Rational design and selection of bivalent peptide ligands of thrombin incorporating P4-P1 tetrapeptide sequences: from good substrates to potent inhibitors

The tetrapeptide Phe-Asn-Pro-Arg is a structurally optimized sequence for binding to the active site of thrombin. By conjugating this tetrapeptide or some variants to a C-terminal fragment of hirudin, we were able to generate a series of new bivalent inhibitors of thrombin containing only genetically encodable natural amino acids. We found that synergistic binding to both the active site and an exosite of thrombin can be enhanced through substitutions of amino acid residues at the P3 and P3' sites of the active-site directed sequence, Phe(P4)-Xaa(P3)-Pro(P2)-Arg(P1)-Pro(P1')-Gln(P2')-Yaa(P3'). Complementary to rational design, a phage library was constructed to explore further the residue requirements at the P4, P3 and P3' sites for bivalent and optimized two-site binding. Very significantly, panning of the phage library has led to thrombin-inhibitory peptides possessing strong anti-clotting activities in the low nanomolar range and yet interfering only partially the catalytic active site of thrombin. Modes of action of the newly discovered bivalent inhibitors are rationalized in light of the allosteric properties of thrombin, especially the interplay between the proteolytic action and regulatory binding occurring at thrombin surfaces remote from the catalytic active site.     

Zur Strömungssimulation in gasgerührten metallurgischen Pfannen

Zur Erfassung der Strömungsverhältnisse in Kaltmodellen bodengeblasener Stahlwerkspfannen wurden theoretische und experimentelle Untersuchungen durchgeführt. Frühere Berechnungen laminarer Strömungen, die unter stark vereinfachenden Annahmen vorgenommen wurden, zeigen nur tendenzielle Übereinstimmungen zu den mit LDA-Verfahren ermittelten Strömungsbildern. Durch die Entwicklung der Großrechneranlagen ist der Einsatz von Strömungssimulationsprogrammen möglich, mit denen auch turbulente Strömungen berechnet werden können. Der Vergleich der berechneten Geschwindigkeitsvektorfelder mit den gemessenen Vektorfeldern zeigt eine grundsätzlich übereinstimmende Darstellung der Strömungsverläufe. Jedoch werden die im Experiment an Wassermodellen beobachteten Gegenwirbel und Ablösungen der Abwärtsströmungen von der Gefäßwand rechnerisch nicht erfaßt. Nur die numerische Simulation für zähere Flüssigkeiten (Paraffinöl) zeigt eine von der Wand abgelöste Abwärtsströmung und die Ausbildung eines Gegenwirbels. Man kommt also nicht umhin, neben der mathematischen Modellierung auch praktische Versuche durchzuführen, wie man umgekehrt die physikalischen Modelle mit mathematischen begleiten sollte.     

Polymer–Ferrocene Conjugates Containing an Ester Function in the Connecting Links

Ferrocene, the parent of the metallocene family of organotransition metal compounds, has come to occupy a significant niche in cancer research. Developmental work in the authors' laboratory has been focused on the synthesis of antiproliferative ferrocene conjugates in which the bioactive ferrocene unit is covalently, yet bioreversibly bound (anchored) to water-soluble carrier polymers designed in accordance with requisite biomedical specifications. The anchoring link in most of these conjugates has been an aliphatic spacer containing the biofissionable amide group. In this communication the synthesis of a class of ferrocene conjugates is reported in which the ferrocene group is carrier-anchored through spacers containing an ester link, of interest here because of potentially different drug release behavior. The carriers are polyamides equipped with variously spaced hydroxyl side groups, to which the ferrocenylation agent, 4-ferrocenylbutanoic acid, is connected through esterification. The coupling reactions, mediated by carbodiimide agent and catalyzed by 4-(dimethylamino)pyridine, are carried out in DMF at temperatures not exceeding 65°C, and the water-soluble product polymers are isolated in yields of typically 70–85% by precipitation, aqueous dialysis, and freeze-drying. With the molar feed ratios chosen in these coupling experiments, the incorporation of ferrocene, assessed by ¹H NMR spectroscopy, corresponds to iron contents of roughly 2.5–5.5%, by mass. The conjugates will be included in a forthcoming bioactivity screening program.     

Cutting force model of orbital single-point micromachining tool

This paper presents an analytical, ductile cutting force model of a novel micromachining tool that is based on micro-orbital motion of a single-point tool tip. The single-point tool tip used in this study is a single crystal diamond stylus that consists of a cone section of 50° and a spherical tip with radius less than 1 μm. The tool is actuated by a piezo tube that generates a high frequency micro-orbital motion of a single-point tool tip in a circular trajectory. Unlike conventional micromilling, where the cutting occurs at the edges of the tool flutes, a single-point tool may utilize any point on the circumference surface of the tool tip. Also, due to its extreme negative rake angle at small depths of cut, the technique can machine brittle materials such as silicon in the ductile regime. Experiments were performed on an aluminum alloy (AL2024) to obtain the specific cutting force and the coefficient of friction in order to calculate the cutting forces in all 3 axes and to verify the model.     

Monte Carlo calculation of the small sample reactivity effect

A monte Carlo method for the calculation of the reactivity effect of a small sample in a nuclear reactor is described. Particle histories are started within the sample. Therefore, it is not necessary to enter the sample from outside with a small probability. After leaving the sample, the histories are terminated at some distance from the sample site using pre-calculated results of the unperturbed reference system. The influence of some approximations is diminished because these pre-calculated results are used only far away from the region of interest. Some numerical results show the efficiency of the method. The method is fast and can also be used at rather small and slow computers.     

How tree shrews (Tupaia belangeri) perform in a searching task: Evidence for strategy use.

This study investigated how male tree shrews (Tupaia balngeri) performed in a searching task while in their home cages and assessed whether different food distributions affected their performance. The animals were faced with a holeboard containing 9 food sources arranged in a 3 X 3 matrix or in 3 clusters, each containing 3 sources. Animals tended to start and end the trials from preferred locations, thereafter solving the task by strategically organizing the reward collection according to a minimum-distance principle. In the cluster configuration, they visited the sources hierarchically. Food distribution did not affect the performance. Comparison with data from mice and capuchin monkeys revealed that tree shrews and capuchins solved the task in a similar strategic way, whereas mice did not. These findings attract particular attention because of the phylogenetic position of tree shrews, which are regarded as closely related to primates. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rheological,microstructural and sensory characterization of low-fat and whole milk set yoghurt as influenced by inulin addition

The effect of inulin addition (0–4%) upon texture and microstructure of set yoghurt with different levels of fat (0.2%–3.5%) was investigated. A two-factor experimental design with four treatments was used for data analysis. Skimmed milk with various inulin and cream concentrations was standardized to 4% protein content, homogenized, heated to 92 °C and fermented at 42 °C until a pH of 4.6 was reached. The chemical composition, pH, consistency and microstructure properties of the yoghurts were analysed after 6 days of storage at 5 °C. The statistical analysis showed that inulin and fat significantly affected the rheological and sensory results. Higher yield stress, “firmness” and “creaminess” values were observed in yoghurt produced with higher inulin additions, whereas the pH value was not affected. A significant correlation was found between yield stress and sensory determined firmness (r = 0.91). The microstructure examined by confocal laser scanning microscopy (CLSM) was only slightly affected by the concentrations of inulin in the range studied, possibly due to weak protein interactions between the inulin and the milk protein network.     

Opportunistic Software Systems Development: Making Systems from What's Available

Despite all the difficulties encountered in each incarnation of software reuse, we persist along the path of trying to figure out how we're going to create systems that meet the ever-increasing demand for capability and, with it, complexity and sheer size. Opportunistic software systems development is a reality today and for the foreseeable future, as the five articles in IEEE Software 's November/December 2008 special issue on OSSD demonstrate. This special issue aims to gather together insights into the viability, or perhaps the inevitability, of OSSD and to bring forward the most effective practices known today. Another goal is to point the way to what needs to be done to make OSSD more accessible to all practitioners. The editors hope to help the software community realize the importance of this new trend and the many aspects of it that have yet to be conquered.