Group Coordinator: João da Costa Pessoa
BIOIN@IST is involved in a broad range of projects in several areas, from metal ions in biology and medicine to the development of organic bioactive compounds or homogeneous/heterogeneous catalysts and also of analytical techniques. The group uses a multidisciplinary approach, founded on polyvalent experience on the design (molecular modelling), synthesis of organic compounds and metal complexes, as well as on their characterization in the solid state and in solution using analytical methods such as potentiometry and spectrometry (IR, UV-Vis, CD, NMR, EPR, MS). The description of the ongoing and planned work is organized into the topics below.
Main Research Topics (more details below)
Metals in biology
Metal ions in Medicine
Pre-biotic chemistry and biological evolution
Reactions of co-ordinated ligands
To undertake the research involved in these topics, the group members have several relevant national and international collaborations.
Short description of studies done or in progress:
Metals in biology
Amavadine and models and cytochromes P-450 models
The study of amavadine (a natural vanadium compound from Amanita muscaria fungi) had new developments: the electrocatalytic oxidation of pyrogallol with amavadine models was observed and several hydroxylation, halogenation and oxofunctionalization reactions of diverse alkanes and aromatic compounds were discovered. Similar results were obtained when vanadium haloperoxidase models were used as catalysts. These findings gave rise to new experiments in which ketones, alcohols and halogenated derivates were synthesised in mild conditions. The studies are carried out in collaboration with group 5 in CQE, and have already allowed several patents. The studies with amavadine models, other vanadium compounds and models of the cytochromes P-450 are being developed to improve the conditions and yields of reactions with potential industrial interest, such as the synthesis of carboxylic acids.
The work on algal vanadium-haloperoxidases from the Portuguese coast as well as the analytical survey of the metal element content of marine sponges collected in Madeira and Angola coasts have been completed. Immobilized cross-linked enzyme aggregates (CLEAs) were used for synthetic purposes. Namely a 3-phytase (enzyme that catalyses the hydrolysis of phosphate from phytic acid) after incorporation of vanadium in the active site was shown to catalyse the sulfoxidation of thioanisole with high yield and moderate enantio-selectivity.
Metal ions in Medicine
Investigations have demonstrated the insulin-mimetic effects of metal complexes. In particular, the possibility of using vanadium complexes as oral insulin substitutes in the therapy of diabetes is object of intensive research. The design and synthesis of new vanadium compounds has been one of the tasks in Group 1 of CQE. Several new ligands and vanadium(IV/V) complexes have been characterised (by EPR/NMR, UV-Vis, IR, CD, MS, X-ray), both in the solid and solution states, their speciation in body fluids evaluated (to understand their pharmaco-kinetics and toxicity), and their insulin-like action tested. As strategy, many of the ligands contain the phenolate donor group, known to bind vanadium strongly, the ligands being synthesized by modular assembly of simple commercially available non-toxic molecules. Studies on diabetic mice involving designed Zn and Mo complexes are also under course. The group is continuing studies involving the synthesis of new ligands (particularly pyridinone, pyrimidinone, Schiff base (SB), reduced SB and hydroxamate type) and complexes, with the aim of obtaining compounds with an optimal impact (with respect to a normal glucose level) and a minimized toxicity. The evaluation of the efficiency of transport of complexes in blood is being done by studying their interaction with plasma proteins, namely with transferrin and albumin, by circular dichroism, EPR and fluorescence spectroscopy. Speciation/modelling studies are carried out to simulate the behaviour of complexes once in the blood and inside the cells, to acquire information on the biologically important/active form of the metal ion in the different bio-fluids and tissues. In vitro and in vivo studies are done in collaboration with other institutions.
The success of several metal complexes as therapeutic agents for Cancer, and the need for the development of new compounds, as well as different mechanisms of action, argue for a future role of non-platinum metal complexes in cancer treatment. The interaction of several vanadium, ruthenium, rhenium and copper complexes with DNA is being studied by CD, fluorescence and UV-Vis spectroscopy, and by electrophoretic techniques. The main objectives are the determination of DNA-binding properties and/or cleavage ability of the complexes, so that their potential as therapeutic agents might be evaluated. The interaction of these metal complexes with plasma proteins is also being studied.
Other applications (related to the bioactive ligands subject)
Metal decorporation (Fe/Al overload-related diseases) and metal carriers to specific tissues for diagnostic purposes, namely SPET/PET ( 67/68Ga, 111In) and MRI (Gd).
The research activity is centred on the development and activity evaluation of target structures with prospective pharmacological or environmental applications, namely: (i) chelating agents for decorporation of specific excessive/misplaced metals ions (Fe/Al); supported chelators for environmental metal decontamination (e.g. actinides in water streams) or for biological applications in extracorporeal devices; (ii) ligands for the delivering of radiotracers or paramagnetic probes to specific targets aimed at diagnostic or therapeutic purposes (67/68Ga, 111In, Gd); (iii) inhibitors of zinc-containing enzymes [Matrix Metalloproteinases (MMPs), Carbonic Anhydrases (CAs), Histone Deacetylase (HDAC)] or Mo-containing enzymes [e.g. Xanthine Oxidase (XO)], which are associated to diseases such as arthritis, cancer metastasis, cardiovascular, inflammatory diseases and gout (hyperuricemia); (iv) anti-oxidants and also anti-neurodegenerative drugs for the delay/prevention of brain disorders (e.g. Parkinson’s and Alzheimer’s diseases). New poly-functional compounds are also being designed to get potential dual drug/synergistic effects: dual enzyme inhibitors [MMPs and CAs /dihydrofolate Reductase (DHFR)]; anti-metabolite associated to MMP or CA inhibitor roles; multi-target anti-neurodegenerative drugs (Fe-chelator, MAO-B inhibitor, inhibitor of AChE); anti-oxidant iron-chelators. The novel potential drugs, containing different number/type of metal chelating units (e.g. hydroxamic acids, hydroxypyridinone and hydroxypyrimidinones) and additional extrafunctional groups, are designed and prepared. They are studied for their chemical-physical properties, namely metal-chelating ability and lipophilic and anti-oxidant capacity, using potentiometry, NMR, UV-Vis, IR, cyclic voltammetry and X-ray. The most promising compounds are bio-assayed in collaboration with other institutions, namely, in vitro (radiochemical evaluation, enzyme inhibitory activity, cell viability assays, cytoprotector capacity, toxicity, antagonistic activity against metal-stimulated-amyloid aggregation), in ex vivo (cytoprotector activity) and in vivo (e.g., in mice to model the chelating therapy as well as the biodistribution of 67/68Ga and 111In radiotracers).
Pre-biotic chemistry and biological evolution
The involvement of boric acid and alkaline earth ions in the phosphorylation and stabilisation of ribose is being the object of recent studies. This work, associated with the so-called “RNA world”, will be continued and complemented with theoretical calculations. The role of the chemical elements in biological evolution and in the human central nervous system, as well as the selective occurrence of D-aminoacids in living organisms, is also being object of research.
Reactions of co-ordinated ligands
The group has been active on synthesis, speciation, structural and spectroscopic studies of V, Cu, Ni and Zn complexes, and on the reactivity of co-ordinated ligands. The objective of the current studies involving mainly Cu and Ni complexes is directed to get better yields in asymmetric synthesis of non-proteinogenic amino acids. For this purpose, the complex of the SB ligand derived from the reaction of S-o-N-(N-benzylprolyl) aminobenzophenone with glycine continues to be used as starting material to produce new optically active amino acids. Molecular mechanics (and DFT) calculations will also continue to evaluate steric factors responsible for the enantiomeric excesses obtained.
Besides the work mentioned above: (i) collaboration with Group 5 of this Unit, in (Amavadine and models and cytochromes P-450 models) and (ii) vanadium phytases (collaboration with TU Delft), the group has been quite active in the development of catalytic oxidative transformations. The development of homogeneous and heterogeneous catalytic systems for the synthesis of several types of organic compounds is in progress. Namely asymmetric synthesis involving homogeneous catalysis by transition metal complexes, catalysts supported in solids, or encapsulated in zeolites, or involving adsorbed ionic liquids are being explored. Particularly the group is developing the use of complexes of reduced Schiff base ligands of the salen-type (and of other Schiff base types) to promote catalytic oxidations and other reactions. This involves the synthesis of novel more stable ligands and the study of their reactivity and selectivity.
The group has experience in analytical techniques, and this has been used to develop procedures for specific purposes, namely the determination of trace and non-trace elements in natural waters used for therapeutic purposes, in biological samples (whole blood, plasma, plants, etc.), mainly by atomic absorption (flame and graphite furnace) and inductively coupled plasma. Besides pursuing these studies, work has involved a project directed to the evaluation of lead poisoning in Portuguese duck and rail populations, and its impact on the survival rates and lead accumulation in their predators. The use of extraction and chromatographic techniques for several types of studies, namely in environmental applications and the characterization of materials used in ancient works of art has been extensively developed.
J.J.R. Fraústo da Silva has published over 200 papers and a series of books in collaboration with R.J.P. Williams, namely The Biological Chemistry of the Elements – the inorganic chemistry of life, Oxford University Press, 1991, 2nd enlarged Ed. 2001, The Natural Selection of the Chemical Elements, Oxford University Press, 1996, Bringing Chemistry to Life – From matter to man, Oxford University Press, 1999, and Chemistry of Evolution – the development of our ecosystem, 2006, Elsevier. In collaboration with Group V of this Unit, J.J.R. Fraústo da Silva has registered 8 patents.
M. Amélia Santos is one of the editors of the book of the series Metal Ions- Metal Ions in Biology and Medicine, Vol. 9, M.C. Alpoim, P.V. Morais, M.A. Santos, A.J. Cristóvão, J.A. Centeno, P. Collery, John Libbey, Paris, 2007.
J. Costa Pessoa is one of the editors of the book: Vanadium the Versatile Metal, ACS Symposium Series Vol. 974, K. Kustin, J. Costa Pessoa, D.C. Crans, Eds., Oxford University Press, Washington, DC, 2007.
A book by J.J.R. Fraústo da Silva, J.A.L. Silva: The Chemistry of the Brain – the chemical elements and the central nervous system, is in the press by Gradiva Publications.
The members of Group I of CQE have been involved in the supervision of many graduate and undergraduate students, and in the organization of International Conferences, e.g.:
– 9th International Symposium on Metal Ions in Biology and Medicine, Lisbon, May 2006 (M. Amélia Santos – co-chair),
– 5th International Symposium on the Chemistry and Biological Chemistry of Vanadium, San Francisco, CA, USA, September 2006 (J. Costa Pessoa – co-chair),
– 6th International Vanadium Symposium, Lisbon, July 2008 (J. Costa Pessoa – chair).