Synthesis And Evaluation Of Inhibitors For β-amyloid In Alzheimer's Disease

As a progressive, fatal neurodegenerative disease, Alzheimer's disease (AD) is the most common form of dementia. Alzheimer's disease not only affects the sufferers'quality of life, it's also a serious social problem faced by the whole humankind.β-amyloid (Aβ), especially Aβ(1-42) that contains 42 amino acid residues, is regarded to be crucial in AD. The mainstream theory considers the production and degradation of Aβin vivo as an equilibrium, once the equilibrium is broken, Aβaccumulation will initiate AD and the neurotoxicity mainly results from the aggregation of Aβ. Currently there is no cure for AD except for a few FDA-approved medications that can help with some cognitive and behavioral symptoms of AD. Just like researchers all over the world, my work is also to find organic compounds that can inhibit the malicious aggregation of Aβ.Most strategies of inhibitor design lie in the interaction between the inhibitors and the target proteins. In regard of the nature of this interaction, if one can replace the common inter-molecular Van der Waals forces with stronger and more stable covalent bonds, one can expect the inhibition to be faster and more sustainable. My work is to design and synthesize inhibitors with covalent-bonding potentials. For the recognition part, I chose stilbene and dimethylamino stilbene that can recognize theπ-πstacking-related regions of Aβ, and a short peptide (LVFF) which is similar with the famous Tjernberg's peptide. Connected with a length-adjustable linear spacer, the recognitive subunit can be further linked to o-hydroxybenzaldehyde which can be expected to form stable Schiff base structure with amino group on the side-chain of lysine in the core region responsible for the Aβaggregation. HPLC and MALDI-TOF spectrum help confirm the formation of the covalently bonded products from Aβand the inhibitors. The introduction of covalent linkage potentials into inhibitor design is a brand new strategy that has emerged recently. Employing this strategy, my work may be shared as useful trials and inspirations in the whole Alzheimer's researching community.I used Thioflavin T (ThT) fluorescence to assess the effects of my compounds'inhibition of Aβaggregation and disaggregation of pre-assembled mature Aβfibrils. Transmission electron microscopy (TEM) images directly confirm the effectiveness of the inhibitors, too. Circular dichroism (CD) spectra have suggested positive results: the inhibitors can block the formation of aggregation -inclinedβ-sheet conformation of Aβmonomers, the inhibitors can also induce the monomers to gain and retainα-helix conformation with less tendency to aggregate. To sum up, I have employed a series of methods to evaluate the inhibitors and screened candidates for further assessment in cell culture or animal models.