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      Albumin-Bound Quercetin Repairs Vitamin E Oxidized by Apolipoprotein Radicals in Native HDL3and LDL†

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          Abstract

          In the minor fraction of HDL3 containing alpha-tocopherol (alphaTocOH), selective one-electron oxidation of Trp and Tyr residues of apolipoproteins A-I and A-II by *Br2- radical-anions produces the corresponding semioxidized species, TyrO* and *Trp. Repair of TyrO* by endogenous alphaTocOH generates the alpha-tocopheroxyl radical (alphaTocO*). Fast spectroscopic studies show that two populations representing 80% of alphaTocO* initially formed are repaired over several seconds with rate constants of 3.0 x 10(6) and 1.5 x 10(5) M-1 s-1 by quercetin bound to human serum albumin (HSA) at physiologically relevant concentration. Formation of HSA-bound quercetin radicals (*Qb) is observed. In the major fraction of HDL3 particles lacking alphaTocOH, TyrO* and *Trp are repaired by free and HSA-bound quercetin. In LDL particles which all contain alphaTocOH, alphaTocO* radicals are formed in the millisecond time scale by repair of TyrO* radicals produced in apolipoprotein B. Then, 75% of initial alphaTocO* are repaired over seconds by HSA-bound quercetin (rate constant: 2.0 x 10(6) M-1 s-1). HSA-bound quercetin can also repair *Trp radicals. In O2-saturated solutions, the fraction of alphaTocO* radicals (more than 50%) not repaired by superoxide radical-anions can be repaired by HSA-bound quercetin with formation of *Qb but to a much lesser extent in LDL than in HDL.

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          Author and article information

          Journal
          Biochemistry
          Biochemistry
          American Chemical Society (ACS)
          0006-2960
          1520-4995
          December 2007
          December 2007
          : 46
          : 49
          : 14305-14315
          Article
          10.1021/bi701419d
          18004880
          d15e120e-30f7-4dc3-9bdb-6551d64a0844
          © 2007
          History

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