Magneto-optical trap for metastable helium at 389 nm

We have constructed a magneto-optical trap (MOT) for metastable triplet helium atoms utilizing the 2 3S1 -> 3 3P2 line at 389 nm as the trapping and cooling transition. The far-red-detuned MOT (detuning Delta = -41 MHz) typically contains few times 10^7 atoms at a relatively high (~10^9 cm^-3) density, which is a consequence of the large momentum transfer per photon at 389 nm and a small two-body loss rate coefficient (2 * 10^-10 cm^3/s < beta < 1.0 * 10^-9 cm^3/s). The two-body loss rate is more than five times smaller than in a MOT on the commonly used 2 3S1 -> 2 3P2 line at 1083 nm. Furthermore, we measure a temperature of 0.46(1) mK, a factor 2.5 lower as compared to the 1083 nm case. Decreasing the detuning to Delta= -9 MHz results in a cloud temperature as low as 0.25(1) mK, at small number of trapped atoms. The 389 nm MOT exhibits small losses due to two-photon ionization, which have been investigated as well.Comment: 11 page

Purification And Preliminary Crystallographic Analysis Of A New Lys49-pla2 From B. Jararacussu

BjVIII is a new myotoxic Lys49-PLA2 isolated from Bothrops jararacussu venom that exhibits atypical effects on human platelet aggregation. To better understand the mode of action of BjVIII, crystallographic studies were initiated. Two crystal forms were obtained, both containing two molecules in the asymmetric unit (ASU). Synchrotron radiation diffraction data were collected to 2.0 Å resolution and 1.9 Å resolution for crystals belonging to the space group P2 12 12 1 (a = 48.4 Å, b = 65.3 Å, c = 84.3 Å) and space group P3 121 (a = b = 55.7 Å, c = 127.9 Å), respectively. Refinement is currently in progress and the refined structures are expected to shed light on the unusual platelet aggregation activity observed for BjVIII. © 2008 by the authors; licensee Molecular Diversity Preservation International.95736750van Deenen, L., de Haas, G., Heemskerk, C.H., Hydrolysis of synthetic mixed-acid phosphatides by phospholipase A from human pancreas (1963) Biochim Biophys Acta, 67, pp. 295-304Higuchi, D.A., Barbosa, C.M.V., Bincoletto, C., Chagas, J.R., Magalhaes, A., Richardson, M., Sanchez, E.F., Pesquero, J., L.. Purification and partial characterization of two phospholipases A2 from Bothrops leucurus (white-tailed-jararaca) snake venom (2007) Biochimie, 89, pp. 319-328Maraganore, J.M., Merutka, G., Cho, W., Welches, W., Kézdy, F.J., Heinrikson, R.L., A new class of phospholipases A2 with lysine in place of aspartate 49. Functional consequences for calcium and substrate binding (1984) J Biol Chem, 259, pp. 13839-13843Nakai, M., Nakashima, K.I., Ogawa, T., Shimohigashi, Y., Hattori, S., Chang, C.C., Ohno, M., Purification and primary structure of a myotoxic lysine-49 phospholipase A2 with low lipolytic activity from Trimeresurus gramineus venom (1995) Toxicon, 33, pp. 1469-1478Koh, D.C.I., Armugam, A., Jeyaseelan, K., Snake venom components and their applications in biomedicine (2006) Cell Mol Life Sci, 63, pp. 3030-3041Andrião-Escarso, S.H., Soares, A.M., Fontes, M.R.M., Fuly, A.L., Corrêa, F.M.A., Rosa, J.C., Greene, L.J., Giglio, J., R.. Structural and functional characterization of an acidic platelet aggregation inhibitor and hypotensive phospholipase A(2) from Bothrops jararacussu snake venom (2002) Biochem Pharmacol, 64, pp. 723-732Fuly, A.L., Soares, A.M., Marcussi, S., Giglio, J.R., Guimarães, J.A., Signal transduction pathways involved in the platelet aggregation induced by a D-49 phospholipase A2 isolated from Bothrops jararacussu snake venom (2004) Biochimie, 86, pp. 731-739Magro, A.J., Murakami, M.T., Marcussi, S., Soares, A.M., Arni, R.K., Fontes, M.R.M., Crystal structure of an acidic platelet aggregation inhibitor and hypotensive phospholipase A2 in the monomeric and dimeric states: Insights into its oligomeric state (2004) Biochem Biophys Res Commun, 323, pp. 24-31Toyama, M.H., Carneiro, E.M., Marangoni, S., Barbosa, R.L., Corso, G., Boschero, A.C., Biochemical characterization of two crotamine isoforms isolated by a single step RP-HPLC from Crotalus durissus terrificus (South American rattlesnake) venom and their action on insulin secretion by pancreatic islets (2000) Biochim Biophys Acta, 1474, pp. 56-60Fonseca, F.V., Antunes, E., Morganti, R.P., Monteiro, H.S.A., Martins, A.M.C., Toyama, D.O., Marangoni, S., Toyama, M., H.. Characterization of a new platelet aggregating factor from crotoxin Crotalus durissus cascavella venom (2006) Protein J, 25, pp. 183-192Schägger, H., von Jagow, G., Tricine-sodium dodecyl sulfate-polyacrylamide gel electrophoresis for the separation of proteins in the range from 1 to 100 kDa (1987) Anal Biochem, 166, pp. 368-379McPherson, A., Current approaches to macromolecular crystallization (1990) Eur J Biochem, 189, pp. 1-23Polikarpov, I., Oliva, G., Castellano, E.E., Garratt, R.C., Arruda, P., Leite, A., Craievich, A., The protein crystallography beamline at LNLS, the Brazilian National Synchrotron Light Source (1998) Nucl Instrum Methods Phys Res A, 405, pp. 159-164Polikarpov, I., Perles, L.A., de Oliveira, R.T., Oliva, G., Castellano, E.E., Garratt, R.C., Craievich, A.. Set-up and Experimental Parameters of the Protein Crystallography Beamline at the Brazilian National Synchrotron Laboratory (1998) J Synchrotron Radiat, 5, pp. 72-76Leslie, A.G., W.. The integration of macromolecular diffraction data (2006) Acta Crystallogr D Biol Crystallogr, 62, pp. 48-57Evans, P., Scaling and assessment of data quality (2006) Acta Crystallogr D Biol Crystallogr, 62, pp. 72-82Navaza, J., Implementation of molecular replacement in AMoRe (2001) Acta Crystallogr D Biol Crystallogr, 57, pp. 1367-1372Kozin, M.B., Svergun, D.I., Automated matching of high- and low-resolution structural models (2001) J Appl Crystallogr, 34, pp. 33-41CCP, Collaborative Computational Project, Number 4. The CCP4 suite: Programs for protein crystallography (1994) Acta Crystallogr D Biol Crystallogr, 50, pp. 760-763. , 4Winn, M., Dodson, E.J., Ralph, A., Collaborative computational project, number 4: Providing programs for protein crystallography (1997) Methods Enzymol, 277, pp. 620-633Spencer, P.J., Aird, S.D., Boni-Mitake, M., Nascimento, N., Rogero, J.R., A single-step purification of bothropstoxin-1 (1998) Braz J Med Biol Res, 31, pp. 1125-1127Soares, A.M., Guerra-Sá, R., Borja-Oliveira, C.R., Rodrigues, V.M., Rodrigues-Simioni, L., Rodrigues, V., Fontes, M.R.M., Giglio, J.R., Structural and functional characterization of BnSP-7, a Lys49 myotoxic phospholipase A2 homologue from Bothrops neuwiedi pauloensis venom (2000) Arch Biochem Biophys, 378, pp. 201-209Arni, R.K., Ward, R.J., Gutiérrez, J.M., Tulinsky, A., Structure of a calcium-independent phospholipase-like myotoxic protein from Bothrops asper venom (1995) Acta Crystallogr D Biol Crystallogr, 51, pp. 311-317Murakami, M.T., Viçoti, M.M., Abrego, J.R.B., Lourenzoni, M.R., Cintra, A.C.O., Arruda, E.Z., Tomaz, M.A., Arni, R., K.. Interfacial surface charge and free accessibility to the PLA2-active site-like region are essential requirements for the activity of Lys49 PLA2 homologues (2007) Toxicon, 49, pp. 378-387Toyama, M.H., Soares, A.M., Vieira, C.A., Novello, J.C., Oliveira, B., Giglio, J.R., Marangoni, S.. Amino acid sequence of piratoxin-I, a myotoxin from Bothrops pirajai snake venom, and its biological activity after alkylation with p-bromophenacyl bromide (1998) J Protein Chem, 17, pp. 713-718Barbosa, P. S. F.Martins, A. M. C.Alves, R. S.Amora, D. N.Martins, R. D.Toyama, M. H.Havt, A.Nascimento, N. R. F.Rocha, V. L. C.Menezes, D. B.Fonteles, M. C.Monteiro, H. S. A. . The role of indomethacin and tezosentan on renal effects induced by Bothrops moojeni Lys49 myotoxin I. Toxicon 2006, 47, 831-837Kramer, R.M., Roberts, E.F., Manetta, J.V., Hyslop, P.A., Jakubowski, J., A.. Thrombin-induced phosphorylation and activation of Ca(2+)-sensitive cytosolic phospholipase A2 in human platelets (1993) J Biol Chem, 268, pp. 26796-26804Puri, R., N.. Phospholipase A2: Its role in ADP- and thrombin-induced platelet activation mechanisms (1998) Int J Biochem Cell Biol, 30, pp. 1107-1122Soares, A.M., Andrião-Escarso, S.H., Angulo, Y., Lomonte, B., Gutiérrez, J.M., Marangoni, S., Toyama, M.H., Giglio, J.R., Structural and functional characterization of myotoxin I, a Lys49 phospholipase A(2) homologue from Bothrops moojeni (Caissaca) snake venom (2000) Arch Biochem Biophys, 373, pp. 7-15Singh, N., Jabeen, T., Pal, A., Sharma, S., Perbandt, M., Betzel, C., Singh, T.P., Crystal structures of the complexes of a group IIA phospholipase A2 with two natural anti-inflammatory agents, anisic acid, and atropine reveal a similar mode of binding (2006) Proteins, 64, pp. 89-100Kini, R.M., Evans, H.J., A model to explain the pharmacological effects of snake venom phospholipases A2 (1989) Toxicon, 27, pp. 613-635Gutiérrez, J.M., Lomonte, B., Phospholipase A2 myotoxins from Bothrops snake venoms (1995) Toxicon, 33, pp. 1405-1424Ownby, C.L., de Araujo, H.S.S., White, S.P., Fletcher, J., E.. Lysine 49 phospholipase A2 proteins (1999) Toxicon, 37, pp. 411-445Yang, C. C.. In Venom Phospholipase A2 enzymes: Structure, Function and MechanismKini, R. M., Ed.John Wiley & Sons: UK, 1997Chapter Chemical modification and functional sites of phospholipases A2, p 185Stiles, B. G.Choumet, V.. In Venom Phospholipase A2 enzymes: Structure, Function and MechanismKini, R. M., Ed.John Wiley & Sons: UK, 1997Chapter Antibodies studies with venom phospholipases A2, p 223Matthews, B., W.. Solvent content of protein crystals (1968) J Mol Biol, 33, pp. 491-497Altschul, S.F., Madden, T.L., Schäffer, A.A., Zhang, J., Zhang, Z., Miller, W., Lipman, D., J.. Gapped BLAST and PSI-BLAST: A new generation of protein database search programs (1997) Nucleic Acids Res, 25, pp. 3389-3402Magro, A.J., Soares, A.M., Giglio, J.R., Fontes, M.R.M., Crystal structures of BnSP-7 and BnSP-6, two Lys49-phospholipases A(2): Quaternary structure and inhibition mechanism insights (2003) Biochem Biophys Res Commun, 311, pp. 713-72

Expansion of a Bose-Einstein Condensate in an atomic waveguide

The expansion of a Bose-Einstein condensate in an atomic waveguide is analyzed. We study different regimes of expansion, and identify a transient regime between one-dimensional and three-dimensional dynamics, in which the properties of the condensate and its further expansion can be well explained by reducing the transversal dynamics to a two-level system. The relevance of this regime in current experiments is discussed.Comment: 4 pages, 3 figs, Accepted for publication in Phys. Rev.

Collapse dynamics of trapped Bose-Einstein condensates

We analyze the implosion and subsequent explosion of a trapped condensate after the scattering length is switched to a negative value. Our results compare very well qualitatively and fairly well quantitatively with the results of recent experiments at JILA.Comment: 4 pages, 3 figure

Spectral method for the time-dependent Gross-Pitaevskii equation with a harmonic trap

We study the numerical resolution of the time-dependent Gross-Pitaevskii equation, a non-linear Schroedinger equation used to simulate the dynamics of Bose-Einstein condensates. Considering condensates trapped in harmonic potentials, we present an efficient algorithm by making use of a spectral Galerkin method, using a basis set of harmonic oscillator functions, and the Gauss-Hermite quadrature. We apply this algorithm to the simulation of condensate breathing and scissors modes.Comment: 23 pages, 5 figure

Ground state and elementary excitations of single and binary Bose-Einstein condensates of trapped dipolar gases

We analyze the ground-state properties and the excitation spectrum of Bose-Einstein condensates of trapped dipolar particles. First, we consider the case of a single-component polarized dipolar gas. For this case we discuss the influence of the trapping geometry on the stability of the condensate as well as the effects of the dipole-dipole interaction on the excitation spectrum. We discuss also the ground state and excitations of a gas composed of two antiparallel dipolar components.Comment: 12 pages, 9 eps figures, final versio

Mean-field description of collapsing and exploding Bose-Einstein condensates

We perform numerical simulation based on the time-dependent mean-field Gross-Pitaevskii equation to understand some aspects of a recent experiment by Donley et al. on the dynamics of collapsing and exploding Bose-Einstein condensates of $^{85}$Rb atoms. They manipulated the atomic interaction by an external magnetic field via a Feshbach resonance, thus changing the repulsive condensate into an attractive one and vice versa. In the actual experiment they changed suddenly the scattering length of atomic interaction from positive to a large negative value on a pre-formed condensate in an axially symmetric trap. Consequently, the condensate collapses and ejects atoms via explosion. We find that the present mean-field analysis can explain some aspects of the dynamics of the collapsing and exploding Bose-Einstein condensates.Comment: 9 Latex pages, 10 ps and eps files, version accepted in Physical Review A, minor changes mad

Expedition 361 summary

International Ocean Discovery Program Expedition 361 drilled six sites on the southeast African margin (southwest Indian Ocean) and in the Indian-Atlantic Ocean gateway, from 30 January to 31 March 2016. In total, 5175 m of core was recovered, with an average recovery of 102%, during 29.7 days of on-site operations. The sites, situated in the Mozambique Channel at locations directly influenced by discharge from the Zambezi and Limpopo River catchments, the Natal Valley, the Agulhas Plateau, and Cape Basin, were targeted to reconstruct the history of the greater Agulhas Current system over the past ~5 My. The Agulhas Current is the strongest western boundary current in the Southern Hemisphere, transporting some 70 Sv of warm, saline surface water from the tropical Indian Ocean along the East African margin to the tip of Africa. Exchanges of heat and moisture with the atmosphere influence southern African climates, including individual weather systems such as extratropical cyclone formation in the region and rainfall patterns. Recent ocean model and paleoceanographic data further point at a potential role of the Agulhas Current in controlling the strength and mode of the Atlantic Meridional Overturning Circulation (AMOC) during the Late Pleistocene. Spillage of saline Agulhas water into the South Atlantic stimulates buoyancy anomalies that may influence basin-wide AMOC, with implications for convective activity in the North Atlantic and global climate change. The main objectives of the expedition were to establish the role of the Agulhas Current in climatic changes during the Pliocene–Pleistocene, specifically to document the dynamics of the Indian-Atlantic Ocean gateway circulation during this time, to examine the connection of the Agulhas leakage and AMOC, and to address the influence of the Agulhas Current on African terrestrial climates and coincidences with human evolution. Additionally, the expedition set out to fulfill the needs of Ancillary Project Letter number 845, consisting of high-resolution interstitial water sampling to help constrain the temperature and salinity profiles of the ocean during the Last Glacial Maximum. The expedition made major strides toward fulfilling each of these objectives. The recovered sequences allowed generation of complete spliced stratigraphic sections that range from 0 to between ~0.13 and 7 Ma. This sediment will provide decadal- to millennial-scale climatic records that will allow answering the paleoceanographic and paleoclimatic questions set out in the drilling proposal