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Exaggerated insulin response to oral glucose was demonstrated in peripheral blood of patients with chronic hepatic diseases. High peripheral insulin levels may be the result of pancreatic hypersecretion or decreased hepatic removal of insulin. The simultaneous assay of insulin and C-Peptide concentrations in peripheral blood enables the determination of both beta-cell activity and hepatic fractional insulin extraction. We have measured peripheral insulin and C-Peptide levels during OGTT in a group of subjects with chronic active hepatitis (CAH). These subjects showed glucose levels and incremental areas significantly higher than controls, but still in the upper range of normality. Insulin response to oral glucose was significantly greater in CAH patients than in controls, whereas C-Peptide levels and areas were quite similar in the two groups. The C-Peptide to insulin molar ratios before and after glucose, and the relations between C-Peptide and insulin incremental areas were lower in CAH patients than in controls. We conclude that the peripheral hyperinsulinemia observed in subjects with CAH is due to diminished insulin removal by the diseased liver rather than pancreatic hypersecretion.

Allosteric regulation plays an important role in many biological processes, such as signal transduction, transcriptional regulation, and metabolism. Allostery is rooted in the fundamental physical properties of macromo-lecular systems, but its underlying mechanisms are still poorly understood. A collection of contributions to a recent interdisciplinary CECAM (Center Européen de Calcul Atomique et Moléculaire) workshop is used here to provide an overview of the progress and remaining limitations in the understanding of the mechanistic foundations of allostery gained from computational and experimental analyses of real protein systems and model systems. The main conceptual frameworks instrumental in driving the field are discussed. We illustrate the role of these frameworks in illuminating molecular mechanisms and explaining cellular processes, and describe some of their promising practical applications in engineering molecular sensors and informing drug design efforts.

Prions are unusual protein assemblies that propagate their conformationally-encoded information in absence of nucleic acids. The first prion identified, the scrapie isoform (PrPSc) of the cellular prion protein (PrPC), caused epidemic and epizootic episodes [1]. Most aggregates of other misfolding-prone proteins are amyloids, often arranged in a Parallel-In-Register-β-Sheet (PIRIBS) [2] or β-solenoid conformations [3]. Similar folding models have also been proposed for PrPSc, although none of these have been confirmed experimentally. Recent cryo-electron microscopy (cryo-EM) and X-ray fiber-diffraction studies provided evidence that PrPSc is structured as a 4-rung β-solenoid (4RβS) [4, 5]. Here, we combined different experimental data and computational techniques to build the first physically-plausible, atomic resolution model of mouse PrPSc, based on the 4RβS architecture. The stability of this new PrPSc model, as assessed by Molecular Dynamics (MD) simulations, was found to be comparable to that of the prion forming domain of Het-s, a naturally-occurring β-solenoid. Importantly, the 4RβS arrangement allowed the first simulation of the sequence of events underlying PrPC conversion into PrPSc. This study provides the most updated, experimentally-driven and physically-coherent model of PrPSc, together with an unprecedented reconstruction of the mechanism underlying the self-catalytic propagation of prions., Author summary Prions are unusual infectious pathogens that do not contain any nucleic acid. They consist of assemblies of misfolded proteins. The scrapie isoform of the mammalian prion protein, PrPSc, is the most notorious prion, and is responsible for deadly neurodegenerative diseases affecting humans, like Creutzfeldt-Jakob disease, and animals, such as bovine spongiform encephalopathy (“mad cow disease”) and chronic wasting disease affecting elk and deer in North America and, more recently, Europe). Understanding the structure (“shape”) of the PrPSc prion is critical to understand how it propagates. We have created a very detailed model of PrPSc, which includes all its atoms, using computational techniques. The model resembles a 4-rung cork-screw. The model is stable and agrees with all available experimental data on PrPSc. This structure allowed us to model for the first time the process of prion propagation at high resolution. These data inspire several new hypotheses to elucidate prion biology and design therapeutics for prion diseases

Transition Path Theory (TPT) provides a rigorous framework to investigate the dynamics of rare thermally activated transitions. In this theory, a central role is played by the forward committor function q^+(x), which provides the ideal reaction coordinate. Furthermore, the reactive dynamics and kinetics are fully characterized in terms of two time-independent scalar and vector distributions. In this work, we develop a scheme which enables all these ingredients of TPT to be efficiently computed using the short non-equilibrium trajectories generated by means of a specific combination of enhanced path sampling techniques. In particular, first, we further extend the recently introduced Self-Consistent Path Sampling (SCPS) algorithm in order to compute the committor q^+(x). Next, we show how this result can be exploited in order to define efficient algorithms which enable us to directly sample the transition path ensemble., Version accepted for publication in J. Chem. Phys

Protein misfolding is implicated in many diseases, including the serpinopathies. For the canonical inhibitory serpin {\alpha}1-antitrypsin (A1AT), mutations can result in protein deficiencies leading to lung disease, and misfolded mutants can accumulate in hepatocytes leading to liver disease. Using all-atom simulations based on the recently developed Bias Functional algorithm we elucidate how wild-type A1AT folds and how the disease-associated S (Glu264Val) and Z (Glu342Lys) mutations lead to misfolding. The deleterious Z mutation disrupts folding at an early stage, while the relatively benign S mutant shows late stage minor misfolding. A number of suppressor mutations ameliorate the effects of the Z mutation and simulations on these mutants help to elucidate the relative roles of steric clashes and electrostatic interactions in Z misfolding. These results demonstrate a striking correlation between atomistic events and disease severity and shine light on the mechanisms driving chains away from their correct folding routes., Comment: Final version. Supplementary Information included

Circular dichroism (CD) is known to be an excellent tool for the determination of protein secondary structure due to fingerprint signatures of α and β domains. However, CD spectra are also sensitive to the 3D arrangement of the chain as a result of the excitonic nature of additional signals due to the aromatic residues. This double sensitivity, when extended to time-resolved experiments, should allow protein folding to be monitored with high spatial resolution. To date, the exploitation of this very appealing idea has been limited, due to the difficulty in relating the observed spectral evolution to specific configurations of the chain. Here, we demonstrate that the combination of atomistic molecular dynamics simulations of the folding pathways with a quantum chemical evaluation of the excitonic spectra provides the missing key. This is exemplified for the folding of canine milk lysozyme protein.

The Bias Functional (BF) approach is a variational method which enables one to efficiently generate ensembles of reactive trajectories for complex biomolecular transitions, using ordinary computer clusters. For example, this scheme was applied to simulate in atomistic detail the folding of proteins consisting of several hundreds of amino acids and with experimental folding time of several minutes. A drawback of the BF approach is that it produces trajectories which do not satisfy microscopic reversibility. Consequently, this method cannot be used to directly compute equilibrium observables, such as free energy landscapes or equilibrium constants. In this work, we develop a statistical analysis which permits us to compute the potential of mean-force (PMF) along an arbitrary collective coordinate, by exploiting the information contained in the reactive trajectories calculated with the BF approach. We assess the accuracy and computational efficiency of this scheme by comparing its results with the PMF obtained for a small protein by means of plain molecular dynamics.

Renormalization Group (RG) theory provides the theoretical framework to define Effective Theories (ETs), i.e. systematic low-resolution approximations of arbitrary microscopic models. Markov State Models (MSMs) are shown to be rigorous ETs for Molecular Dynamics (MD). Based on this fact, we use Real Space RG to vary the resolution of a MSM and define an algorithm for clustering microstates into macrostates. The result is a lower dimensional stochastic model which, by construction, provides the optimal coarse-grained Markovian representation of the system's relaxation kinetics. To illustrate and validate our theory, we analyze a number of test systems of increasing complexity, ranging from synthetic toy models to two realistic applications, built form all-atom MD simulations. The computational cost of computing the low-dimensional model remains affordable on a desktop computer even for thousands of microstates., Comment: 23 pages, 8 figures

This paper deals with a comparison among recent structure and seismicity in the hinge zone between northern Sicily and southern Tyrrhenian, corresponding to both emerged and submerged northern portion of the Maghrebian chain. This hinge zone is part of a wider W–E trending right-lateral shear zone, mainly characterized by both a synthetic NW-SE/W–E oriented, and antithetic left-lateral N–S/NE-SW fault systems, which has been affecting the tectonic edifice, since the Pliocene. The inland structures have been mapped using aerial-photo interpretation, geological mapping and mesostructural analysis to reconstruct the stress regime in the study area. On the contrary, the offshore structures have been inferred from the available morpho-bathymetric and geological maps of the southern Tyrrhenian basin. A seismological analysis was carried out on a data set of about 11,000 seismic events occurred between January 1981 and December 2005 in the study area. The observed local magnitude is mainly comprised between 2.0 and 2.3, reaching in places peak values greater than 5.5. The distribution of the hypocenters allowed to recognize three major seismogenic zones. The deepest events (down to about 600 km) of the easternmost area are related to the Ionian lithospheric slab subducting beneath the Calabrian arc. A set of events is substantially depending by the Etna volcano activity. The third set of events is heterogeneously distributed mainly in the southern Tyrrhenian and in the eastern Sicily. This latter seismogenic zone is strictly connected to the deformation field active within the hinge zone. A statistical analysis of the seismological data allowed to individuate several clusters of events occurred in the hinge zone, which have been subsequently relocated with a relative location method. Furthermore, the seismogenic processes, relative to the most numerous clusters, were characterized in the space, time and magnitude domains with statistical techniques. The collected focal mechanisms, even if highlight the complexity of the relationships between seismogenic volumes of the clusters and single dislocations, also show some spatial trends useful to the seismotectonic analysis. On the whole, both structural and seismological data seem to be consistent with a neotectonic model related to NW-SE trending maximum compressional stress axis producing a non-coaxial strain, even if in particular areas different seismogenic conditions are possible, due to the accommodation of rock volumes leading a marked mechanical heterogeneity.

We introduce an iterative algorithm to efficiently simulate protein folding and other conformational transitions, using state-of-the-art all-atom force fields. Starting from the Langevin equation, we obtain a self-consistent stochastic equation of motion, which directly yields the reaction pathways. From the solution of this set of equations we derive a stochastic estimate of the reaction coordinate. We validate this approach against the results of plain MD simulations of the folding of a small protein, which were performed on the Anton supercomputer. In order to explore the computational efficiency of this algorithm, we apply it to generate a folding pathway of a protein that consists of 130 amino acids and has a folding rate of the order of s-1.

An integrated research on the hinge zone between northern Sicily and its Tyrrhenian off-shore has been carried out, by means of structural, seismological and statistical analyses. The main structural features of the area are represented by both NWSE to W–E striking right-lateral and N–S to NE-SW striking leftlateral fault systems, responsible of uplifting (restraining) and subsiding (releasing) zones. Within this hinge zone the seismicity is mainly located between 10 and 20 km of depth and clustered according to the orientation of the outcropping fault systems. The brittle strain partitioning related to a right-lateral simple shear zone has been reconstructed in the onshore sector, while in the offshore the structural setting has been inferred from morpho-bathymetric and geological maps of the southern Tyrrhenian basin. Moreover, in this latter zone, a new seismological study has been carried out on a part of 2002 seismic sequence (more than 600 events), using a database obtained by merging the CSI 1.1 catalogue of INGV and new data recorded by 7 three-components stations of a temporary network installed by INGV. These seismic events, occurred between September and December 2002, have been relocated using an eight layered velocity model optimized for the southern Tyrrhenian. The focal mechanisms of 40 events have been determined. The Coulomb stress changes related to the main event have been also calculated. The general geometric characters of the whole set of investigated parameters well fit the simple shear deformational style reconstructed of the onshore study zone. Moreover, both focal mechanisms and principal stress components of about 100 events of 1992-1993 Pollina seismic swarm (Eastern Madonie Mts.) has been also carried out. The main focal mechanisms typologies and stress axis trends show a good agreement with the seismogenic volume anisotropy required by the seismotectonic model. This model is also supported by the high resolution tomographic results of the more shallow structures in the Pollina area, and by the study of two recent minor seismic sequences affecting the northern Sicilian sector (2010-2012) in the Caprileone area (Messina) and in the Isola delle Femmine offshore (west of Palermo). In this last sector high resolution morphobatimetric (multibeam) data highlight the presence of very young morphological features related to the ENE-WSW and NNW-SSE trending structural systems, probably responsible of the recent events.

Il saggio si propone di tracciare le conclusioni del lavoro progettuale svolto durante il Workshop "I cortili di Cervia. Lo spazio pubblico nella città storica" (Cervia-Cesena, 16-25 giugno 2011), sottolineando gli aspetti che costituiscono un possibile contributo rispetto alle politiche e ai progetti che potranno essere intraprese in futuro dall'amministrazione comunale. Per quanto riguarda le politiche da intraprendere, i temi che emergono sono: - priorità alla rigenerazione urbana; - promozione di eventi; - comunicazione; - cooperazione pubblico/privato; - promozione di un turismo consapevole. Fra i molteplici aspetti del progetto urbanistico, la mobilità lenta, gli spazi di prossimità, le reti di luoghi, il rapporto con la storia, la leggibilità, l'integrazione di funzioni sono i temi-chiave dei progetti da intraprendere in futuro.

Il saggio esamina alcuni aspetti legati al progetto di riqualificazione degli spazi aperti attorno alla cinta muraria della città di Cervia, in relazione al tema del progetto dei "margini" (Lynch) e di tutti gli altri elementi che concorrono alla "figurabilità" dello spazio urbano.

Il testo tratta dell'importanza dei luoghi collettivi all'interno della città. In particoalre viene messo in risalto il ruolo che lo spazio collettivo assume nella progettazione degli insediamenti urbani e delle città di fondazione. La città di fondazione e l'atto di fondazione in generle sono assunti come paradigmi di riferimento della progettazione urbana dei luoghi e degli edifici collettivi. sono altresì messi a confronto le nozioni di preesistenza ambientale e teatralità urbana. Due modi di leggere elementi e forme della città e di prefigurazione progettuale.

ORGANIZZAZIONE SOCIALE E ISTITUZIONALE DELL'AREA DI RACCORDO FRA RAVENNA CAPITALE ESARCALE E ROMA SEDE DEL PAPATO FINO ALL'VIII SECOLO E SPECIFICITA' REGIONALE DEL CETO DIRIGENTE DI INFLUENZA BIZANTINA (CARILE) GLI ALTRI RELATORI HANNO ESAMINATO I RAPPORTI FRA CORTE DUCALE DI SPOLETO E Gix DA tOSSIGNANO ARCIVESCOVO DI RAVENNA (SAVIGNI); ASPETTI AGIOGRAFICI (BOESCH GAJANO. MARCHESELLI, ORSELLI), PRESENZE ORIENTALI (ORIOLI), INFLUENZA ICONOGRAFICHE BIZANTINE (PASI, MONTANARI, TOSCANO), REPERTI ARCHEOLOGICI (NOVARA)