Oxidative degradations, functionalization

The parallel synthesis of furans from a-hydroxycarbonyl compounds is frequently conducted using aldoses or ketoses as readily available sources of this functional grouping, especially as the resulting polyhydroxyalkyl side-chain can be removed easily by oxidative degradation (Schemes 67d and 67e) 56MI30300). 

For a ToF-SIMS investigation of the surface oxidative degradation of low-density polyethylene (LDPE), the polymer was exposed to 1802 rather than 1602 in order to be able to readily discriminate oxygen introduced by the ageing process from that in the polymer prior to ageing [102], Figure 36 shows an example series of ToF-SIMS spectra from this investigation, which shows the clear separation of the lsO species from the lsO species. In the study, close correlation was observed between the intensity of the lsO carbonyl species determined by mid-infrared spectroscopy with the ToF-SIMS 180- peak intensity as a function of 1802 exposure time. ToF-SIMS spectra obtained from microtomed cross-sections showed no... 

Ferredoxins from thermoacidophilic archaea such as Thermoplasma acidophi-lum and Sulfolobus sp. contain, in addition to one 3Fe-4S (cluster I) and one 4Fe-4S (cluster II) cluster, one zinc centre tetrahedrally co-ordinated to three histidines in the N-terminal region and to one aspartate in the ferredoxin core domain. These Fds contain an unusually long N-terminal extension region of unknown function, which was not detected in other bacterial type Fds. Upon oxidative degradation of Fd from Sulfolobus sp. strain 7 (Fopt = 80 cluster II is selectively converted into a cubane 3Fe-4S,... 

Transition metals (iron, copper, nickel and cobalt) catalyse oxidation by shortening the induction period, and by promoting free radical formation [60]. Hong et al. [61] reported on the oxidation of a substimted a-hydroxyamine in an intravenous formulation. The kinetic investigations showed that the molecule underwent a one-electron transfer oxidative mechanism, which was catalysed by transition metals. This yielded two oxidative degradants 4-hydroxybenzalde-hyde and 4-hydroxy-4-phenylpiperidine. It has been previously shown that a-hydroxyamines are good metal ion chelators [62], and that this can induce oxidative attack on the a-hydroxy functionality. 

This three-step process for transferring fatty acids into the mitochondrion—esterification to CoA, transesterification to carnitine followed by transport, and transesterification back to CoA—links two separate pools of coenzyme A and of fatty acyl-CoA, one in the cytosol, the other in mitochondria These pools have different functions. Coenzyme A in the mitochondrial matrix is largely used in oxidative degradation of pyruvate, fatty acids, and some amino acids, whereas cytosolic coenzyme A is used in the biosynthesis of fatty acids (see Fig. 21-10). Fatty acyl-CoA in the cytosolic pool can be used for membrane lipid synthesis or can be moved into the mitochondrial matrix for oxidation and ATP production. Conversion to the carnitine ester commits the fatty acyl moiety to the oxidative fate. 

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