Kinetics of the reversible reaction of CO2(aq) with ammonia in aqueous solution

The kinetics of the interactions of aqueous ammonia with aqueous carbon dioxide/carbonate species has been investigated using stopped-flow techniques by monitoring the pH changes via indicators. The reactions include the reversible formation of ammonium carbamate/carbamic acid. A complete reaction mechanism has been established, and the temperature dependence of all rate and equilibrium constants including the protonation constant of the amine between 15 and 45 °C are reported and analyzed in terms of Arrhenius, Eyring, and van't Hoff relationships.     

A new method for precise determination of iron,zinc and cadmium stable isotope ratios in seawater by double-spike mass spectrometry

The study of Fe, Zn and Cd stable isotopes (δ⁵⁶Fe, δ⁶⁶Zn and δ¹¹⁴Cd) in seawater is a new field, which promises to elucidate the marine cycling of these bioactive trace metals. However, the analytical challenges posed by the low concentration of these metals in seawater has meant that previous studies have typically required large sample volumes, highly limiting data collection in the oceans. Here, we present the first simultaneous method for the determination of these three isotope systems in seawater, using Nobias PA-1 chelating resin to extract metals from seawater, purification by anion exchange chromatography, and analysis by double spike MC-ICPMS. This method is designed for use on only a single litre of seawater and has blanks of 0.3, 0.06 and <0.03 ng for Fe, Zn and Cd respectively, representing a 1–20 fold reduction in sample size and a 4–130 decrease in blank compared to previously reported methods. The procedure yields data with high precision for all three elements (typically 0.02–0.2‰; 1σ internal precision), allowing us to distinguish natural variability in the oceans, which spans 1–3‰ for all three isotope systems. Simultaneous extraction and purification of three metals makes this method ideal for high-resolution, large-scale endeavours such as the GEOTRACES program.     

Impaired neurogenesis, learning and memory and low seizure threshold associated with loss of neural precursor cell survivin

Background

Survivin is a unique member of the inhibitor of apoptosis protein (IAP) family in that it exhibits antiapoptotic properties and also promotes the cell cycle and mediates mitosis as a chromosome passenger protein. Survivin is highly expressed in neural precursor cells in the brain, yet its function there has not been elucidated.

Results

To examine the role of neural precursor cell survivin, we first showed that survivin is normally expressed in periventricular neurogenic regions in the embryo, becoming restricted postnatally to proliferating and migrating NPCs in the key neurogenic sites, the subventricular zone (SVZ) and the subgranular zone (SGZ). We then used a conditional gene inactivation strategy to delete the survivin gene prenatally in those neurogenic regions. Lack of embryonic NPC survivin results in viable, fertile mice (Survivin ^Camcre ) with reduced numbers of SVZ NPCs, absent rostral migratory stream, and olfactory bulb hypoplasia. The phenotype can be partially rescued, as intracerebroventricular gene delivery of survivin during embryonic development increases olfactory bulb neurogenesis, detected postnatally. Survivin ^Camcre brains have fewer cortical inhibitory interneurons, contributing to enhanced sensitivity to seizures, and profound deficits in memory and learning.

Conclusions

The findings highlight the critical role that survivin plays during neural development, deficiencies of which dramatically impact on postnatal neural function.