117,746 research outputs found
Monitoring the preparation of protein derivative crystals via Raman-microscopy
No full textRaman microscopy is having increasing applications into molecular biology. Primary structure features can be analyzed, such as Se-Met labeled protein crystals to be used for MAD crystallography [1] or to check heavy metal incorporation in isomorphous derivative crystals. Secondary structure modification can be clearly identified according to relationships between amide band frequencies and Ramachandran angles [2]. Ligand binding [3] and protein dynamics/reactivity can also be efficiently followed.
The combined Raman and X-ray crystallography approach reinforces the interpretation of biophysical data. In particular, reactivity and dynamics of metal proteins have been investigated. This approach is particularly informative and well developed for hemoproteins [4, 5].
[1] A. Vergara, A. Merlino, E. Pizzo, G. D'Alessio, L. Mazzarella, Acta Cryst. D. (2008) D64, 167-171. [2] A. Merlino, F. Sica, A. Zagari, L. Mazzarella, A. Vergara, Biophys. Chem. (2008), 137, 24-27. [3] P. R. Carey, Ann. Rev. Phys. Chem. 2006, 57, 527-554. [4] L. Vitagliano, A. Vergara, G. Bonomi, A. Merlino, G. Smulevich, B. Howes, G. di Prisco, C. Verde, L. Mazzarella, J. Am. Chem. Soc. (2008) 130, 10527-10535. [5] A. Merlino, L. Vitagliano, B. Howes, C. Verde, G. di Prisco, G. Smulevich, F. Sica, A. Vergara, Biopolymers (2009), 91(12), 1117-1125.
PRIN is acknowledged for financial support.
Keywords: metal protein, ligand soaking, secondary structur
Optimized Schwarz methods for spherical interfaces with application to fluid-structure interaction
No full textIn this work we consider the optimized Schwarz method designed for computational domains that feature spherical or almost spherical interfaces. In the first part, we consider the diffiusion-reaction problem. We provide a convergence analysis of the generalized Schwarz method and, following [G. Gigante and C. Vergara, Numer. Math., 131 (2015), pp. 369{404], we discuss an optimization procedure for constant interface parameters leading to a Robin{Robin scheme. Finally, we present some numerical results both in spherical and in ellipsoidal domains. In the second part of the work, we address the uid-structure interaction problem. Again, we provide a convergence analysis and discuss optimized choices of constant interface parameters. Finally, we present three- dimensional numerical results inspired by hemodynamic applications, to validate the proposed choices in the presence of large added mass effect. In particular, we consider numerical experiments both in an ideal spherical domain and in a realistic abdominal aortic aneurysm
Searching for additional functions of fish hemoglobins: evidence of multiple quaternary structures and exogeneous coordination states
No full textAll fish hemoglobins (Hb) show a high auto-oxidation rate, and some fish Hbs are endowed with Root effect (drastic drop of cooperativity at acidic pH). Differently from temperate fish Hbs, at physiological pH Antarctic fish Hbs (AFHbs) in the ferric state show both an aquomet form and two distinct hemichromes within a R / T intermediate quaternary structure (1). Interestingly, AFHbs exhibit a peroxidase activity higher than that observed for mammalian and temperate fish Hbs, thus suggesting that a partial hemichrome state in tetrameric Hbs does not protect them from peroxidation as previously proposed (2). At acidic pH, a combined EPR / x-ray crystallography approach has revealed, only for Root-effect AFHbs, significant amount of pentacoordinated (5C) high-spin Fe(III) species.(3) Furthermore, along the oxidation pathway, a combined x-ray crystallography / Resonance Raman spectroscopy of AFHbs has revealed a hybrid valence state [α(O2)/β(Fe3+, pentacoordinate)].(4) This valence hybrid states prompted us to test a FeSOD activity, that is as low as human Hb. A combined x-ray crystallography / FT-IR study has revealed at least two coordination states of the carbomonoxy form of AFHbs, one corresponding to a His assisted CO binding (band III at 1951 cm-1), and another to a not-His assisted CO binding (band IV at 1968 cm-1). The band IV, typical of both temperate fish (carp and trout) Hbs and AFHbs, assigned to the second CO coordination state, justifies the high auto-oxidation rate of fish Hbs. Furthermore, this novel CO coordination in AFHb occurs within a R-T intermediate quaternary structure. These findings provide an alternative structural explanation of the Root effect, in terms of a three state model .(5) This work was financially supported by PNRA (Italian National Programme for Antarctic Research) 1. Vergara, A., Franzese, M., Merlino, A., Vitagliano, L., di Prisco, G., Verde, C., Lee, H. C., Peisach, J., and Mazzarella, L. (2007) Biophys. J. 93, 2822-2829 2. Feng, L., Zhou, S., Gu, L., Gell, D., Mackay, J., Weiss, M., Gow, A., and Shi, Y. (2005) Nature 435, 697-701 3. Vergara, A., Franzese, M., Merlino, A., Bonomi, G., Verde, C., di Prisco, G., Lee, H., Peisach, J., and Mazzarella, L. . submitted. 4. Vitagliano, L., Vergara, A., Bonomi, G., Merlino, A., Smulevich, G., Howes, B., di Prisco, G., Verde, C., and Mazzarella, L., submitted. 5. Edelstein, S. J. (1996) J. Mol. Biol. 256, 737-74
Optimized Schwarz methods for the coupling of cylindrical geometries along the axial direction
No full textIn this work, we focus on the Optimized Schwarz Method for circular flat interfaces and geometric heterogeneous coupling arising when cylindrical geometries are coupled along the axial direction. In the first case, we provide a convergence analysis for the diffusion-reaction problem and jumping coefficients and we apply the general optimization procedure developed in Gigante and Vergara (Numer. Math. 131 (2015) 369–404). In the numerical simulations, we discuss how to choose the range of frequencies in the optimization and the influence of the Finite Element and projection errors on the convergence. In the second case, we consider the coupling between a three-dimensional and a one-dimensional diffusion-reaction problem and we develop a new optimization procedure. The numerical results highlight the suitability of the theoretical findings
RUTHENIUM-BASED ANTICANCER ACTIVITY: A RAMAN-ASSISTED X-RAY CRYSTALLOGRAPHY APPROACH
No full textRaman microspectroscopy proved to be a valuable support to protein crystallography in all the steps of 3D structure determination. Authors have been using this approach to study changes in chemical composition [1, 2, 3], in secondary [3,4] and tertiary structure [5], and to follow chemical mechanisms [3, 6, 7].
The binding properties of AziRu (Fig. 1), a Ru(III) complex with high antiproliferative activity, toward hen egg white lysozyme [7], RNase A and human serum albumin have been investigated by X-ray crystallography and Raman microspectroscopy. The data provide clues on the mechanism of AziRu-protein adduct formation and clear evidences of ligand exchange in the crystal state (Figs. 2). The combined use of Raman and X-ray crystallography has provided complementary information that a single technique alone would not produce. For instance, in the case of hen egg white lysozyme [7], Raman spectra show not only the ligand exchange that is apparent in the X-ray structures but also the presence of Ru−O−Ru bonds (Fig. 3), which are not revealed by crystallography.
References
[1] Vergara, et al., Acta Cryst. Sect D: Biol Crystallogr. 64, 167-171 (2008).
[2] Caterino et al., A. Vergara , J. Sol. Chem., in press.
[3] Merlino, et al. Vergara, A., Acta Cryst. Sect D: Biol Crystallogr , 69, 137-40 (2013).
[4] Merlino, et al. A. Vergara, Biophys. Chem. 137, 24-27 (2008).
[5] Vergara, et al., J. Biol. Chem. 285, 32568-32575 (2010) .
[6] Vitagliano, L., Vergara, et al.., J Am Chem Soc. 130, 10527-10535 (2008).
[7] Vergara, et al, Inorg Chem 52, 4157-9 (2013)
Leptis Magna. Présentation de R. Bianchi Bandinelli, texte de G. Caputo et E. Vergara Caffarelli
No full textDesanges Jehan. Leptis Magna. Présentation de R. Bianchi Bandinelli, texte de G. Caputo et E. Vergara Caffarelli. In: Revue belge de philologie et d'histoire, tome 43, fasc. 1, 1965. pp. 104-106
Optimized Schwarz Methods for Spherical Interfaces With Application to Fluid-Structure Interaction
No full textIn this work we consider the optimized Schwarz method designed for computational domains that feature spherical or almost spherical interfaces. In the first part, we consider the diffusion-reaction problem. We provide a convergence analysis of the generalized Schwarz method and, following [G. Gigante and C. Vergara, Numer. Math., 131 (2015), pp. 369–404], we discuss an optimization procedure for constant interface parameters leading to a Robin–Robin scheme. Finally, we present some numerical results both in spherical and in ellipsoidal domains. In the second part of the work, we address the fluid-structure interaction problem. Again, we provide a convergence analysis and discuss optimized choices of constant interface parameters. Finally, we present three-dimensional numerical results inspired by hemodynamic applications, to validate the proposed choices in the presence of large added mass effect. In particular, we consider numerical experiments both in an ideal spherical domain and in a realistic abdominal aortic aneurysm
Il valore della "cultura" e la cultura del "valore" nel governo delle aziende
No full textLa fusione fra le conoscenze, competenze ed esperienze in ambito economico aziendale, che costituiscono patrimonio intangibile, personale, di chi ha responsabilità di governo aziendale, l’insieme delle sue idee e delle sue aspettative, in ordine alla funzione e al ruolo dell’azienda che egli governa e i valori impliciti nel riconoscere all’operatività di questa, una maggiore o minore rilevanza sociale, determina l’atteggiamento mentale e strategico, la “cultura” che costituisce la matrice del modo di governare e, per conseguenza, della performance che ciascuna azienda è in grado di generare.
Se gli elementi che compongono detto atteggiamento mentale e strategico risultano particolarmente diffusi in un certo territorio, o ambito sociale, si può parlare di una vera e propria “cultura” aziendale, che sulla base dei suoi contenuti, può fungere da remora, ovvero da stimolo, oltre che al “successo” delle singole aziende, anche al più generale livello di benessere economico e sociale.
Da ciò, l’importanza degli studi sulla “cultura” aziendale, sugli elementi che ne costituiscono il contenuto, sul loro impatto in relazione al consolidamento e allo sviluppo del “successo” aziendale e del benessere economico- sociale
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