scholarly journals Exploration of insulin amyloid polymorphism using Raman spectroscopy and imaging

2019 ◽  
Author(s):  
M. Ishigaki ◽  
K. Morimoto ◽  
E. Chatani ◽  
Y. Ozaki
Keyword(s):  
Disulfide Bond ◽  
Amyloid Fibrils ◽  
Amyloid Fibril ◽  
Relative Proportion ◽  
Raman Imaging ◽  
Hydroxyl Groups ◽  
Structural Differences ◽  
Α Helix ◽  
Β Sheet

AbstractWe aimed to investigate insulin amyloid fibril polymorphism caused by salt effects and heating temperature, and to visualize the structural differences of the polymorphisms in situ using Raman imaging without labeling. The time course monitoring for amyloid formation was carried out in an acidic condition without any salts and with two species of salts (NaCl and Na2SO4) by heating at 60, 70, 80, and 90 ℃. The intensity ratio of two Raman bands at 1672 and 1657 cm-1 due to β-sheet and α-helix structures was revealed to be an indicator of amyloid fibril formation, and the relative proportion of the β-sheet structure was higher in the case with salts, especially at a higher temperature and with Na2SO4. In conjunction with the secondary structural changes of proteins, the S-S stretching vibrational mode of a disulfide bond (∼514 cm-1) and the ratio of the tyrosine doublet R(I850⁄I826) were also found to be markers distinguishing polymorphisms of insulin amyloid fibrils by principal component analysis (PCA). Especially, amyloid fibrils with Na2SO4 media formed the g-g-g conformation of disulfide bond at a higher rate and without any salts; on the contrary, the g-g-g conformation was partially transformed into the g-g-t conformation at higher temperatures. The different environments of the hydroxyl groups of the tyrosine residue were assumed to be caused by fibril polymorphism. Raman imaging using these marker bands also successfully visualized the two- and three-dimensional structural differences of amyloid polymorphisms. The present results indicate the potential of Raman imaging as a diagnostic tool for polymorphisms in tissues of amyloid-related diseases.Statement of SignificanceOur results revealed three Raman markers distinguishing amyloid fibril polymorphisms caused by salt and temperature effects; the relative proportion of protein secondary structures (α–helix and β-sheet), the ratio of tyrosine doublet, and the conformational differences of disulfide bonds. The lower values of tyrosine doublet in the case with salts were interpreted as the anions rob the hydration water from proteins which induced protein misfolding. Using these parameters, Raman images captured their higher order structural differences in situ without labeling. The images of hydrogen bonds strength variations due to tyrosine doublet is believed to include significant novelty. The present results imply the potential of Raman imaging for use as a diagnostic imaging tool for tissues with amyloid-induced diseases.

scholarly journals FTIR reveals structural differences between native β-sheet proteins and amyloid fibrils

2009 ◽  
Vol 13 (12) ◽  
pp. 3314-3321 ◽  
Author(s):  
Giorgia Zandomeneghi ◽  
Mark R.H. Krebs ◽  
Margaret G. McCammon ◽  
Marcus Fändrich
Keyword(s):  
Amyloid Fibrils ◽  
Structural Differences ◽  
Β Sheet

scholarly journals Prion Interaction with Normal Protein in Topological Changing Secondary Structure to Aggregation

2020 ◽  
Vol 9 (2) ◽  
pp. 53
Author(s):  
Yao Yao
Keyword(s):  
Hydrogen Bond ◽  
Secondary Structure ◽  
Amyloid Fibril ◽  
Double Helix ◽  
Β Amyloid ◽  
Structural Analogy ◽  
Β Sheets ◽  
Α Helix ◽  
Dna Double Helix ◽  
Β Sheet

<p>Prion is a protein smaller than virus and it infects host in the absence of nucleic acid. The secondary structure of protein folds incorrectly from α-helices to β-sheets through breaking and re-formation of hydrogen bond. Structural analogy of α-helix and DNA double helix and comparing differences between α-helix and β-sheet show prion's infectivity and propagation. Aggregates of dimers and polymers generate β-amyloid fibril in Alzheimer's disease.</p>

Enhanced mechanical performance of biocompatible silk fibroin films through mesoscopic construction of hierarchical structures

2020 ◽  
pp. 004051752097562
Author(s):  
Yifan Zhang ◽  
Ronghui Wu ◽  
Aniruddha Patil ◽  
Liyun Ma ◽  
Rui Yu ◽  
...  
Keyword(s):  
Silk Fibroin ◽  
Mechanical Performance ◽  
Hierarchical Structures ◽  
Rheological Measurement ◽  
Mesoscopic Structure ◽  
Flexible Protein ◽  
Α Helix ◽  
Β Sheet ◽  
Structure Properties

Silk fibroin (SF) material receives a great deal of attention in the biomedical field for its extensive mechanical performance and applications due to its singular structure/properties and applications, especially hierarchical structure. Here, we blended polyethylene glycol (PEG) into SF solutions that reconstruct the hierarchical micro structure of SF. The effect of PEG on the SF gelation process was in situ observed through rheological measurement and optical density changes. The structural change of SF/PEG blended films with different concentrations and their effects on the mechanical performance were investigated. The results indicated that with increasing PEG content, the β-sheet content of the films increased with the α-helix declining, which enables a composite film with a fracture strain exceeding 300%, Young's modulus exceeding 200 MPa and a fracture strength exceeding 20 MPa. The culture of MC-3T3 proves that the film is beneficial for cell proliferation and adhesion. By constructing the mesoscopic structure of SF, the plasticized silk materials provide great options for biodegradable and flexible protein-based materials.

scholarly journals Nanostructure and stability of calcitonin amyloids

2017 ◽  
Vol 292 (18) ◽  
pp. 7348-7357 ◽  
Author(s):  
Federica Rigoldi ◽  
Pierangelo Metrangolo ◽  
Alberto Redaelli ◽  
Alfonso Gautieri
Keyword(s):  
Amyloid Fibrils ◽  
Md Simulations ◽  
Full Length ◽  
Structural Basis ◽  
Human Calcitonin ◽  
Nmr Data ◽  
Parallel Arrangement ◽  
Β Sheets ◽  
Α Helix ◽  
Β Sheet

Calcitonin is a 32-amino acid thyroid hormone that can form amyloid fibrils. The structural basis of the fibril formation and stabilization is still debated and poorly understood. The reason is that NMR data strongly suggest antiparallel β-sheet calcitonin assembly, whereas modeling studies on the short DFNKF peptide (corresponding to the sequence from Asp15 to Phe19 of human calcitonin and reported as the minimal amyloidogenic module) show that it assembles with parallel β-sheets. In this work, we first predict the structure of human calcitonin through two complementary molecular dynamics (MD) methods, finding that human calcitonin forms an α-helix. We use extensive MD simulations to compare previously proposed calcitonin fibril structures. We find that two conformations, the parallel arrangement and one of the possible antiparallel structures (with Asp15 and Phe19 aligned), are highly stable and ordered. Nonetheless, fibrils with parallel molecules show bulky loops formed by residues 1 to 7 located on the same side, which could limit or prevent the formation of larger amyloids. We investigate fibrils formed by the DFNKF peptide by simulating different arrangements of this amyloidogenic core sequence. We show that DFNKF fibrils are highly stable when assembled in parallel β-sheets, whereas they quickly unfold in antiparallel conformation. Our results indicate that the DFNKF peptide represents only partially the full-length calcitonin behavior. Contrary to the full-length polypeptide, in fact, the DFNKF sequence is not stable in antiparallel conformation, suggesting that the residue flanking the amyloidogenic peptide contributes to the stabilization of the experimentally observed antiparallel β-sheet packing.

scholarly journals The growth of amyloid fibrils: rates and mechanisms

2019 ◽  
Vol 476 (19) ◽  
pp. 2677-2703 ◽  
Author(s):  
Alexander K. Buell
Keyword(s):  
Amyloid Fibrils ◽  
Amyloid Fibril ◽  
Experimental Studies ◽  
Amyloid Protein ◽  
Protein Polymers ◽  
Human Disorders ◽  
Functional Context ◽  
Basic Ideas ◽  
Β Sheet

Abstract Amyloid fibrils are β-sheet-rich linear protein polymers that can be formed by a large variety of different proteins. These assemblies have received much interest in recent decades, due to their role in a range of human disorders. However, amyloid fibrils are also found in a functional context, whereby their structural, mechanical and thermodynamic properties are exploited by biological systems. Amyloid fibrils form through a nucleated polymerisation mechanism with secondary processes acting in many cases to amplify the number of fibrils. The filamentous nature of amyloid fibrils implies that the fibril growth rate is, by several orders of magnitude, the fastest step of the overall aggregation reaction. This article focusses specifically on in vitro experimental studies of the process of amyloid fibril growth, or elongation, and summarises the state of knowledge of its kinetics and mechanisms. This work attempts to provide the most comprehensive summary, to date, of the available experimental data on amyloid fibril elongation rate constants and the temperature and concentration dependence of amyloid fibril elongation rates. These data are compared with those from other types of protein polymers. This comparison with data from other polymerising proteins is interesting and relevant because many of the basic ideas and concepts discussed here were first introduced for non-amyloid protein polymers, most notably by the Japanese school of Oosawa and co-workers for cytoskeletal filaments.

scholarly journals Cofactors are essential constituents of stable and seeding-active tau fibrils

2018 ◽  
Vol 115 (52) ◽  
pp. 13234-13239 ◽  
Author(s):  
Yann Fichou ◽  
Yanxian Lin ◽  
Jennifer N. Rauch ◽  
Michael Vigers ◽  
Zhikai Zeng ◽  
...  
Keyword(s):  
Room Temperature ◽  
Amyloid Fibrils ◽  
Amyloid Fibril ◽  
Future Studies ◽  
Biophysical Studies ◽  
Stable Forms ◽  
Β Sheet ◽  
Tau Fibrils

Amyloid fibrils are cross-β–rich aggregates that are exceptionally stable forms of protein assembly. Accumulation of tau amyloid fibrils is involved in many neurodegenerative diseases, including Alzheimer’s disease (AD). Heparin-induced aggregates have been widely used and assumed to be a good tau amyloid fibril model for most biophysical studies. Here we show that mature fibrils made of 4R tau variants, prepared with heparin or RNA, spontaneously depolymerize and release monomers when their cofactors are removed. We demonstrate that the cross-β-sheet assembly formed in vitro with polyanion addition is unstable at room temperature. We furthermore demonstrate high seeding capacity with transgenic AD mouse brain-extracted tau fibrils in vitro that, however, is exhausted after one generation, while supplementation with RNA cofactors resulted in sustained seeding over multiple generations. We suggest that tau fibrils formed in brains are supported by unknown cofactors and inhere higher-quality packing, as reflected in a more distinct conformational arrangement in the mouse fibril-seeded, compared with heparin-induced, tau fibrils. Our study suggests that the role of cofactors in tauopathies is a worthy focus of future studies, as they may be viable targets for diagnosis and therapeutics.

Scorpion toxin-potassium channel interaction law and its applications.

2020 ◽  
Vol 01 ◽  
Author(s):  
Zheng Zuo ◽  
Zongyun Chen ◽  
Zhijian Cao ◽  
Wenxin Li ◽  
Yingliang Wu
Keyword(s):  
Potassium Channel ◽  
Scorpion Toxin ◽  
Scorpion Toxins ◽  
Toxin Binding ◽  
Channel Interaction ◽  
Binding Interface ◽  
Α Helix ◽  
Interaction Law ◽  
Binding Interfaces ◽  
Β Sheet

: The scorpion toxins are the largest potassium channel-blocking peptide family. The understanding of toxin binding interfaces is usually restricted by two classical binding interfaces: one is the toxin α-helix motif, the other is the antiparallel β-sheet motif. In this review, such traditional knowledge was updated by another two different binding interfaces: one is BmKTX toxin using the turn motif between the α-helix and antiparallel β-sheet domains as the binding interface, the other is Ts toxin using turn motif between the β-sheet in the N-terminal and α-helix domains as the binding interface. Their interaction analysis indicated that the scarce negatively charged residues in the scorpion toxins played a critical role in orientating the toxin binding interface. In view of the toxin negatively charged amino acids as “binding interface regulator”, the law of scorpion toxin-potassium channel interaction was proposed, that is, the polymorphism of negatively charged residue distribution determines the diversity of toxin binding interfaces. Such law was used to develop scorpion toxin-potassium channel recognition control technique. According to this technique, three Kv1.3 channel-targeted peptides, using BmKTX as the template, were designed with the distinct binding interfaces from that of BmKTX through modulating the distribution of toxin negatively charged residues. In view of the potassium channel as the common targets of different animal toxins, the proposed law was also shown to helpfully orientate the binding interfaces of other animal toxins. Clearly, the toxin-potassium channel interaction law would strongly accelerate the research and development of different potassium channelblocking animal toxins in the future.

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