0000000000501309
AUTHOR
Chiara Caronna
showing 7 related works from this author
The protein dynamical transition does not require the protein polypeptide chain
2011
We give experimental evidence that the main features of protein dynamics revealed by neutron scattering, i.e., the “protein dynamical transition” and the “boson peak”, do not need the protein polypeptide chain. We show that a rapid increase of hydrogen atoms fluctuations at about 220 K, analogous to the one observed in hydrated myoglobin powders, is also observed in a hydrated amino acids mixture with the chemical composition of myoglobin but lacking the polypeptide chain; in agreement with the protein behavior, the transition is abolished in the dry mixture. Further, an excess of low-frequency vibrational modes around 3 meV, typically observed in protein powders, is also observed in our mi…
Direct Evidence of the Amino Acid Side Chain and Backbone Contributions to Protein Anharmonicity
2010
Elastic incoherent neutron scattering has been used to study the temperature dependence of the mean-square displacements of nonexchangeable hydrogen atoms in powders of a series of homomeric polypeptides (polyglycine, polyalanine, polyphenylalanine and polyisoleucine) in comparison with myoglobin at the same hydration level (h = 0.2). The aim of the work was to measure the dynamic behavior of different amino acid residues separately and assess the contribution of each type of side chain to the anharmonic dynamics of proteins. The results provide direct experimental evidence that the first anharmonic activation, at approximately 150 K, is largely due to methyl group rotations entering the ti…
Incoherent elastic and quasi-elastic neutron scattering investigation of hemoglobin dynamics.
2005
In this work we investigate the dynamic properties of hemoglobin in glycerolD(8)/D(2)O solution using incoherent elastic (ENS) and quasi-elastic (QENS) neutron scattering. Taking advantage of complementary energy resolutions of backscattering spectrometers at ILL (Grenoble), we explore motions in a large space-time window, up to 1 ns and 14 A; moreover, in order to cover the harmonic and anharmonic protein dynamics regimes, the elastic experiments have been performed over the wide temperature interval of 20-300 K. To study the dependence of the measured dynamics upon the protein quaternary structure, both deoxyhemoglobin (in T quaternary conformation) and carbonmonoxyhemoglobin (in R quater…
Dynamics of myoglobin in confinement: An elastic and quasi-elastic neutron scattering study
2008
In order to clarify the role of hard confinement on protein dynamics, elastic and quasi-elastic neutron scattering experiments have been performed on ferric horse myoglobin in two different systems: the protein embedded in a porous silica matrix, and the corresponding hydrated protein powder. Elastic data have been analysed using two different models (dynamical heterogeneity and anharmonic double-well potential) that take into account deviations of elastic intensity from Gaussian behaviour. The profile of quasi-elastic spectra has been approximated by a combination of Lorentzian and Gaussian components. Comparison between the data relative to the two different samples indicates that geometr…
Molecular origin and hydration dependence of protein anharmonicity: an elastic neutron scattering study.
2010
Two main onsets of anharmonicity are present in protein dynamics. Neutron scattering on protein hydrated powders revealed a first onset at about 150 K and a second one at about 230 K (the so called dynamical transition). In order to assess the molecular origin of protein anharmonicity, we study different homomeric polypeptides by incoherent elastic neutron scattering, thus disentangling the contribution of different molecular groups in proteins. We show that methyl group rotations are the main contributors to the low temperature onset. Concerning the dynamical transition, we show that it also occurs in absence of side chains; however, the presence and mobility of side chains substantially i…
A benchmark for protein dynamics: Ribonuclease A measured by neutron scattering in a large wavevector-energy transfer range
2008
The dynamics of Ribonuclease A was explored in the full range of time and length-scales accessible by neutron spectroscopy, on time-of-flight, backscattering and spin-echo spectrometers. Samples were examined in dry and hydrated powder forms and in concentrated and dilute solutions. The aim of the study was an experimental characterisation of the full variety of protein dynamics arising from stabilisation forces. The results provide a benchmark against which other sample dynamics can be compared.
Dynamics of nanoparticles in a supercooled liquid
2008
The dynamic properties of nanoparticles suspended in a supercooled glass forming liquid are studied by x-ray photon correlation spectroscopy. While at high temperatures the particles undergo Brownian motion the measurements closer to the glass transition indicate hyperdiffusive behavior. In this state the dynamics is independent of the local structural arrangement of nanoparticles, suggesting a cooperative behavior governed by the near-vitreous solvent.