Peptide-small molecule hybrids via orthogonal deprotection-chemoselective conjugation to cysteine-anchored scaffolds. A model study

The feasibility of an orthogonal deprotection-conjugation protocol, holding the promise of libraries of functionally diverse chemical probes attached to cysteine-anchored peptide scaffolds, has been explored with a model system. The necessary tools for assembly of the hybrid libraries have been prepared and the tandem procedure optimized. S-alkylation and S-sulfenylation are featured as the chemoselective ligation reactions. [reaction: see text]     

Search for the scalar top quark in pp collisions at square root[s] = 1.8 TeV

We have performed a search for scalar top quark (stop) pair production in the inclusive electron-muon-missing transverse energy final state, using a sample of pp events corresponding to 108.3 pb(-1) of data collected with the D0 detector at Fermilab. The search is done in the framework of the minimal supersymmetric standard model assuming that the sneutrino is the lightest supersymmetric particle. For the dominant decays of the lightest stop, t-->b chi+1 and t-->blnu, no evidence for signal is found. We derive cross-section limits as a function of stop ( t ), chargino ( chi+1), and sneutrino ( nu) masses.     

The use of thin-layer chromatography in the analysis of lubricating oils

Summary A report is given on the application of thin-layer chromatography to the analysis of additives in lubricating oils. The separation and identification of antioxidants, phenates, sulphonates, zinc dialkyl dithiophosphates and polymeric additives is described. A measurement of additive depletion in used oils is possible by comparison of corresponding chromatograms.

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Zusammenfassung Es wird über die Verwendung der Dünnschicht-Chromatographie bei der Analyse der Additive von Schmierölen berichtet. Die Abtrennung und Identifizierung von Antioxydantien, Phenolaten, Sulfonaten, Zinkdialkyldithiophosphaten und polymeren Additiven wird beschrieben. Eine Messung der Abnahme der Additivkonzentration in gebrauchten Ölen ist durch Vergleich entsprechender Chromatogramme möglich.

     

Comparison of small-angle p and pp elastic scattering at 52.8 GeV center-of-mass energy at the CERN intersecting storage rings

Proton-antiproton and proton-proton elastic scattering have been measured in the four-momentum transfer range 0.001|t|0.06 GeV² for center-of-mass energy 52.8 GeV at the CERN Intersecting Storage Rings (ISR). Using the known pp total cross section, a simultaneous fit to the p and pp differential cross sections yields the p total cross section; in addition, we obtain the ratio of the real-to-imaginary part of the forward nuclear-scattering amplitude and the nuclear-slope parameter for both p and pp. Our results show conclusively that the p total cross section is rising at ISR energies and lend support to conventional theories in which the difference between the p and pp total cross section vanishes at very high energy.     

X-ray structure of trichloro-oxo-(N-pyridylmethylene-N′-salicyloylhydrazine-NO)molybdenum(V) · acetonitrile (1/1). An example of isomerization by complexation

Summary The synthesis, i.r. spectrum and x-ray crystal structure of the title, complex are described, Crystals are monoclinic space groupP 2₁/n, witha = 19.901(7),b = 13.163(8),c = 7.273(6) A, = 90.58(5)° Z = 4, The structure was solved from diffractometer data by direct methods and refined by least-squares techniques toR = 0.053 for 923 independent reflections. The complex has a distortedmer-octahedral geometry [Mo-O = 1,70(1), 2.15(1), Mo-Cl = 2.340(7), 1.352(7), 2.280(7), Mo-N = 2.19(2) A], The starting ligand Hsip, which is in theE configuration when free and in a number of metal complexes where it is terdentate, assumes here theZ configuration and is hiclentate.     

Inelastic proton scattering to the lowest 1+ state in58Ni

A microscopic, antisymmetrized Distorted Wave approximation is used in an analysis of the inelastic scattering of 17.8 MeV protons from⁵⁸Ni in which the 1⁺ (2.90 MeV) state is excited. Two step resonance amplitudes complement the usual direct reaction transition amplitudes in this analysis. In particular, resonance amplitudes associated with the virtual excitation of a giant dipole and of a giant octupole resonances are considered, and are essential for the model to fully explain the experimental data.     

Neighborly combinatorial 3-manifolds with 9 vertices

A complete classification is given for neighborly combinatorial 3-manifolds with 9 vertices. It is found that there are 51 types, only one of which is not a sphere.     

(+)-Sorangicin A synthetic studies. Construction of the C(1-15) and C(16-29) subtargets

[structure: see text] Effective stereocontrolled syntheses of subtargets (-)-2 and (-)-4, comprising respectively the C(16-29) and C(1-15) tetrahydropyran and dihydropyran moieties of the potent antibiotic (+)-sorangicin A (1), have been achieved. The cornerstone for the synthesis of (-)-2 involved an aldol tactic exploiting 1,4-induction, followed in turn by an acid-mediated cyclization/ketalization and hydrosilane reduction promoted by TMSOTf, while construction of (-)-4 entailed a stereoselective conjugate addition/alpha-oxygenation sequence.     

Microtubule structure and its stabilisation

Microtubules are designed to be dynamically unstable. GTP hydrolysis converts an initially stable polymeric structure into an unstable one in which strain at the interfaces between longitudinal neighbours in the helical lattice of subunits is balanced by lateral interactions. However, stability can be modulated by a variety of factors, including associated proteins and a variety of drug molecules. Stabilising drugs such as Taxol and the assembly-promoting repeat motifs of tau protein occupy a special pocket in beta-tubulin. Microtubule destabilizing drugs such as colchicine alter the longitudinal interfaces of the subunits so that they cannot assemble into a microtubule lattice. These mechanisms are discussed in terms of the atomic structure of the protein.