32 research outputs found
Palladium-Catalyzed Intermolecular Alkene Carboacylation via Ester C–O Bond Activation
No full textWe report palladium-catalyzed intermolecular carboacylation of alkenes with ester electrophiles and tetraarylborate nucleophiles. Bicyclic alkenes react with a variety of pentafluorophenyl benzoate and alkanoate esters and sodium tetraarylborates to form ketone products in ≤99% yields. These reactions occur in the absence of a directing group and demonstrate esters are competent acyl electrophiles for intermolecular alkene carboacylation reactions.This is a manuscript of an article published as Banovetz, Haley K., Kevin L. Vickerman, Colton M. David, Melisa Alkan, and Levi M. Stanley. "Palladium-Catalyzed Intermolecular Alkene Carboacylation via Ester C–O Bond Activation." Organic Letters 23, no. 9 (2021): 3507-3512.
DOI: 10.1021/acs.orglett.1c00940.
Copyright 2021 American Chemical Society.
Posted with permission
Recent advances in transition metal-catalysed hydroacylation of alkenes and alkynes
No full textThis highlight discusses developments in transition metal-catalysed alkene and alkyne hydroacylation reactions over the past three years. The discussion summarizes the development of new catalyst systems for alkene and alkyne hydroacylation and applications to the synthesis of important ketone building blocks. The highlight captures transition metal-catalysed alkene and alkyne hydroacylation at a time of impressive growth when cobalt, nickel, ruthenium, and iridium catalysts are emerging as complements or replacements for traditional rhodium catalysts.This article is published as Ghosh, Avipsa, Kirsten F. Johnson, Kevin L. Vickerman, James A. Walker, and Levi M. Stanley. "Recent advances in transition metal-catalysed hydroacylation of alkenes and alkynes." Organic Chemistry Frontiers 3, no. 5 (2016): 639-644. doi: 10.1039/C6QO00023A. Posted with permission.</p
Hematodinium infection seasonality in the Firth of Clyde (Scotland) nephrops norvegicus population: a re-evaluation
No full textHematodinium infections in Norway lobster Nephrops norvegicus from the Clyde Sea area (CSA) population, Scotland, UK, have previously been undetected in summer. This study aimed to establish if the CSA is actually devoid of infected N. norvegicus in this season. Two PCR assays, an ELISA and 2 tests that detect only patent infection (pleopod and body colour methods) were applied in a 21 mo study. Patent infection was seasonal, appearing predominantly in spring, while subpatent infection diagnosed by ELISA and PCR was highly prevalent in all seasons. Generalised linear modelling supported this assertion, as sampling in September and February significantly increased the probability of finding infected N. norvegicus (p < 0.01); infections were predominantly subpatent and patent respectively, at these times. Therefore, Hematodinium seasonality in N. norvegicus populations is likely to have been an artefact of insensitive diagnostic tests. Light Hematodinium infections were found using PCR assays when patent infections were at their most prevalent and intense, suggesting that infection develops at different rates in different N. norvegicus individuals and that only a portion of the total number of infected N. norvegicus die within a single year. These new data were added to a long-term data series for the CSA (1990 to 2008), which showed that after an initial 5 yr epidemic period, prevalence stabilised at 20 to 25%. Comparisons with ‘susceptible-infected-recovered/removed’ (SIR) models suggest that this high prevalence is maintained through high birth rates of susceptible host N. norvegicus
Lubricant Properties of ω − 1 Hydroxy Branched Fatty Acid-Containing Natural and Synthetic Lipids
No full textHydroxy fatty acids, such as those derived from castor and lesquerella seed oils make ideal substrates for the synthesis of biolubricants, cosmetics, coatings, plastics, and lubricants. However, feedstocks of such fatty acids suffer from major drawbacks, such as a lack of a cropping system to produce those seeds, toxic side-products in generating the seed oil, all of which limits availability and thus adds to costs. In this study, we explore lubrication properties of microbially derived hydroxy fatty acids, and demonstrate that such microbial ω-1 hydroxy fatty acids, and their derivatives, exhibit lubrication traits (e.g., anti-friction and anti-wear properties) comparable to those of seed derived hydroxy fatty acids. These ω-1 hydroxy fatty acids can be recovered from sophorolipids produced by the yeast Candida bombicola ATCC 22214, or by bioengineering bacterial systems to produce them from sugar [Garg et al, Microbial production of bi-functional molecules by diversification of the fatty acid pathway, Metab Eng 35 (2016) 9-20]. Optimization of this latter system can pave the way for a less-costly and sustainable alternative to plant-derived bio-lubricants.This is a manuscript of an article published as Sturms, R., White, D., Vickerman, K.L. et al. Lubricant Properties of ω − 1 Hydroxy Branched Fatty Acid-Containing Natural and Synthetic Lipids. Tribol Lett 65, 99 (2017). https://doi.org/10.1007/s11249-017-0883-z. Posted with permission
Catalytic, Enantioselective Synthesis of Polycyclic Nitrogen, Oxygen, and Sulfur Heterocycles via Rh-Catalyzed Alkene Hydroacylation
No full textCytochrome oxidase subunit VI of Trypanosoma brucei is imported without a cleaved presequence and is developmentally regulated at both RNA and protein levels
No full textMitochondrial respiration in the African trypanosome undergoes dramatic developmental stage regulation. This requires co-ordinated control of components encoded by both the nuclear genome and the kinetoplast, the unusual mitochondrial genome of these parasites. As a model for understanding the co-ordination of these genomes, we have examined the regulation and mitochondrial import of a nuclear-encoded component of the cytochrome oxidase complex, cytochrome oxidase subunit VI (COXVI). By generating transgenic trypanosomes expressing intact or mutant forms of this protein, we demonstrate that COXVI is not imported using a conventional cleaved presequence and show that sequences at the N-terminus of the protein are necessary for correct mitochondrial sorting. Analyses of endogenous and transgenic COXVI mRNA and protein expression in parasites undergoing developmental stage differentiation demonstrates a temporal order of control involving regulation in the abundance of, first, mRNA and then protein. This represents the first dissection of the regulation and import of a nuclear-encoded protein into the cytochrome oxidase complex in these organisms, which were among the earliest eukaryotes to possess a mitochondrion
Genetic diversity in the Leishmania donovani complex.
No full textThe Leishmania donovani complex comprises four described species: L.
donovani, L. archibaldi, L. infantum and L. chagasi. L. chagasi is the only New World
species and has been considered similar to L. infantum, although some authors insist
on maintenance of its independent species status. L. donovani has at least two major
epidemiological subgroups whose relationships are poorly understood.
In this thesis, molecular biological techniques were used to investigate the
taxonomy and phylogenetic relationships within the L. donovani complex, with
isoenzyme analysis (lEA) as reference technique. Random amplification of
polymorphic DNA (RAPD) was used to provide anonymous genetic markers which
allowed overall comparisons of genomes. Selected target genes and intergenic
regions were also amplified by the polymerase chain reaction (PCR), namely the
major surface protease (msp or gp63), the mini-exon and the ribosomal internal
transcribed spacer (ITS). PCR products of intergenic regions between msp genes
(ITG/CS and ITG/L), mini-exon and ITS were analysed by restriction fragment length
polymorphism (RFLP). Phylogenies generated from each of the methods were
compared with that of IEA.
L. infantum and L. chagasi were found to be synonymous, whilst L. donovani
was found to be more polymorphic than L. infantum and a fourth possible species in
the complex, L. archibaldi, was not supported. Six genetic groups of strains were
identified in the L. donovani complex, based on all DNA based analyses, which
agreed with IEA typing. Pooled data from RFLP and RAPD analyses generated
robust phylogenies which were congruent with ITG/CS RFLP and msp DNA
sequence based phylogenies, but not with lEA phylogenies. The evolutionary history
of the L. donovani complex is analysed in the light of the present results. The diverse
typing methods were also evaluated and genetic markers suggested, that are
applicable to classification and typing of L. donovani species and strains
"From Common Market to Emu: A Historical Perspective of European Economic and Monetary Integration"
No full textThis paper traces the history and the institutional background of European integration to the establishment of the economic and monetary union in the European Union (EU). After the establishment of the European Economic Community (EEC) in the late 1950s, attempts at monetary integration, and ultimately monetary union, tended to assume importance only as a result of financial crisis and then returned to being a vague objective as soon as the crisis recedes. In recent years, however, monetary integration has assumed greater urgency. Economic union, on the other hand, has followed a smoother transition. Economic integration was used after the Second World War to realize political goals, chiefly to anchor West Germany within the western European alliance. Since that time the economies of member states have slowly integrated. The economic environment of the 1950s is a far cry from the integrated community of today. In the 1950s European currencies were not convertible and domestic trade was highly protected. Intra-European trade was based on bilateral clearing arrangements institutionalized by the European Payments Union. Today EU currencies are fully convertible; capital controls, intra-EU tariffs, and quotas have been eliminated; and the single market has been completed. Monetary union has gone through a number of stages. The Werner Plan of the early 1970s, which set the goal of economic and monetary union by the end of the decade, was only partially implemented. Its failure can be put down to unfavorable international economic conditions and poor institutional structures. In the early 1980s a new monetary initiative, the European Monetary System (EMS), was launched. It struggled through its initial phase until it was replaced by the current euro arrangements. These successive stages ultimately culminated in the Maastricht Treaty, which laid out a precise path and timetable for economic and monetary union.
Human Capital Externalities and Employment Differences across Metropolitan Areas of the U.S.
No full textIt has been well documented that employment outcomes often differ considerably across areas. This paper examines the extent to which the local human capital level, measured as the share of adults with a college degree, has positive external effects on labor force participation and employment for U.S. metropolitan area residents. We find that the local human capital level has positive externalities on participation for women, but an inconsistent effect on participation for men. However, the local human capital level reduces unemployment for both men and women. We also find that less educated workers generally receive the largest external benefits.employment; unemployment; human capital externalities; agglomeration
