Date of Award

12-31-2015

Document Type

Campus Access Thesis

Degree Name

Master of Science (MS)

Department

Chemistry

First Advisor

Michelle Foster

Second Advisor

Marianna Török

Third Advisor

Béla Török

Abstract

The irreversible aggregation of fibrils formed from various proteins is associated with such diseases as Alzheimer’s, Parkinson’s, Huntington’s, and Creutzfeldt-Jakob. Generally, amyloid fibrils are several micrometers long, twisted structures that are only a few nanometers in diameter. Therefore, an advanced technique that is capable of resolving individual fibrils such as atomic force microscopy (AFM) is needed to image amyloid fibrils. Quantitative analysis of AFM data has several challenges. Because of the variety of manufacturers of AFMs and the corresponding unique software, consistent methods are not found within the literature and often method details for quantitative analyses are not explicitly provided. Furthermore, the analysis must be tailored to the specific type of sample and the quantitative data being investigated.

In this work, methods for obtaining fibril length using ImageJ and fibril maximum height using NanoScope section analysis and particle analysis techniques from AFM images were found to be valid by examining the repeatability, reproducibility, and robustness of the methods. Hen egg-white lysozyme (HEWL) was used as a model protein for the method validation as well as for an investigation of the stability of prepared AFM amyloid fibril samples over time at room temperature and under refrigeration. AFM amyloid fibril samples at room temperature were found to be stable for at least 31 days and for 22 days under refrigeration.

The ultimate goal of this work was to qualitatively and quantitatively analyze AFM images of fibrils grown from amyloid-beta (Aβ), the protein associated with Alzheimer’s disease (AD) treated with small molecule phenylhydrazine derivatives. The effects of the phenylhydrazine derivatives at dissembling preformed Aβ fibrils were investigated by analyzing the length and maximum height of the AFM fibril images using the previously validated methods. Furthermore, the effects of varying the concentration of the small molecules were examined using the parent disassembler molecule, phenylhydrazine.

The results indicated that the preformed Aβ fibrils treated with the phenylhydrazine derivatives showed a significant reduction in length even at the lowest concentration of disassembler molecule analyzed in this study. The results of this work showed no discernable effect on Aβ fibril maximum height when treated with the phenylhydrazine derivatives.

Comments

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