Oxygen independent degradation

Koh MY, Damay BG, Powis G. HAF, a novel E3-ubiquitin ligase, binds and ubiquiti-nates HIF-l alpha leading to its oxygen-independent degradation. Mol Cell Biol 2008. 

In the experiments described above, accelerated degradation occurred at 90°C in an atmosphere maintained at 100% relative humidity. Under this condition, both the oxygen-independent and the atmospheric oxidation processes contributed about equally to the degradation of the rag and newsprint papers. The 100% relative humidity condition allowed an examination of the influence of acidity on both processes, but whether... 

Norrish type I chemistry is claimed to be responsible for about 15% of the chain scission of ethylene—carbon monoxide polymers at room temperature, whereas at 120°C it promotes 59% of the degradation. Norrish I reactions are independent of temperature and oxygen concentration at temperatures above the T of the polymer (50). 

The operation of these hydrolytic reactions is independent of the oxygen concentration of the system so that—in contrast to biotic degradation and transformation—these reactions may occur effectively under both aerobic and anaerobic conditions. 

The assumption can be made that degradation is dependent on total radiation dose but is independent of dose rate (see Section 6.13). However, acceleration levels can be very high and this is a prime reason why, in practice, it is often found that the effect of a given dose decreases with increased dose rate. The limiting factor is the rate of oxygen diffusion. Recommended practice is to test at two or more dose rate levels to determine the magnitude of this effect. 

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