The Mitochondrial Free Radical Theory of Aging - Supernova: Pliki

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44 The Mitochondrial Free Radical Theory of Aging Fig. 3.3. A highly oxidizable, but necessary, juxtaposition of C=C double bonds. 3.8. Downstream Products—A Virtually Infinite Variety One class of reaction involving LECs was not included in Table 3.3, because in order to describe it one must describe the structure of the participating lipids in detail. Reaction 18, whereby a lipid peroxyl radical becomes a hydroperoxide, can sometimes occur intramolecularly: the unpaired electron forms a bond with a carbon atom of the same carbon chain, making a ring. The molecule is still a radical: a lipid radical that is also an endoperoxide (Fig. 3.2). Molecules with an endoperoxide ring are particularly unstable with regard to their molecular structure: the oxygens can move around the molecule, creating even more exotic multi-ringed molecules (Fig. 3.2). 6 Eventually these complex molecules are prone to break apart, and one of the major products (both in vitro and in vivo) is malondialdehyde (Fig. 3.2), which can be used in biological systems as a measure of the rate of lipid peroxidation. The other molecules most often used as measures of lipid peroxidation are ethane and pentane, which are two of many unreactive molecules formed by reactions 20 and 16 but are the easiest to assay because they are gaseous. 7 3.9. Fatty Acid Double Bonds: Fluidity but Oxidizability In the above description of lipid peroxidation I have treated all lipids as equal, but they are very far from that. Lipids are a large family of compounds, and some are much more oxidizable than others. Unfortunately for us, the characteristic that makes lipids particularly oxidizable is one that we cannot do without, because membranes need lipids of that type in order to maintain physical integrity in vivo. This characteristic is the possession of carbon chains with C=C double bonds spaced at a particular distance, as shown in Figure 3.3. The circled hydrogen atoms, attached to the carbon in the middle, are called doubly allylic, or bisallylic: they are particularly susceptible to removal by oxidizing LECs. 8
An Introduction to Free Radicals References 1. a) Hanson KM, Simon JD. Epidermal trans-urocanic acid and the UV-A induced photoaging of the skin. Proc Natl Acad Sci USA 1998; 95:10576-10578. 1. b) Beckman JS, Beckman TW, Chen J et al. Apparent hydroxyl radical production by peroxynitrite: Implications for endothelial injury from nitric oxide and superoxide. Proc Natl Acad Sci USA 1990; 87:1620-1624. 2. Bielski BHJ. Reevaluation of the spectral and kinetic properties of HO2 and O2 — free radicals. Photochem Photobiol 1978; 28:645-649. 3. van Zutphen H, Cornwell DG. Some studies on lipid peroxidation in monomolecular and bimolecular lipid films. J Membr Biol 1973; 13:79-88. 4. Ivanov AS, Putvinskii AV, Antonov VF et al. Magnitude of the protein permeability of liposomes following photoperoxidation of lipids. Biophysics 1977; 22:644-648. 5. Kappus H. Lipid peroxidation: Mechanisms, analysis, enzymology and biological relevance. In: Sies H, ed. Oxidative stress. London: Academic Press, Inc., 1985:273-310. 6. Pryor WA, Stanley JP, Blair E. Autoxidation of polyunsaturated fatty acids: II. A suggested mechanism for the formation of TBA-reactive materials from prostaglandin-like endoperoxides. Lipids 1976; 11:370-379. 7. Riely CA, Cohen G, Lieberman M. Ethane evolution: A new index of lipid peroxidation. Science 1974; 183:208-210. 8. Cosgrove JP, Church DF, Pryor WA. The kinetics of the autoxidation of polyunsaturated fatty acids. Lipids 1987; 22:299-304. 45
Page 1 and 2: COMPANY de Grey The Mitochondrial F
Page 3 and 4: ISBN: 1-57059-564-X MOLECULAR BIOLO
Page 5 and 6: 7. The Status of Gerontological The
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Page 9 and 10: I cannot overstate my profound grat
Page 11 and 12: CHAPTER 1 Introduction 1.1. What Is
Page 13 and 14: Introduction Some may feel that all
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The Search for How Mutant mtDNA is
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The Search for How Mutant mtDNA is
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CHAPTER 9 The Search for How So Few
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The Search for How So Few Anaerobic
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CHAPTER 10 Frequently-Asked Questio
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Frequently-Asked Questions The effe
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Frequently-Asked Questions Table 10
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Frequently-Asked Questions through
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Frequently-Asked Questions has been
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Frequently-Asked Questions SOS, sin
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Frequently-Asked Questions for almo
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Frequently-Asked Questions Fig. 10.
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Frequently-Asked Questions Fig. 10.
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Frequently-Asked Questions of elect
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Frequently-Asked Questions Referenc
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Frequently-Asked Questions 45. Clay
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CHAPTER 11 A Challenge from Textboo
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A Challenge from Textbook Bioenerge
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160 The Mitochondrial Free Radical
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CHAPTER 14 Ablation of Anaerobic Ce
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Ablation of Anaerobic Cells: Techni
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CHAPTER 15 Transgenic Copies of mtD
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Transgenic Copies of mtDNA: Techniq
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CHAPTER 16 Prospective Impact on th
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Prospective Impact on the Healthy H
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Prospective Impact on the Healthy H
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Index Symbols “~”, 19 A Acetald
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Index Copper 35, 107 see also trans
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Index Heart comparison to man-made
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Index genetic code 23, 115-118, 177
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Index Perhydroxyl radical 41, 122,
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Index protonation see protonation (
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MOLECULAR BIOLOGY INTELLIGENCE UNIT
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