728 research outputs found
Conformational fluctuations and electronic properties in myoglobin
Abstract: In this article we use the recently developed perturbed matrix method (PMM) to investigate the effect of conformational fluctuations on the electronic properties of heme in Myoglobin. This widely studied biomolecule has been chosen as a benchmark for evaluating the accuracy of PMM in a large and complex system. Using a long, 80-ns, molecular dynamics simulation and unperturbed Configuration Interaction (CISD) calculations in PMM, we reproduced the main spectroscopic features of deoxy-Myoglobin. Moreover, in line with our previous results on a photosensitive protein, this study reveals a clear dynamical coupling between electronic properties and conformational fluctuations, suggesting that this correlation could be a general feature of proteins
Relaxation dynamics of a protein solution investigated by dielectric spectroscopy
In the present work, we provide a dielectric study on two differently
concentrated aqueous lysozyme solutions in the frequency range from 1 MHz to 40
GHz and for temperatures from 275 to 330 K. We analyze the three dispersion
regions, commonly found in protein solutions, usually termed beta-, gamma-, and
delta-relaxation. The beta-relaxation, occurring in the frequency range around
10 MHz and the gamma-relaxation around 20 GHz (at room temperature) can be
attributed to the rotation of the polar protein molecules in their aqueous
medium and the reorientational motion of the free water molecules,
respectively. The nature of the delta-relaxation, which often is ascribed to
the motion of bound water molecules, is not yet fully understood. Here we
provide data on the temperature dependence of the relaxation times and
relaxation strengths of all three detected processes and on the dc conductivity
arising from ionic charge transport. The temperature dependences of the beta-
and gamma-relaxations are closely correlated. We found a significant
temperature dependence of the dipole moment of the protein, indicating
conformational changes. Moreover we find a breakdown of the
Debye-Stokes-Einstein relation in this protein solution, i.e., the dc
conductivity is not completely governed by the mobility of the solvent
molecules. Instead it seems that the dc conductivity is closely connected to
the hydration shell dynamics.Comment: 11 pages, 7 figure
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