scholarly journals Valorization of Apple Peels through the Study of the Effects on the Amyloid Aggregation Process of κ-Casein

Molecules ◽  
2021 ◽  
Vol 26 (8) ◽  
pp. 2371
Author(s):  
Valeria Guarrasi ◽  
Giacoma Cinzia Rappa ◽  
Maria Assunta Costa ◽  
Fabio Librizzi ◽  
Marco Raimondo ◽  
...  
Keyword(s):  
Protein Aggregation ◽  
Environmental Sustainability ◽  
Bovine Milk ◽  
Amyloid Formation ◽  
Aggregation Process ◽  
Amyloid Aggregation ◽  
Social Challenges ◽  
Force Microscopy ◽  
Atomic Force ◽  
Apple Peels

Waste valorization represents one of the main social challenges when promoting a circular economy and environmental sustainability. Here, we evaluated the effect of the polyphenols extracted from apple peels, normally disposed of as waste, on the amyloid aggregation process of κ-casein from bovine milk, a well-used amyloidogenic model system. The effect of the apple peel extract on protein aggregation was examined using a thioflavin T fluorescence assay, Congo red binding assay, circular dichroism, light scattering, and atomic force microscopy. We found that the phenolic extract from the peel of apples of the cultivar “Fuji”, cultivated in Sicily (Caltavuturo, Italy), inhibited κ-casein fibril formation in a dose-dependent way. In particular, we found that the extract significantly reduced the protein aggregation rate and inhibited the secondary structure reorganization that accompanies κ-casein amyloid formation. Protein-aggregated species resulting from the incubation of κ-casein in the presence of polyphenols under amyloid aggregation conditions were reduced in number and different in morphology.

Effect of curcumin on amyloidogenic property of molten globule-like intermediate state of 2,5-diketo-d-gluconate reductase A

2009 ◽  
Vol 390 (10) ◽  
Author(s):  
Nandini Sarkar ◽  
Abhay Narain Singh ◽  
Vikash Kumar Dubey
Keyword(s):  
Protein Concentration ◽  
Molten Globule ◽  
Molar Ratio ◽  
Amyloid Formation ◽  
Molten Globule State ◽  
Force Microscopy ◽  
Atomic Force ◽  
Sheet Structure ◽  
Amyloid Diseases ◽  
Β Sheet

Abstract We identified a molten globule-like intermediate of 2,5-diketo-d-gluconate reductase A (DKGR) at pH 2.5, which has a prominent β-sheet structure. The molten globule state of the protein shows amyloidogenic property >50 μm protein concentration. Interestingly, a 1:1 molar ratio of curcumin prevents amyloid formation as shown by the Thioflavin-T assay and atomic force microscopy. To the best of our knowledge, this is the first report on amyloid formation by an (α/β)8-barrel protein. The results presented here indicate that the molten globule state has an important role in amyloid formation and potential application of curcumin in protein biotechnology as well as therapeutics against amyloid diseases.

scholarly journals Effects of the Toxic Metals Arsenite and Cadmium on α-Synuclein Aggregation In Vitro and in Cells

2021 ◽  
Vol 22 (21) ◽  
pp. 11455
Author(s):  
Emma Lorentzon ◽  
Istvan Horvath ◽  
Ranjeet Kumar ◽  
Joana Isabel Rodrigues ◽  
Markus J. Tamás ◽  
...  
Keyword(s):  
Parkinson’S Disease ◽  
Parkinson's Disease ◽  
Yeast Cells ◽  
Amyloid Formation ◽  
Amyloid Fibers ◽  
Force Microscopy ◽  
Atomic Force ◽  
In Vitro Characterization ◽  
Underlying Mechanisms

Exposure to heavy metals, including arsenic and cadmium, is associated with neurodegenerative disorders such as Parkinson’s disease. However, the mechanistic details of how these metals contribute to pathogenesis are not well understood. To search for underlying mechanisms involving α-synuclein, the protein that forms amyloids in Parkinson’s disease, we here assessed the effects of arsenic and cadmium on α-synuclein amyloid formation in vitro and in Saccharomyces cerevisiae (budding yeast) cells. Atomic force microscopy experiments with acetylated human α-synuclein demonstrated that amyloid fibers formed in the presence of the metals have a different fiber pitch compared to those formed without metals. Both metal ions become incorporated into the amyloid fibers, and cadmium also accelerated the nucleation step in the amyloid formation process, likely via binding to intermediate species. Fluorescence microscopy analyses of yeast cells expressing fluorescently tagged α-synuclein demonstrated that arsenic and cadmium affected the distribution of α-synuclein aggregates within the cells, reduced aggregate clearance, and aggravated α-synuclein toxicity. Taken together, our in vitro data demonstrate that interactions between these two metals and α-synuclein modulate the resulting amyloid fiber structures, which, in turn, might relate to the observed effects in the yeast cells. Whilst our study advances our understanding of how these metals affect α-synuclein biophysics, further in vitro characterization as well as human cell studies are desired to fully appreciate their role in the progression of Parkinson’s disease.

Diffusion Limited Aggregation of PMMA Stereocomplex in Thin Films

2001 ◽  
Vol 710 ◽  
Author(s):  
Yves Grohens ◽  
Gilles Castelein ◽  
Pascal Carriere ◽  
Jiri Spevacek
Keyword(s):  
Aggregation Process ◽  
Diffusion Limited Aggregation ◽  
Force Microscopy ◽  
Cluster Aggregation ◽  
Diffusion Limited ◽  
Atomic Force ◽  
Slow Aggregation ◽  
Nanoscale Patterns ◽  
Surface Nature ◽  
Aggregation Phenomena

ABSTRACTThe nanoscale patterns formed by poly(methyl methacrylate) (PMMA) stereocomplexes at the surface of silicon wafers, glass and mica, were investigated by tapping mode atomic force microscopy (TM-AFM). The effects of the solvent nature, PMMA concentration, i/s-ratio (stoechimetry) and surface nature on the morphology of the stereocomplex thin layer at a surface were addressed. The aggregation phenomena are well described by the diffusion limited cluster-cluster aggregation model (DLA) and the fractal exponent D calculated. The i/s-ratio strongly influences the fractal exponent D which is equal to 1.35 for the 1:2 ratio is lower than for the other i:s ratios which are 1.46, 1.61, 1.82 for 1:1, 2:1 and 4:1 ratios, respectively. The low values of the fractal dimension D are indicative of a fast aggregation process and higher values of D correspond to a slow aggregation process.

scholarly journals Understanding the Role of Protein Glycation in the Amyloid Aggregation Process

2021 ◽  
Vol 22 (12) ◽  
pp. 6609
Author(s):  
Ivana Sirangelo ◽  
Clara Iannuzzi
Keyword(s):  
Protein Structure ◽  
Protein Function ◽  
The Body ◽  
Protein Glycation ◽  
Amyloid Formation ◽  
Aggregation Process ◽  
Amyloid Aggregation ◽  
Post Translational Modification

Protein function and flexibility is directly related to the native distribution of its structural elements and any alteration in protein architecture leads to several abnormalities and accumulation of misfolded proteins. This phenomenon is associated with a range of increasingly common human disorders, including Alzheimer and Parkinson diseases, type II diabetes, and a number of systemic amyloidosis characterized by the accumulation of amyloid aggregates both in the extracellular space of tissues and as intracellular deposits. Post-translational modifications are known to have an active role in the in vivo amyloid aggregation as able to affect protein structure and dynamics. Among them, a key role seems to be played by non-enzymatic glycation, the most unwanted irreversible modification of the protein structure, which strongly affects long-living proteins throughout the body. This study provided an overview of the molecular effects induced by glycation on the amyloid aggregation process of several protein models associated with misfolding diseases. In particular, we analyzed the role of glycation on protein folding, kinetics of amyloid formation, and amyloid cytotoxicity in order to shed light on the role of this post-translational modification in the in vivo amyloid aggregation process.

scholarly journals All-or-none amyloid disassembly via chaperone-triggered fibril unzipping favors clearance of α-synuclein toxic species

2021 ◽  
Vol 118 (36) ◽  
pp. e2105548118
Author(s):  
Aitor Franco ◽  
Pablo Gracia ◽  
Adai Colom ◽  
José D. Camino ◽  
José Ángel Fernández-Higuero ◽  
...  
Keyword(s):  
Neurodegenerative Disorders ◽  
High Speed ◽  
Amyloid Formation ◽  
Kinetic Characterization ◽  
Force Microscopy ◽  
Toxic Species ◽  
Disassembly Process ◽  
Atomic Force ◽  
Selective Processing

α-synuclein aggregation is present in Parkinson’s disease and other neuropathologies. Among the assemblies that populate the amyloid formation process, oligomers and short fibrils are the most cytotoxic. The human Hsc70-based disaggregase system can resolve α-synuclein fibrils, but its ability to target other toxic assemblies has not been studied. Here, we show that this chaperone system preferentially disaggregates toxic oligomers and short fibrils, while its activity against large, less toxic amyloids is severely impaired. Biochemical and kinetic characterization of the disassembly process reveals that this behavior is the result of an all-or-none abrupt solubilization of individual aggregates. High-speed atomic force microscopy explicitly shows that disassembly starts with the destabilization of the tips and rapidly progresses to completion through protofilament unzipping and depolymerization without accumulation of harmful oligomeric intermediates. Our data provide molecular insights into the selective processing of toxic amyloids, which is critical to identify potential therapeutic targets against increasingly prevalent neurodegenerative disorders.

Insights into the mechanism of Alzheimer’s β-amyloid aggregation as a function of concentration by using atomic force microscopy

2012 ◽  
Vol 100 (13) ◽  
pp. 133704 ◽  
Author(s):  
Gina-Mirela Mustata ◽  
Gajendra S. Shekhawat ◽  
Mary P. Lambert ◽  
Kirsten L. Viola ◽  
Pauline T. Velasco ◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
Amyloid Aggregation ◽  
Force Microscopy ◽  
Atomic Force ◽  
Β Amyloid
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