2,477 research outputs found
Self-assembly and DNA binding of the blocking factor in X chromosome inactivation
No full textX chromosome inactivation (XCI) is the phenomenon occurring in female mammals whereby dosage compensation of
X-linked genes is obtained by transcriptional silencing of one of their two X chromosomes, randomly chosen during
early embryo development. The earliest steps of random X-inactivation, involving counting of the X chromosomes and
choice of the active and inactive X, are still not understood. To explain "counting and choice," the longstanding
hypothesis is that a molecular complex, a "blocking factor" (BF), exists. The BF is present in a single copy and can
randomly bind to just one X per cell which is protected from inactivation, as the second X is inactivated by default. In
such a picture, the missing crucial step is to explain how the molecular complex is self-assembled, why only one is
formed, and how it binds only one X. We answer these questions within the framework of a schematic Statistical
Physics model, investigated by Monte Carlo computer simulations. We show that a single complex is assembled as a
result of a thermodynamic process relying on a phase transition occurring in the system which spontaneously breaks
the symmetry between the X’s. We discuss, then, the BF interaction with X chromosomes. The thermodynamics of the
mechanism that directs the two chromosomes to opposite fates could be, thus, clarified. The insights on the selfassembling
and X binding properties of the BF are used to derive a quantitative scenario of biological implications
describing current experimental evidences on "counting and choice.
Correction to: Biaxial bending of SFRC slabs: Is conventional reinforcement necessary? (Materials and Structures, (2019), 52, 1, (1), 10.1617/s11527-018-1302-0)
No full textThe article ‘‘Biaxial bending of SFRC slabs: Is conventional reinforcement necessary?’’, written by Marco di Prisco, Matteo Colombo and Ali Pourzarabi, was originally published electronically on the publisher’s Internet portal (currently SpringerLink) on 22 December 2018 without open access. The copyright of the article changed in December 2019 to The Author(s) 2019, and the article is forthwith distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creativecommons.org/licenses/by/4.0/), which permits use, duplication, adaptation, distribution and reproduction in any medium or format, as long as you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license and indicate if changes were made. Open Access This article is distributed under the terms of the Creative Commons Attribution 4.0 International License (http:// creativecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give appropriate credit to the original author(s) and the source, provide a link to the Creative Commons license, and indicate if changes were made
Portrait of Dr. Salvatore Prisco
No full textThis is a circa 1975 portrait of Dr. Salvatore Prisco, professor and author
Two-dimensional members
No full textLa presente pubblicazione è stata redatta allo scopo di fornire uno sguardo di insieme ai risultati tecnico-scientifici di maggior rilievo raggiunti nell’ambito del Progetto Cofinanziato dal Ministero dell’Università e della Ricerca Scientifica nel biennio 2004-2006, che si è concluso nel Dicembre del 2006, dal titolo “Calcestruzzi fibrorinforzati per strutture ed infrastrutture resistenti, durevoli ed economiche”, avente come coordinatore il Prof. Marco di Prisco, che figura come editore. I risultati descritti nel volume possono essere suddivisi in due principali tematiche di ricerca: la prima inerente il comportamento del materiale (capitoli 1-3) e la seconda inerente il comportamento delle strutture (capitoli 4-7). Nel seguito vengono riassunti brevemente i principali risultati raccolti con riferimento a tale suddivisione
ALLPA : tejiendo la vida : comercialización de tejidos artesanales B2B
No full textFil: García Prisco, M. Celeste. Universidad de San Andrés. Escuela de Negocios; Argentina
Thermodynamic pathways to genome spatial organization in the cell nucleus
No full textThe architecture of the eukaryotic genome is characterized by a high degree of spatial organization. Chromosomes occupy preferred territories correlated to their state of activity and, yet, displace their genes to interact with remote sites in complex patterns requiring the orchestration of a huge number of DNA loci and molecular regulators. Far from random, this organization serves crucial functional purposes, but its governing principles remain elusive. By computer simulations of a Statistical Mechanics model, we show how architectural patterns spontaneously arise from the physical interaction between soluble binding molecules and chromosomes via collective thermodynamics mechanisms. Chromosomes colocalize, loops and territories form and find their relative positions as stable hermodynamic states. These are selected by “thermodynamic switches” which are regulated by concentrations/affinity of soluble mediators and by number/location of their attachment sites along chromosomes. Our “thermodynamic switch model” of nuclear architecture, thus, explains on quantitative grounds how well known cell strategies of upregulation of DNA binding proteins or modification of chromatin structure can dynamically shape the organization of the nucleus
The technical causes of the collapse of Annone overpass on SS.36
No full textThe paper presents the technical causes of the collapse of Annone overpass, which occurred in October 2016. The tests carried out to identify the characteristics of the materials used for the construction, the verification calculations that led to the identification of the critical mechanism in the collapse and the test on the structural element deemed critical at the time of collapse are summarized. The paper highlights the critical issues occurring concurrently with the passage of the exceptional transports, the safety coefficient in relation to the project loads at the time of construction and that at the time of the passage of the exceptional convoy. The note also highlights some critical aspects of the national infrastructural system, with particular reference to exceptional transports and the methods that could be used to prevent future accidents in the absence of macro-design mistake
Sandwich structures for sustainable buildings
No full textThe growing interest in cost-effective solutions for the structural upgrading of existing buildings and infrastructures has gradually oriented research towards the optimization of high-performance cement-based composites conceived for new lightweight constructions. These materials, known as textile reinforced concretes (TRCs) and/or fabric-reinforced cementitious mortars (FRCMs) in their recent developments are generally employed in the form of thin layers and have proven capable to significantly enhance the load-bearing and deformation capacities of underperforming structures. Considering the large surfaces targeted by the retrofitting interventions, a primary objective is to avoid material wastage; in this sense, there is a major need of guidelines and simplified predictive models that can effectively assist the identification of optimum design solutions. Being the tensile behaviour of TRC strongly influenced by the matrix composition, the geometrical and chemo-mechanical characteristic of the embedded fabrics and the possible presence of short fibres, in this paper we aim at tracing the sustainable potentialities of TRC sandwich solutions as multifunctional light structures for façades and roofing
Underground tunnels exposed to internal blast: Effect of the explosive source position
No full textThe design procedure recently proposed by the same authors and based on a simplified FE model for underground tunnels subjected to internal explosion is extended in this work taking into account different possible positions of the explosive source inside the tunnel. The situation in which the internal explosion is preceded by fire accidents is also analyzed. The reference situation is represented by the explosive source located at the center of the tunnel cross-section. The tunnel geometry considered is that of the metro line in Brescia, Italy. It has an internal diameter of about 8.15 m and is located about 23.1 m below the surface. Six segments and a smaller key segment (6+1) make up the tunnel. The ring has an average width of about 1.5 m. Dynamic analyses were carried out in order to reproduce the blast scenario. The aim of this work is to evaluate the influence of the position of the explosive source on the tunnel dynamic response. An ultimate limit state criterion based on the eccentric ultimate flexural capacity and capable of including fire-blast interaction is adopted. An innovative layered precast tunnel segment solution made of different fiber-reinforced cementitious composites is considered
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
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