A Peroxygenase from Chaetomium globosum Catalyzes the Selective Oxygenation of Testosterone

Unspecific peroxygenases (UPO, EC 1.11.2.1) secreted by fungi open an efficient way to selectively oxyfunctionalize diverse organic substrates, including less‐activated hydrocarbons, by transferring peroxide‐borne oxygen. We investigated a cell‐free approach to incorporate epoxy and hydroxyl functionalities directly into the bulky molecule testosterone by a novel unspecific peroxygenase (UPO) that is produced by the ascomycetous fungus Chaetomium globosum in a complex medium rich in carbon and nitrogen. Purification by fast protein liquid chromatography revealed two enzyme fractions with the same molecular mass (36 kDa) and with specific activity of 4.4 to 12 U mg^?1. Although the well‐known UPOs of Agrocybe aegerita (AaeUPO) and Marasmius rotula (MroUPO) failed to convert testosterone in a comparative study, the UPO of C. globosum (CglUPO) accepted testosterone as substrate and converted it with total turnover number (TTN) of up to 7000 into two oxygenated products: the 4,5‐epoxide of testosterone in β‐configuration and 16α‐hydroxytestosterone. The reaction performed on a 100 mg scale resulted in the formation of about 90 % of the epoxide and 10 % of the hydroxylation product, both of which could be isolated with purities above 96 %. Thus, CglUPO is a promising biocatalyst for the oxyfunctionalization of bulky steroids and it will be a useful tool for the synthesis of pharmaceutically relevant steroidal molecules.     

Fabrication of porous silicon by metal-assisted etching using highly ordered gold nanoparticle arrays

ABSTRACT: A simple method for the fabrication of porous silicon (Si) by metal-assisted etching was developed using gold nanoparticles as catalytic sites. Etching masks were prepared by spin-coating of colloidal gold nanoparticles onto Si. Appropriate functionalization of the gold nanoparticle surface prior to the deposition step enabled the formation of quasi-hexagonally ordered arrays by self-assembly which were translated into an array of pores by subsequent etching in a HF solution containing H2O2. The quality of the pattern transfer depended on the chosen preparation conditions for the gold nanoparticle etching mask. The influence of the Si surface properties were investigated by using either hydrophilic or hydrophobic Si substrates resulting from piranha solution or HF treatment, respectively. The polymer coated gold nanoparticles had to be thermally treated in order to provide direct contact at the metal/Si interface which is required for the following metal-assisted etching. Plasma-treatment as well as flame annealing were successfully applied. Best results were obtained for Si substrates which were treated with HF prior to spin-coating and flame annealed in order to remove the polymer matrix. The presented method opens up new resources for the fabrication of porous silicon by metal-assisted etching. Here, the vast variety of metal nanoparticles accessible by well-established wet-chemical synthesis can be employed for the fabrication of the etching masks.     

All-conjugated block copolymers

All-conjugated block copolymers of the rod-rod type came into the focus of interest because of their unique and attractive combination of nanostructure formation and electronic activity. Potential applications in a next generation of organic polymer materials for photovoltaic devices ("bulk heterojunction"-type solar cells) or (bio)sensors have been proposed. Combining the fascinating self-assembly properties of block copolymers with the active electronic and/or optical function of conjugated polymers in all-conjugated block copolymers is, therefore, a very challenging goal of synthetic polymer chemistry. First examples of such all-conjugated block copolymers from a couple of research groups all over the world demonstrate possible synthetic approaches and the rich application potential in electronic devices. A crucial point in such a development of novel polymer materials is a rational control over their nanostructure formation. All-conjugated di- or triblock copolymers may allow for an organization of the copolymer materials into large-area ordered arrays with a length scale of nanostructure formation of the order of the exciton diffusion length of organic semiconductors (typically ca. 10 nm). Especially for amphiphilic, all-conjugated copolymers the formation of well-defined supramolecular structures (vesicles) has been observed. However, intense further research is necessary toward tailor-made, all-conjugated block copolymers for specific applications. The search for optimized block copolymer materials should consider the electronic as well as the morphological (self-assembly) properties.     

Pain, depression, and physical functioning following burn injury.

Objective: Little is known about how pain and depression after burn injury may influence long-term outcomes such as physical functioning. This prospective study examined associations between pain, depression, and physical functioning in a sample of burn injury survivors. Design and Participants: Questionnaires assessing pain, depression, and physical functioning were completed by 64 (52% of original sample) adult burn survivors shortly after discharge from burn care and at 1- and 2-year follow-ups. Results: Pain and physical functioning improved over the 2 years of the study, whereas depression levels were stable. Pain and depression were associated with poorer physical functioning over time, but associations varied according to the time span under consideration. Also, the association between pain and physical functioning was strongest among persons with higher depression scores. Conclusions: Pain and depression may contribute independently to compromises in physical functioning. The co-occurrence of pain and depression represents even greater risk for reduced physical functioning over time among burn survivors. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The role of IL-4, IL-10, and TNF-alpha in the immune suppression induced by ultraviolet radiation

The two main catalytic residues Cys25 and His159 of the monomeric cysteine protease papain are located on different walls of a cleft formed by two domains. This topology suggests a possible relationship between relative domain organization and catalytic mechanism. The effect on enzymatic parameters of structural modifications at various locations of the two-domain interface of papain was examined by individual or double replacements by Ala of pairs of interacting residues. Most modifications had no effect on enzyme activity. However, the enzyme's substrate turnover (kcat) decreased following simultaneous alteration of the two most conserved residues, forming an apolar contact located 15 A away from the active site. The pH activity profile of the double mutant was unchanged, indicating a conserved ionization state of the active site thiolate-imidazolium ion pair. This state is strongly dependent on the distance separating the two residues, thus suggesting that the active site geometry has not been significantly altered. Efficient enzymatic activity in papain requires more than a correct active site geometry and is influenced by domain packing properties in a region remote from the active site.     

Mapping of Ras-related GTP-binding proteins by GTP overlay following two-dimensional gel electrophoresis

For identification of Rab, Rac, Rho, Ral, Rap, and Arf proteins on two-dimensional polyacrylamide gels, we have expressed full-length cDNAs of members of these protein families with the T7 RNA polymerase-recombinant vaccinia virus expression system. Membrane preparations from cells expressing the cDNAs were subjected to high-resolution two-dimensional polyacrylamide gel electrophoresis followed by [alpha-32P]GTP ligand blotting. We have mapped 28 small GTP-binding proteins relative to their isoelectric points and according to their molecular weights and by immunoblotting with specific antibodies. Rab and Rho proteins could be specifically identified by extraction of streptolysin O-permeabilized Madin-Darby canine kidney (MDCK) cells with Rab- and Rho-GDP dissociation inhibitor. We applied the reference mapping to analyze the GTP-binding patterns of synaptosome fractions from rat brain. The purified synaptosomes exhibited specific enrichment of Rab3a, Rab5a, Ral, and several other GTPases. This approach and the map we have produced should provide a useful aid for the analysis of the expression and localization of members of all families of small GTP-binding proteins in various cell types and subcellular fractions.     

Einfluß der Schrottvorwärmung mit Erdgas und Sauerstoff im Konverter auf den Sauerstoffumsatz des LD-Verfahrens

Stand der Erkenntnisse und Ziel der eigenen Versuche. Anlagenbeschreibung und Betriebsbeobachtungen. Untersuchung der Schlackenbildung während der Schrottvorwärmung. Änderungen der Roheisenzusammensetzung durch Reaktionen mit den Vorwärmschlacken. Betrachtungen zur Sauerstoffbilanz.     

The production of highly charged Ar and Xe recoil ions by fast uranium impact

The multiple ionization of Ar and Xe atoms by fast U⁷⁵⁺ impact has been measured with a projectile-recoil ion time-of-flight technique at 3.6, 5.9, 9.4 and 15.5 MeV/u. Using this technique, the recoil-ion production cross sections can be determined as a function of the final recoil and projectile charge states, i.e. one can distinguish between direct multiple ionization and those processes accompanied by charge transfer. Due to the high projectile charge and high velocity, the direct multiple ionization cross sections to produce highly ionized systems are very large, e.g. the multiple ionization cross section to produce in one collision hydrogen-like Ar exceeds the geometrical Ar-K-shell area. As a consequence of this long range interaction, the kinetic energy of Ar¹⁷⁺ recoil ions is only of the order of some 10 eV.     

Dielectric–Semiconductor Interface Limits Charge Carrier Motion at Elevated Temperatures and Large Carrier Densities in a High‐Mobility Organic Semiconductor

The fundamental nature of charge transport in highly ordered organic semiconductors is under constant debate. At cryogenic temperatures, effects within the semiconductor such as traps or the interaction of charge carriers with the insulating substrate (dipolar disorder or Fröhlich polarons) are known to limit carrier motion. In comparison, at elevated temperatures, where charge carrier mobility often also decreases as function of temperature, phonon scattering or dynamic disorder are frequently discussed mechanisms, but the exact microscopic cause that limits carrier motion is debated. Here, the mobility in the temperature range between 200 and 420 K as function of carrier density is explored in highly ordered perylene‐diimide from 3 to 9 nm thin films. It is observed that above room temperature increasing the gate electric field or decreasing the semiconducting film thickness leads to a suppression of the charge carrier mobility. Via X‐ray diffraction measurements at various temperatures and electric fields, changes of the thin film structure are excluded as cause for the observed mobility decrease. The experimental findings point toward scattering sites or traps at the semiconductor–dielectric interface, or in the dielectric as limiting factor for carrier mobility, whose role is usually neglected at elevated temperatures.