No abstract

Amyloid -peptide (AP) deposition in senile plaques and cerebral vessels is a neuropathological feature of Alzheimer disease (AD). We examined the possibility that commonly observed variability in Af8 deposition in late-onset AD might be related to apolipoprotein E genotype (APOE gene; the two most common alleles are 3 and 4), since APOE4 is a susceptibility gene for late-onset AD and apolipoprotein E interacts strongly with A.8 in vitro. In an autopsy series of brains of late-onset AD patients, we found a strong association of APOE4 allele with increased vascular and plaque Af3 deposits. Late-onset AD patients with one or two APOE4 alleles have a distinct neuropathological phenotype compared with patients homozygous for APOE3.

Addition of nanoparticulate zero-valent iron (nZVI) to oxygen-containing water results in oxidation of organic compounds. To assess the potential application of nZVI for oxidative transformation of organic contaminants, the conversion of benzoic acid (BA) to p-hydroxybenzoic acid (p-HBA) was used as a probe reaction. When nZVI was added to BA-containing water, an initial pulse of p-HBA was detected during the first 30 min, followed by the slow generation of additional p-HBA over periods of at least 24 h. The yield of p-HBA increased with increasing BA concentration, presumably due to the increasing 'ability of BA to compete with alternate oxidant sinks, such as ferrous iron. At pH 3, maximum yields of p-HBA during the initial phase of the reaction of up to 25% were observed. The initial rate of nZVI-mediated oxidation of BA exhibited a marked reduction at pH values above 3. Despite the decrease in oxidant production rate, p-HBA was observed during the initial reaction phase at pH values up to 8. Competition experiments with probe compounds expected to exhibit different affinities for the nZVI surface (phenol, aniline, o-hydroxybenzoic acid, and synthetic humic acids) indicated relative rates of reaction that were similar to those observed in competition experiments in which hydroxyl radicals were generated in solution. Examination of the oxidizing capacity of a range of Fe0 particles reveals a capacity in all cases to induce oxidative transformation of benzoic acid, but the high surface areas that can be achieved with nanosized particles renders such particles particularly effective oxidants.

Degradation of the carbothiolate herbicide, molinate, has been investigated in oxic solutions containing nanoscale zero-valent iron particles and found to be effectively degraded by an oxidative pathway. Both ferrous iron and superoxide (or, at pH < 4.8, hydroperoxy) radicals appearto be generated on corrosion of the zero-valent iron with resultant production of strongly oxidizing entities capable of degrading the trace contaminant.