Publications

Abstract Previous results have shown that an oxidizing product of firefly luciferin, dehydroluciferyl-adenylate, is the main intermediate in the process of synthesis of dinucleoside polyphosphates catalyzed by firefly luciferase (EC 1.13.12.7). However, we have found that the pH effects on the luciferase oxidizing processes and on the synthesis of dinucleoside polyphosphate are opposite: acidic assay media enhance the synthesis of dinucleoside polyphosphate and inhibit the oxidizing processes. The reason for this apparent contradiction lies on the activation effect of low pH on the adenylate transfer reaction from dehydroluciferyl-adenylate to the acceptor nucleotide. (C) 2003 Published by Elsevier Science B.V. on behalf of the Federation of European Biochemical Societies.

Abstract The standard (p(0) = 0.1 MPa) molar enthalpies of formation of crystalline bis(N,N-diethyl-N'-pivaloylthioureato)copper(II), Cu(PVET)(2), and bis(N,N-diethyl-N'-pivaloylthioureato)nickel(II), Ni(PVET)(2), were measured, at T = 298.15 K, by solution-reaction isoperibol calorimetry. The standard molar enthalpies of sublimation, at T = 298.15 K, of both complexes were obtained using a Knudsen effusion technique. These values were used to derive the standard molar enthalpy of formation of Cu(PVET)(2) and Ni(PVET)(2) in gaseous phase, and to evaluate the difference between the mean metal-ligand and the hydrogen-ligand bond dissociation enthalpies, in these compounds. The N-H homolytic bond dissociation enthalpy in N,N-diethyl-N'-pivaloylthiourea ligand (HPVET) was calculated by high-level density functional theory based calculations. The three-dimensional structures of Cu(PVET)(2) and Ni(PVET)(2) are presented and show a planar coordination around the metal in both molecules.

Abstract "MOCHO" (www.mocho.pt) is the first Portuguese web portal on science and scientific culture. It is a project of the Centre for Computational Physics of the University of Coimbra, which is sponsored by the Portuguese programs "Nonio - 21(st) century" and "Ci (e) over cap ncia Viva". Students who are now attending primary and middle schools were born in the middle of the 80s and belong to the so-called net generation (or zap generation). They grew up in the digital era being, therefore, familiar with cell-phones, computers, Internet, etc. The challenge for them is to select information among the enormous amount which is available in the Internet. The offer of valuable scientific and pedagogical information which is made by "MOCHO" can be an important help for their work, both at school and at home. We describe the portal here.

Abstract We present a study made in Portugal, in 2001/2002, on the use of Information and Communication Technologies (ICT) by teachers of all teaching levels (except high education), in both public and private schools. It was an initiative of the Ministry of Education ("Nonio - 21(st) Century" program), which was carried out by the Competence Centre "Softsciences" and the Centre for Computational Physics of the University of Coimbra. Some of the conclusions of this study, that has collected data from 19337 teachers, are the following: the majority of Portuguese teachers own a PC and approximately half of them use it in several activities, though their use of computers with students is limited. Primary school teachers use often the PC in their schools, though, probably, in an incipient way. The self-training of teachers in ICT is quite common. The Internet is more used by 3rd cycle (last part of middle school) and high school teachers, being most of its users male and young. These and other conclusions should be taken into account in a strategy towards incrementing a better use of new technologies in schools.

Abstract The adsorption of glucose oxidase (GOx) was studied at the interface between two immiscible electrolyte solutions (ITIES) by interfacial capacitance and surface tension measurements and at the air/water (phosphate buffer) interface by surface tension and neutron reflection measurements. The adsorption at both interfaces was found to be time, enzyme concentration, and ionic strength dependent. There was a switch from one interfacial adsorption state to another, as the enzyme concentration was increased. At the ITIES, there was evidence of an interaction between the adsorbed enzyme and the hydrophobic cation in the organic phase (1,2-dichloroethane). The enzyme adsorbed at the air/water interface was found to dissociate into monomers at the lower buffer total concentration of 2 mM while, at the higher buffer concentration of 0.2 M, the adsorbed enzyme retained its dimer structure. The adsorption mostly formed monolayers and the layer thickness varied with bulk concentration, indicating deformation related to the packing of the enzyme at the interface. For enzyme concentrations above 1 muM, in high ionic strength medium, bilayers of enzyme started to form, and the interlayer interactions resulted in a less densely packed second layer forming on the aqueous side of the first one. The switch in properties of the adsorbed layer observed in interfacial tension and capacitance measurements at the ITIES occurred over the same enzyme concentration range as the formation of a more densely packed layer detected from neutron reflection at the air/water interface.

Abstract The reaction between the arginine's guanidino group and alpha-dicarbonyl functionalities was used to develop a novel surface modification chemistry. The first modification step consists of the electrostatic adsorption of a poly-L-arginine layer onto ionizable alkanethiol modified gold surfaces. The strongly basic character of the guanidino group of the arginine residues (pK(a) > 12) guarantees the robust attachment of the polypeptide to negatively charged gold surfaces until very high pH. By varying the pH of the solution from which poly-L-arginine is electrostatically adsorbed, it is possible to control the amount deposited. The availability of the surface guanidino groups of the poly-L-arginine layer for further derivatization with alpha-dicarbonyl reaction probes, yielding stable heterocyclic condensation adducts, is demonstrated. In addition, the reaction with the heterobifunctional reagent p-azidophenyl glyoxal (APG) provides a surface terminated with a photosensitive aryl azide group which was employed for the photochemical immobilization of proteins to the surface. The application of this surface modification chemistry to immobilize antibodies is demonstrated.