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Search Results: 1 - 10 of 4333 matches for " Jakob Bl?sbjerg Nielsen "
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Heterologous Reconstitution of the Intact Geodin Gene Cluster in Aspergillus nidulans through a Simple and Versatile PCR Based Approach
Morten Thrane Nielsen, Jakob Blsbjerg Nielsen, Dianna Chinyere Anyaogu, Dorte Koefoed Holm, Kristian Fog Nielsen, Thomas Ostenfeld Larsen, Uffe Hasbro Mortensen
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0072871
Abstract: Fungal natural products are a rich resource for bioactive molecules. To fully exploit this potential it is necessary to link genes to metabolites. Genetic information for numerous putative biosynthetic pathways has become available in recent years through genome sequencing. However, the lack of solid methodology for genetic manipulation of most species severely hampers pathway characterization. Here we present a simple PCR based approach for heterologous reconstitution of intact gene clusters. Specifically, the putative gene cluster responsible for geodin production from Aspergillus terreus was transferred in a two step procedure to an expression platform in A. nidulans. The individual cluster fragments were generated by PCR and assembled via efficient USER fusion prior to transformation and integration via re-iterative gene targeting. A total of 13 open reading frames contained in 25 kb of DNA were successfully transferred between the two species enabling geodin synthesis in A. nidulans. Subsequently, functions of three genes in the cluster were validated by genetic and chemical analyses. Specifically, ATEG_08451 (gedC) encodes a polyketide synthase, ATEG_08453 (gedR) encodes a transcription factor responsible for activation of the geodin gene cluster and ATEG_08460 (gedL) encodes a halogenase that catalyzes conversion of sulochrin to dihydrogeodin. We expect that our approach for transferring intact biosynthetic pathways to a fungus with a well developed genetic toolbox will be instrumental in characterizing the many exciting pathways for secondary metabolite production that are currently being uncovered by the fungal genome sequencing projects.
Aspergillus nidulans Synthesize Insect Juvenile Hormones upon Expression of a Heterologous Regulatory Protein and in Response to Grazing by Drosophila melanogaster Larvae
Morten Thrane Nielsen, Marie Louise Klejnstrup, Marko Rohlfs, Diana Chinyere Anyaogu, Jakob Blsbjerg Nielsen, Charlotte Held Gotfredsen, Mikael R?rdam Andersen, Bjarne Gram Hansen, Uffe Hasbro Mortensen, Thomas Ostenfeld Larsen
PLOS ONE , 2013, DOI: 10.1371/journal.pone.0073369
Abstract: Secondary metabolites are known to serve a wide range of specialized functions including communication, developmental control and defense. Genome sequencing of several fungal model species revealed that the majority of predicted secondary metabolite related genes are silent in laboratory strains, indicating that fungal secondary metabolites remain an underexplored resource of bioactive molecules. In this study, we combine heterologous expression of regulatory proteins in Aspergillus nidulans with systematic variation of growth conditions and observe induced synthesis of insect juvenile hormone-III and methyl farnesoate. Both compounds are sesquiterpenes belonging to the juvenile hormone class. Juvenile hormones regulate developmental and metabolic processes in insects and crustaceans, but have not previously been reported as fungal metabolites. We found that feeding by Drosophila melanogaster larvae induced synthesis of juvenile hormone in A. nidulans indicating a possible role of juvenile hormone biosynthesis in affecting fungal-insect antagonisms.
Chris Mathieu & Jesper Strandgaard Pedersen: Dansk film i krydsfeltet mellem samarbejde og konkurrence. Lund: Ariadne F rlag. 2009. Chris Mathieu & Jesper Strandgaard Pedersen (eds.): Dansk film i krydsfeltet mellem samarbejde og konkurrence. Lund: Ariadne F rlag. 2009.
Jakob Isak Nielsen
MedieKultur : Journal of Media and Communication Research , 2010,
Abstract:
‘No absolute privacy’: Henry James and the Ethics of Reading Authors’ Letters
Jakob Stougaard-Nielsen
Authorship , 2012,
Abstract: Authors’ private letters play a significant role in Henry James’s fiction, literary criticism and in his literary and authorial legacy. They are privileged discursive objects activating fundamental issues of privacy and publicity, canonicity and the material condition of literature. The letter is a contested discursive object in James’s work, since it is at one and the same time a potent figure for authenticity and interiority, and consequently poses a threat to the author’s desire to control his own literary corpus and his privacy. In this article, James’s personal and private investment in designing his literary testament (his private letters and his definitive collected edition) is discussed in the context of his ethical and aesthetic concerns with reading the publications of authors’ private correspondences.
Harmonic Sums, Polylogarithms, Special Numbers, and their Generalizations
Jakob Ablinger,Johannes Blümlein
Computer Science , 2013,
Abstract: In these introductory lectures we discuss classes of presently known nested sums, associated iterated integrals, and special constants which hierarchically appear in the evaluation of massless and massive Feynman diagrams at higher loops. These quantities are elements of stuffle and shuffle algebras implying algebraic relations being widely independent of the special quantities considered. They are supplemented by structural relations. The generalizations are given in terms of generalized harmonic sums, (generalized) cyclotomic sums, and sums containing in addition binomial and inverse-binomial weights. To all these quantities iterated integrals and special numbers are associated. We also discuss the analytic continuation of nested sums of different kind to complex values of the external summation bound N.
3-Arylisothiazoloquinols As Potent Ligands for the Benzodiazepine Site of GABAA Receptors  [PDF]
Jakob Nilsson, Elsebet ?stergaard Nielsen, Tommy Liljefors, Mogens Nielsen, Olov Sterner
Journal of Biomedical Science and Engineering (JBiSE) , 2012, DOI: 10.4236/jbise.2012.51001
Abstract: 3-Arylisothiazolo[5,4-b]quinolin-4(9H)-ones and 3-arylisoxazolo[5,4-b]quinolin-4(9H)-ones were synthesized and assayed for affinity for the benzodiazepine binding site of the GABAA receptors. While the 3-arylisothiazoloquinolin-4-ones were found to be potent ligands, with affinities (expressed as the affinity Ki value) down to 1 nM, the 3-arylisoxazoloquinolin-4-ones are less potent. This is suggested to depend on sterical repulsive interaction of the 3-arylisoxazoloquinolin-4-ones with the receptor essential volume of the binding site, and a higher electron density at the nitrogen in the azole ring (N-2) as well as the carbonyl oxygen in the isothiazoloquinolin-4-ones enabling them to interact stronger with hydrogen bond donor sites at the binding site.
Counterexamples to the B-spline conjecture for Gabor frames
Jakob Lemvig,Kamilla Haahr Nielsen
Mathematics , 2015,
Abstract: The frame set conjecture for B-splines $B_n$, $n \ge 2$, states that the frame set is the maximal set that avoids the known obstructions. We show that any hyperbola of the form $ab=r$, where $r$ is a rational number smaller than one and $a$ and $b$ denote the sampling and modulation rates, respectively, has infinitely many pieces, located around $b=2,3,\dots$, \emph{not} belonging to the frame set of the $n$th order B-spline. This, in turn, disproves the frame set conjecture for B-splines. On the other hand, we uncover a new region belonging to the frame set for B-splines $B_n$, $n \ge 2$.
Analytic and Algorithmic Aspects of Generalized Harmonic Sums and Polylogarithms
Ablinger, Jakob;Blümlein, Johannes;Schneider, Carsten
High Energy Physics - Phenomenology , 2013,
Abstract: In recent three--loop calculations of massive Feynman integrals within Quantum Chromodynamics (QCD) and, e.g., in recent combinatorial problems the so-called generalized harmonic sums (in short $S$-sums) arise. They are characterized by rational (or real) numerator weights also different from $\pm 1$. In this article we explore the algorithmic and analytic properties of these sums systematically. We work out the Mellin and inverse Mellin transform which connects the sums under consideration with the associated Poincar\'{e} iterated integrals, also called generalized harmonic polylogarithms. In this regard, we obtain explicit analytic continuations by means of asymptotic expansions of the $S$-sums which started to occur frequently in current QCD calculations. In addition, we derive algebraic and structural relations, like differentiation w.r.t. the external summation index and different multi-argument relations, for the compactification of $S$-sum expressions. Finally, we calculate algebraic relations for infinite $S$-sums, or equivalently for generalized harmonic polylogarithms evaluated at special values. The corresponding algorithms and relations are encoded in the computer algebra package {\tt HarmonicSums}.
Analytic and Algorithmic Aspects of Generalized Harmonic Sums and Polylogarithms
Jakob Ablinger,Johannes Blümlein,Carsten Schneider
Computer Science , 2013, DOI: 10.1063/1.4811117
Abstract: In recent three--loop calculations of massive Feynman integrals within Quantum Chromodynamics (QCD) and, e.g., in recent combinatorial problems the so-called generalized harmonic sums (in short $S$-sums) arise. They are characterized by rational (or real) numerator weights also different from $\pm 1$. In this article we explore the algorithmic and analytic properties of these sums systematically. We work out the Mellin and inverse Mellin transform which connects the sums under consideration with the associated Poincar\'{e} iterated integrals, also called generalized harmonic polylogarithms. In this regard, we obtain explicit analytic continuations by means of asymptotic expansions of the $S$-sums which started to occur frequently in current QCD calculations. In addition, we derive algebraic and structural relations, like differentiation w.r.t. the external summation index and different multi-argument relations, for the compactification of $S$-sum expressions. Finally, we calculate algebraic relations for infinite $S$-sums, or equivalently for generalized harmonic polylogarithms evaluated at special values. The corresponding algorithms and relations are encoded in the computer algebra package {\tt HarmonicSums}.
Harmonic Sums and Polylogarithms Generated by Cyclotomic Polynomials
Jakob Ablinger,Johannes Blümlein,Carsten Schneider
Computer Science , 2011, DOI: 10.1063/1.3629472
Abstract: The computation of Feynman integrals in massive higher order perturbative calculations in renormalizable Quantum Field Theories requires extensions of multiply nested harmonic sums, which can be generated as real representations by Mellin transforms of Poincar\'e--iterated integrals including denominators of higher cyclotomic polynomials. We derive the cyclotomic harmonic polylogarithms and harmonic sums and study their algebraic and structural relations. The analytic continuation of cyclotomic harmonic sums to complex values of $N$ is performed using analytic representations. We also consider special values of the cyclotomic harmonic polylogarithms at argument $x=1$, resp., for the cyclotomic harmonic sums at $N \rightarrow \infty$, which are related to colored multiple zeta values, deriving various of their relations, based on the stuffle and shuffle algebras and three multiple argument relations. We also consider infinite generalized nested harmonic sums at roots of unity which are related to the infinite cyclotomic harmonic sums. Basis representations are derived for weight {\sf w = 1,2} sums up to cyclotomy {\sf l = 20}.
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