Atmosphere Pasteur point

The next stage in the development of the atmosphere began when formation of oxygen exceeded its consumption (Mason, 1971). This occurred in the period between 1.7 and 1.2 b.y. ago at about 1 b.y., at the boundary of the Proterozoic and Paleozoic, the amounts of Oj reached the level of the Pasteur point ( 1% of the present oxygen content), as a result of which more complex organisms could appear in the biosphere. The CO2 content at this stage was controlled by carbonate-silicate equilibria in the hydrosphere. 

Fig, 35. Stages in the evolution of animals (after Fisher) I = animals live in total respiratory dependence on the number of plants the atmosphere is practically devoid of free oxygen. II = the atmosphere reaches the Pasteur point , animals can leave plants but seek water-air interface. Ill = the atmosphere and water contain a large amount of oxygen, animals are widespread. 

After incubation at S7°C in a 5% CO atmosphere, wash the cells with 150 pi PBS per well at different time points posttransfection, and aspirate the supernatant with a Pasteur pipette. To remove extracellularly bound complexes, add 100 pi per well 100 U/ml heparin solution containing 75 mM sodium azide to inhibit endocytosis (17). 

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