Elasticity in Physically Cross-Linked Amyloid Fibril Networks

Cao, Yiping; Bolisetty, Sreenath; Adamčík, Jozef; Mezzenga, Raffaele

doi:10.1103/physrevlett.120.158103

Cited by 48 publications

(57 citation statements)

References 44 publications

(82 reference statements)

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“…The shear storage modulus (G′) exhibited a scaling power law as a function of peptide concentration (G′ vs C gc ) with a power law index of 3.2 (Figure 1d), allowing us to tune the storage modulus ≈25-fold over a narrow range of peptide concentration. We note that this power law index is significantly higher than the "universal" scaling law determined for protein-based semiflexible networks [22][23][24] where G′ scales as C 11/5 or for cross-linked gels that exhibit a G′ ∝ C 2.5 scaling law. [25] Instead, this behavior is well captured by the fractal gel model, ′ ∝ (…”

Section: Rheology Characterizationmentioning

confidence: 69%

A Short Peptide Hydrogel with High Stiffness Induced by 3₁₀‐Helices to β‐Sheet Transition in Water

et al. 2019

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Biological gels generally require polymeric chains that produce long‐lived physical entanglements. Low molecular weight colloids offer an alternative to macromolecular gels, but often require ad‐hoc synthetic procedures. Here, a short biomimetic peptide composed of eight amino acid residues derived from squid sucker ring teeth proteins is demonstrated to form hydrogel in water without any cross‐linking agent or chemical modification and exhibits a stiffness on par with the stiffest peptide hydrogels. Combining solution and solid‐state NMR, circular dichroism, infrared spectroscopy, and X‐ray scattering, the peptide is shown to form a supramolecular, semiflexible gel assembled from unusual right‐handed 310‐helices stabilized in solution by π–π stacking. During gelation, the 310‐helices undergo conformational transition into antiparallel β‐sheets with formation of new interpeptide hydrophobic interactions, and molecular dynamic simulations corroborate stabilization by cross β‐sheet oligomerization. The current study broadens the range of secondary structures available to create supramolecular hydrogels, and introduces 310‐helices as transient building blocks for gelation via a 310‐to‐β‐sheet conformational transition.

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Section: Rheology Characterizationmentioning

confidence: 69%

A Short Peptide Hydrogel with High Stiffness Induced by 3₁₀‐Helices to β‐Sheet Transition in Water

et al. 2019

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“…There are many electromagnetic techniques proposed in literature to test the Kerr hypothesis (Torres 2002;Bambi, & Freese 2009;Stuchlík, & Kotrlová 2009;Bambi et al 2009b;Schee, & Stuchlík 2009;Bambi, & Barausse 2011;Bambi 2012;Johannsen, & Psaltis 2013;Broderick et al 2014;Li, & Bambi 2014). Among all these methods, X-ray reflection spectroscopy seems to be the most promising for the present and near future, and surely the only one with observational constraints already published (Cao et al 2018;Xu et al 2018;Tripathi et al 2019a,b,c;). In the disk-corona model, thermal photons from the disk can inverse Compton scatter off free electrons in the so-called corona, which is some hot material (∼ 100 keV) in the strong gravity region.…”

Section: Introductionmentioning

confidence: 99%

Tests of the Kerr Hypothesis with GRS 1915+105 Using Different relxill Flavors

Zhang

Abdikamalov

Ayzenberg

et al. 2019

ApJ

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In a previous paper, we tried to test the Kerr nature of the stellar-mass black hole in GRS 1915+105 by analyzing NuSTAR data of 2012 with our reflection model relxill nk. We found that the choice of the intensity profile of the reflection component is crucial and eventually we were not able to get any constraint on the spacetime metric around the black hole in GRS 1915+105. In the present paper, we study the same source with Suzaku data of 2007. We confirm that the intensity profile plays an important role, but now we find quite stringent constraints consistent with the Kerr hypothesis. The key differences with respect to our previous study are likely the lower disk temperature in the Suzaku observation and the higher energy resolution near the iron line of the Suzaku data. We also apply different relxill flavors (different descriptions of the coronal spectrum and variable disk electron density) obtaining essentially the same results. We thus conclude that this choice is not very important for our tests of the Kerr hypothesis while the intensity profile does play an important role, and that with high quality data it is possible to measure both the spacetime metric and the intensity profile.

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“…The latter is characterized by some narrow fluorescent emission lines in the soft X-ray band, in particular the iron Kα complex at 6.4 to 6.97 keV depending on the ionization of iron atoms, and by the Compton hump peaked at 20-30 keV. In the presence of high quality data and with the correct astrophysical model, X-ray reflection spectroscopy can be quite a powerful tool to study the strong gravity region of black holes (Brenneman 2013;Reynolds 2014) and even to test Einstein's theory of general relativity (Bambi 2013;Cao et al 2018;Abdikamalov et al 2019b).…”

Section: Introductionmentioning

confidence: 99%

Reflection spectra of thick accretion discs

Riaz

Ayzenberg

Bambi

et al. 2019

Monthly Notices of the Royal Astronomical Society

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Relativistic reflection features are commonly observed in the X-ray spectra of stellarmass and supermassive black holes and originate from illumination of the inner part of the accretion disk by a hot corona. All the available relativistic reflection models assume that the disk is infinitesimally thin and the inner edge is at the innermost stable circular orbit or at a larger radius. However, we know that several sources, especially among supermassive black holes, have quite high mass accretion rates. In such a case, the accretion disk becomes geometrically thick and the inner edge of the disk is expected to be inside the innermost stable circular orbit. In this work, we employ the Polish donut model to describe geometrically thick disks and we study the iron line shapes from similar systems. We also simulate full reflection spectra and we analyze the simulated observations with a thin disk relativistic reflection model to determine the impact of the disk structure on the estimation of the model parameters, in particular in the case of tests of the Kerr hypothesis.

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Elasticity in Physically Cross-Linked Amyloid Fibril Networks

Cited by 48 publications

References 44 publications

A Short Peptide Hydrogel with High Stiffness Induced by 3₁₀‐Helices to β‐Sheet Transition in Water

A Short Peptide Hydrogel with High Stiffness Induced by 3₁₀‐Helices to β‐Sheet Transition in Water

Tests of the Kerr Hypothesis with GRS 1915+105 Using Different relxill Flavors

Reflection spectra of thick accretion discs

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Elasticity in Physically Cross-Linked Amyloid Fibril Networks

Cited by 48 publications

References 44 publications

A Short Peptide Hydrogel with High Stiffness Induced by 310‐Helices to β‐Sheet Transition in Water

A Short Peptide Hydrogel with High Stiffness Induced by 310‐Helices to β‐Sheet Transition in Water

Tests of the Kerr Hypothesis with GRS 1915+105 Using Different relxill Flavors

Reflection spectra of thick accretion discs

Contact Info

Product

Resources

About

A Short Peptide Hydrogel with High Stiffness Induced by 3₁₀‐Helices to β‐Sheet Transition in Water

A Short Peptide Hydrogel with High Stiffness Induced by 3₁₀‐Helices to β‐Sheet Transition in Water