J. Costa Pessoa

Transport of therapeutic vanadium and ruthenium complexes by blood plasma components.

Low molecular weight and high molecular weight metal ion binders present in blood plasma are shortly described. The binding of vanadium and ruthenium complexes by these components has received much attention, namely their interactions with human serum albumin and transferrin, and these studies are critically reviewed. The influence of the protein binding on the bioavailability of the prospective drugs, namely on the transport by blood plasma and uptake by cells is also discussed. It is concluded that vanadium compounds are mainly transported in blood by transferrin, but that no study has properly addressed the influence of albumin and transferrin in the vanadium uptake by cells. Ruthenium complexes bind strongly to HSA, most likely at the level of His residues, leading to the formation of stable adducts. If the kinetics of binding to this protein is fast enough, probably they are mainly transported by this serum protein. Nevertheless, at least for a few Ru(III)-complexes, hTf seems to play an active role in the uptake of ruthenium, while HSA may provide selectivity and higher activity for the compounds due to an enhanced permeability effect.

Preparation and characterisation of new oxovanadium(IV) Schiff base complexes derived from amino acids and aromatic o-hydroxyaldehydes

Abstract A range of mostly new oxovanadium(IV) complexes is described. They contain coordinated Schiff bases, made from natural amino acids (glycine, alanine, valine, leucine, isoleucine, methionine, phenylalanine, threonine, aspartic acid, and histidine) and salicylaldehyde or such derivatives as 3-, 4-, or 5-methoxy-salicylaldehyde. The coordination sphere is completed by simple ligands like water, 2,2′-bipyridyl or pyridine. The compounds are characterised and the nature of their coordination spheres shown by analysis, TLC, and by appropriate spectroscopy (EPR, IR, electronic and circular dichroism of solution and solids). In a few cases, magnetic properties are described to establish oxidation state. In several cases, the solubility of the compounds from racemic amino acids differs markedly from those containing the single enantiomer. The crystal and molecular structure of the related (and novel) compound with N-pyridoxylidene- d , l -isoleucinate, [VO(pyr- d , l -Ile)(bipy)]·H2O is described. It contains two diastereomers. Denoting the chiral vanadium centres as A or C, these are and [A(pyr- l -Ile)(bipy)] [C(pyr- d -Ile)(bipy)].

Micro-focused ultrasonic solid–liquid extraction (μFUSLE) combined with HPLC and fluorescence detection for PAHs determination in sediments: optimization and linking with the analytical minimalism concept

Analytical minimalism is a concept that deals with the optimization of all stages of an analytical procedure so that it becomes less time, cost, sample, reagent and energy consuming. The guide-lines provided in the USEPA extraction method 3550B recommend the use of focused ultrasound (FU), i.e., probe sonication, for the solid-liquid extraction of Polycyclic Aromatic Hydrocarbons, PAHs, but ignore the principle of analytical minimalism. The problems related with the dead sonication zones, often present when high volumes are sonicated with probe, are also not addressed. In this work, we demonstrate that successful extraction and quantification of PAHs from sediments can be done with low sample mass (0.125g), low reagent volume (4ml), short sonication time (3min) and low sonication amplitude (40%). Two variables are here particularly taken into account for total extraction: (i) the design of the extraction vessel and (ii) the solvent used to carry out the extraction. Results showed PAHs recoveries (EPA priority list) ranged between 77 and 101%, accounting for more than 95% for most of the PAHs here studied, as compared with the values obtained after soxhlet extraction. Taking into account the results reported in this work we recommend a revision of the EPA guidelines for PAHs extraction from solid matrices with focused ultrasound, so that these match the analytical minimalism concept.

Oxovanadium(IV) complexes with aromatic aldehydes.

The synthesis, structure and spectroscopic properties of complexes with the formula [V(IV)O(dsal)2(H2O)], where Hdsal = salicylaldehyde, o-vanillin and 3-ethoxysalicylaldehyde, are presented. The crystal and molecular structures of [V(IV)O(o-van)2(H2O)] (1) (o-Hvan = o-vanillin = 3-methoxysalicylaldehyde) is studied by single-crystal X-ray diffraction. Each molecule exhibits an octahedral geometry with the two o-van ligands coordinated cis to the V(IV)O2+ group. 1 is the first example of a structurally characterized vanadium complex involving O(aldehyde) as the donor atom and this enables a comparison between the bonding characteristics and the contributions of O(aldehyde), O(amide), O(carboxylate) and O(ketone) (in acetylacetone) to the parallel hyperfine coupling constant in VOL2 complexes.

Oxovanadium(IV) and amino acids. I: The system L-alanine+VO2+; A potentiometric and spectroscopic study

Abstract The equilibria in aqueous solution in the system L -alanine+VO 2+ have been studied by a combination of pH-potentiometric and spectroscopic methods (EPR, visible absorption and circular dichroism) in the pH range 1.5–13. For pH > 4, high ligand to metal ratios were used. The results of the various methods are made self-consistent, then rationalized assuming an equilibrium model including the species MAH, MA, MAH −2 , MA 2 H 2 , MA 2 H, MA 2 , MA 2 H −1 , M 2 A 2 H −2 , M 2 A 2 H −3 (where HA denotes L -alanine) and several hydrolysis products; their formation constants and individual electronic spectra (isotropic and circular dichroism) are given. The isomerism arising from the combination of the lop-sided oxovanadium ion with the asymmetric carbon ligand is analysed.

Preparation and characterisation of new oxovanadium(IV) Schiff base complexes derived from salicylaldehyde and simple dipeptides

Abstract A range of mostly new oxovanadium(IV) complexes is described. They contain coordinated Schiff bases, made from simple dipeptides (glycylglycine, glycylsarcosine, l -alanylglycine, l -alanyl- l -alanine, d , l -alanyl- d , l -alanine and l -serylglycine), and salicylaldehyde. The compounds are characterised and the nature of their coordination spheres shown by analysis, TLC, by appropriate spectroscopy (EPR, IR, electronic and circular dichroism of solution and solids) and by magnetic susceptibility measurements. Serylglycine and threonylglycine are formed by reaction of VO(salGlyGly) with formaldehyde and acetaldehyde, respectively.

Thirty years through vanadium chemistry.

The relevance of vanadium in biological systems is known for many years and vanadium-based catalysts have important industrial applications, however, till the beginning of the 80s research on vanadium chemistry and biochemistry did not receive much attention from the scientific community. The understanding of the broad bioinorganic implications resulting from the similarities between phosphate and vanadate(V) and the discovery of vanadium dependent enzymes gave rise to an enormous increase in interest in the chemistry and biological relevance of vanadium. Thereupon the last 30years corresponded to a period of enormous research effort in these fields, as well as in medicinal applications of vanadium and in the development of catalysts for use in fine-chemical synthesis, some of these inspired by enzymatic active sites. Since the 80s my group in collaboration with others made contributions, described throughout this text, namely in the understanding of the speciation of vanadium compounds in aqueous solution and in biological fluids, and to the transport of vanadium compounds in blood plasma and their uptake by cells. Several new types of vanadium compounds were also synthesized and characterized, with applications either as prospective therapeutic drugs or as homogeneous or heterogenized catalysts for the production of fine chemicals. The developments made are described also considering the international context of the evolution of the knowledge in the chemistry and bioinorganic chemistry of vanadium compounds during the last 30years. This article was compiled based on the Vanadis Award presentation at the 9th International Vanadium Symposium.

The system VO2++oxidized glutathione: A potentiometric and spectroscopic study

The equilibria in the system VO2+ +oxidized glutathione in aqueous solution have been studied in the pH range 2-11 by a combination of pH potentiometry and spectroscopy (EPR, visible absorption and circular dichroism). The results of the various methods are self-consistent and the equilibrium model includes the species MLH4, MLH3, MLH2, MLH, ML, MLH(-1), MLH(-2) and several hydrolysis products (where H4L denotes oxidized glutathione); individual formation constants and spectra are given. Plausible structures for each stoichiometry are discussed.

Preparation and characterisation of vanadium complexes derived from salicylaldehyde or pyridoxal and sugar derivatives

Abstract By reaction of salicylaldehyde (Hsal) with the amino-sugars d -glucosamine (glsmN), d -galactosamine (galacN) or d -glucamine (glcN) in the presence of VOSO4 or VOCl2, Schiff base (SB) complexes were obtained. By using pyridoxal (pyr) instead of Hsal, a solid containing the SB derived from its reaction with glcN was isolated. The compounds were characterised in the solid state by elemental analyses, IR, EPR, CD and magnetic susceptibility measurements. The complexes are not simple monomers in the solid state and were formulated as {VIVO(sal– d -galacN)}n, {VIVO(sal– d -glsmN)}n, (VIVVVO3)(sal– d -glcN) and (VIVO)3(pyr– d -glcN)2, the SB ligands being coordinated through the imine–N, phenolato-O−, sugar–O− and sugar–OH moieties. The complexes 3–5 were studied in solution by UV–Vis and CD spectrophotometry. The CD band pattern and λmax are normally the same both in the solid state and in MeOH, indicating that the binding mode is mostly preserved. Complex 6 is only slightly soluble and the spectroscopic studies were not conclusive in this respect. Upon dissolution of complexes 3–6, the oxovanadium(IV) is progressively oxidized and the SB hydrolysed.

Oxovanadium(IV) and amino acids—II. The systems l-serine and l-threonine+VO2+. A potentiometric and spectroscopic study

Abstract The equilibria in aqueous solution in the systems l -serine and l -threonine +VO2+ have been studied by a combination of pH-potentiometric and spectroscopic methods (EPR, visible absorption and circular dichroism) in the pH range 1.5–13.6. For pH > 4, high ligand-to-metal ratios were used. The results of the various methods are made self-consistent, then rationalized assuming an equilibrium model including species, MLH, ML, MLH−2, MLH−3, ML2H2, ML2H, ML2, ML2H−1, ML2H−2, M2L2H−2 and M2L2H−3 (where HL denotes l -serine or l -threonine) and several hydrolysis products; their formation constants and individual electronic spectra (isotropic and circular dichroism) are given. Plausible isomeric structures for each of the stoichiometries are discussed.