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. (2000). C.R. Acad. Sci. Paris, 330, 457–467.
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Cherel Y. & Hobson K.A. (2007). Geographical variation in carbon stable isotope signatures of marine predators: a tool to investigate their foraging areas in the Southern Ocean. Mar. Ecol. Prog. Ser., 329, 281–287.
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Collins T., Meuwis M.A, Gerday C. & Feller G. (2003). Activity, stability and flexibility in glycosisases adapted to extreme thermal environments. J. Mol. Biol., 328(2), 419–428.
Abstract: To elucidate the strategy of low temperature adaptation for a cold-adapted family 8 xylanase, the thermal and chemical stabilities, thermal inactivation, thermodependence of activity and conformational flexibility, as well as the thermodynamic basis of these processes, were compared with those of a thermophilic homolog. Differential scanning calorimetry, fluorescence monitoring of guanidine hydrochloride unfolding and fluorescence quenching were used, among other techniques, to show that the cold-adapted enzyme is characterized by a high activity at low temperatures, a poor stability and a high flexibility. In contrast, the thermophilic enzyme is shown to have a reduced low temperature activity, high stability and a reduced flexibility. These findings agree with the hypothesis that cold-adapted enzymes overcome the quandary imposed by low temperature environments via a global or local increase in the flexibility of their molecular edifice, with this in turn leading to a reduced stability. Analysis of the guanidine hydrochloride unfolding, as well as the thermodynamic parameters of irreversible thermal unfolding and thermal inactivation shows that the driving force for this denaturation and inactivation is a large entropy change while a low enthalpy change is implicated in the low temperature activity. A reduced number of salt-bridges are believed to be responsible for both these effects. Guanidine hydrochloride unfolding studies also indicate that both family 8 enzymes unfold via an intermediate prone to aggregation.
Programme: 193
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Crouzet, N., Guillot, T., Fressin, F., Blazit, A. (2007). the A STEP team 2007, Front- vs. back-illuminated CCD cameras for photometric surveys: a noise budget analysis. Astronomische nachrichten, 328, 805.
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. (2007). Telescope and instrument robotization at Dome C. Astronomische nachrichten, 328(6), 451.
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Nevitt, G. A., Bergstrom, D. M. & Bonadonna, F. (2006). The potential roles of ammonium as signal molecule for procellariiform seabirds. Mar. Ecol. Prog. Ser., 325, 271–277.
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C. Tape, Q. Liu, A. Maggi, J. Tromp. (2009). Adjoint tomography of the southern California crust. Science, 325, 988–992.
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Hyrenbach K.D., Veit R.R., Weimerskirch H. & Hunt G.L. Jr. (2006). Seabird associations with mesoscale eddies: the subtropical Indian Ocean. Mar. Ecol. Prog. Ser., 324, 271–279.
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Ebinghaus R., Temme C. & Einax J. (2004). Du mercure aux poles. Pour la science, 322.
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Morin, S.; Savarino, J.; Frey, M.M.; Yan, N.; Bekki, S.; Bottenheim, J.W.; Martins, J.M.F. (2008). Tracing the Origin and Fate of NOx in the Arctic Atmosphere Using Stable Isotopes in Nitrate. Science, 322(5902), 730–732.
Abstract: Atmospheric nitrogen oxides (NOx =NO+ NO2) play a pivotal role in the cycling of reactive nitrogen (ultimately deposited as nitrate) and the oxidative capacity of the atmosphere. Combined measurements of nitrogen and oxygen stable isotope ratios of nitrate collected in the Arctic atmosphere were used to infer the origin and fate of NOx and nitrate on a seasonal basis. In spring, photochemically driven emissions of reactive nitrogen from the snowpack into the atmosphere make local oxidation of NOx by bromine oxide the major contributor to the nitrate budget. The comprehensive isotopic composition of nitrate provides strong constraints on the relative importance of the key atmospheric oxidants in the present atmosphere, with the potential for extension into the past using ice cores.
Programme: 1011
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