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A Trick of the Tail: The Effect of Amyloid Formation on the pKa Values of α-synuclein

Pálmadóttir, Tinna LU (2015) KEMT30 20151
Department of Chemistry
Abstract
The formation of α-synuclein amyloid fibrils and accumulation in inclusion bodies termed Lewy bodies are considered the hallmark of Parkinson’s disease. It has been found that the formation of fibrils is highly pH dependent, which is thought to be linked to the highly negatively charged C-terminal tail of α-synuclein. The aim of this project was to study if the pKa values of the C-terminal tail in fibrils are upshifted compared to monomers. In order to investigate this, a method for the determination of pKa values of monomers and fibrils was developed and evaluated. The formation of fibrils in water was kinetically followed using Thioflavin-T dye and the morphology was observed by Cryo-TEM . Potentiometric titrations were performed on... (More)
The formation of α-synuclein amyloid fibrils and accumulation in inclusion bodies termed Lewy bodies are considered the hallmark of Parkinson’s disease. It has been found that the formation of fibrils is highly pH dependent, which is thought to be linked to the highly negatively charged C-terminal tail of α-synuclein. The aim of this project was to study if the pKa values of the C-terminal tail in fibrils are upshifted compared to monomers. In order to investigate this, a method for the determination of pKa values of monomers and fibrils was developed and evaluated. The formation of fibrils in water was kinetically followed using Thioflavin-T dye and the morphology was observed by Cryo-TEM . Potentiometric titrations were performed on monomers and fibrils in water. Moreover, Metropolis Monte Carlo simulations were performed. One of the findings of this project was that the pH increases about one pH unit (5.3-6.3) as monomers form fibrils, providing strong indications of proton uptake during fibrillation and an upshift in the pKa values of the acidic residues. This is most likely linked to close proximity between the acidic residues of the C-terminal tail of monomers within the fibrils. Further experimental and theoretical studies need to be performed in order to get better understandings of the pH dependence of the underlying mechanism and the electrostatic interaction in amyloid formation of α-synuclein. (Less)
Popular Abstract
Parkinson’s disease is the second most common neurodegenerative disease. The most common symptoms of this disease are shaking, rigidity and difficulties with motion, such as walking. The disease is caused by a loss of cells in the brain. The loss of cells is associated with the formation of rope-like structures. These structures are called amyloid fibrils and are formed from a smaller structural unit – a protein – that is called α-synuclein. The process of the formation of the fibrillar structure is toxic and kills the cells. Therefore, it is very important to understand how these fibrils form and what can affect their formation. In the case of Parkinson’s disease, research on the protein α-synuclein is important.
A part of this protein... (More)
Parkinson’s disease is the second most common neurodegenerative disease. The most common symptoms of this disease are shaking, rigidity and difficulties with motion, such as walking. The disease is caused by a loss of cells in the brain. The loss of cells is associated with the formation of rope-like structures. These structures are called amyloid fibrils and are formed from a smaller structural unit – a protein – that is called α-synuclein. The process of the formation of the fibrillar structure is toxic and kills the cells. Therefore, it is very important to understand how these fibrils form and what can affect their formation. In the case of Parkinson’s disease, research on the protein α-synuclein is important.
A part of this protein is thought to affect the formation of the fibrils. This part of the protein is flexible and is called “the tail”. The tail has many negative charges. They negative charges do not like to be close to each other and therefore they push each other away. Because of that, the tail is flexible and stretched out. The tail is thought to affect the formation of the fibrils. For example, it is believed that the negative charges and flexibility of the tail has a protecting role and decreases the likelihood of the protein forming fibrils. Studies of the tail are therefore important and can provide a better understanding of the formation of fibrils.
The tail was of central interest in this project. The goal was to measure special values – called pKa values – of the tail. The aim was to measure the values both before the protein forms fibrils and after the protein forms fibrils. These values are related to the pH scale which tell us how acidic or basic solutions are. The pKa values that we are interested in in this project tell us at which pH value the tail loses its negative charges. The hypothesis of the project was that these values change when the protein forms fibrils. Knowing this can increase our understanding about the behaviour of the tail and the effect of the tail on the formation of fibrils. One of the findings of this project was that when the protein forms fibrils the pH value of the sample increases. This finding strongly indicates that the pKa values increase as the protein forms fibrils. Further studies are important to increase our understanding of the fibril formation and the effects of the tail. (Less)
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author
Pálmadóttir, Tinna LU
supervisor
organization
course
KEMT30 20151
year
type
H2 - Master's Degree (Two Years)
subject
keywords
potentiometric titration, pKa values, fibrils, amyloid, α-synuclein, C-terminal tail, protein science, proteinvetenskap, Parkinson's disease
language
English
id
7373747
date added to LUP
2015-07-02 15:28:44
date last changed
2015-07-02 15:28:44
@misc{7373747,
  abstract     = {The formation of α-synuclein amyloid fibrils and accumulation in inclusion bodies termed Lewy bodies are considered the hallmark of Parkinson’s disease. It has been found that the formation of fibrils is highly pH dependent, which is thought to be linked to the highly negatively charged C-terminal tail of α-synuclein. The aim of this project was to study if the pKa values of the C-terminal tail in fibrils are upshifted compared to monomers. In order to investigate this, a method for the determination of pKa values of monomers and fibrils was developed and evaluated. The formation of fibrils in water was kinetically followed using Thioflavin-T dye and the morphology was observed by Cryo-TEM . Potentiometric titrations were performed on monomers and fibrils in water. Moreover, Metropolis Monte Carlo simulations were performed. One of the findings of this project was that the pH increases about one pH unit (5.3-6.3) as monomers form fibrils, providing strong indications of proton uptake during fibrillation and an upshift in the pKa values of the acidic residues. This is most likely linked to close proximity between the acidic residues of the C-terminal tail of monomers within the fibrils. Further experimental and theoretical studies need to be performed in order to get better understandings of the pH dependence of the underlying mechanism and the electrostatic interaction in amyloid formation of α-synuclein.},
  author       = {Pálmadóttir, Tinna},
  keyword      = {potentiometric titration,pKa values,fibrils,amyloid,α-synuclein,C-terminal tail,protein science,proteinvetenskap,Parkinson's disease},
  language     = {eng},
  note         = {Student Paper},
  title        = {A Trick of the Tail: The Effect of Amyloid Formation on the pKa Values of α-synuclein},
  year         = {2015},
}