1,720,980 research outputs found
Molecular dynamics of microperoxidases in aqueous and nonaqueous solutions
No full textWe report an extended molecular dynamics study of the heme-containing peptide ''microperoxidase'' (MP), a model system of several heme-proteins. The most commonly studied forms of MP, the octa- and the undecapeptide, are studied both in pure water conditions and in mixed solvent (80% methanol and 20% water) conditions that stabilize the monomeric form. The equilibrium structures and their stability are visualized by graphical tools and analyzed in terms of the molecular shape, the vibrational amplitudes, and torsional angles along the backbone. The obtained structures are used to confirm the experimental data on aggregation of Urry and Pettegrew(7.8) by using simple geometric arguments based on the possible assemblies of several monomeric units in space. We have investigated in detail the H-bond network and the influence on the heme conformational properties. We have found that heme interacts with the peptide through H-bonds formed by the propionates, the axial histidine, and different partners of the peptidic chain. These interactions are regulated by the degree of exposure of HIS to the solvent. These results permit us to predict that the undecapeptide and the octapeptide can be good model systems for horseradish peroxidase and cytochrome c', respectively
Influence of glycerol on the structure and stability of ferric horse heart myoglobin: A SAXS and circular dichroism study
No full textThe influence of glycerol on the structural properties of Fe(III)-horse heart myoglobin has been investigated by absorbance, CD and SR-SAXS spectroscopy. The results obtained indicate that both the tertiary and the secondary (alpha-helix) conformations of the protein are influenced by glycerol; in particular, an increase of approx. 8% in helical content was observed. Further, analysis of both the acid- and guanidine-induced denaturation transitions points to a glycerol-induced decreased stability of the tertiary structure; conversely, the alpha-helix conformation is found to be stabilized by the organic solvent. Finally, the SR-SAXS data show that gyration radius, cross-section and thickness of the protein increase in the presence of the organic solvent; however, the protein maintains a compact state
Chiral discrimination in the energetics of formation of diastereomeric adducts involving polypeptides
No full textQuantitative evaluation of the metallurgical effects on the strengthening of AISI 304 stainless steels
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Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Conformational changes involved in the switch from ovalbumin to S-ovalbumin
No full textFor the first time a comparative study on conformational differences between native ovalbumin and its heat-stable form, called S-ovalbumin, using small angle x-ray scattering, is reported. To detect a different pathway in the folding mechanism of the two proteins, scattering measurements have been performed on ovalbumin and S-ovalbumin denatured with different concentrations of guanidine hydrochloride, and by heating the proteins at acid pH. The intensity scattering curves provide evidence that the intermediate states in the unfolding process are globular for both proteins while their compactness changes. The reported experimental results suggest that the ovalbumin to S-ovalbumin transformation can be considered a protein-switch triggered by changes in the chemical conditions of the protein environment. Because the conformational changes are likely to be of functional importance, we infer that the occurrence in vivo of S-ovalbumin is thus determined by the transformation of ovalbumin, with a functional role for embryonic development, into a new protein with a different function
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