A proton magnetic resonance investigation of the glycosyl torsion angle of uracil nucleosides and nucleotides.

The use of line-shape decomposition techniques permitted the small 5-bond (5-J51') and 4-bond (4-J61') proton-proton coupling constants of a series of uracil nucleosides and nucleotides to be determined accurately. From an analysis of these coupling constants we have determined that the uracil base is in a predominantly anti conformation in aqueous solution and the mean position is not substantially altered by phosphate substitution at the 2', 3', or 5' positions, by changing the furanose stereochemistry from a ribose to a deoxyribose or an arabinose, or by an increase in temperature of 43 degree C

Investigating the effects of diesel exhaust and flower color on flower visitation by free-flying honey bees

Previous laboratory studies have shown that diesel exhaust can differentially degrade the volatile organic compounds (VOCs) that constitute floral odors. Furthermore, in proboscis extension response studies honey bees have been shown to have reduced recognition to these degraded floral odors. In this study, we investigated whether flower odors exposed to diesel exhaust reduce foraging in free-flying bees and if flower color influences bees’ behavior. Therefore, we conducted a field study in which honey bees were trained to visit the locations of two arrays of artificial flowers. From the artificial flowers, honey bees were presented with floral VOCs combined with either fresh air or diesel exhaust, through different colored flowers (black, blue, red, and yellow). Honey bee visitation rate did not differ between volatiles delivered with fresh air or with diesel exhaust, suggesting that revisitation of previously rewarding flower patches may be unaffected by air pollution. We also observed a significant interaction between treatment and color: blue flowers were more attractive when volatiles were delivered with diesel exhaust, which was the other way around for red and black and played no role in yellow flowers. Generally, honey bee foraging behavior seemed to be influenced by their previous experiences

Chemical diversity and potential biological functions of the pygidial gland secretions in two species of Neotropical dung roller beetles

Dung roller beetles of the genus Canthon (Coleoptera: Scarabaeinae) emit an odorous secretion from a pair of pygidial glands. To investigate the chemical composition of these secretions, we used stir bar sorptive extraction (SBSE), coupled with gas chromatography–mass spectrometry (GC–MS) for analysis of extracts of pygidial gland secretions secreted by the dung roller beetles Canthon femoralis femoralis and Canthon cyanellus cyanellus. Chemical analyses of volatiles collected from pygidial gland secretions comprise a great diversity of the functional groups. Chemical profile comparisons showed high intra- and interspecific variability. The pygidial gland secretion of Canthon f. femoralis was dominated by sesquiterpene hydrocarbons, whereas the profile of Canthon c. cyanellus was dominated by carboxylic acids. The different pygidial secretions have a high diversity of chemical compounds suggesting a multifunctional nature involving some key functions in the biology. We discuss the biological potential of these compounds found in the pygidial glands of each species with respect to their ecological and behavioral relevance.We are grateful to CONACYT Mexico for awarding a doctoral scholarship (14643) and a postdoctoral fellowship (184878 and 203310) to V.C.G. This paper is partly based on the Ph.D. thesis of V.C.G. This work was supported by CONACYT Mexico (168373-Etapa II) and the Ministerio de Ciencia e Innovación (Spain) (CGL2008-03878)