Study Of The Effect Of The Peptide And Protein On The Oxidative Stress Induced By Aβ-Cu(Ⅱ) Complex

A major hallmark of Alzheimer disease (AD) is the deposition of aggregates of amyloid-β (Aβ) peptides in the senile plaques. Due to their accumulation inside the senile plaques, metal ions are purported to be involved in the Aβ aggregation process and are capable of binding with Aβ. The Aβ-Cu(Ⅱ) complex has been proven to induce oxidative stress in the pathogenesis of AD, or accelerate the aggregation process of Aβ and increase the production of toxic Aβ oligomers. To inhibit the aggregation of Aβ and suppress the oxidation stress induced by the Aβ-Cu(Ⅱ) complex, a bifunctional peptide molecule has been designed. Furthermore, the effect of the peptide and protein on the oxidative stress induced by Aβ-Cu(Ⅱ) complex has been investigated. The thesis include the following parts:The effect of the synthesized Zn7MT on the catalytic effect of Aβ(1-16)-Cu(Ⅱ) complex toward the oxidation of ascorbic acid (AA), which results in the oxidative stress, has been investigated. The synthesized Zn7MT is capable of binding to Cu(Ⅱ) selectively.The stability constant of the Cu(Ⅱ)-Aβ complex was determined based on the electrochemical measurements. The results indicated that Zn7MT induced the reduction of Cu(Ⅱ) to Cu(Ⅰ) and favored the formation of Cu(Ⅰ)4Zn4MT. Various techniques such as fluorescence spectroscopy, UV-vis spectrophotometry and electrochemistry have been involved. The results indicate that Zn7MT could sequester Cu(Ⅱ) from Aβ(1-16)-Cu(Ⅱ) complex, thus inhibiting the catalytic effect of Aβ(1-16)-Cu(Ⅱ) complex toward the oxidation of AA and the formation of H2O2. The formed Cu(I)4Zn4MT complex was not capable of inducing the oxidative stress process.A novel bifunctional peptide molecule with sequences of KLVFFKK WGQPHGGGWGQPHGGGWG QPHGGGWGQPHGGGWGQ(CH141) or KLVFFKKWGQHGHGHGHG (CH142) has been designed and synthesized. The synthesized peptide molecule is capable of inhibiting the aggregation of Aβ and in the same time, chelating with metal ions. The results indicate that the synthesized peptide molecule could inhibit the catalytic effect of Aβ-Cu(Ⅱ) complex toward the oxidation of AA with the formation of H2O2. Furthermore, the results by fluorescence spectrometry and atomic force microscopy (AFM) suggest that the peptide molecule could inhibit the formation of toxic oligomers and fibres. The synthesized peptide is capable of inhibiting the aggregation of Aβ and chelating with Cu(II), thus suppressing the formation of reactive oxygen species to some extent.