2,721 research outputs found
The effect of inhomogenities on single molecule imaging by hard XFEL pulses
We study the local distortion of the atomic structure in small biological
samples illuminated by x-ray free electron laser (XFEL) pulses. We concentrate
on the effect of inhomogenities: heavy atoms in a light matrix and
non-homogeneous spatial distribution of atoms. In biological systems we find
both. Using molecular-dynamics type modeling it is shown that the local
distortions about heavy atoms are larger than the average distortion in the
light matrix. Further it is also shown that the large spatial density
fluctuations also significantly alter the time evolution of atomic
displacements as compared to samples with uniform density. This fact has
serious consequences on single particle imaging. This is discussed and the
possibility of a correction is envisaged.Comment: Movies: http://www.szfki.hu/~jurek/art2009_1/index.htm
Protein folding, protein structure and the origin of life: Theoretical methods and solutions of dynamical problems
Theoretical methods and solutions of the dynamics of protein folding, protein aggregation, protein structure, and the origin of life are discussed. The elements of a dynamic model representing the initial stages of protein folding are presented. The calculation and experimental determination of the model parameters are discussed. The use of computer simulation for modeling protein folding is considered
Universal behavior of localization of residue fluctuations in globular proteins
Localization properties of residue fluctuations in globular proteins are
studied theoretically by using the Gaussian network model. Participation ratio
for each residue fluctuation mode is calculated. It is found that the
relationship between participation ratio and frequency is similar for all
globular proteins, indicating a universal behavior in spite of their different
size, shape, and architecture.Comment: 4 pages, 3 figures. To appear in Phys. Rev.
Ab initio analysis of the x-ray absorption spectrum of the myoglobin-carbon monoxide complex: Structure and vibrations
We present a comparison between Fe K-edge x-ray absorption spectra of
carbonmonoxy-myoglobin and its simulation based on density-functional theory
determination of the structure and vibrations and spectral simulation with
multiple-scattering theory. An excellent comparison is obtained for the main
part of the molecular structure without any structural fitting parameters. The
geometry of the CO ligand is reliably determined using a synergic approach to
data analysis. The methodology underlying this approach is expected to be
especially useful in similar situations in which high-resolution data for
structure and vibrations are available.Comment: 13 pages, 3 figure
Evolutionary and Functional Relationships in the Truncated Hemoglobin Family
Predicting function from sequence is an important goal in current biological research, and although, broad functional assignment is possible when a protein is assigned to a family, predicting functional specificity with accuracy is not straightforward. If function is provided by key structural properties and the relevant properties can be computed using the sequence as the starting point, it should in principle be possible to predict function in detail. The truncated hemoglobin family presents an interesting benchmark study due to their ubiquity, sequence diversity in the context of a conserved fold and the number of characterized members. Their functions are tightly related to O2affinity and reactivity, as determined by the association and dissociation rate constants, both of which can be predicted and analyzed using in-silico based tools. In the present work we have applied a strategy, which combines homology modeling with molecular based energy calculations, to predict and analyze function of all known truncated hemoglobins in an evolutionary context. Our results show that truncated hemoglobins present conserved family features, but that its structure is flexible enough to allow the switch from high to low affinity in a few evolutionary steps. Most proteins display moderate to high oxygen affinities and multiple ligand migration paths, which, besides some minor trends, show heterogeneous distributions throughout the phylogenetic tree, again suggesting fast functional adaptation. Our data not only deepens our comprehension of the structural basis governing ligand affinity, but they also highlight some interesting functional evolutionary trends.Fil: Bustamante, Juan Pablo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Química Física; ArgentinaFil: Radusky, Leandro Gabriel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química Biológica de la Facultad de Ciencias Exactas y Naturales; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Biológica; ArgentinaFil: Boechi, Leonardo. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Cálculo; ArgentinaFil: Estrin, Dario Ariel. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Química Inorgánica, Analítica y Química Física; ArgentinaFil: Ten Have, Arjen. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mar del Plata. Instituto de Investigaciones Biológicas. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales. Instituto de Investigaciones Biológicas; ArgentinaFil: Marti, Marcelo Adrian. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Cálculo; Argentin
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