Pulse EPR measurements of intramolecular distances in a TOPP-labeled transmembrane peptide in lipids.

We present the performance of nanometer-range pulse electron paramagnetic resonance distance measurements (pulsed electron-electron double resonance/double electron-electron resonance, PELDOR/DEER) on a transmembrane WALP24 peptide labeled with the semirigid unnatural amino acid 4-(3,3,5,5-tetra-methyl-2,6-dioxo-4-oxylpiperazin-1-yl)-l-phenylglycine (TOPP). Distances reported by the TOPP label are compared to the ones reported by the more standard MTSSL spin label, commonly employed in protein studies. Using high-power pulse electron paramagnetic resonance spectroscopy at Q-band frequencies (34 GHz), we show that in contrast to MTSSL, our label reports one-peak, sharp (Δr ≤ 0.4 nm) intramolecular distances. Orientational selectivity is not observed. When spin-labeled WALP24 was inserted in two representative lipid bilayers with different bilayer thickness, i.e., DMPC and POPC, the intramolecular distance reported by TOPP did not change with the bilayer environment. In contrast, the distance measured with MTSSL was strongly affected by the hydrophobic thickness of the lipid. The results demonstrate that the TOPP label is well suited to study the intrinsic structure of peptides immersed in lipids

Legitimität und Illegalität – Avantgarde und Menschenopfer

Diedrich Diederichsen analysiert in seinem 1994 erstmals erschienenen Beitrag Legitimität und Illegalität – Avantgarde und Menschenopfer die Funktionsmechanismen der Künstlergruppe, die als Konstrukt einer prekären Verbindung von individualanarchistisch-elitärem Einzelanspruch und sozialen Durchsetzungsregeln auf Opferfiguren angewiesen ist, die die Wertsetzungen innerhalb der (opinion leaders einer) Gruppe durch die Exklusion beglaubigen. In Bauers Change ist für Diederichsen Ferys selbststabilisierende Beherrschungsabsicht durch Manipulation deswegen zum Scheitern verurteilt, weil sich Blasi als „post-bohemistischer Typ, zwischen Cretin, Karrierist und Rebell“ gegenüber dem Elitismus durchsetzen muss: ein (leider kaum adäquat rezipierter) Ansatz, der – jenseits der früheren und späteren häufig moralistischen oder billig sozialkritischen Interpretationsansätze – Bauers Abgesang auf die Selbststilisierung der „avantgardistischen“ Boheme in sozialen und mentalitätsgeschichtlichen Strukturbedingungen verortet, die individuelle Intentionen prägen, überformen oder zum Scheitern bringen

Keeping Control: The Role of Senescence and Development in Plant Pathogenesis and Defense

Many plant pathogens show interactions with host development. Pathogens may modify plant development according to their nutritional demands. Conversely, plant development influences pathogen growth. Biotrophic pathogens often delay senescence to keep host cells alive, and resistance is achieved by senescence- like processes in the host. Necrotrophic pathogens promote senescence in the host, and preventing early senescence is a resistance strategy of plants. For hemibiotrophic pathogens both patterns may apply. Most signaling pathways are involved in both developmental and defense reactions. Increasing knowledge about the molecular components allows to distinguish signaling branches, cross-talk and regulatory nodes that may influence the outcome of an infection. In this review, recent reports on major molecular players and their role in senescence and in pathogen response are reviewed. Examples of pathosystems with strong developmental implications illustrate the molecular basis of selected control strategies. A study of gene expression in the interaction between the hemibiotrophic vascular pathogen Verticillium longisporum and its cruciferous hosts shows processes that are fine-tuned to counteract early senescence and to achieve resistance. The complexity of the processes involved reflects the complex genetic control of quantitative disease resistance, and understanding the relationship between disease, development and resistance will support resistance breeding. View Full-Tex

Studies of transmembrane peptides by pulse dipolar spectroscopy with semi-rigid TOPP spin labels

Electron paramagnetic resonance (EPR)-based pulsed dipolar spectroscopy measures the dipolar interaction between paramagnetic centers that are separated by distances in the range of about 1.5–10 nm. Its application to transmembrane (TM) peptides in combination with modern spin labelling techniques provides a valuable tool to study peptide-to-lipid interactions at a molecular level, which permits access to key parameters characterizing the structural adaptation of model peptides incorporated in natural membranes. In this mini-review, we summarize our approach for distance and orientation measurements in lipid environment using novel semi-rigid TOPP [4-(3,3,5,5-tetramethyl-2,6-dioxo-4-oxylpiperazin-1-yl)-L-phenylglycine] labels specifically designed for incorporation in TM peptides. TOPP labels can report single peak distance distributions with sub-angstrom resolution, thus offering new capabilities for a variety of TM peptide investigations, such as monitoring of various helix conformations or measuring of tilt angles in membranes

Trypsin inhibition by macrocyclic and open-chain variants of the squash inhibitor MCoTI-II

MCoTl-I and MCoTl-II from the seeds of Momordica cochinchinensis are inhibitors of trypsin-like proteases and the only known members of the large family of squash inhibitors that are cyclic and contain an additional loop connecting the amino- and the carboxy-terminus. To investigate the contribution of macrocycle formation to biological activity, we synthesized a set of open-chain variants of MCoTl-II that lack the cyclization loop and contain various natural and non-natural amino acid substitutions in the reactive-site loop. Upon replacement of P1 lysine residue \#10 within the open-chain variant of MCoTl-II by the non-natural isosteric nucleo amino acid AlaG{[}beta-(guanin-9-yl)-L-alanine], a conformationally restricted arginine mimetic, residual inhibitory activity was detected, albeit reduced by four orders of magnitude. While the cyclic inhibitors MCoTl-I and MCoTl-II were found to be very potent trypsin inhibitors, with picomolar inhibition constants, the open-chain variants displayed an approximately 10-fold lower affinity. These data suggest that the formation of a circular backbone in the MCoTI squash inhibitors results in enhanced affinity and therefore is a determinant of biological activity

A Natural Value Unit - Econophysics as Arbiter between Finance and Economics

Foreign exchange markets show that currency units (= accounting or nominal price units) are variables. Technical and economic progress evidence that the consumer baskets (= purchasing power units or real price units) are also variables. In contrast, all physical measurement units are constants and either defined in the SI (= metric) convention or based upon natural constants (= "natural" or Planck units). Econophysics can identify a constant natural value scale or vaue unit (natural numaraire) based upon Planck energy. In honour of the economist L. Walras, this "Planck value" could be called walras (Wal), thereby using the SI naming convention. One Wal can be shown to have a physiological and an economic interpretation in that it is equal to the annual minimal real cost of physiological life of a reference person at minimal activity. The price of one Wal in terms of any currency can be estimated by hedonic regression techniques used in inflation measurement (axiometry). This pilot research uses official disaggregated Swiss Producer and Consumer Price Index data and estimates the hedonic walras price (HWP), quoted in Swiss francs in 2003, and its inverse, the physical purchasing power (PhPP) of the Swiss franc in 2003.Comment: 19 pages, 1 table, Appendix with 2 tables, RevTex4, APFA5 200

Der Nullpunkt und der Ausstieg aus der linearen Zeit

Für diesen Beitrag ist leider kein Abstract verfügbar. ----------