Electroweak Parity-Violating Energy Shifts of Amino Acids: The “Conformation Problem”

The preceding paper described our coupled-perturbed Hartree-Fock (CPHF) and density functional theory (DFT) methods of computing the parity-violating energy shift (PVES). This paper addresses the “conformation problem”—the difficulty determining which hand of amino acids in solution is favoured by the weak force due to the difficulty determining the solution conformation. We attempt to resolve this by using the methods of the preceding paper to compute the PVES of solution and gas-phase amino acid structures determined by other groups from high level optimizations that include solvation. We conclude that the conformational hypersensitivity of the PVES still precludes a definite conclusion as to the sign of the PVES of L-alanine in solution, but that there is no problem in the gas phase: the PVES of gas-phase L-alanine is decisively negative. We show that the PVES is very sensitive to certain torsion angles, but is not hypersensitive to bondlengths or bond angles. In determining structures for PVES computations, there is therefore no need for expensive full optimizations: one can just optimize the crucial torsion angles. We present new computations of gas-phase amino acids PVESs, using partial optimizations with small basis sets, and the results agree well with those from higher level techniques. In the following paper we apply these less costly techniques to larger amino acids. The “conformation problem” has led some to dismiss the PVES as the source of life’s handedness, but we believe this is premature: we show here that amino acids are a special case because their favoured conformations are almost achiral.     

The Expression of Partial Resistance to Puccinia striiformis in Wheat. Effects on Colony Growth and Spore Production

Abstract The resistance of wheat to Puccinia striiformis f. sp. tritici was investigated. The durable resistance of Hybride de Bersée and that resistance controlled by the factor YR14 , in cvs Solitaire and Wembley were studied at the second and sixth leaf stages, using a point inoculation technique. Both resistance types had significant effects at both leaf stages but the most marked effects were evident on adult plants. At both leaf stages there was a high correlation between colony, length and urediniospore prodction.     

The reactivity of the thiol groups of calf thymus deoxyribonucleohistone

The reactivities of the two cysteine thiol groups of calf thymus F3 histone were investigated using 5,5'-dithiobis-[2- nitrobenzoic acid], (DTNB). In isolated histone, both thiol groups were available for reaction. However, analysis of reaction profiles of native deoxyribonucleohistone, (DNH), in various solvent conditions, together with gel electrophoresis studies of DNH modified with DTNB, showed that only one of the thiol groups is normally modified by the reagent. If NaCl is present (above 1.OM) the other thiol group can also be modified. The reactivities of both groups were largely independent of the degree of DNH supercoiling and of the binding of F3 to the DNA.     

Lanceispora phyllophila sp. nov. on petioles of unknown dicotyledonous leaves in Singapore

Lanceispora phyllophila is described based on specimens of petioles from an unidentified dicotyledonous host collected at Bukid Timan, Singapore. It is illustrated with interference contrast micrographs and compared with the type speciesL. amphibia. Lanceispora phyllophila differs fromL. amphibia in having smaller ascomata and longer ascospores.     

Blockade of immune tolerance induction by puromycin aminonucleoside.

A tranfser system was used to explore the metabolic requirements for tolerance induction to human gamma globulin in the murine thymocyte. CBF1 (BALB/c × C57BL/6) mice were treated with a metabolic inhibitor and deaggregated HGG. Twenty-four hours later these mice were used as donors of thymus cells for irradiated recipients reconstituted with normal bone marrow cells. After a course of immunogenic HGG, the recipient animals were sacrificed and their immunocompetence assessed by use of the hemolytic plaque assay. It was determined that puromycin aminonucleoside (PAN), an inhibitor of RNA and protein synthesis, was capable of obviating tolerance induction in this system. This obviation was found to be temporal, and was not due to increased activity of the reticuloendothelial system. Radioautography revealed that these observed effects with PAN were not due to interference with specific interactions at the cellular membrane. The possible role of PAN in this system is discussed.