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(18) MEASUREMENT OF THE OXIDATION STATE OF MANGANESE INSIDE MITOCHONDRIA USING XANES SPECTROSCOPY T.E. Gunter, L.M. Miller, A.
Alexandrov, L. Buntinas, R. Eliseev and K.K. Gunter
X-ray absorption near edge structure (XANES) spectroscopy can be used to determine the oxidation states of elements heavier than calcium. Manganese, which often acts as a Ca2+ analog, is currently being added to gasoline as methyl cyclopentadienyl manganese tricarbonyl (MMT). Excessive brain manganese can induce neurological symptoms somewhat resembling those of Parkinsonism which are associated with loss of dopamine in the striatum and cell death in the globus pallidus. In considering how Mn causes these symptoms, an important question is the Mn oxidation state. Intracellular Mn is largely sequestered by mitochondria. Mn3+ is known to be a strong oxidizing agent and is thought to act by oxidizing dopamine and other neuronal components. Mn2+ inhibits mitochondrial Ca2+ efflux via both Na+-dependent and independent mechanisms and by this means can cause Ca2+ accumulation in mitochondria, which may lead to cell death. Determination of the oxidation state of intramitochondrial Mn would help identify the type of mechanism most prevalent in Mn toxicity. We have used XANES spectroscopy to determine the oxidation state of intramitochondrial Mn in liver, heart, and brain mitochondria over a range of concentrations from around 0.7 to 35 nmole/mg protein and over this range have compared Mn incubated intramitochondrially for 10 min with that incubated for 90 and 120 min. Over that wide range of concentration, the results show that intramitochondrial Mn is in the 2+ oxidation state. This work was supported by HEI contract 99-11 and by a pilot grant from NIEHS Center Grant P30-ES01247.
For further information contact...Carmen Mannella: carmen@wadsworth.org |
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