Diss. (sammanfattning) Umeå : Umeå Universitet, 2007. / Härtill 3 uppsatser. I publikationen saknas serienummer.

Diss. (sammanfattning) Stockholm : Karol. inst. / Härtill 5 uppsatser.

Thesis (Ph. D.)--University of Chicago, Dept. of Chemistry, March 2002. / Includes bibliographical references. Also available on the Internet.

Many of the fundamental characteristics of amyloid formation are still unknown, largely due to the limitations present in currently available techniques. This is particularly problematic for disease-associated amyloid-forming species such as betaamyloid (A/3) , due to the tremendous impact that they cause on human well-being (Alzheimer's disease). In this dissertation three new methodologies were developed in order to provide mechanistic insights into A/3 amyloid formation. In Chapter 3 the optimisation of an A/3 purification methodology was achieved, greatly improving the reproducibility and purity of the samples obtained. This methodology was then applied to the production of a tandem A/3 construct, a dimeric form of A/3 that has been previously studied in a D. melanogaster model, which had not been recombinantly produced before. A preliminary biophysical characterisation was performed, providing some surprising insights into the toxicity of its aggregates. In Chapter 4 a novel methodology for using Tyr10 solvent exposure as a structural probe of A/3 formation was created using acrylamide quenching of tyrosine fluorescence. The data obtained exhibited similar solvent exposures between free tyrosine, monomers of both the A/31_ 40 and A/31_ 42 variants, and ADDLs of A/31_ 42 , results that agree with our current understanding of their structure. Fibrils of A/31_ 40 and A/31_ 42 exhibited solvent exposures similar to each other, but both.had significant reductions compared to the other species, in agreement with fibril structure models. � Lastly, in Chapter 5, the development of a technique for the creation, long-term storage and observation of aggregation events inside micro droplets was achieved. This technique exhibits remarkable temporal and spatial resolution for sample sizes that are ten orders of magnitude smaller than standard biophysical techniques. The methodology was applied to the study of glucagon, and the versatility of this technique was demonstrated by the collection of data including the total THT fluorescence evolution, the spatial growth of the aggregates and information on aggregate morphology, in conformity with spherulite formation.

Human calcitonin (hCT) is a peptide hormone that is produced by the thyroid gland where it regulates blood calcium and stimulates bone formation. However, increased concentrations can cause hCT to aggregate into amyloid fibrils where they can cause cellular toxicity. In this dissertation, we investigated the role of the N-terminal intramolecular disulfide bond, the effects cholesterol derivatives, the inhibitory effects of a group of polyphenolic molecules, and membrane interactions on hCT amyloid formation. To better understand hCT amyloid formation, we investigated the role of the N-terminal intramolecular disulfide bond has on the aggregation kinetics of hCT. Our results demonstrated that the presence of the disulfide bond is key to the formation of the oligomeric nucleus that is needed for amyloid formation. We also investigated the role of cholesterol, cholesterol sulfate, and 3β-[N-(dimethylaminoethane)carbamoyl]-cholesterol (DC-cholesterol) in moderating hCT fibril formation. We showed that cholesterol does not significantly affect hCT fibrillization while high concentrations of cholesterol sulfate has a moderate inhibiting effect. However, DC-cholesterol strongly inhibits hCT fibril formation in a concentration-dependent manner suggesting the role of electrostatic and hydrogen bonding interactions have in moderating the interactivity between hCT and the surface of DC-cholesterol vesicles. We also probed the inhibitory effects of a group of polyphenolic molecules on hCT fibril formation. Our results showed that molecules containing vicinal hydroxyl groups on the phenyl ring effectively inhibits hCT fibril formation though a plausible covalent linkage between the oxidized polyphenol and hCT. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2020. / FAU Electronic Theses and Dissertations Collection

It is a striking observation that tissue of patients invaded by the deep mycoses often lacks evidence of an inflammatory response. This lack of host response is often attributed to neutropenia secondary to chemotherapy. However, systematic studies do not support this simplistic explanation. However, invasive fungal lesions are characterized by abundant fungal functional amyloid, which in turn is bound by serum amyloid P component (SAP). We postulate that SAP is important in the local immune response in invasive fungal infections. The interaction between fungal functional amyloid, SAP, and the immune response in deep mycoses is discussed.

Diss. (sammanfattning) Linköping : Linköpings universitet, 2006. / Härtill 4 uppsatser.

Amyloid formation occurs when normally soluble proteins and peptides misfold and aggregate into intractable threadlike structures called fibrils. There are currently more than 30 proteins associated with this aberrant structure, including the Aβ peptide in Alzheimer’s disease (AD) and transthyretin (TTR) in TTR amyloidosis. TTR is a homotetrameric transporter protein present in both cerebrospinal fluid and plasma. Dissociation of its tetrameric structure is required for the formation of amyloid fibrils. Small molecule ligands able to bind and stabilize the tetrameric structure of TTR thus represent a potential therapeutic intervention. Interestingly, apart from TTR’s role as a toxic agent in TTR amyloidosis, it also has a role as an inhibitor of the Aβ toxicity associated with AD. The work presented in this thesis focused on small molecules that have the potential ability to prevent TTR amyloidosis. We also sought to gain a greater understanding of the interaction between TTR and the Aβ peptide with respect to Aβ fibril formation. The ability of a drug to stabilize TTR is directly correlated to its binding affinity. However, since TTR is a plasma protein, it is of great importance that the drug binds selectively to TTR. In paper I, we used a newly developed urea denaturation assay, in combination with isothermal titration calorimetry, to show that, in a complex environment such as plasma, the enthalpy of binding correlates better with a drug’s ability to stabilize TTR than the binding affinity. In paper II, we modified the highly selective but rapidly degraded TTR ligand luteolin in order to increase its resistance against biotransformation. Using a liver-based microsome assay, in combination with HPLC, we show how the luteolin analogues have gained increased stability. However, using the urea assay, we also show that the analogues have lost much of luteolin’s selectivity. In paper III, we show that tetrabromobisphenol A is a highly selective binder of TTR in plasma and is able to rescue cells from TTR-induced toxicity. In paper IV, we studied the interaction of TTR with Aβ and its effect on Aβ fibril formation. We used a ThT fluorescence-based assay and dot blotting to show that TTR inhibits Aβ amyloid formation and promotes the formation of high molecular weight assemblies with an open N-terminus. Using surface plasmon resonance, we further show how TTR is unable to inhibit fibril elongation and instead targets the nucleation processes, both primary and fibril-catalyzed secondary nucleation. To conclude, we present new molecules with the ability to selectively stabilize TTR that can serve as scaffolds in drug design. We also elucidate TTR’s inhibiting effects on toxic Aβ amyloid formation.

Alzheimer’s disease (AD) has been defined as a type of dementia that causes problems with memory, thinking, and behavior. AD is characterized by tau tangles and Aβ plaques in and around neurons, respectively. The impact this disease has on its victims’ health, both physically and mentally, is unimaginable and the rate of progression is not expected to decrease any time soon. This threat to our minds encourages the importance of understanding AD. Amongst the theories as to what bio mechanisms cause the brain to intertwine is the amyloid cascade hypothesis. The purpose of this thesis is to review the amyloid cascade hypothesis and discuss treatments which utilize this model. We also wish to examine social aspects such as loneliness and socioeconomic factors which are associated with the progression of AD. Research presented provides evidence that targeting the accumulation of Aβ in the brain will prevent further biochemical responses to form neurodegenerative pathology. From the collected data, we observe that therapies targeting the amyloidogenic pathway have received positive feedback in the medical community. Amongst them, an Aβ synthetic peptide vaccine which made history in vaccine development due to their responder rate. The impact of social factors such as loneliness in the advancement of AD is also supported by research. While it is acknowledged that any neurodegenerative disease is far too complex to narrow its cause specifically, this thesis provides an association with multiple aspects that can be understood and applied to future research in this field. / Includes bibliography. / Thesis (M.S.)--Florida Atlantic University, 2018. / FAU Electronic Theses and Dissertations Collection

Alzheimer’s disease (AD) is a deleterious neurodegenerative disease caused in major part by the aberrant processing and accumulation of amyloid beta peptides. In this dissertation, we systematically investigated the role of N-terminal region (NTR) residues of amyloid (1-40) (Aβ40) peptide in amyloidogenesis, lipid bilayer membrane interaction and damage, as well as neurotoxicity. Herein, we investigated the role of NTR residues on the aggregation and amyloid fibril formation process, to gain understanding on the electrostatic and hydrophobic constituents of the mechanism. This was achieved by substituting specific charged residues located in the NTR of Aβ40 and investigating their effects through a variety of techniques. We also investigated the role of NTR charged residues in their interaction with supported phospholipid bilayer membranes through the use of Quartz Crystal Microbalance with Dissipation (QCM-D) monitoring to gain insight on the mechanistic details of the interaction. To further understand the implications of substituting charged NTR residues on membrane interaction, pore formation and damage, we utilized a carboxyfluorescein dye leakage assay to quantify the membrane damage caused by Aβ40 and the NTR mutants. We also performed neurotoxicity assay with SH-SY5Y neuroblastoma cells to shed light on the effects of NTR substitutions on cellular toxicity. Finally, we synthesized a polymer, trimethyl chitosan (TMC), and utilized it as a polyelectrolyte monitor of electrostatic interactions occurring between TMC and the NTR of Aβ40. Our results demonstrate that the NTR charged residues of Aβ40 contribute significantly to the aggregation process, amyloidogenesis, and phospholipid membrane interaction and perturbation by means of electrostatic, thermodynamic and hydrophobic forces. / Includes bibliography. / Dissertation (Ph.D.)--Florida Atlantic University, 2019. / FAU Electronic Theses and Dissertations Collection