Structural and functional diversity of glutaredoxins in yeast

Glutaredoxins are defined as thiol disulfide oxidoreductases that reduce disulfide bonds employing reduced glutathione as electron donor. They constitute a complex family of proteins with a diversity of enzymatic and functional properties. Thus, dithiol glutaredoxins are able to reduce disulfide bonds and deglutathionylate mixed disulfides between glutathione and cysteine protein residues. They could act regulating the redox state of sulfhydryl residues of specific proteins, while thioredoxins (another family of thiol disulfide oxidoreductases which employ NADPH as electron donor) would be the general sulfhydryl reductants. Some dithiol glutaredoxins such as human Grx2 form dimers bridged by one iron-sulfur cluster, which acts as a sensor of oxidative stress, therefore regulating the activity of the glutaredoxin. The ability to interact with iron-sulfur clusters as ligands is also characteristic of monothiol glutaredoxins with a CGFS-type active site. These do not display thiol oxidoreductase activity, but have roles in iron homeostasis. The three members of this subfamily in Saccharomyces cerevisiae participate in the synthesis of the iron-sulfur clusters in mitochondria (Grx5), or in signalling the iron status inside the cell for regulation of iron uptake and intracellular iron relocalization (Grx3 and Grx4). Such a role in iron metabolism seems to be evolutionary conserved. Fungal cells also contain membrane-associated glutaredoxins structurally and enzymatically similar to dithiol glutaredoxins, which may act as redox regulators at the early stages of the protein secretory machinery.     

Rapid passage signals from a vibrationally excited target molecule: a pump and probe experiment with continuous wave quantum cascade lasers

Two 5 μm continuous wave quantum cascade lasers are used to perform a counterpropagating pump and probe experiment on a low pressure sample of nitric oxide. The strong pump field excites a fundamental rovibrational transition and the weaker probe field is tuned to the corresponding rotationally resolved hot band transition. When both light fields are in resonance, rapid passage is observed in the hot band absorption lineshape arising from a minimally damped and velocity-selected sample of molecules in the v=1 state. The measured rapid passage signals are well described by a two-level model based on the optical Bloch equations.     

Fundamentals of Plasma Polymerization

The plasma polymerization of ethylene is used as an example through which to discuss the elementary steps involved in forming a polymer in an electric discharge. The relationship of the experimentally controlled variables to the rate of formation of first generation active species is discussed. These species are related, in turn, to the overall rate of polymerization through a simple model. Two asymptotic conditions are discussed which correspond to minimal and total conversion of monomer to polymer. The dependence of polymer deposition rate on monomer flow rate predicted by the model is found to correspond very closely to that observed experimentally. The predicted effect of gas pressure on polymer deposition rate also agrees with that found experimentally.     

Analytic regularization in Soft-Collinear Effective Theory

In high-energy processes which are sensitive to small transverse momenta, individual contributions from collinear and soft momentum regions are not separately well-defined in dimensional regularization. A simple possibility to solve this problem is to introduce additional analytic regulators. We point out that in massless theories the unregularized singularities only appear in real-emission diagrams and that the additional regulators can be introduced in such a way that gauge invariance and the factorized eikonal structure of soft and collinear emissions is maintained. This simplifies factorization proofs and implies, at least in the massless case, that the structure of Soft-Collinear Effective Theory remains completely unchanged by the presence of the additional regulators. Our formalism also provides a simple operator definition of transverse parton distribution functions.     

Untersuchung von Fetten und ?len

Ohne Zusammenfassung     

An interstitial model for fluid water

As in the usual interstitial model, disorder is introduced by the displacement of molecules from a bonded ice-like framework onto interstitial sites. However, in this model the interstitial sites are distributed in such a way that its properties can be derived from those of an Ising model on the framework sites. Frameworks considered are the three-dimensional diamond lattice and the two-dimensional honeycomb and square lattices. Accurate liquid/vapour phase diagrams are obtained, density maxima and compressibility minima being found on the liquid branch for appropriate ratios of the non-bonding interaction energy ε to the bonding energy w. Results are compared with those of the zeroth-order and first-order approximations and isobars are calculated using the latter. For the range of ε/w giving best qualitative agreement between the three-dimensional model and experiment, the first-order and accurate results are very close in the part of the state surface where anomalous water-like properties occur.     

Structural Characterization of Plasma-Polymerized Hydrocarbons

Oils and films were produced by passage of ethylene, acetylene, and butadiene gases as well as benzene vapor through a radio-frequency electric discharge. The hydrocarbon oils produced in the plasma were dissolved in carbon tetrachloride and were analyzed by infrared and nuclear magnetic resonance spectroscopy. Based on these analyses, concentrations of characteristic functional groups were determined and used to propose molecular structures. The hydrocarbon oils are postulated to consist of irregular sequences of highly branched and incompletely crosslinked aliphatic backbone chains with pendant aromatic rings. Double bonds are interspersed along the chains. Hydrogen/carbon ratios in the proposed structures are consistent with the results from elemental analyses. Products from py-rolysis mass spectrometry can also be interpreted on the basis of the proposed structures. Similar techniques are used to analyze the structures of insoluble plasma polymerized films obtained from the same hydrocarbons. The major distinguishing feature in the films is the very high degree of crosslinking; of the order of one crosslink per six to ten chain carbon atoms.