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Subunit II of cytochrome c oxidase (Cox2) is usually encoded in the mitochondrial genome, synthesized in the organelle, inserted co-translationally into the inner mitochondrial membrane, and assembled into the respiratory complex. In chlorophycean algae however, the cox2 gene was split into the cox2a and cox2b genes, and in some algal species like Chlamydomonas reinhardtii and Polytomella sp. both fragmented genes migrated to the nucleus. The corresponding Cox2A and Cox2B subunits are imported into mitochondria forming a heterodimeric Cox2 subunit. When comparing the sequences of chlorophycean Cox2A and Cox2B proteins with orthodox Cox2 subunits, a C-terminal extension in Cox2A and an N-terminal extension in Cox2B were identified. It was proposed that these extensions favor the Cox2A/Cox2B interaction. In vitro studies carried out in this work suggest that the removal of the Cox2B extension only partially affects binding of Cox2B to Cox2A. We conclude that this extension is dispensable, but when present it weakly reinforces the Cox2A/Cox2B interaction.

Basalt chemical weathering can be related to chemical composition of both atmospheric dust and rainfall, in published works authors have shown that weathered basalt exhibits a raise in anions like sulfate, nitrate, phosphate, chloride and carbonate, and doing a follow up of rainfall chemistry during 2009 at downtown Puebla, it was shown that rainfall has not an acid pH because there is a strong contribution from atmospheric dust.In this paper it is reported obtained results for dust samples collected during the dry season, collection was done in 3 places exposed to different environment, analysis of solid samples clearly reflect anthropogenic activities since the highest oil and grease content corresponds to a site with high population, also mineral carbonate amounts 30% in weight. An analytical sample was prepared and the filtrate used to measure pH which ranges from 6.3 to 7.84, and conductivity from 11.91-13.87 mS-cm-1. Main soluble ions range are as follow: sulfate 3.4-5.9 mg g-1, nitrate 0.19-0.54 mg g-1, chloride 0.7-8.91 mg g-1, sulfide 4-7 mg g-1, carbonate 304-364 mg g-1, this last correspond to 10% of the mineral content. Also, metals were determined as total (applying an acid digestion) and water soluble, obtained results allow to affirm that there are highly soluble metals like Ca, Pb (up to 97%), moderately soluble ones such as Cu and Mn (60% and 20% respectively) and non soluble ones like Al, Fe and Zn.It was confirmed that atmospheric dust has all properties, which could produce an alkalinization of rainwater. Also, its water soluble ionic content can be a source for those ions causing basalt weathering.

Significant intrusion of geothermal water into fresh groundwater takes place in the Puebla Valley aquifer system, Mexico. The decline in the potentiometric surface due to the overexploitation of the groundwater induces this intrusion. This hydrological system comprises three aquifers located in Plio-Quaternary volcanic sediments and Mesozoic calcareous rocks. The hydraulic balance of the aquifer shows that the annual output exceeds the natural inputs by 12 million m3. Between 1973 and 2002, a drop in the potentiometric surface, with an 80 m cone of depression, was identified in a 5-km-wide area located southwest of the city of Puebla. Chemical analyses performed on water samples since 1990 have shown an increase in total dissolved solids (TDS) of more than 500 mg/L, coinciding with the region showing a cone of depression in the potentiometric surface. A three-dimensional flow and transport model, based on the hydrogeological and geophysical studies, was computed by using the MODFLOW and MT3D software. This model reproduces the evolution of the aquifer system during the last 30 years and predicts for 2010 an additional drawdown in the potentiometric surface of 15 m, and an increase in the geothermal water intrusion.

Unequivocal identification of irrigation return water through routine chemical analyses does not appear possible in tropical volcanic islands. Several constituents, nevertheless, will suggest an agricultural source if they are present in large concentrations. Nitrate is the most useful indicator; background concentrations are generally less than 2 ppm but return irrigation water will commonly have concentrations of between 5 and 50 ppm. Sulfate appears to be the next most useful indicator. Calcium, silica, and bicarbonate have also been reported to be significant. Where detailed studies have been made of agricultural water balances, regional ground-water flow directions, and deep-well hydraulics, hydrochemistry can provide critical supporting data for the identification of return irrigation water which could be a potential ground-water pollutant.