No abstract

Abstract--The chemical ecology of host-and mate-finding in the pine shoot beetles, Tomicus minor and T. piniperda, was studied in southern Sweden. Beetles were collected in the field from defined attack phases on Scots pine. Using gas chromatography-mass spectroscopy, a number of oxygen-containing monoterpenes, e.g., 3-carene-10-ol, myrtenol, trans-verbenol, and verbenone, were identified from hindgut extracts of both sexes of both species. Compared to T. minor, T. piniperda contained additional compounds and in larger amounts. The amounts were highest in both species at the time when the beetles had bored into contact with the resin-producing xylem-phloem tissue. The synthesis of (1S,6R)-3-carene-10-ol by photooxidation of (+)-(1S,6R)-3-carene is described. In comparative electroantennogram (EAG) measurements on males and females of both species, the most active of the tested compounds was trans-verbenol. Laboratory bioassays of walking beetles showed that T. piniperda was attracted to uninfested.Pine logs. T. minor was more strongly attracted to pine logs infested with females than to uninfested pine logs, indicating a female-produced aggregation pheromone. Field tests confirmed that 7". piniperda was strongly attracted to pine logs. The attraction of T. minor to logs was significant only when logs were combined with racemic trans-verbenol and (1S,6R)-3-carene-10-ol. T. minor was also Coleoptem: Scolytidae. ~This study was made within the project "Odour signals for control of pest insects." 5Present address: VDP Laboratories, P.O. Box 1547, 1200 BM, Hilversum, The Netherlands. attracted to a combination of these monoterpene alcohols alone. We suggest that host and mate location in T. piniperda is achieved by means of a kairomone composed of host monoterpenes, while T. minor utilizes a primitive pheromone synergized by host odors. Evolution of host colonization strategies of the two beetles are discussed.

No abstract

Two strategies based on the use of subsets for calculating the enantioselectivity in lipase-catalyzed transesterifications using the CHARMM force field were investigated. Molecular dynamics was used in our search for low energy conformations. Molecular mechanics was used for refining these low energy conformations. A tetrahedral intermediate with a rigid central part was used for mimicking the transition state. The energy differences between the transition states of the diastereomeric enzyme-substrate complexes were calculated. The way of defining the subsets was based on two fundamentally different strategies. The first strategy used predefined parts of the enzyme and the substrate as subsets. The second approach formed energy-based subsets, varying in size with the substrates studied. The selection of residues to be included in these energy-based subsets was based on the energy of the interaction between the specific residue or water molecule and the transition state. The reaction studied was the kinetic resolution of secondary alcohols in transesterifications using the Candida antarctica lipase B as chiral biocatalyst. The secondary alcohols used in the study were 2-butanol, 3-methyl-2-butanol, and 3,3-dimethyl-2-butanol.

No abstract

No abstract

No abstract

No abstract