Carbohydrates, oxidative damage

Typical spectra obtained are shown in Fig. 1.2. Moreover, substantial radiolytically-mediated elevations in the concentration of serum formate, arising from the oxidation of carbohydrates present by OH radical, were also detectable. In addition to the above modifications, 7-radiolysis of inflammatory knee-joint synovial fluid generated an oligosaccharide species of low molecular mass derived from the radiolytic fragmentation of hyaluronate as outlined in the previous section dealing with oxidative damage to carbohydrates. The... 

Lipid alkoxyl and peroxyl radicals abstract H s from any available sources, including nonlipid molecules such as amino acids (346, 379-382), proteins (99, 383, 384), nucleic acids (385, 386), antioxidants (318), carotenoids and other pigments, and even carbohydrates (387). As was noted in the discussion above (Sections 3.1.1 and 3.2.1), this quenches the lipid radical and stops propagation of the immediate radical chain. However, there is increasing evidence that the radicals transferred to proteins and carbohydrates, in particular, may follow processes similar to lipids, i.e., add oxygen to form peroxyl radicals that abstract H s and initiate new radical chains. In this way, lipids serve to broadcast oxidation damage to other molecules in foods and biological systems (186, 390). 

The overproduction of RONS may damage biological systems through peroxidation of membrane hpids, oxidative damage of nucleic acids and carbohydrates, and oxidation of... 

Oxidative damage may be an important factor in the development of age-related diseases [1,2]. Chemically, oxidation refers to the removal of electrons, and when it occurs within the body, it can result in the formation of cytotoxic chain reactions. Reactive oxygen species (ROS) is a term used to describe some types of free radicals, hydrogen peroxide, and singlet oxygen, which are aU capable of damaging membrane lipids, proteins, nucleic acids, and carbohydrates via oxidation [3]. 

Fleming C, Maldjian A, Da Costa D, Rullay AK, Haddletrai DM, John JS, Ptamy P, Noble RC, Cameron NR, Davis BG (2005) A carbohydrate-antioxidant hybrid polymer reduces oxidative damage in spermatozoa and enhances futility. Nat Chem Biol l(5) 270-274... 

The citric acid cycle is the final common pathway for the aerobic oxidation of carbohydrate, lipid, and protein because glucose, fatty acids, and most amino acids are metabolized to acetyl-CoA or intermediates of the cycle. It also has a central role in gluconeogenesis, lipogenesis, and interconversion of amino acids. Many of these processes occur in most tissues, but the hver is the only tissue in which all occur to a significant extent. The repercussions are therefore profound when, for example, large numbers of hepatic cells are damaged as in acute hepatitis or replaced by connective tissue (as in cirrhosis). Very few, if any, genetic abnormalities of citric acid cycle enzymes have been reported such ab-normahties would be incompatible with life or normal development. 

For the release of an unaltered base, the sugar moiety must be damaged. In principle, the base could already be released from a radical site at the sugar moiety, i.e. on the time-scale of the lifetime of the DNA radicals. The observation of 2-dRL incorporated into DNA as a product formed upon OH attack shows that a damage at C(l ) contributes to the release of an unaltered base. In the carbohydrate series, hydrolytic scission at the glycosidic linkage when this site contains a free-radical is a well-documented phenomenon, and it has been estimated that the rate of reaction must be faster than 35 s 1 (von Sonntag and Schuchmann 2001). As it stands, it cannot be excluded, that under certain conditions the base release from the C(l ) radical [reaction (38)] occurs in competition to its oxidation [reaction (2)]. In a cellular environment, there is also the reduction of DNA... 

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