Transport of the precursor to neurospora ATPase subunit 9 into yeast mitochondria

Isolated yeast mitochondria were able to take up Neurospora ATPase subunit 9 in vitro although the homologous yeast protein is synthesized within the mitochondria and inserted into the membrane from the matrix side (Tzagoloff, A., and Meagher, P. (1972) J. Biol. Chem. 247, 594- 603). The transfer of the protein was dependent on an energized mitochondrial inner membrane. It was accompanied by proteolytic processing of the precursor to the mature protein with the correct NH2 terminus as determined by Edman degradation of the transferred protein. The possibility is discussed that there are common features in the uptake machinery neither specific for one species nor specific for individual precursor proteins in the same species

Receptor sites involved in posttranslational transport of apocytochrome c into mitochondria

Assembly of cytochrome c involves a series of steps: synthesis of apocytochrome c on free ribosomes, specific binding of apocytochrome c to the mitochondrial surface, transfer across the outer membrane, covalent addition of protoheme, refolding of the polypeptide chain, and association of holocytochrome c with its functional sites at the inner membrane. The binding step of apocytochrome c to Neurospora crassa mitochondria was studied by inhibiting the subsequent transfer steps with the heme analogue deuterohemin. The binding sites are highly specific for mitochondrial apocytochromes c. Bound labeled Neurospora apocytochrome c was competitively displaced by unlabeled apocytochrome c from various species. These exhibited different abilities for displacement. Apocytochrome c from Paracoccus denitrificans, the amino-terminal (heme-binding) fragment of Neurospora apocytochrome c, and Neurospora holocytochrome c did not recognize the binding sites. Polylysine did not interfere with apocytochrome c binding. Apocytochrome c is reversibly bound. The binding sites are present in limited number. High-affinity binding sites were present at about 90 pmol/mg of mitochondrial protein. They displayed an association constant of 2.2 X 10(7) M-1. Apocytochrome c was imported into mitochondria and converted to holocytochrome c directly from the binding sites when inhibition by deuterohemin was relieved. We conclude that the apocytochrome c binding sites on mitochondria represent receptors that function in the recognition and import of this precursor by mitochondria

Nickel(BiPhePhos)-catalyzed hydrocyanation of styrene - highly increased catalytic activity by optimized operational procedures

Nitriles are versatile and highly desired chemical intermediates for a range of products. Their economic large-scale production requires highly efficient and selective synthesis. The nickel- catalyzed hydrocyanation of C=C double bonds provides such selective and 100% atom-economical access to nitriles, but the catalysts hitherto lack activity and longevity. Yet, the literature focusing on increased catalytic activity or optimized operational procedures is scarce, at the least. Here, we present a thorough investigation and optimization of operational procedures using a commercially available diphosphite ligand and styrene as a model substrate. This led us to achieve a TOF20 of more than 300,000 h−1

Elementary studies on the inducement and relaxation of residual stress

In order to qualify residual stress relaxation as an indicator of mechanical overloading of machined parts, an individually designed residual stress profile has to be allocated. Even though numerous investigations have been carried out in the past, residual stress profiles cannot be predicted to a satisfactory degree. For this reason, essential studies on the reproducibility of residual stress profiles for several external cylindrical turning parameters are conducted and it is demonstrated that identical residual stress profiles can be induced successfully. Subsequently, specimens with defined residual stress profiles are loaded in bending tests with various numbers of test cycles. The amount of residual stress relaxation in the specimen's surface layer is measured to determine the influence of theapplied load on the stress relaxation. By applying single tensile and compressive loads below and above thematerial's yield and ultimate strength, the stress relaxation can be evaluated in detail.DFG/CRC/SFB/65

Elastic Wave Fields Generated by Shear Horizontal Piezoelectric Fiber Patch (SH-PFP) Transducers: Parameter Study by Modelling and Laser Vibrometric Measurements

Recently, a novel lightweight and thin piezoelectric transducer was proposed [1-3]. It generates in-plane surface tractions and thus shear horizontal elastic waves in both bulk materials and waveguides. The paper describes the principle of operation of this Shear Horizontal Piezoelectric Fiber Patch (SH-PFP). In continuation of the previous work, several variants of the SH-PFP are studied. The generated wavefield is characterized bywavefield snapshots and directivity functions. Both numerical simulation and measurements by 3D Laser Vibrometry are performed and the results are compared, showing a good agreement. We discuss possible further developments of the SH-PFP transducer to allow 1D directivity and we also discuss various possible sensor applications

Entwicklung einer neuen Technologie zur Probenpräparation für die Transmissions-Elektronenmikroskopie (TEM) auf der Basis der Ionenfeinstrahlbearbeitung

Aufgabe des Projektes war die Entwicklung einer neuen Technologie zur Probenpräparation für die Transmissions-Elektronenmikroskopie (TEM) auf der Basis der Ionenfeinstrahlbearbei-tung. Dazu wurden Prozesse der ionenstrahlgestützten Abtragung (Sputtern), der Abschei-dung, des Probenhandling sowie systemeigener Komponenten untersucht. Als Alternative zur Ga- Quelle wurde eine Flüssigmetall-Ionenquelle auf der Basis einer AuGeSi Legierung entwi-ckelt, charakterisiert und in der FIB 4400 eingesetzt. Um eine automatische Bearbeitung bei der Herstellung von TEM-Lamellen zu ermöglichen, erfolgte eine Modifikation der FIB-4400 Software. Das LabView Programm wurde entsprechend modifi-ziert und zusätzlich um nützliche Komponenten ergänzt. Abtragsraten auf der Basis der Volumenverlustmethode wurden experimentell bestimmt. Diese Werte dienen als Ausgangspunkt für eine weiter ausbaubare Datensammlung, die die entwi-ckelte Prozessautomatisierung verfeinert. Für den Tranfer von TEM -Lamellen, die aus dem Volumen präpariert werden, wurde ein spe-zieller lift-off Manipulator entwickelt, gebaut und getestet. Es wurde ein Angebotskatalog erarbeitet, der anhand von Applikationsbeispielen mit verschie-denen Anforderungen (raue Oberflächen, Hochauflösung, poröse Materialien, Materialien mit verminderter Leitfähigkeit) die Kooperationsmöglichkeiten im Dresdener Raum im Rahmen des Materialforschungsverbundes aufzeigt

The influence of deep rolling on the surface integrity of AISI 1060 high carbon steel

The aim of this work is to study the influence of selected deep rolling parameters (rolling pressure and number of passes) on the surface integrity of fully annealed AISI 1060 high carbon steel. In addition to the mechanical properties, a comprehensive investigation on surface integrity is carried out. The findings indicate that despite the increase in surface hardness and ultimate tensile stress, deep rolling can negatively affect the yield strength. The amplitude and functional roughness parameters show a considerable reduction after deep rolling, however, increasing rolling pressure and number of passes leads to poorer surface finish. Finally, the tensile residual stress generated by turning shifts to compressive values after deep rolling and the microhardness and microstructure analyses indicate that the depth of the layer affected by deep rolling depends on both the rolling pressure and number of passes.DFG/CRC/653CAPES Foundation, Ministry of Education of Brazi

Novel Approach in Mechanical Characterization of Thin Films for Nano Electronics

Mechanical characterization of nano-thin layers with high lateral resolution is as important for nanoelectronics as challenging. We have investigated mechanical properties of porous organosilicate glasses (OSG) with ultralow values of dielectric permittivity (dielectric constant k \u3c 2.4). We have used the atomic force acoustic microscopy (AFAM) method to determine the indentation modulus for two sets of the OSG thin films. The first set has consisted of three samples of nominal porosity varying from 27% to 40% with thickness of 650 nm. The values of the indentation modulus obtained for these samples have varied from 4 GPa to 7 GPa depending on the pore concentration and been in excellent agreement with those determined by nanoindentation. Having confirmed the reliability of the AFAM method, we have determined the indentation modulus of OSG films with the nominal porosity of 30% and film thickness decreasing from 350 nm to 46 nm, a level challenging for standard nanoindentation methods. Interestingly, we have observed an increase of the indentation modulus with the decreasing film thickness. To ensure that our results were free of the substrate influence, we have used tips of different radii and applied them within different ranges of the static load. We have also analyzed the ratio of the sample deformation as well as the tip radius to the film thickness. The results of our analysis have been compared for all the measurement series and showed, which ones have been free of the substrate influence. The stiffening observed for the porous films could be explained by evolution of the pore topology as a function of the film thickness. Our results prove the capabilities of the AFAM method in studies of mechanical properties of thin films, especially those made of novel functional material used in nanoelectronics and lacking a bulk equivalent