not only can control the density of the immobilized functional units, we introduce a completely new and alternative concept for the stabilization of lipid bilayers, i.e., the protein-tethered membrane.Our efforts in experimentally characterizing the resulting membrane functions and correlating the data with the structural details of the bilayer architectures are complemented by theoretical studies modeling the electrical and electrochemical response of functional tethered lipid bilayer membranes by extended SPICE simulations.     

A contribution to the dispute on the Ortega hypothesis: Connection between publication rate and stratification of scientists,tested by various methods

It was tested whether the publication rate of scientists as a rough measure of their eminence, influences their stratification. The stratification is reflected in cooperation, in co-authorships, in the structure of the citations and in the distribution of publications among the various problem areas of a scientific discipline. The findings of these investigations was discussed as a contribution to the dispute among authors who accept or reject the Ortega hypothesis which states that the research done by average scientists substantially contributes to the advance of science.Some discussion papers abont the Ortega hypothesis were published in Scientometrics, 12 (1987) 293–353.     

Increased sleep pressure reduces resting state functional connectivity

Object

In humans, even a single night of partial sleep deprivation (PSD) can have a negative impact on cognition and affective processing, suggesting that sleep pressure represents a basic physiological constraint of brain function. Among the spontaneously fluctuating resting state networks, the default mode network (DMN) and its anticorrelated network (ACN) hold key functions in segregating internally and externally directed awareness. Task fMRI after sleep deprivation has revealed altered activation patterns in both networks. We hypothesized that effects of PSD in these intrinsically coupled networks can be detected by resting state fMRI.

Methods

We obtained 6-minute echoplanar imaging time series (1.5 Tesla) during eyes-closed, wakeful-resting experiments from 16 healthy volunteers after normal sleep and after PSD. We used independent component and cross-correlation analysis to study functional connectivity (fc), focusing on the DMN and ACN.

Results

After PSD, focal reductions of auto-correlation strength were detected in the posterior and anterior midline node of the DMN and in the lateral parietal and insular nodes of the ACN. Cross-correlation analysis confirmed reduced cortico-cortical connectivity within and between the DMN and ACN.

Conclusions

Increased sleep pressure is reflected in reduced fc of main DMN and ACN nodes during rest. Results have implications for understanding perceptual and cognitive changes after sleep deprivation and are relevant to clinical studies on conditions in which increased sleep propensity is present.     

Beitr?ge zur Kenntnis der Parasitenfauna des Wildes in Nordrhein-Westfalen. 2. Der Endoparasitenbefall des Damwildes

Zusammenfassung Die Endoparasitenfauna von 64 Damhirschen (26 Kälber < 1 Jahr, 8 1 Jahr) aus den Jagdjahren 1997/98 und 1998/99 aus 3 Herkunftsgebieten im südlichen Nordrhein-Westfalen wurde untersucht. Dabei wurden 20 Nematodenarten nachgewiesen, 19 Arten im Magen-Darm-Kanal und eine Spezies in der Lunge. Alle Tiere waren mit Magen-Darm-Nematoden befallen und 10,9% mit 1 bis 11 Lungenwürmern der ArtDictyocaulus eckerti. 93,8% der Damhirsche waren mit Labmagennematoden infiziert, 57,8% mit im Dünndarm und 87,5% mit im Dickdarm parasitierenden Nematoden. Die am häufigsten gefundenen Nematodenarten warenSpiculopteragia asymmetrica (84,4%),Oesophagostomum sikae (71,9%),Spiculopteragia böhmi (45,3%),Nematodirus roscidus (37,5%),Capillaria bovis undOesophagostomum venulosum (jeweils 35,9%),Ostertagia leptospicularis (34,4%) undApteragia quadrispiculata (25,0%). Erstmals als Parasiten des einheimischen Damwildes wurden nachgewiesenTrichostrongylus askivali, Trichostrongylus capreoli, Nematodirus battus, Nematodirus roscidus sowieAscaris suum (Larven 4 und 5). Der Labmagen war der am stärksten parasitierte Abschnitt des Verdauungskanals, gefolgt von Dünn- und Dickdarm (geometrisches Mittel der Befallsintensität: 106, 9 bzw. 5 Nematoden). Kälber beherbergten durchschnittlich (geometrisches Mittel) 184, die etwa einjährigen Tiere 204 und die > 1 Jahr alten Tiere 190 Magen-Darm-Nematoden. Die Parasitierung des Labmagens und des Dickdarms stieg mit zunehmendem Alter der Tiere an, der Wurmbefall des Dünndarms ging parallel dazu zurück. Adulte Bandwürmer, Bandwurmfinnen, Leberegel, Pansenegel und Filarien auf den serösen Häuten waren nicht nachweisbar. Die sehr geringe Befallsintensität der Damhirsche mit Magen-Darm- und Lungenwürmern bestätigt die dieser Wildart nachgesagte geringe Anfälligkeit für Parasiten.Eingesetzt wurde ein Druckkostenzuschuß der LÖBF NRW, Dez. Forschungsstelle für Jagdkunde und Wildschadenverhütung, für dessen Gewährung verbindlich gedankt wird. — Die Schriftleitung.     

Adaptive rejection Metropolis sampling using Lagrange interpolation polynomials of degree 2

A crucial problem in Bayesian posterior computation is efficient sampling from a univariate distribution, e.g. a full conditional distribution in applications of the Gibbs sampler. This full conditional distribution is usually non-conjugate, algebraically complex and computationally expensive to evaluate. We propose an alternative algorithm, called ARMS2, to the widely used adaptive rejection sampling technique ARS [Gilks, W.R., Wild, P., 1992. Adaptive rejection sampling for Gibbs sampling. Applied Statistics 41 (2), 337-348; Gilks, W.R., 1992. Derivative-free adaptive rejection sampling for Gibbs sampling. In: Bernardo, J.M., Berger, J.O., Dawid, A.P., Smith, A.F.M. (Eds.), Bayesian Statistics, Vol. 4. Clarendon, Oxford, pp. 641-649] for generating a sample from univariate log-concave densities. Whereas ARS is based on sampling from piecewise exponentials, the new algorithm uses truncated normal distributions and makes use of a clever auxiliary variable technique [Damien, P., Walker, S.G., 2001. Sampling truncated normal, beta, and gamma densities. Journal of Computational and Graphical Statistics 10 (2) 206-215]. Furthermore, we extend this algorithm to deal with non-log-concave densities to provide an enhanced alternative to adaptive rejection Metropolis sampling, ARMS [Gilks, W.R., Best, N.G., Tan, K.K.C., 1995. Adaptive rejection Metropolis sampling within Gibbs sampling. Applied Statistics 44, 455-472]. The performance of ARMS and ARMS2 is compared in simulations of standard univariate distributions as well as in Gibbs sampling of a Bayesian hierarchical state-space model used for fisheries stock assessment.     

Decidability by Resolution for Propositional Modal Logics

The paper shows that satisfiability in a range of popular propositional modal systems can be decided by ordinary resolution procedures. This follows from a general result that resolution combined with condensing, and possibly some additional form of normalization, is a decision procedure for the satisfiability problem in certain so-called path logics. Path logics arise from normal propositional modal logics by the optimized functional translation method. The decision result provides an alternative method of proving decidability for modal logics, as well as closely related systems of artificial intelligence. This alone is not interesting. A more far-reaching consequence of the result has practical value, namely, many standard first-order theorem provers that are based on resolution are suitable for facilitating modal reasoning.     

Phosphorylation by COP9 Signalosome-Associated CK2 Promotes Degradation of p27 during the G1 Cell Cycle Phase

The cell cycle regulator p27^Kip1 (p27) is controlled by 26S proteasome-mediated proteolysis by two different pathways. From the S till the G2 phase of the cell cycle, degradation of p27 takes place in the nucleus and is initiated by CDK2-dependent phosphorylation of threonine 187 with subsequent ubiquitination by the SCF^Skp2 ubiquitin ligase. During the G1 cell cycle phase (G1), p27 breakdown is cytosolic and is initiated by nuclear export with subsequent ubiquitination by a RING finger ligase called kip1 ubiquitination complex. Here we show that the COP9 signalosome (CSN) is a regulator of p27 proteolysis during G1. The CSN interacts with p27 and the CSN-associated kinase CK2 phosphorylates p27 at two regions. One is central to the protein (amino acids 101–113), and the other was mapped near to the C-terminus (amino acids 170–189). Elimination of the putative C-terminal phosphorylation sites stabilizes ectopic p27 towards proteasomal degradation and abolishes CSN–p27 binding. Inhibition of CSN-associated kinase activity by curcumin attenuates loss of p27 upon cell cycle re-entry. Similar but not additive effects of the phosphoinositol-3-kinase blocker LY 290042 may point to a common pathway of CSN-associated CK2 and protein kinase B/Akt (Akt) in regulating p27 abundance. Akt is found in Flag pulldowns of lysates obtained from cells permanently expressing Flag-tagged CSN2, indicating that Akt is a novel kinase associated with the CSN. Thus, the CSN seems to regulate p27 proteolysis at G1 downstream of Ras-mediated signal pathways.     

Increased proteolytic resistance of ribonuclease A by protein engineering

Although highly stable toward unfolding, native ribonucleaseA is known to be cleaved by unspecific proteases in the flexibleloop region near Ala20. With the aim to create a protease-resistantribonuclease A, Ala20 was substituted for Pro by site-directedmutagenesis. The resulting mutant enzyme was nearly identicalto the wild-type enzyme in the near-UV and far-UV circular dichroismspectra, in its activity to 2',3'-cCMP and in its thermodynamicstability. However, the proteolytic resistance to proteinaseK and subtilisin Carlsberg was extremely increased. Pseudo-first-orderrate constants of proteolysis, determined by densitometric analysisof the bands of intact protein in SDS–PAGE, decreasedby two orders of magnitude. In contrast, the rate constant ofproteolysis with elastase was similar to that of the wild-typeenzyme. These differences can be explained by the analysis ofthe fragments occurring in proteolysis with elastase. Ser21–Ser22was identified as the main primary cleavage site in the degradationof the mutant enzyme by elastase. Obviously, this bond is notcleavable by proteinase K or subtilisin Carlsberg. The resultsdemonstrate the high potential of a single mutation in proteinstabilization to proteolytic degradation.     

Projection in surrogate decisions about life-sustaining medical treatments.

To honor the wishes of an incapacitated patient, surrogate decision makers must predict the treatment decisions patients would make for themselves if able. Social psychological research, however, suggests that surrogates' own treatment preferences may influence their predictions of others' preferences. In 2 studies (1 involving 60 college student surrogates and a parent, the other involving 361 elderly outpatients and their chosen surrogate decision maker), surrogates predicted whether a close other would want life-sustaining treatment in hypothetical end-of-life scenarios and stated their own treatment preferences in the same scenarios. Surrogate predictions more closely resembled surrogates' own treatment wishes than they did the wishes of the individual they were trying to predict. Although the majority of prediction errors reflected inaccurate use of surrogates' own treatment preferences, projection was also found to result in accurate prediction more often than counterprojective predictions. The rationality and accuracy of projection in surrogate decision making is discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An ethnographic study of design knowledge reuse in the architecture, engineering, and construction industry

This paper presents an ethnographic study of knowledge reuse in the architecture/engineering/construction industry. Reuse occurs largely through social knowledge networks. Even when reuse from an external repository occurs, a human expert is needed to provide input on what to reuse and contextual information about the designs being reused. This is attributed to the effectiveness of internal knowledge reuse, the reuse of knowledge from one’s personal experiences. Internal knowledge reuse is effective because the designer can find items to reuse, and can recall the context of these items and can therefore understand them. This ethnographic study was used to develop a corporate memory, a rich, detailed repository of knowledge in context. The corporate memory will support finding and understanding. Understanding can be brought about by enabling the designer to explore the item’s context. This helps the designer to manage the tradeoff between productivity and creativity in deciding what to reuse.