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Dive into the research topics where Vittorio Picciarelli is active.

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Featured researches published by Vittorio Picciarelli.


Biophysical Journal | 2004

Effect of Sterols on β-Amyloid Peptide (AβP 1–40) Channel Formation and their Properties in Planar Lipid Membranes

Silvia Micelli; Daniela Meleleo; Vittorio Picciarelli; Enrico Gallucci

We investigate the role played by membrane composition on the interaction and self-assembly of b-amyloid peptide (AbP1-40) during pore formation in planar lipid membranes (PLMs). Incorporation studies showed that AbP does not interact with zwitterionic membranes made up of phosphatidylcholine, whereas the addition of cholesterol or ergosterol to the membranes leads to channel formation. Among the PLMs used, a higher propensity of AbP to form channels at low applied potential (620 mV) was observed in 7-dehydrocholesterol and in oxidized cholesterol PLMs. These channels present long lifetimes, high-occurrence frequencies, and are voltage dependent. In particular, the AbP channel in oxidized cholesterol showed anion selectivity. Thus cholesterol (and sterols in general) could be considered as targets for AbP, which prevents the fibrillation process by increasing incorporation into membranes. Furthermore, by switching the channel selectivity versus anions, cholesterol helps to reduce the imbalance of the cellular ions, calcium included, induced by membrane depolarization, which could be one of the factors responsible for cytotoxicity in Alzheimers disease.


European Biophysics Journal | 2003

Magainin 2 channel formation in planar lipid membranes: the role of lipid polar groups and ergosterol

Enrico Gallucci; Daniela Meleleo; Silvia Micelli; Vittorio Picciarelli

Abstract. Magainin 2, a polycationic peptide, displays bactericidal and tumoricidal activity, presumably interacting with negatively charged phospholipids in the membrane hosts. In this work, we investigate the role played by the lipid head-group in the interactions and self-association of magainin 2 during pore formation in lipid bilayers. Two methods are used: single-channel and macroscopic incorporation into planar lipid membranes. Single-channel incorporation showed that magainin 2 did not interact with zwitterionic membranes, while the addition of negatively charged dioleoylphosphatidylglycerol to the membrane leads to channel formation. On the other hand, magainin 2 did not form channels in membranes made up of dioleoylphosphatidylserine (DOPS), although the addition of ergosterol to DOPS membranes leads to channel formation. This finding could indicate that ergosterol may be a possible target of magainin 2 in fungal membranes. Further support for this hypothesis comes from experiments in which the addition of ergosterol to palmitoyloleoylphosphatidylcholine membranes induced channel formation. Besides the role of negatively charged membranes, this study has shown that magainin 2 also forms channels in membranes lacking heads, such as monoolein and oxidized cholesterol, indicating an interaction of magainin 2 with acyl chains and cholesterol, respectively. This finding provides further evidence that peptide binding and assembly in lipid membranes is a complex process driven by electrostatic and/or hydrophobic interactions, depending on the structure of the peptide and the membrane composition.


European Journal of Engineering Education | 1991

A Study of University Students' Understanding of Simple Electric Circuits Part 1: Current in d.c. Circuits

Vittorio Picciarelli; M. Di Gennaro; R. Stella; E. Conte

SUMMARY RIASSUNTO A written questionnaire was submitted to two samples of sophomore students mainly from the Faculty of Engineering at Ban University (Southern Italy). The eight problems proposed in the questionnaire concerned the functioning of simple d.c. circuits. Analysis of the results shows the presence of a common misunderstanding (sequential reasoning) based on a ‘local’ interpretation of the current flow (i.e. the current value at a given position is not influenced by the passive elements not yet ‘encountered’ by the current). This form of reasoning has been found to be very tenacious since it is still largely shared after teaching on circuitry at university level and is present even in students who have passed the physics examination at university. The implications of these results are considered RISSUNTO A due campioni di studenti appartenenti soprattutto al secondo e terzo anno delta Facolta di Ingegneria dell’Universita di Bari e stato proposto un questionario (8 problemi) sul funzionamento d...


Bioelectrochemistry | 2002

Mitochondrial porin incorporation into black lipid membranes: ionic and gating contribution to the total current

Silvia Micelli; Enrico Gallucci; Daniela Meleleo; Valentina Stipani; Vittorio Picciarelli

We present a new ac device useful for simultaneous measurements of ionic charge movement (conductance) and gating charge displacement (capacitance) in mitochondrial porin channels incorporated in two kinds of black lipid membranes (BLMs), made up of phosphatidylinositol (charged surface) and oxidized cholesterol (neutral surface). In particular, we investigated the conductance/capacitance variations during the process of porin incorporation (VDAC) at different porin concentrations. While conductance variations are present throughout the porin concentration range investigated, a threshold value seems to be necessary in order to detect a significant capacitance variation. A clear steady state in both conductance and capacitance is reached for the phosphatidylinositol bilayer, while for the oxidized cholesterol membranes, the steady state is reached only for the conductance. The dependence of capacitance characteristics on the membrane applied voltage V(m) is investigated before porin incorporation and at the ionic current steady state. The results obtained confirm that before porin incorporation, there is a small dependence on V(m)(2), while afterwards we find evidence of a dual exponential voltage dependence (a result similar to that found for conductance). Finally, we investigated the capacitance dependence on the radius of the hole separating the two compartments of the cell used in the measurements. In this study, performed only with oxidized cholesterol, the radius was varied from 200 to 1050 microm. We observed a significant variation in the specific capacitance in particular for smaller radii. The results were interpreted by a simple geometrical model taking into account the influence of the torus.


Physics Education | 1999

A DESKTOP APPARATUS FOR STUDYING ROLLING MOTION

M Basta; M Di Gennaro; Vittorio Picciarelli

We describe a simple desktop apparatus online with a PC which has been used in a physics laboratory for university mathematics students to study the rolling motion of a sphere down a grooved track under experimental conditions both with and without slipping. An efficient data reduction and interactive analysis performed with an electronic spreadsheet makes it possible to carry out appropriate tests on the theoretical model and to promote a more hands-on understanding among students of the role played by the frictional force.


International Journal of Mathematical Education in Science and Technology | 1990

The role of cognitive level, cognitive style and information processing abilities in children's understanding of fractions as part‐whole

M. Di Gennaro; Vittorio Picciarelli; M. T. Rienzi

Analysis of the answers given by two Italian student samples of 5th and 7th grade to 12 items of the concept assessment (CA) test on the rational number, yielded the result that the students experience great difficulties in mastering the fraction concept. In particular, about 34 per cent (11 per cent) of 5th (7th) grade subjects interpret the fraction as part‐to‐part. We report a detailed study of the relationship between the test scores and individual characteristics, such as cognitive style, intellectual development and information processing capabilities.


International Journal of Science Education | 1985

The logic of hypothesis testing and the control of variables formal schema: Is there a link ?

C. dell'Aquila‡; M. di Gennaro; Vittorio Picciarelli

In this study, the mastery of the hypothesis testing (HT) skill and its relationship with the control‐of‐variables (CV) formal schema are investigated. A paper‐and‐pencil test, consisting of 4 items on the CV and 2 items on the ht, was administered to a sample of 144 high school students (from grades 9 to 13) majoring in science in a region in southern Italy. Students of this sample experienced more difficulties in ht logic than in the CV formal schema. The detailed analysis of the answers given to the ht items indicates that there are a few common ‘wrong’ hypothesis testing strategies. The implications of this for the teaching of science are discussed.


Physics Education | 2010

Coupled pendulums: a physical system for laboratory investigations at upper secondary school

Vittorio Picciarelli; Rosa Stella

The topic of coupled oscillations is rich in physical content which is both interesting and complex. The study of the time evolution of coupled oscillator systems involves a mathematical formalization beyond the level of the upper secondary school students competence. Here, we present an original approach, suitable even for secondary students, to investigate a coupled pendulum system through a series of carefully designed hands-on and minds-on modelling activities. We give a detailed description of these activities and of the strategy developed to promote both the understanding of this complex system and a sound epistemological framework. Students are actively engaged (1) in system exploration; (2) in simple model building and its implementation with an Excel spreadsheet; and (3) in comparing the measurements of the system behaviour with predictions from the model.


Physics Education | 2000

A simple experiment to study parabolic surfaces

M Basta; Vittorio Picciarelli; R Stella

A parabolic surface was obtained by rotating, at measurable angular velocity, water containing dissolved food gelatine. The shape of the solidified surface was determined first, then its optical properties were investigated and the location of the focus was defined by means of a laser. The results obtained are in agreement with those predicted by the dynamic model. The equipment and the procedure employed make this experiment useful for laboratory activities.


Research in Science & Technological Education | 1992

Incidental Science Knowledge in Fifth Grade Children: A Study of Its Relationship with Cognitive Development and Cognitive Style.

Menina Di Gennaro; Vittorio Picciarelli; Daniela Schirinzi; Luigi Bilancia

Abstract Fifty‐three elementary school children were tested on Incidental Science Knowledge (ISK), i.e. the knowledge of science acquired by chance outside school, and the results obtained were correlated with their Intellectual Development (ID) and Cognitive Style (CS). While the ID was evaluated by Piagetian‐like clinical interviews, the data on CS and ISK were collected during normal classroom activities by group tests. Analysis of the data indicated that there is a statistically significant correlation among the three variables and multiple stepwise regression analysis shows that the best predictor for ISK is CS. The results obtained support the finding that cognitive variables play a fundamental role even before formal science teaching. For this reason, elementary school teachers should take into account the presence of individual cognitive differences and should plan their teaching methods to conform to students’ cognitive level and promote their cognitive development. Also, it is not sufficient to ...

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M Basta

Instituto Politécnico Nacional

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