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M. U. Palma

Other affiliations: University of Palermo
Bio: M. U. Palma is an academic researcher from European Union. The author has contributed to research in topics: Coagulation (water treatment) & Conformational change. The author has an hindex of 2, co-authored 3 publications receiving 86 citations. Previous affiliations of M. U. Palma include University of Palermo.

Papers
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Journal ArticleDOI
01 Oct 1999-Proteins
TL;DR: Experiments on bovine serum albumin are reported, showing that the process of conformational change of this protein towards an intermediate form required for coagulation occurs simultaneously and interacts with two more processes: mesoscopic demixing of the solution and protein cross‐linking.
Abstract: A strong interest is currently focused on protein self-association and deposit. This usually involves conformational changes of the entire protein or of a fragment. It can occur even at low concentrations and is responsible for pathologies such as systemic amyloidosis, Alzheimer's and Prion diseases, and other neurodegenerative pathologies. Readily available proteins, exhibiting at low concentration self-association properties related to conformational changes, offer very convenient model systems capable of providing insight into this class of problems. Here we report experiments on bovine serum albumin, showing that the process of conformational change of this protein towards an intermediate form required for coagulation occurs simultaneously and interacts with two more processes: mesoscopic demixing of the solution and protein cross-linking. This pathway of three interacting processes allows coagulation even at very low concentrations, and it has been recently observed also in the case of a nonpeptidic polymer. It could therefore be a fairly common feature in polymer coagulation/gelation. Proteins 1999;37:116-120.

46 citations

Journal ArticleDOI
TL;DR: In this paper, the interplay among processes of molecular conformational changes, spinodal demixing of the solution, and molecular crosslinking involved in the physical gelation of a biopolysaccharide-water system was studied under largely different absolute and relative values of their individual rates by appropriate choices of the quenching temperature at constant polymer concentration.
Abstract: We report studies of the interplay among processes of molecular conformational changes, spinodal demixing of the solution, and molecular crosslinking involved in the physical gelation of a biopolysaccharide-water system. Multiple interactions and kinetic competition among these processes were studied under largely different absolute and relative values of their individual rates by appropriate choices of the quenching temperature at constant polymer concentration. Quenching temperature strongly affects the rate of growth but not the final value of the fractal dimension of the gel. Kinetic competition plays a central role in determining the final conformation of individual molecules and the structure and properties of the final gel. This behavior highlights the frustrated nature of the system, and the need of bringing kinetics sharply into focus in gelation theories. General aspects of the present findings and, specifically, the interplay of molecular conformation changes, solution demixing, and molecular crosslinking extend the relevance of these studies to the fast growing field of amyloid condensation and Prion diseases.

43 citations

Proceedings ArticleDOI
22 Nov 2000
TL;DR: In this paper, the authors report experiments on bovine serum albumin (BSA) showing that the overall mechanism is the result of at least three distinct and strongly intertwined processes, on both length scales: molecular conformational changes, solution demixing and intermolecular crosslinking.
Abstract: It has recently been recognized that pathological protein coagulation is responsible for lethal pathologies as diverse as amyloidosis, Alzheimer and TSE Understanding the coagulation mechanisms is therefore stirring great interest In previous studies we have shown that on profoundly different systems coagulation is the result of a strong interaction between two processes on different length scales (mesoscopic and microscopic) Here we report experiments on bovine serum albumin (BSA) showing that the overall mechanism is the result of at least 3 distinct and strongly intertwined processes, on both length scales: molecular conformational changes, solution demixing and intermolecular crosslinking This mechanism involves the statistical mechanics of protein-solvent interaction, its relation to the protein’s landscape of configurational free energy and to the solution’s thermodynamic stability, and its relation to the topological problem of crosslink-percolation, responsible for coagulation

Cited by
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Journal ArticleDOI
TL;DR: Not only did flexible macromolecules exhibit greater mobility in the gel than did comparable-size rigid spherical particles, they also proved to be a more useful probe of available space between fibers.

549 citations

Journal ArticleDOI
TL;DR: In this article, a mean field model was proposed to model the global protein gel networks with the possibility of cooperative linear aggregation (nucleation and growth) for acid β-lactoglobulin gels.

290 citations

Journal ArticleDOI
TL;DR: A general mechanism of aggregation composed by partial unfolding of the tertiary structure and by the decrease of alpha-helix and random coil contents in favor of beta-sheet aggregates is indicated for BSA.

279 citations

Journal ArticleDOI
TL;DR: The cold unfolding of myoglobin is studied with Fourier transform infrared spectroscopy and compared it with pressure and heat unfolding to suggest that the pathways of the cold and pressure unfolding are substantially different from that of the heat unfolding.

182 citations

Journal ArticleDOI
TL;DR: The gel pore size determined using turbidity measurements has been verified by electrophoretic mobility measurements, and the relationship between the induction time and the driving force which is determined by the final setting temperature follows the 3D nucleation model.
Abstract: Kinetics as well as the evolution of the agarose gel topology is discussed, and the agarose gelation mechanism is identified. Aqueous high melting (HM) agarose solution (0.5% w/v) is used as the model system. It is found that the gelation process can be clearly divided into three stages: induction stage, gelation stage, and pseudoequilibrium stage. The induction stage of the gelation mechanism is identified using an advanced rheological expansion system (ARES, Rheometric Scientific). When a quench rate as large as 30 deg C/min is applied, gelation seems to occur through a nucleation and growth mechanism with a well-defined induction time (time required for the formation of the critical nuclei which enable further growth). The relationship between the induction time and the driving force which is determined by the final setting temperature follows the 3D nucleation model. A schematic representation of the three stages of the gelation mechanism is given based on turbidity and rheological measurements. Aggregation of agarose chains is promoted in the polymer-rich phase and this effect is evident from the increasing mass/length ratio of the fiber bundles upon gelation. Continuously increasing pore size during gelation may be attributed to the coagulation of the local polymer-rich phase in order to achieve the global minimum of the free energy of the gelling system. The gel pore size determined using turbidity measurements has been verified by electrophoretic mobility measurements.

171 citations