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359 results on '"Chiti, F."'

1. Low redshift constraints on energy-momentum-powered gravity models

Author

Faria, M. C. F., Martins, C. J. A. P., Chiti, F., and Silva, B. S. A.

Subjects
Astrophysics - Cosmology and Nongalactic Astrophysics, General Relativity and Quantum Cosmology, High Energy Physics - Phenomenology, High Energy Physics - Theory
Abstract

There has been recent interest in the cosmological consequences of energy-momentum-powered gravity models, in which the matter side of Einstein's equations is modified by the addition of a term proportional to some power, $n$, of the energy-momentum tensor, in addition to the canonical linear term. In this work we treat these models as phenomenological extensions of the standard $\Lambda$CDM, containing both matter and a cosmological constant. We also quantitatively constrain the additional model parameters using low redshift background cosmology data that are specifically from Type Ia supernovas and Hubble parameter measurements. We start by studying specific cases of these models with fixed values of $n,$ which lead to an analytic expression for the Friedmann equation; we discuss both their current constraints and how the models may be further constrained by future observations of Type Ia supernovas for WFIRST complemented by measurements of the redshift drift by the ELT. We then consider and constrain a more extended parameter space, allowing $n$ to be a free parameter and considering scenarios with and without a cosmological constant. These models do not solve the cosmological constant problem per se. Nonetheless these models can phenomenologically lead to a recent accelerating universe without a cosmological constant at the cost of having a preferred matter density of around $\Omega_M\sim0.4$ instead of the usual $\Omega_M\sim0.3$. Finally we also briefly constrain scenarios without a cosmological constant, where the single component has a constant equation of state which needs not be that of matter; we provide an illustrative comparison of this model with a more standard dynamical dark energy model with a constant equation of state., Comment: 13+2 pages, 12+1 figures; A&A (in press)

Published
2019
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4. Structural differences between toxic and nontoxic HypF-N oligomers

Author

Capitini, C, Patel, J, Natalello, A, D'Andrea, C, Relini, A, Jarvis, J, Birolo, L, Peduzzo, A, Vendruscolo, M, Matteini, P, Dobson, C, De Simone, A, Chiti, F, Capitini C., Patel J. R., Natalello A., D'Andrea C., Relini A., Jarvis J. A., Birolo L., Peduzzo A., Vendruscolo M., Matteini P., Dobson C. M., De Simone A., Chiti F., Capitini, C, Patel, J, Natalello, A, D'Andrea, C, Relini, A, Jarvis, J, Birolo, L, Peduzzo, A, Vendruscolo, M, Matteini, P, Dobson, C, De Simone, A, Chiti, F, Capitini C., Patel J. R., Natalello A., D'Andrea C., Relini A., Jarvis J. A., Birolo L., Peduzzo A., Vendruscolo M., Matteini P., Dobson C. M., De Simone A., and Chiti F.

Abstract

We have studied two misfolded oligomeric forms of the protein HypF-N, which show similar morphologies but very different toxicities. We measured over 80 intermolecular distance-dependent parameters for each oligomer type using FRET, in conjunction with solution- and solid-state NMR and other biophysical techniques. The results indicate that the formation of a highly organised hydrogen bonded core in the toxic oligomers results in the exposure of a larger number of hydrophobic residues than in the nontoxic species, causing the former to form aberrant interactions with cellular components.

Published
2018

20. The induction of α-helical structure in partially unfolded HypF-N does not affect its aggregation propensity

Author

Ahmad, B., Vigliotta, I., Tatini, F., Campioni, S., Mannini, B., Winkelmann, J., Tiribilli, B., and Chiti, F.

Abstract

The conversion of proteins into structured fibrillar aggregates is a central problem in protein chemistry, biotechnology, biology and medicine. It is generally accepted that aggregation takes place from partially structured states of proteins. However, the role of the residual structure present in such conformational states is not yet understood. In particular, it is not yet clear as to whether the α-helical structure represents a productive or counteracting structural element for protein aggregation. We have addressed this issue by studying the aggregation of pH-unfolded HypF-N. It has previously been shown that the two native α-helices of HypF-N retain a partial α-helical structure in the pH-unfolded state and that these regions are also involved in the formation of the cross-β structure of the aggregates. We have introduced mutations in such stretches of the sequence, with the aim of increasing the α-helical structure in the key regions of the pH-unfolded state, while minimizing the changes of other factors known to influence protein aggregation, such as hydrophobicity, β-Sheet propensity, etc. The resulting HypF-N mutants have higher contents of α-helical structure at the site(s) of mutation in their pH-unfolded states, but such an increase does not correlate with a change of aggregation rate. The results suggest that stabilisation of α-helical structure in amyloidogenic regions of the sequence of highly dynamic states does not have remarkable effects on the rate of protein aggregation from such conformational states. Comparison with other protein systems indicate that the effect of increasing α-helical propensity can vary if the stabilised helices are in non-amyloidogenic stretches of initially unstructured peptides (accelerating effect), in amyloidogenic stretches of initially unstructured peptides (no effect) or in amyloidogenic stretches of initially stable helices (decelerating effect)

Published
2017

23. The polyphenol Oleuropein aglycone hinders the growth of toxic transthyretin amyloid assemblies

Author

Leri, M, Nosi, D, Natalello, A, Porcari, R, Ramazzotti, M, Chiti, F, Bellotti, V, Doglia, S, Stefani, M, Bucciantini, M, NATALELLO, ANTONINO, DOGLIA, SILVIA MARIA, Bucciantini, M., Leri, M, Nosi, D, Natalello, A, Porcari, R, Ramazzotti, M, Chiti, F, Bellotti, V, Doglia, S, Stefani, M, Bucciantini, M, NATALELLO, ANTONINO, DOGLIA, SILVIA MARIA, and Bucciantini, M.

Abstract

Transthyretin (TTR) is involved in a subset of familial or sporadic amyloid diseases including senile systemic amyloidosis (SSA), familial amyloid polyneuropathy and cardiomyopathy (FAP/FAC) for which no effective therapy has been found yet. These conditions are characterized by extracellular deposits primarily found in the heart parenchyma and in peripheral nerves whose main component are amyloid fibrils, presently considered the main culprits of cell sufferance. The latter are polymeric assemblies grown from misfolded TTR, either wt or carrying one out of many identified mutations. The recent introduction in the clinical practice of synthetic TTR-stabilizing molecules that reduce protein aggregation provides the rationale to search natural effective molecules able to interfere with TTR amyloid aggregation by hindering the appearance of toxic species or by favoring the growth of harmless aggregates. Here we carried out an in depth biophysical and morphological study on the molecular features of the aggregation of wt- and L55P-TTR involved in SSA or FAP/FAC, respectively, and on the interference with fibril aggregation, stability and toxicity to cardiac HL-1 cells to demonstrate the ability of Oleuropein aglycone (OleA), the main phenolic component of the extra virgin olive oil. We describe the molecular basis of such interference and the resulting reduction of TTR amyloid aggregate cytotoxicity. Our data offer the possibility to validate and optimize the use of OleA or its molecular scaffold to rationally design promising drugs against TTR-related pathologies that could enter a clinical experimental phase.

Published
2016

24. Context-Awareness in Autonomic Communication and in Accessing Web Information: Issues and Challenges

Author

Chiti, F, Fantacci, R, Pasi, G, Tisato, F, Chiti, F, Fantacci, R, Pasi, G, and Tisato, F

Abstract

In recent years, after the proposal of the Internet of Things and, later, of the Web of Things, context awareness is a central issue at various levels including devices, communications and applications. In this chapter we present an overview of the current state of research in autonomic communications by focusing on aspects of context awareness on which the emerging new paradigm of Context-Aware Autonomic Communication systems is based. As an example of application we also provide a synthetic analysis of the problem of contextual search and of the issues related to defining contextual search systems.

Published
2016

25. Integrated communications framework for context aware continuous monitoring with body sensor networks

Author

Chiti, F, Fantacci, F, Toscani, D., ARCHETTI, FRANCESCO ANTONIO, MESSINA, VINCENZINA, Chiti, F, Fantacci, F, Archetti, F, Messina, V, and Toscani, D

Subjects
body sensor networks, INF/01 - INFORMATICA
Abstract

This paper deals with a wireless pervasive communication system to support advanced healthcare applications. The proposed system is based on an ad hoc interaction of mobile body sensor networks with independent wireless sensor networks already deployed within the environments in order to allow a continuous and context aware health monitoring for patients along their daily life scenarios with an unprecedented precision and flexibility of sensing. After an accurate protocol characterization, simulation results are provided, underlining remarkable performance with respect to existing solutions, for different mobility models and node density values. © 2006 IEEE.

Published
2009

26. Structure, folding dynamics, and amyloidogenesis of D76N β2-microglobulin: roles of shear flow, hydrophobic surfaces, and α-crystallin

Author

Mangione, P. P., Esposito, Gennaro, Relini, A., Raimondi, S., Porcari, R., Giorgetti, S., Corazza, Alessandra, Fogolari, Federico, Penco, A., Goto, Y., Lee, Y. H., Yagi, H., Cecconi, C., Naqvi, M. M., Gillmore, J. D., Hawkins, P. N., Chiti, F., Rolandi, R., Taylor, G. W., Pepys, M. B., Stoppini, M., and Bellotti, V.

Subjects
Amyloid, Protein Structure, Protein Folding, Protein Stability, Chaperones, D76N β2-Microglobulin, Protein Aggregation, Protein Misfolding, Shear Stress, Systemic Amyloidosis, Amino Acid Substitution, Amyloidosis, Familial, Humans, Protein Structure, Quaternary, alpha-Crystallins, beta 2-Microglobulin, Mutation, Missense, Biochemistry, Molecular Biology, Cell Biology, Amyloidosis, Quaternary, Familial, Mutation, Missense
Published
2013

37. Chaperones suppress the toxicity of aberrant protein aggregates. Molecular insight into the mechanism of action

Author

Mannini, B, Campioni, S, Boninsegna, M, Penco, A, Cascella, R, Zampagni, M, Wilson, M, Meehan, S, Roodveldt, C, Dobson, C, Relini, A, Cecchi, C, Chiti, F, Mannini, B, Campioni, S, Boninsegna, M, Penco, A, Cascella, R, Zampagni, M, Wilson, M, Meehan, S, Roodveldt, C, Dobson, C, Relini, A, Cecchi, C, and Chiti, F

Abstract

of poster presentations presented at 22nd IUBMB & 37th FEBS Congress, Seville, Spain, September 4-9, 2012.

Published
2012

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