The stabilization of thiepin by substitution

Resonance energies of 430 substituted thiepins have been calculated using a simple Hückel method described before. The results predict that thiepins substituted with electron-withdrawing groups (methoxycarbonyl and fluorine) will be less antiaromatic than the parent thiepin. Thus the calculated REPE of the only known type of monocyclic thiepin viz. 3,4 - bis(methoxycarbonyl) - 5 pyrrolidinothiepin (-0.007β) is less negative than that of the parent thiepin

Overview and analysis of the polyprotein cleavage sites in the family Potyviridae

The genomes of plant viruses in the family Potyviridae encode large polyproteins that are cut by virus-encoded proteases into ten mature proteins. Three different types of protease have been identified, each of which cuts at sites with a distinctive sequence pattern. The experimental evidence for this specificity is reviewed and the cleavage site patterns are compiled for all sequenced species within the family. Seven of the nine cleavage sites in each species are cut by the viral Nla-Pro and patterns around these sites are related where possible to the active site-substrate interactions recently deduced following the resolution of the crystal structure of Tobacco etch virus (TEV) Nla-Pro (Phan et al., 2002. J. Biol. Chem. 277,50564-50572). In particular, a revised series of cleavage sites for Sweetpotato mild mottle virus (genus Ipomovirus) is proposed with a conserved His at the P1 position. This is supported by homology modelling studies using the TEV structure as a template. The data also provide a standard to correct the annotation of some other published sequences and to help predict these sites in further virus sequences as they become available. Comprehensive data for all sequences of each virus in the family, together with some summaries, have been made available at http://www.rothamsted.bbsrc.ac.uk/ppi/links/pplinks/potycleavage/ index.html

Limits on the production of pointlike, charged spin-0 particles in e+e−e^+e^- annihilations at 29 GeV

A search for charged, pointlike, spin-0 particles with large couplings to the τ lepton has been done at the PEP e+e- storage ring (Stanford Linear Accelerator Center). No evidence for such particles is seen, and limits are placed on the branching fraction to τντ as a function of mass. © 1982 The American Physical Society