Genome analysis of sphingolipid metabolism-related genes in Tetrahymena thermophila and identification of a fatty acid 2-hydroxylase involved in the sexual stage of conjugation

Sphingolipids are bioactive lipids present in all eukaryotes. Tetrahymena thermophila is a ciliate that displays remarkable sphingolipid moieties, that is, the unusual phosphonate-linked headgroup ceramides, present in membranes. To date, no identification has been made in this organism of the functions or related genes implicated in sphingolipid metabolism. By gathering information from the T. thermophila genome database together with sphingolipid moieties and enzymatic activities reported in other Tetrahymena species, we were able to reconstruct the putative de novo sphingolipid metabolic pathway in T. thermophila. Orthologous genes of 11 enzymatic steps involved in the biosynthesis and degradation pathways were retrieved. No genes related to glycosphingolipid or phosphonosphingolipid headgroup transfer were found, suggesting that both conserved and innovative mechanisms are used in ciliate. The knockout of gene TTHERM_00463850 allowed to identify the gene encoding a putative fatty acid 2-hydroxylase, which is involved in the biosynthesis pathway. Knockout cells have shown several impairments in the sexual stage of conjugation since different mating types of knockout strains failed to form cell pairs and complete the conjugation process. This fatty acid 2-hydroxylase gene is the first gene of a sphingolipid metabolic pathway to be identified in ciliates and have a critical role in their sexual stage.Fil: Cid, Nicolás Gonzalo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Nanobiotecnología. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Nanobiotecnología; ArgentinaFil: Puca, Gervasio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Nanobiotecnología. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Nanobiotecnología; ArgentinaFil: Nudel, Berta Clara. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Nanobiotecnología. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Nanobiotecnología; ArgentinaFil: Nusblat, Alejandro David. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Houssay. Instituto de Nanobiotecnología. Universidad de Buenos Aires. Facultad de Farmacia y Bioquímica. Instituto de Nanobiotecnología; Argentin

Semiclassical quantization of Rotating Strings in Pilch-Warner geometry

Some of the recent important developments in understanding string/ gauge dualities are based on the idea of highly symmetric motion of ``string solitons'' in $AdS_5\times S^5$ geometry originally suggested by Gubser, Klebanov and Polyakov. In this paper we study symmetric motion of certain string configurations in so called Pilch-Warner geometry. The two-form field $A_2$ breaks down the supersymmetry to $\mathcal{N}=1$ but for the string configurations considered in this paper the classical values of the energy and the spin are the same as for string in $AdS\times S^5$. Although trivial at classical level, the presence of NS-NS antisymmetric field couples the fluctuation modes that indicates changes in the quantum corrections to the energy spectrum. We compare our results with those obtained in the case of pp-wave limit in hep-th/0206045.Comment: 31 pages, no figures, v2 - a few typos correcte

Flavoured Large N Gauge Theory in an External Magnetic Field

We consider a D7-brane probe of AdS$_{5}\times S^5$ in the presence of pure gauge $B$-field. In the dual gauge theory, the $B$-field couples to the fundamental matter introduced by the D7-brane and acts as an external magnetic field. The $B$-field supports a 6-form Ramond-Ramond potential on the D7-branes world volume that breaks the supersymmetry and enables the dual gauge theory to develop a non-zero fermionic condensate. We explore the dependence of the fermionic condensate on the bare quark mass $m_{q}$ and show that at zero bare quark mass a chiral symmetry is spontaneously broken. A study of the meson spectrum reveals a coupling between the vector and scalar modes, and in the limit of weak magnetic field we observe Zeeman splitting of the states. We also observe the characteristic $\sqrt{m_{q}}$ dependence of the ground state corresponding to the Goldstone boson of spontaneously broken chiral symmetry.Comment: 22 pages, 7 figures, references added, few typos correcte

Automatic tonic identification in Indian art music: approaches and evaluation

The tonic is a fundamental concept in Indian art music. It is the base pitch, which an artist chooses in order to construct the melodies during a rāg(a) rendition, and all accompanying instruments are tuned using the tonic pitch. Consequently, tonic identification is a fundamental task for most computational analyses of Indian art music, such as intonation analysis, melodic motif analysis and rāg recognition. In this paper we review existing approaches for tonic identification in Indian art music and evaluate them on six diverse datasets for a thorough comparison and analysis. We study the performance of each method in different contexts such as the presence/absence of additional metadata, the quality of audio data, the duration of audio data, music tradition (Hindustani/Carnatic) and the gender of the singer (male/female). We show that the approaches that combine multi-pitch analysis with machine learning provide the best performance in most cases (90% identification accuracy on average), and are robust across the aforementioned contexts compared to the approaches based on expert knowledge. In addition, we also show that the performance of the latter can be improved when additional metadata is available to further constrain the problem. Finally, we present a detailed error analysis of each method, providing further insights into the advantages and limitations of the methods.This work is partly supported by the European Research Council/nunder the European Union’s Seventh Framework Program, as/npart of the CompMusic project (ERC grant agreement 267583)