421 research outputs found
Symmetry and asymmetry in the unwinding of nucleic acids
No full textThe forming and melting of complementary base pairs in RNA and DNA duplexes are conformational transitions re- quired to accomplish a plethora of biological functions. Using fully atomistic simulation we have shown that RNA unwind- ing occurs by a stepwise process in which the probability of unbinding of the base on the 5’ strand is significantly higher than that on the 3’ strand [Colizzi and Bussi JACS, 2012]. The asymmetry in the RNA unwinding dynamics is compli- ant with the mechanism of helicase activity shown by proto- typical DEx(H/D) RNA helicases and could allow decipher- ing the basis of the evolutionary pressure responsible for the unwinding mechanism catalyzed by RNA-duplex processing enzymes. In this spirit and from a broader standpoint, here we use a topology-based coarse-grain model to compare and characterize the mechanism of unwinding for both DNA and RNA. The (a)symmetric behavior of the 3’- and 5’-strand could be related to the (bi)directionality observed in molecular machineries processing nucleic acids
Concerto a Violino Concertante ô Mandolino Due Violini di Ripieno Violetta Due Corni ad Libitum e Basso
No full textdedicato al Serenissimo Principe Michele di Wolkonskoy da G.A.K. Colizzi, à LeidenVgl. auch mit Incipit bei C. Johansson, Hummel, Bd. 3, T. 65C. Johannson, Hummel, Bd. 2, F. 9RISM CC 3365
RNA Unwinding from Reweighted Pulling Simulations
No full textThe forming and melting of complementary base pairs in RNA duplexes are conformational transitions required to accomplish a plethora of biological functions. Yet the dynamic steps of these transitions have not been quantitatively characterized at the molecular level. In this work, the base opening process was first enforced by atomistic pulling simulations and then analyzed with a novel reweighting scheme, which allowed the free-energy profile along any suitable reaction coordinate, for example, solvation, to be reconstructed. The systematic application of such approach to different base-pair combinations provides a molecular motion picture of helix opening, which is validated by comparison with an extensive set of experimental observations and links them to the enzyme-dependent unwinding mechanism. The RNA intrinsic dynamics disclosed in this work could rationalize the directionality observed in RNA-processing molecular machineries
Ligand-induced stabilization of the aptamer terminal helix in the add adenine riboswitch
No full textRiboswitches are structured mRNA elements that modulate gene expression. They undergo conformational changes triggered by highly specific interactions with sensed metabolites. Among the structural rearrangements engaged by riboswitches, the forming and melting of the aptamer terminal helix, the so called P1 stem, is essential for genetic control. The structural mechanisms by which this conformational change is modulated upon ligand binding mostly remain to be elucidated. Here, we used pulling molecular dynamics simulations to study the thermodynamics of the P1 stem in the add adenine riboswitch. The P1 ligand-dependent stabilization was quantified in terms of free energy and compared with thermodynamic data. This comparison suggests a model for the aptamer folding in which direct P1-ligand interactions play a minor role on the conformational switch when compared with those related to the ligand-induced aptamer preorganization
Histoire de Piero, un designer entre deux mondes / Story of Piero. A designer between two worlds / Storia di Piero. Un designer fra due mondi
No full textIl documentario ripercorre la vita e l’opera del designer Piero Ottinetti (1927–2018) tra Milano e Chicago. Grafico, fotografo e illustratore, Ottinetti è stato una figura di spicco della cosiddetta ‘scuola milanese’ degli anni cinquanta e sessanta. Fra i suoi clienti più importanti si annoverano Montecatini, Pirelli, Philips, Salmoiraghi, OM, Busnelli, La Cimbali, Lorenz, Ceramiche Marazzi, Lebole, Cotonificio Cantoni. Piemontese, ex-partigiano, dopo la guerra Ottinetti si trasferisce a Roma per frequentare l’Accademia d’arte San Luca, più tardi a Milano frequenta corsi di grafica presso il Convitto Rinascita, una scuola professionale per ex combattenti. Debutta come assistente di Remo Muratore; quindi, dopo un breve periodo alla Rinascente, va a lavorare con Max Huber. Nel 1954 apre un proprio studio: i primi riconoscimenti arrivano grazie alla lunga collaborazione con Montecatini e Pirelli, per i quali cura annunci stampa, cataloghi e grafica per allestimenti (Fiera di Milano). Spinto dalla recessione economica e dalla crisi politica che attanaglia il paese, nel 1971 Ottinetti si trasferisce negli Stati Uniti, stabilendosi a Chicago. Dopo un’esperienza freelance, Ottinetti assume il ruolo di art director per il gruppo assicurativo Kemper, di cui rinnova marchio e identità aziendale. Lascia la professione alla metà degli anni ottanta per dedicarsi alla pittura.
A seguito della sua emigrazione in America, il nome di Ottinetti è stato letteralmente rimosso da ogni successiva indagine storica. Grazie a un primo fortuito incontro nel 2011, l’autore ha più volte intervistato Ottinetti. Fin dall’inizio l’incontro ha preso la forma di una complessa ricerca di storia orale. Il formato del documentario, pur privilegiando una dimensione narrativa personale, consente un commento critico e un confronto tra il contesto culturale italiano e quello americano in cui Ottinetti si è trovato a operare dagli anni settanta. La testimonianza di Ottinetti offre inoltre un racconto senza censure della realtà quotidiana nell’ambiente del design milanese. La ricostruzione ‘giornalistica’ della sua carriera, piuttosto che ricorrere a nozioni astratte di talento o di merito, mette in evidenza il ruolo dei fattori personali e sociali nel determinare il percorso e la fortuna critica di un designer.The documentary retraces the life and works of Italian designer Piero Ottinetti (1927–2018) between Milan and Chicago. Graphic designer, photographer and illustrator, Ottinetti was a leading figure in 1960s Milan, and had a host of important clients, such as Montecatini, Pirelli, Philips, Salmoiraghi, OM, Busnelli, La Cimbali, Lorenz, Ceramiche Marazzi, Lebole, Cotonificio Cantoni. From native Piedmont, after the war Ottinetti went to Rome to attend the San Luca Art Academy, and later in Milan took courses in graphic design at the Convitto Rinascita, a professional school for ex-combatants. He made his debut as study assistant to Remo Muratore; then, after a stint at La Rinascente, went to work with Max Huber. By 1954 he opened his own studio. The first recognitions came thanks to his long-lasting collaboration with Montecatini and Pirelli, for whom over nearly two decades he produced print ads, catalogues, and exhibition graphics. Pushed by the economical recession and the political turmoil that gripped the country, in 1971 Ottinetti decided to move to the United States, settling in Chicago. Following a freelance experience, Ottinetti joined the Kemper Insurance group as art director, where he overhauled the whole corporate identity. He retired by the mid-eighties, devoting himself to painting. He lived in Waukegan, Illinois.
Following his emigration to America, Ottinetti’s name was literally removed from all subsequent historical investigations. After an happenstance discovery in 2011, the author met and interviewed Ottinetti several times. From the start the encounter took the shape of a complex oral history investigation. The documentary format, while privileging a personal narrative dimension, allows a critical commentary and a comparison between the Italian and American cultural context in which Ottinetti operated. Moreover, Ottinetti's testimony offers an uncensored, behind-the-scenes account of the everyday reality of Milan’s design circles. In particular, the journalistic-style reconstruction of his career, rather than resorting to abstract notions of talent or merit, highlights the role of personal and social factors in determining a designer's path
Mycobacterium tuberculosis and human macrophage: the bacillus with "environment-sensing"
No full text- …
