Neodymium isotopes and concentrations in Caribbean seawater during METEOR cruise M78/1

Neodymium isotopes and concentrations from 11 stations in the Caribbean, Gulf of Mexico, Florida Straits and close to the mouth of the Orinoco. CTD data (potential temperature, salinity, potential density and oxygen concentration) for the same samples are also reported. Sampling took place during February and March 2009 as part of the Meteor Cruise 78, Leg 1.

Sedimentology and Nd isotope ratios of sediment core PS72/410-1

The freshwater budget of the Arctic Ocean is a key component governing the deep water formation in the North Atlantic and the global climate system. We analyzed the isotopic composition of neodymium (epsilon-Nd) in authigenic phases of marine sediments on the Mendeleev Ridge in the western Arctic Ocean spanning an estimated time interval from present to about 75 ka BP. This continuous record was used to reconstruct the epsilon-Nd of the polar deep water (PDW) and changes in freshwater sources to the PDW through time. Three deviations in epsilon-Nd from a long term average of -10.2 were identified at estimated 46-51, 35-39 and 13-21 ka BP. The estimated 46-51 ka BP event can be traced to bursting of ice-dammed lakes accompanying the collapse of the Barents-Kara Ice Sheet, which would have released radiogenic Nd to the eastern Arctic Ocean. The cyclonic surface circulation in the eastern Arctic Ocean must have been stronger than at present for the event to be recorded on the Mendeleev Ridge. For the 35-39 and 13-21 ka BP events, it is likely that the Laurentide Ice Sheet (LIS) supplied the unradiogenic freshwater. The configuration of the anticyclonic circulation in the western Arctic was probably similar to today or expanded eastward. Our simple mass balance calculations suggest that large amounts of freshwater were released but due to significant deep water formation within the Arctic Ocean, the effect on the formation of NADW was probably minor.

(Table 1) Strontium concentrations and isotope ratios of anhydrite from DSDP/ODP Hole 504B

In samples from 1575 to 1982 mbsf anhydrite leached from whole-rock powders. 87Sr/86Sr and Sr/Ca determined following methods described in (Teagle et al., 1996, doi:10.2973/odp.proc.sr.148.113.1996, Teagle et al., 1998, doi:10.2973/odp.proc.sr.158.223.1998). For the period of the analysis (Jan. 1994-Dec. 1995) NIST SRM 987 gave 87Sr/86Srs0.710244 +/- 0.000018 (2 sigma, n = 115). Full analytical procedural blanks were <50 pg for Sr. delta18O following (Pickthorn and O´Neil, 1985). Repeated extractions and measurements of samples and standards were reproducible within +/- 0.5.

The LAR/PTP delta/PTP sigma subfamily of transmembrane protein-tyrosine-phosphatases: multiple human LAR, PTP delta, and PTP sigma isoforms are expressed in a tissue-specific manner and associate with the LAR-interacting protein LIP.1.

The transmembrane protein-tyrosine-phosphatases (PTPases) LAR, PTP delta, and PTP sigma each contain two intracellular PTPase domains and an extracellular region consisting of Ig-like and fibronectin type III-like domains. We describe the cloning and characterization of human PTP sigma (HPTP sigma) and compare the structure, alternative splicing, tissue distribution, and PTPase activity of LAR, HPTP delta, and HPTP sigma, as well their ability to associate with the intracellular coiled-coil LAR-interacting protein LIP.1. Overall, these three PTPases are structurally very similar, sharing 64% amino acid identity. Multiple isoforms of LAR, HPTP delta, and HPTP sigma appear to be generated by tissue-specific alternative splicing of up to four mini-exon segments that encode peptides of 4-16 aa located in both the extracellular and intracellular regions. Alternative usage of these peptides varies depending on the tissue mRNA analyzed. Short isoforms of both HPTP sigma and HPTP delta were also detected that contain only four of the eight fibronectin type III-like domains. Northern blot analysis indicates that LAR and HPTP sigma are broadly distributed whereas HPTP delta expression is largely restricted to brain, as is the short HPTP sigma isoform containing only four fibronectin type III-like domains. LAR, HPTP delta, and HPTP sigma exhibit similar in vitro PTPase activities and all three interact with LIP.1, which has been postulated to recruit LAR to focal adhesions. Thus, these closely related PTPases may perform similar functions in various tissues.

QSAR e dinâmica molecular no estudo de sistemas biomoleculares: predição da atividade biológica de antagonistas do receptor sigma-1 e simulações de bicamadas lipídicas

Diferentes abordagens teóricas têm sido utilizadas em estudos de sistemas biomoleculares com o objetivo de contribuir com o tratamento de diversas doenças. Para a dor neuropática, por exemplo, o estudo de compostos que interagem com o receptor sigma-1 (Sig-1R) pode elucidar os principais fatores associados à atividade biológica dos mesmos. Nesse propósito, estudos de Relações Quantitativas Estrutura-Atividade (QSAR) utilizando os métodos de regressão por Mínimos Quadrados Parciais (PLS) e Rede Neural Artificial (ANN) foram aplicados a 64 antagonistas do Sig-1R pertencentes à classe de 1-arilpirazóis. Modelos PLS e ANN foram utilizados com o objetivo de descrever comportamentos lineares e não lineares, respectivamente, entre um conjunto de descritores e a atividade biológica dos compostos selecionados. O modelo PLS foi obtido com 51 compostos no conjunto treinamento e 13 compostos no conjunto teste (r² = 0,768, q² = 0,684 e r²teste = 0,785). Testes de leave-N-out, randomização da atividade biológica e detecção de outliers confirmaram a robustez e estabilidade dos modelos e mostraram que os mesmos não foram obtidos por correlações ao acaso. Modelos também foram gerados a partir da Rede Neural Artificial Perceptron de Multicamadas (MLP-ANN), sendo que a arquitetura 6-12-1, treinada com as funções de transferência tansig-tansig, apresentou a melhor resposta para a predição da atividade biológica dos compostos (r²treinamento = 0,891, r²validação = 0,852 e r²teste = 0,793). Outra abordagem foi utilizada para simular o ambiente de membranas sinápticas utilizando bicamadas lipídicas compostas por POPC, DOPE, POPS e colesterol. Os estudos de dinâmica molecular desenvolvidos mostraram que altas concentrações de colesterol induzem redução da área por lipídeo e difusão lateral e aumento na espessura da membrana e nos valores de parâmetro de ordem causados pelo ordenamento das cadeias acil dos fosfolipídeos. As bicamadas lipídicas obtidas podem ser usadas para simular interações entre lipídeos e pequenas moléculas ou proteínas contribuindo para as pesquisas associadas a doenças como Alzheimer e Parkinson. As abordagens usadas nessa tese são essenciais para o desenvolvimento de novas pesquisas em Química Medicinal Computacional.

Radiogenic neodymium, strontium and lead isotopes of authigenic and detrital sedimentary phases and stable oxygen and carbon isotopes of benthic foraminifera from gravity cores SO213-59-2 and SO213-60-1 (central South Pacific).

The South Pacific is a sensitive location for the variability of the global oceanic thermohaline circulation given that deep waters from the Atlantic Ocean, the Southern Ocean, and the Pacific Basin are exchanged. Here we reconstruct the deep water circulation of the central South Pacific for the last two glacial cycles (from 240,000 years ago to the Holocene) based on radiogenic neodymium (Nd) and lead (Pb) isotope records complemented by benthic stable carbon data obtained from two sediment cores located on the flanks of the East Pacific Rise. The records show small but consistent glacial/interglacial changes in all three isotopic systems with interglacial average values of -5.8 and 18.757 for epsilon Nd and 206Pb/204Pb, respectively, whereas glacial averages are -5.3 and 18.744. Comparison of this variability of Circumpolar Deep Water (CDW) to previously published records along the pathway of the global thermohaline circulation is consistent with reduced admixture of North Atlantic Deep Water to CDW during cold stages. The absolute values and amplitudes of the benthic delta13C variations are essentially indistinguishable from other records of the Southern Hemisphere and confirm that the low central South Pacific sedimentation rates did not result in a significant reduction of the amplitude of any of the measured proxies. In addition, the combined detrital Nd and strontium (87Sr/86Sr) isotope signatures imply that Australian and New Zealand dust has remained the principal contributor of lithogenic material to the central South Pacific.