171,954 research outputs found
Materials and techniques of Art Nouveau architecture in Italy and Portugal: a first insight for an European route to consistent restoration
No full textThe results of the investigations on building materials and techniques of Casa Major Pessoa, a typical Art
Nouveau construction in Aveiro (Portugal), and two coeval Art Nouveau buildings in Bologna (Italy) are presented
as a methodological contribution to the restoration of this kind of buildings. This is the first step to
ascertain the existence of a common thread between local materials, technologies and architecture in European
countries at the same period. A holistic approach was adopted: materials were investigated along with
architectural, structural and technological features, in order to achieve a first insight into the Art Nouveau
architecture in Europe in particular for its consistent restoration without loss of historical memory
Interactions of cytoplasmic retinol-binding proteins with phospholipid vesicles: insights into the physiological functions
No full textVitamin A plays a key role in vision, cell growth and differentiation. In the cell, retinol has several fates: (a) it can be stored as retinyl ester of long chain fatty acids through the action of lecithin-retinol acyl transferase (LRAT) [1, 2]; (b) most non-esterified retinol is probably bound to cellular retinol-binding protein I (CRBP-I); (c) retinol can enter the oxidative pathway for the synthesis of retinoic acid, through the action of retinol dehydrogenases (RDH) [3]. CRBP-I is ubiquitous, whereas the homologous CRBP-II is expressed solely in the enterocytes. Our current understanding of these processes remains largely incomplete, but there is evidence that while LRAT is able to access CRBP-bound retinol, the membrane-bound RDH are inactive towards the protein/ligand complex, suggesting that the membrane microenvironment may trigger retinol transfer from the holo protein to the oxidative enzymes.
To address this hypothesis we have performed a suite of NMR experiments with retinol-bound CRBP-I and CRBP-II in the presence of model membranes composed of either anionic or zwitterionic phospholipids, at varying protein:lipid molar ratios and ionic strength. Besides NMR, other biophysical techniques were employed to achieve a better understanding of the ongoing processes.
The results in the presence of phospholipid bilayers will be discussed, in comparison with our previous data collected in buffer [4, 5]. All these studies may help to understand certain aspects of the distinct physiological functions of CRBPs.
References
[1] J. Amengual et al. J. Biol. Chem. 287, 24216-24227 (2012).
[2] W. Jiang and J.L. Napoli Biochim. Biophys. Acta 1820, 859-869 (2012).
[3] S. Portè et al. Chemico-Biological Interactions 202, 186-194 (2013).
[4] T. Mittag, L. Franzoni et al. J. Am. Chem. Soc. 128, 9844-9848 (2006).
[5] L. Franzoni et al. J. Lipid Res. 51, 1332-1343 (2010)
The complex process of vitamin A uptake: a first insight by NMR and other biophysical techniques
No full textVitamin A is essential for diverse aspects of life, ranging from embryogenesis to the proper functioning of most adult organs. It circulates in blood bound to serum retinol binding protein (RBP) and is transported into cells by a multitransmembrane receptor termed stimulated by retinoic acid 6 (STRA6)(1). A STRA6-mediated release of retinol from holo-RBP to target organs through a new mechanism has an evolutionary advantage that prevents a possible toxicity deriving from an excessive accumulation of free vitamin A (2). There is also evidence that a specific binding site for the apo-form of the cellular carriers (CRBP) might exist on the cytoplasmic side of the membrane (3).
To gain a first insight into this complex process, we have investigated the effects of biomembrane mimetic systems on CRBP-I and CRBP-II, by means of NMR, Circular Dichroism and Fluorescence measurements.
The interactions of the two homologous proteins with model membranes were studied by recording 15N-HSQC and 15N-TROSY spectra at different molar ratios. Chemical shifts perturbations and line shape analysis provided insights into the interacting residues and proteins conformational dynamics. As the signals were broadened beyond detection at latest steps of the titration, the NMR data have been complemented by CD and Fuorescence measurements.
The results revealed striking differences between the two homologs (4), despite having nearly identical backbone structures (a beta-barrel with two short alpha-helices) and identical retinol-binding motifs. Apo-CRBP-I interacts with model membranes and very likely the helical domain participates in the formation of a protein-membrane “collisional complex” that results in structural changes of the retinol entry site and in a slower protein tumbling. In contrast, NMR data reveal a higher structural flexibility of apo-CRBP-II that allows the existence of more than one conformation. Line shapes analysis performed in the course of the titrations indicated that the protein conformational dispersion is reduced to one preferred state in the presence of phospholipids bilayers. CD spectra showed that the overall structural integrity of the protein is not affected by the presence of the liposomes.
These new evidences complement our earlier results, which had suggested that the two primary cellular retinol carriers exhibit different mechanisms of ligand uptake (5, 6); combined with their distinct tissue distribution this may imply different roles in an intracellular context.
References:
1. Kawaguchi R., Yu J., Honda J., Hu J., Whitelegge J., Ping P., Wiita P., Bok D. and H. Sun Science 315, 820-825 (2007).
2. Kawaguchi R., Yu J., Ter-Stepanian M., Zhong M., Cheng G., Yuan Q., Jin M., Travis G.H., Ong D. and Sun H. ACS Chemical Biology 6, 1041-1051 (2011).
3. Redondo C., Vouropoulou M., Evans J. and Findlay J.B.C. The FASEB J. 22, 1043-1054 (2008).
4. Franzoni L., Baroni F., Cavazzini D., Rossi G.L. and Lücke C., in preparation.
5. Mittag T., Franzoni L., Cavazzini D., Schaffhausen B., Rossi G.L. and Günther U.L. J. Am. Chem. Soc. 128, 9844-9848 (2006).
6. Franzoni L., Cavazzini D., Rossi G.L. and Lücke C. J. Lipid Res. 51, 1332-1343 (2010).
Acknowledgements: the EU-NMR infrastructure HWB●NMR @ Birmingham (UK) is acknowledged for providing access to instrumentation
The organization, economics, and policy of scientific research: what we do know and what we don't know--an agenda for research
No full textThe knowledge and instruments developed in recent years have paved the way to a substantial contribution from economics to support political and social decision making in matters of scientific progress, such as efficient funding, institutional settings, and allocation. We review the progress made in recent years and predict future directions. Copyright 2011 The Author 2011. Published by Oxford University Press on behalf of Associazione ICC. All rights reserved., Oxford University Press.
Changing incentives to publish
No full textMany national governments have implemented policies providing incentives for researchers to publish, especially in highly ranked international journals. Although still the top publishing nation, the United States has seen its share of publications decline from 34.2% in 1995 to 27.6% in 2007 as the number of articles published by U.S. scientists and engineers has plateaued and that of other countries has grown (1, 2). Hicks (3) argues that the two events are not unrelated: The decline in the relative performance of the United States relates to increased international competition engendered by newly adopted incentives that have crowded out some work by U.S. author
Materiales y tecnologías en la Arquitectura Modernista: casos de estudio de decoración de fachadas en Italia, Portugal y Polonia persiguiendo una restauración racional
No full textThe results of a diagnostic survey on the materials of representative Art Nouveau buildings in Italy, Portugal and Poland are here presented and compared, as a contribution to their understanding and, hence, to support compatible restoration. In particular, the facade decorations were investigated for the appraisal of their materials and technologies, often neglected in current maintenance/restoration works and so cancelled, leading to a severe loss in architectural image. The ongoing diagnostic campaign, in collaboration among different universities, is aimed to set up a database on materials and technologies of Art Nouveau facade decorations at a European scale, as a technical-scientific background for the highlighting of preservation guidelines
Biomolecular NMR, a versatile tool for the understanding of protein science: retinoid-binding proteins as an example
No full textProtein science stands at the heart of modern life sciences because it unravels fundamental biological mechanisms and forms the basis for rapid advances in biomedicine and biotechnology. NMR spectroscopy is uniquely suited to study various aspects of protein structure, dynamics, molecular interactions and function, because information for individual residues can be obtained; moreover, kinetic data, low-populated states and the possible formation of intermediates on the reaction pathway can be determined.
The case of retinoid-binding proteins is discussed here, as an example. Vitamin A has diverse biological functions and is essential for human survival. It circulates in blood bound to serum retinol binding protein (RBP) and is transported into cells by a membrane receptor termed STRA6 (1). The cellular trafficking and metabolism of vitamin A are regulated primarily by specific high-affinity carriers called CRBP-I and CRBP-II. They represent an interesting case where structure determination as well as the study of fast dynamics (ps-ns time scale) (2) failed to elucidate the mode of retinol binding and thus to explain their diverse tissue distribution, functional roles and different ligand affinities.
The highly similar structure of the apo and holo forms (a beta-barrel with two short alpha-helices, see the cartoon) exhibits a closed conformation in both proteins, that seemingly offer no access for the ligand. Given the biological relevance of retinoids, the characterization of their protein interactions and targeted release is of special interest. To tackle this challenging subject we have employed a suite of NMR techniques: 15N relaxation dispersion experiments to investigate the proteins dynamics in the slower micros-ms timescale, line-shape analysis of 15N-HSQC spectra recorded during a retinol titration to get insights into the mechanism of ligand binding and H/D exchange experiments to investigate conformational stability. The results allowed to derive a model of retinol uptake, which is different for CRBP-I and CRBP-II (3, 4); moreover, a distinct local flexibility was found to modulate their binding properties (5).
The two proteins deliver retinol to microsomal membrane-bound enzymes, either for esterification with fatty acids (LRAT) (6, 7) or for oxidation to retinaldehyde (RDH) (8). Our current understanding of these processes remains incomplete, but there is evidence that the membrane microenvironment plays a role in the interactions of holo CRBPs with enzymes (8). To address this hypothesis, we have performed a series of NMR experiments with retinol-bound CRBP-I and CRBP-II in the presence of model membranes composed of either anionic or zwitterionic phospholipids, at varying protein:lipid molar ratios and ionic strength.
Both homologues interact with liposomes of anionic phospholipids, but in a significantly different way (9). A conformational rearrangement of the portal region, coupled to a change in protein dynamics, are required for retinol exchange; these processes seem to be triggered by a membrane-collision.
All the differences between CRBP-I and CRBP-II, when dissolved either in buffer or in the presence of biomembrane mimetic systems, may account for their distinct functional roles in the modulation of intracellular retinoid metabolism. Further experiments are in progress to better describe the ongoing processes in a biological context.
(1) Kawaguchi R., Yu J., Honda J., Hu J., Whitelegge J., Ping P., Wiita P., Bok D., Sun H. (2007) Science, 315, 820-825.
(2) Franzoni L., Lücke C., Pérez C., Cavazzini D., Rademacher M., Ludwig C., Spisni A., Rossi G.L., Rüterjans H. (2002) J. Biol. Chem., 277, 21983-21997.
(3) Mittag T., Franzoni L., Cavazzini D., Schaffhausen B., Rossi G.L., Günther U.L. (2006) J. Am. Chem. Soc., 128, 9844-9848.
(4) Franzoni L., Reed M., Cavazzini D., Rossi G.L., Günther U.L., in preparation.
(5) Franzoni L., Cavazzini D., Rossi G.L., Lücke C. (2010) J. Lipid Res., 51, 1332-1343.
(6) Amengual J., Golczak M., Palczewski K., von Lintig J. (2012) J. Biol. Chem., 287, 24216-24227.
(7) Jiang W., Napoli J.L. (2012) Biochim. Biophys. Acta, 1820, 859-869.
(8) Napoli J.L. (2012) Biochim. Biophys. Acta, 1821, 152-167.
(9) Franzoni L., Baroni F., Cavazzini D., Rossi G.L., Lücke C., in preparation
The grace period in international patent law and its effect on the timing of disclosure
No full textThe paper applies a novel methodology to US and EPO patent data to assess how often the "general grace period" exception is used in the USA and the likely impact of international patent regulations that almost invariably deny Such use on the pace of new disclosures in academia. Comparisons of average publication delays of European academic inventors show that the grace period accelerates knowledge communication and that variations are likely to depend on a lack of harmonisation of international legal systems, transaction costs and the presence of a firm among patent assignees. (C) 2009 Elsevier B.V. All rights reserved
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