Search results for "Globin"
showing 10 items of 734 documents
Observation of ventilation-induced Spo(2) oscillations in pigs: first step to noninvasive detection of cyclic recruitment of atelectasis?
2010
High arterial partial oxygen pressure (Pao(2)) oscillations within the respiratory cycle were described recently in experimental acute lung injury. This phenomenon has been related to cyclic recruitment of atelectasis and varying pulmonary shunt fractions. Noninvasive detection of Spo(2) (oxygen saturation measured by pulse oximetry) as an indicator of cyclic collapse of atelectasis, instead of recording Pao(2) oscillations, could be of clinical interest in critical care. Spo(2) oscillations were recorded continuously in three different cases of lung damage to demonstrate the technical feasibility of this approach. To deduce Pao(2) from Spo(2), a mathematical model of the hemoglobin dissoci…
2015
AbstractLight absorption can trigger biologically relevant protein conformational changes. The light-induced structural rearrangement at the level of a photoexcited chromophore is known to occur in the femtosecond timescale and is expected to propagate through the protein as a quake-like intramolecular motion. Here we report direct experimental evidence of such ‘proteinquake’ observed in myoglobin through femtosecond X-ray solution scattering measurements performed at the Linac Coherent Light Source X-ray free-electron laser. An ultrafast increase of myoglobin radius of gyration occurs within 1 picosecond and is followed by a delayed protein expansion. As the system approaches equilibrium i…
Inter- and intramolecular motions in proteins
1992
The use of 57 Fe Mossbauer radiation allows the study of protein crystal dynamics by a time-resolved analysis of X-ray scattering. In myoglobin crystals, the main source of the root mean squared amplitude of motions come from intramolecular protein dynamics. Segments of the size of an α-helix move collectively. Long-range correlated motions give only a minor contribution. Comparison with Mossbauer absorption spectroscopy shows that protein-specific dynamics is frozaen out below 200 K and the lattice dynamics in mainly responsible for the low-temperature behavior
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…
Communication: Protein dynamical transition vs. liquid-liquid phase transition in protein hydration water
2013
In this work, we compare experimental data on myoglobin hydrated powders from elastic neutron scattering, broadband dielectric spectroscopy, and differential scanning calorimetry. Our aim is to obtain new insights on the connection between the protein dynamical transition, a fundamental phenomenon observed in proteins whose physical origin is highly debated, and the liquid-liquid phase transition (LLPT) possibly occurring in protein hydration water and related to the existence of a low temperature critical point in supercooled water. Our results provide a consistent thermodynamic/dynamic description which gives experimental support to the LLPT hypothesis and further reveals how fundamental …
Spectral hole burning study of protoporphyrin IX substituted myoglobin.
1992
Protoporphyrin IX substituted myoglobin reveals excellent hole burning properties. We investigated the frequency shift of persistent spectral holes under isotropic pressure conditions in a range from 0 to 2.4 MPa. In this range, the protein behaves like an elastic solid. The shift of the holes under pressure shows a remarkable frequency dependence from which the compressibility of the protein can be determined. The compressibility, in turn, allows for an estimation of the equilibrium volume fluctuations. Within the frame of the model used to interpret the pressure data, it is possible to determine the absorption frequency of the isolated chromophore and the associated solvent shift in the p…
Quaternary relaxations in sol-gel encapsulated hemoglobin studied via NIR and UV spectroscopy.
2007
In this work, we study the kinetics of the R --T transition in hemoglobin using a combination of near-infrared and near-ultraviolet spectroscopy. We use a sol-gel encapsulation protocol to decelerate the conformational transitions and to avoid spectral perturbations arising from ligand migration and recombination. We monitor two spectroscopic markers: band III in the near-IR, which is a fine probe of the heme pocket conformation, and the tryptophan band in the near-UV, which probes the formation of the Trpbeta37-Aspalpha94 hydrogen bond, characteristic of the T structure, at the critical alpha1beta2 subunit interface. The time evolution of these two bands is monitored after deoxygenation of…
Observing myoglobin proteinquake with an X-ray free-electron laser
2015
The events following the photodissociation of the bond be- tween myoglobin and its ligand have been extensively studied with a variety of experimental, theoretical and computational methods [1]. The results of these investigations have been rationalized in terms of a model that implies a protein quake- like motion [2], i.e. the propagation of the strain released upon photoexcitation through the protein similar to the prop- agation of acoustic waves during an earthquake. The exper- imental investigations performed so far have been based on spectroscopic measurements or did not have sufficient time- resolution to measure the timescale of such “proteinquake”. We have obtained direct experiment…