Ligand binding and structural analysis of a human putative cellular retinol-binding protein.

Three cellular retinol-binding protein (CRBP) types (CRBP I, II, and III) with distinct tissue distributions and retinoid binding properties have been structurally characterized thus far. A human binding protein, whose mRNA is expressed primarily in kidney, heart, and transverse colon, is shown here to be a CRBP family member (human CRBP IV), according to amino acid sequence, phylogenetic analysis, gene structure organization, and x-ray structural analysis. Retinol binding to CRBP IV leads to an absorption spectrum distinct from a typical holo-CRBP spectrum and is characterized by an affinity (K(d) = approximately 200 nm) lower than those for CRBP I, II, and III, as established in direct and competitive binding assays. As revealed by mutagenic analysis, the presence in CRBP IV of His(108) in place of Gln(108) is not responsible for the unusual holo-CRBP IV spectrum. The 2-A resolution crystal structure of human apo-CRBP IV is very similar to those of other structurally characterized CRBPs. The side chain of Tyr(60) is present within the binding cavity of the apoprotein and might affect the interaction with the retinol molecule. These results indicate that human CRBP IV belongs to a clearly distinct CRBP subfamily and suggest a relatively different mode of retinol binding for this binding protein

Towards a Wind Tunnel Testing Environment for Rotorcraft Operations Close to Obstacles

The correct identification of the aerodynamic loads due to interaction between rotorcraft and obstacles requires to run computationally intensive numerical models characterized by a high level of uncertainty. Wind tunnel data can be used as a source of information to improve those models. The present paper investigates the aerodynamic interaction of a helicopter and ship airwake exploiting wind tunnel data. A series of wind tunnel experiment, using a scaled helicopter model and Simple Frigate Shape 1, has been performed to measure forces and moments acting on the rotor, while the helicopter is approaching the flight deck. In addition, the velocity components along the longitudinal symmetry plane of the rotor have been visualized using PIV technique. With the rotor positioned at the starting point of the landing trajectory, the load measurements are used to modify the distribution of the inflow over the rotor in multibody simulation environment, in order to generate same loads, including thrust, torque and in-plane moments. Then, an identification algorithm is developed to capture the effect of ship airwake on the rotor loads during the maneuvers, modeling it as an external gust to the rotor inflow. The gust velocity is obtained through an optimization algorithm with the objective of generating same load coefficients as the experiment. The simulation results show that the same load coefficients as the experiment can be generated by implementing a linear gust over the rotor with a magnitude that changes as the rotor moves through the wake of ship. The experiment showed that this test setup could be used for identification of aerodynamic interaction to be used for maneuver analysis

Crystal structure of liganded and unliganded forms of bovine plasma retinol-binding protein.

The three-dimensional structures of bovine plasma retinol-binding protein (bRBP) complexed with retinol (space group P2(1)2(1)2(1), a = 46.08, b = 49.12, c = 76.10 A) and of the unliganded protein prepared in vitro by extracting retinol with ethyl ether (space group P2(1)2(1)2(1), a = 46.55, b = 48.97, c = 76.87 A) have been solved at 1.9 and 1.7 A resolution, respectively. The final crystallographic R factors are 0.190 for holobRBP and 0.196 for the unliganded bRBP. The model for the bovine holoprotein is quite similar to that of the human protein, with which it exhibits 92% sequence similarity. The root mean square deviation between the alpha-carbons in the two proteins is 0.31 A. The retinol binding site is almost completely preserved. The loops that surround the opening of the beta-barrel are also particularly conserved, in contrast with the presence of several substitutions in parts of the RBP molecule opposite the opening of the calyx that binds retinol. Despite the fact that unliganded bovine RBP was prepared and crystallized using procedures completely different from those used to obtain the unliganded human RBP, the conformational differences between unliganded and liganded forms of bRBP are almost identical to those found previously between the same forms of human RBP. They mainly involve a few residues in the region extending from amino acid residues 32 to 37. Therefore, similar differences are very likely to exist between holoRBP and the physiologically occurring apoprotein. A not yet identified electron density, different in shape and orientation from retinol, also occupies the central cavity of the beta-barrel in the unliganded bRBP, as found for unliganded human RBP. The functional consequences of the conformational change induced by the removal of retinol on the interaction between RBP and transthyretin, coupled with the conservation of the entrance loops of the beta-barrel in mammalian RBPs, are consistent with their participation in molecular interactions

Vibration-based monitoring and diagnosis of cultural heritage: A methodological discussion in three examples

Modern monitoring techniques contribute to accurately describing the structural health conditions of historical buildings and to optimizing the plan of maintenance as well as the restoring intervention. Particularly, dynamic testing gives knowledge about global structural behavior and can be used to calibrate numerical models and to predict the response to dynamic and earthquake loading. In some circumstances, vibration-based monitoring can also help in evaluating safety conditions. The present article proposes a discussion about the methodological multidisciplinary approach to modal testing when applied to architectural heritage buildings and structures, along with the description of selected case studies. These examples were chosen to cover the various issues connected to test design and interpretation

Wind-Tunnel Tests of a Tilt-Rotor Aircraft

A wide aerodynamic test campaign has been carried out on the tiltrotor aircraft ERICA at the Large Wind Tunnel of Politecnico di Milano by means of a modular 1:8 scale model in order to produce a dataset necessary to better understand the aerodynamic behaviour of the aircraft and to state its definitive design. The target of the tests was the measurement of the aerodynamic forces and moments in several different configurations and different attitudes. The test program included some conditions at very high incidence and sideslip angles that typically belong to the helicoptermode flight envelope and measurements of forces on the tail and on the tilting wings. A large amount of data has been collected that will be very useful to refine the aircraft design. In general the aircraft aerodynamics do not present any critical problems, but further optimisation is still possible. From the viewpoint of drag in the cruise configuration, the sponsons of the landing gear seem to be worth some further design refinement since they are responsible for a 20% drag increase with respect to the pure fuselage configuration. On the contrary, the wing fairing has proved to work well when the aircraft longitudinal axis is aligned with the wind, providing just a slight drag increase. Two other interesting aspects are the quite nonlinear behaviour of the side force for the intermediate sideslip angles as well as the noticeable hysteresis in the moment coefficient at very high incidence angles

Experimental investigation of a helicopter rotor with Gurney flaps

The present work describes an experimental activity carried out to investigate the performance of Gurney flaps on a helicopter rotor model in hovering. The four blades of the articulated rotor model were equipped with Gurney flaps positioned at 95% of the aerofoil chord, spanning 14% of the rotor radius. The global aerodynamic loads and torque were measured for three Gurney flap configurations characterised by different heights. The global measurements showed an apparent benefit produced by Gurney flaps in terms of rotor performance with respect to the clean blade configuration. Particle image velocimetry surveys were also performed on the blade section at 65% of the rotor radius with and without the Gurney flaps. The local velocity data was used to complete the characterisation of the blade aerodynamic performance through the evaluation of the sectional aerodynamic loads using the the control volume approach

Indagine sui tributi comunali in Piemonte

Contributi di ricerca ; n.200/2006- Indice #3- Introduzione #5- Struttura e dinamica del sistema dei tributi comunali in Italia e in Piemonte #11- L'indagine sul sistema dei tributi in un gruppo di Comuni piemontesi #27- Riflessioni conclusive #47- Bibliografia #4

Retinoids in Mammals: A Crystallographic Perspective

Retinoids are involved in several essential processes in mammals, including vision, morphogenesis, spermatogenesis and maintenance of epithelial tissue. Since they are labile compounds, nearly insoluble in water, they are present in body fluids and within the cell bound to specific retinoid-binding proteins. In plasma, a single protein, called retinol-binding protein, delivers the alcoholic form of vitamin A from its store sites to target cells. In the cytoplasm, four different cellular retinol-binding proteins and two retinoic acid-binding proteins have been discovered and structurally characterized to date. Finally, two classes of nuclear receptors for retinoic acid isomers have been characterized. The structure/function relationship for several retinoid-binding proteins is discussed here

Experimental Investigation on the Aerodynamic Interaction Between a Helicopter and Ground Obstacles

In this study, experiments were performed to investigate the aerodynamic interaction between a helicopter and ground obstacles. A new experimental set-up was realised and validated. The motorised helicopter model, which included the fuselage, was positioned in different positions relative to a model building in order to replicate different hovering configurations. The use of a helicopter model with a six-component balance and a building model with several pressure taps allowed a database to be compiled for the loads on the helicopter and obstacle. First several tests were performed without the building in order to develop a reference database and assess the experimental set-up through a comparison with results in the literature. The measured loads were analysed to investigate the interference effects of the building model on the helicopter performance. A physical interpretation of the flow phenomena was obtained through analysis of the obstacle pressure measurements and particle image velocimetry surveys of relevant configurations

A novel mutation in isoform 3 of the plasma membrane Ca2+ pump impairs cellular Ca2+ homeostasis in a patient with cerebellar ataxia and laminin subunit 1\u3b1 mutations.

The particular importance of Ca2+ signaling to neurons demands its precise regulation within their cytoplasm. Isoform 3 of the plasma membrane Ca2+ ATPase (the PMCA3 pump), which is highly expressed in brain and cerebellum, plays an important role in the regulation of neuronal Ca2+. A genetic defect of the function of the PMCA3 pump has been described in one family with X-linked congenital cerebellar ataxia. Here we describe a novel mutation of the PMCA3 pump (ATP2B3) in a patient with global developmental delay, generalized hypotonia and cerebellar ataxia. The mutation (a R482H replacement) impairs the Ca2+ ejection function of the pump. It reduces the ability of the pump expressed in model cells to control Ca2+ transients generated by cell stimulation and impairs its Ca2+ extrusion function under conditions of low resting cytosolic Ca2+ as well. In silico analysis of the structural effect of the mutation suggests a reduced stabilization of the portion of the pump surrounding the mutated residue in the Ca2+-bound state. The patient also carries two missense mutations in LAMA1, encoding for laminin subunit 1\u3b1. On the basis of the family pedigree of the patient, the presence of both PMCA3 and LAMA1 mutations appears to be necessary for the development of the disease. Considering the observed defect in cellular Ca2+ homeostasis and the previous finding that PMCAs act as digenic modulators in Ca2+-linked pathologies, the PMCA3 dysfunction along with LAMA1 mutations could act synergistically to cause the neurological phenotype