Free scavenger

The above data suggest an important role of reactive oxygen species in the development of heart diseases. This suggestion has been supported by many studies, which also demonstrated a potential efficacy of antioxidants, free scavengers, and chelators in the treatment of these diseases. Mitochondrial oxygen radical overproduction can probably be one of the critical causes. 

There are, indeed, many biological implications that have been triggered by the advent of fullerenes. They range from potential inhibition of HIV-1 protease, synthesis of dmgs for photodynamic therapy and free radical scavenging (antioxidants), to participation in photo-induced DNA scission processes [156, 157, 158, 159, 160, 161, 162 and 163]. These examples unequivocally demonstrate the particular importance of water-soluble fullerenes and are summarized in a few excellent reviews [141, 1751. 

Scavengers such as diphenylpicrylhydrazyl radicals [II] react with other radicals and thus provide an indirect method for analysis of the number of free radicals in a system ... 

Concern for personnel exposure to hydrazine has led to several innovations in packaging to minimize direct contact with hydrazine, eg, Olin s E-Z dmm systems. Carbohydrazide was introduced into this market for the same reason it is a soHd derivative of hydrazine, considered safer to handle because of its low vapor pressure. It hydrolyzes to release free hydrazine at elevated temperatures in the boiler. It is, however, fairly expensive and contributes to dissolved soHds (carbonates) in the water (193). In field tests, catalyzed hydrazine outperformed both hydrazine and carbohydrazide when the feedwater oxygen and iron levels were critical (194). A pubUshed comparison is available (195) of these and other proposed oxygen scavengers, eg, diethyUiydroxylarnine, ydroquinone, methyethylketoxime, and isoascorbic acid. 

The ultimate fate of the oxygen-centered radicals generated from alkyl hydroperoxides depends on the decomposition environment. In vinyl monomers, hydroperoxides can be used as efficient sources of free radicals because vinyl monomers generally are efficient radical scavengers which effectively suppress induced decomposition. When induced decomposition occurs, the hydroperoxide is decomposed with no net increase of radicals in the system (see eqs. 8, 9, and 10). Hydroperoxides usually are not effective free-radical initiators since radical-induced decompositions significantly decrease the efficiency of radical generation. Thermal decomposition-rate studies in dilute solutions show that alkyl hydroperoxides have 10-h HLTs of 133—172°C. 

Foam. PhenoHc resin foam is a cured system composed of open and closed ceUs with an overall density of 16—800 g/cm. Principal appHcations are in the areas of insulation and sponge-like floral foam. The resins are aqueous resoles cataly2ed by NaOH at a formaldehyde phenol ratio of ca 2 1. Free phenol and formaldehyde content should be low, although urea may be used as a formaldehyde scavenger. 

A related mechanism of degradation involves the direct interaction of the radioactive emission with other tracer molecules in the preparation. This phenomenon is likely to occur in high specific activity compounds stored at high radiochemical concentrations in the absence of free-radical scavengers. 

In contrast, antioxidants can have an opposite effect when peroxide curing. Because peroxide cross-linking involves a free-radical mechanism, and antioxidants are designed to scavenge free radicals, it is obvious that peroxide efficiency can be compromised by the addition of antioxidants. Thus the decomposition products of the ppds were acting as accelerators (29). 

Vitamin E can also act as an antioxidant (qv) in animals and humans alone or in combination with vitamin C (qv). Both are good free-radical scavengers with the vitamin C acting to preserve the levels of vitamin E (35). Vitamin E in turn can preserve the levels of vitamin A in animals (13). It has been shown that vitamin E reduces the incidence of cardiovascular disease (36—39). This most likely results from the antioxidant property of the vitamin which inhibits the oxidation of low density Hpoproteins (LDLs) (40—42). The formation of the oxidized LDLs is considered important in decreasing the incidence of cardiovascular disease (43). 

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