3,136 research outputs found
Crystal structure of the catalytic fragment of murine poly(ADP-ribose) polymerase-2.
Poly(ADP-ribose) polymerase-1 (PARP-1) has become an important pharmacological target in the treatment of cancer due to its cellular role as a 'DNA-strand break sensor', which leads in part to resistance to some existing chemo- and radiological treatments. Inhibitors have now been developed which prevent PARP-1 from synthesizing poly(ADP-ribose) in response to DNA-breaks and potentiate the cytotoxicity of DNA damaging agents. However, with the recent discoveries of PARP-2, which has a similar DNA-damage dependent catalytic activity, and additional members containing the 'PARP catalytic' signature, the isoform selectivity and resultant pharmacological effects of existing inhibitors are brought into question. We present here the crystal structure of the catalytic fragment of murine PARP-2, at 2.8 A resolution, and compare this to the catalytic fragment of PARP-1, with an emphasis on providing a possible framework for rational drug design in order to develop future isoform-specific inhibitors
Matter effects in the D0-D0bar system
We discuss the impact of matter effects in the D0-D0bar system. We show that
such effects could, in principle, be measured, but that they cannot be used to
probe the mass difference x_D or the lifetime difference y_D. This occurs
because the mixing effects and the matter effects decouple at short times. We
also comment briefly on the B systems.Comment: 6 pages, RevTe
Relaxin gene family in teleosts: phylogeny, syntenic mapping, selective constraint, and expression analysis
<p>Abstract</p> <p>Background</p> <p>In recent years, the relaxin family of signaling molecules has been shown to play diverse roles in mammalian physiology, but little is known about its diversity or physiology in teleosts, an infraclass of the bony fishes comprising ~ 50% of all extant vertebrates. In this paper, 32 relaxin family sequences were obtained by searching genomic and cDNA databases from eight teleost species; phylogenetic, molecular evolutionary, and syntenic data analyses were conducted to understand the relationship and differential patterns of evolution of relaxin family genes in teleosts compared with mammals. Additionally, real-time quantitative PCR was used to confirm and assess the tissues of expression of five relaxin family genes in <it>Danio rerio </it>and <it>in situ </it>hybridization used to assess the site-specific expression of the insulin 3-like gene in <it>D. rerio </it>testis.</p> <p>Results</p> <p>Up to six relaxin family genes were identified in each teleost species. Comparative syntenic mapping revealed that fish possess two paralogous copies of human <it>RLN3</it>, which we call <it>rln3a </it>and <it>rln3b</it>, an orthologue of human <it>RLN2</it>, <it>rln</it>, two paralogous copies of human <it>INSL5</it>, <it>insl5a and insl5b</it>, and an orthologue of human <it>INSL3</it>, <it>insl3</it>. Molecular evolutionary analyses indicated that: <it>rln3a, rln3b </it>and <it>rln </it>are under strong evolutionary constraint, that <it>insl3 </it>has been subject to moderate rates of sequence evolution with two amino acids in <it>insl3/INSL3 </it>showing evidence of positively selection, and that <it>insl5b </it>exhibits a higher rate of sequence evolution than its paralogue <it>insl5a </it>suggesting that it may have been neo-functionalized after the teleost whole genome duplication. Quantitative PCR analyses in <it>D. rerio </it>indicated that <it>rln3a </it>and r<it>ln3b </it>are expressed in brain, <it>insl3 </it>is highly expressed in gonads, and that there was low expression of both <it>insl5 </it>genes in adult zebrafish. Finally, <it>in situ </it>hybridization of <it>insl3 </it>in <it>D. rerio </it>testes showed highly specific hybridization to interstitial Leydig cells.</p> <p>Conclusions</p> <p>Contrary to previous studies, we find convincing evidence that teleosts contain orthologues of four relaxin family peptides. Overall our analyses suggest that in teleosts: 1) <it>rln3 </it>exhibits a similar evolution and expression pattern to mammalian <it>RLN3</it>, 2) <it>insl3 </it>has been subject to positive selection like its mammalian counterpart and shows similar tissue-specific expression in Leydig cells, 3) <it>insl5 </it>genes are highly represented and have a relatively high rate of sequence evolution in teleost genomes, but they exhibited only low levels of expression in adult zebrafish, 4) <it>rln </it>is evolving under very different selective constraints from mammalian <it>RLN</it>. The results presented here should facilitate the development of hypothesis-driven experimental work on the specific roles of relaxin family genes in teleosts.</p
Testing the Principle of Equivalence by Solar Neutrinos
We discuss the possibility of testing the principle of equivalence with solar
neutrinos. If there exists a violation of the equivalence principle quarks and
leptons with different flavors may not universally couple with gravity. The
method we discuss employs a quantum mechanical phenomenon of neutrino
oscillation to probe into the non-universality of the gravitational couplings
of neutrinos. We develop an appropriate formalism to deal with neutrino
propagation under the weak gravitational fields of the sun in the presence of
the flavor mixing. We point out that solar neutrino observation by the next
generation water Cherenkov detectors can improve the existing bound on
violation of the equivalence principle by 3-4 orders of magnitude if the
nonadiabatic Mikheyev-Smirnov-Wolfenstein mechanism is the solution to the
solar neutrino problem.Comment: Latex, 17 pages + 6 uuencoded postscript figures, KEK-TH-396,
TMUP-HEL-9402 (unnecessary one reference was removed
The Cross Section of 3He(3He,2p)4He measured at Solar Energies
We report on the results of the \hethet\ experiment at the underground
accelerator facility LUNA (Gran Sasso). For the first time the lowest
projectile energies utilized for the cross section measurement correspond to
energies below the center of the solar Gamow peak (=22 keV). The
data provide no evidence for the existence of a hypothetical resonance in the
energy range investigated. Although no extrapolation is needed anymore (except
for energies at the low-energy tail of the Gamow peak), the data must be
corrected for the effects of electron screening, clearly observed the first
time for the \hethet\ reaction. The effects are however larger than expected
and not understood, leading presently to the largest uncertainty on the quoted
value for bare nuclides (=5.40 MeV b).Comment: 18 pages, 10 postscript figures, Calculations concerning hypothetical
resonanz added, Submitted to Phys. Rev. C., available at this URL:
HTTP://www.lngs.infn.it/lngs/htexts/luna/luna.htm
Análise do acúmulo de transcritos de ?-3-dessaturases em genótipos de soja contrastantes para o teor de ácido linolênico.
Os ácidos graxos poliinsaturados, como linoléico e linolênico, são os principais responsáveis pela alta instabilidade oxidativa a altas temperaturas do óleo destinado a frituras e à fabricação de biodiesel. A biossíntese de ácidos graxos poliinsaturados é catalisada pelas dessaturases. A -6-dessaturase converte ácido oléico (18:19) a linoléico (18:29,12) e a -3-dessaturase produz ácido linolênico (18:39,12,15) a partir de 18:29,12. Três genes principais (GmFAD3A, GmFAD3B e GmFAD3C) foram caracterizados como responsáveis pela produção de -3-dessaturase em soja. Os mecanismos precisos de regulação da produção de ácido linolênico ainda não são muito claros, o que dificulta o processo de obtenção de genótipos com baixo conteúdo desse ácido graxo. A análise molecular de mutantes de soja com baixo conteúdo de ácido linolênico poderá ajudar a elucidar tais mecanismos. Os objetivos principais deste trabalho foram determinar os níveis de mRNAs das principais -3-dessaturases, correlacionando-os com as concentrações relativas de ácidos linolênico durante a ontogenia da semente de soja em genótipos normais e mutantes. Para isso, foram utilizados três genótipos contrastantes para essa característica: A29, (~1% 18:315,12,9); N85-2176 (~3% 18:315,12,9) e Tucunaré (Variedade comercial, ~8% 18:315,12,9). As plantas foram cultivadas em casa de vegetação e suas sementes foram coletadas separadamente em 5 estádios de desenvolvimento de acordo com o peso úmido da semente: 1º estádio: 0 a 125 mg; 2º estádio: 126 a 250 mg; 3º estádio: 251 a 375 mg; 4º estádio: superior a 376 mg; 5 º estádio: semente madura. Os teores de ácidos graxos na fração óleo das sementes nos cinco estádios de desenvolvimento foram determinados por cromatografia gasosa e a expressão gênica, por PCR quantitativo, utilizando como o controle endógeno o gene da GAPDH (gliceraldeído-3-fosfato desidrogenase). De modo geral, o conteúdo de 18:39,12,15 decresceu drasticamente nos estádios iniciais em todos os genótipos. No entanto, não foi observada expressão diferencial entre os genes GmFAD3A, GmFAD3B e GmFAD3C, que pudessem explicar tais alterações. O genótipo A29, seguido de N85-2176, apresentou a menor concentração de 18:39,12,15 durante todo o desenvolvimento da semente. Estes genótipos apresentaram expressão praticamente nula do gene GmFAD3A. Além disso, A29 apresentou expressão reduzida do gene GmFAD3B. Assim, pelo menos em parte, os níveis de transcritos dos genes GmFAD3A e GmFAD3B explicam as diferenças na concentração de ácidos graxos da fração óleo em A29 e N85-2176. Apoio financeiro: CNPq e CAPES
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