Maria Pia Picchi

Changes in Erythrocyte Properties during the First Hours of Life: Electron Spin Resonance of Reacting Sulfydryl Groups

ABSTRACT: In an attempt to clarify the mechanism by which the red cells (RBC) of newborn infants are protected against oxidative agents, electron spin resonance (ESR) assays were carried out using the nitroxide radical 4-maleimide-2,2,6,6-tetramethylpiperidinyl-1-oxyl (Mal-6), a sulfydryl-reacting agent. The ESR assays were performed in 24 samples of cord blood, 20 samples of blood from 4-day-old infants, and eight samples of 8-h-old infants. The analyses were carried out on whole blood and washed erythrocytes were resuspended in buffered saline. The same experiments were performed in 10 blood samples from healthy adults as controls. Whole blood, before and after removing the buffy coat, and cell-free plasma were also examined by ESR assay. Cell-free plasma and buffy coats proved not to be appreciably involved in the Mal-6 behavior. The data of the ESR spectroscopy demonstrated a significantly slower reaction rate in the samples of cord blood and in blood of 8-h-old infants, compared to that of 4-day-old infants and adults. No significant differences in Mal-6 behavior could be detected between cord blood and 4-day-old infant blood in the results of ESR assays performed in washed red cells. Chemical determination of RBC-reacting sulfydryl groups and the assays of glutathione also demonstrated the absence of differences between cord blood and blood of 4-day-old infants. The results of our investigation suggest that the RBC-sulfydryl-reacting groups are less involved in the detoxification of oxidative agents during the first hours of life than in the following days. This peculiarity of RBC of younger infants appears to be due, to a considerable extent, to the modulation by plasma factors of the interactions between Mal-6 and RBC-reacting sulfydryl groups. Therefore, the changes in plasma components occurring during the first hours of life appear to modify the interactions between the RBC and the oxidative agents.

Vanadium complexes as models for vanadium species of marine organisms. Synthesis, X-ray structure of oxo(O,O-sulfate)(2,2′:6′,2″-terpyridine)vanadium(IV) hydrate, and density functional geometry optimization analysis of vanadyl complexes

Abstract The addition of an alcoholic solution of 2,2′:6′,2″-terpyridine (terpy) to a vanadyl sulfate (VOSO4·3H2O) aqueous solution (molar ratio 1:1) produced a dark green solution from which brown single crystals suitable for X-ray diffraction studies grew within 12 h. The crystals contain neutral complex molecules [VO(terpy)(O,O-SO4)] and water molecules (at a ratio 1:0.5). The complex molecules have a hexacoordinate vanadium(IV) center linked to the three nitrogen atoms from terpy, to the apical oxo ligand and to two oxygen atoms from sulfate. The analysis of the geometrical parameters relevant to the VSO4 group shows some significant distortion of the SO42− ligand upon chelation to the V(IV)O core. The two S–O(d, donor) bonds (lengths: 1.495(3) trans to oxo; 1.546(3) A cis to oxo) are stretched differently when compared to the S–O(t, terminal) bonds (1.447(3) A). The effect is not due to packing forces but comes from electronic effects. This is shown by a DFT geometry optimization analysis carried out at the density functional B3LYP/LANL2DZ level on model complexes of the type [VO(H2O)]2+, [VOL]2+ (L, NHCH–CHN–C(CH2)–CHNH), [VO(H2O)2L]2+ and [VOL(O,O-SO4)]. This analysis shows also that the [VOL]2+ moiety has a very large affinity for the sulfate anion; the formation energy at the gas phase for [VOL(O,O-SO4)] from [VOL]2+ and SO42− is −448.11 kcal mol−1, much higher than the corresponding value for [VO(H2O)2L]2+ (−91.47). This can be a rationale for the role vanadyl–sulfate interactions play in blood cells of Ascidians.

DNA-ligand interaction detected by proton selective and non-selective spin-lattice relaxation rate analysis

In this paper, a method based on NMR measurements for studying the ability of ligands to interact with macromolecule surfaces is proposed. It is based on temperature-dependent NMR proton selective and non-selective spin-lattice relaxation rate experiments and assumes fast chemical exchange conditions of the ligand between free and bound states. The results obtained appear able to identify DNA-psoralen complex formation. The use of this methodology for monitoring non-covalent interaction of ligands and bipolymers is suggested.

SPECTROSCOPIC INVESTIGATION OF THE CONFORMATIONAL PROPERTIES AND SELF-ASSOCIATION BEHAVIOR OF NATURAL COMPOUNDS IN SOLUTION

ABSTRACT The conformational properties and self-association behaviour of rifaximin and rifaximin OR (Open Ring) were investigated in solution by NMR and IR spectroscopy. The dependence of proton chemical shift on concentration and temperature were analysed to study the self-association process. IR spectra of rifaximin and rifaximin OR were also used at different concentrations to investigate the entity of specific inter- and intra-molecular interactions. Although similar in structure the two molecules had different chemical properties in solution. This could be of some interest in view of the biological importance of this class of antibiotic molecules.

Structural and dynamical characterization of piroxicam by 1H- and 13C-NMR relaxation studies

Carbon spin-lattice relaxation rates of an anti-inflammatory drug, piroxicam, have been measured. These results have been used in determining the reorientational rates of the proton carbon vectors. An analysis of internal motions within the pyridinyl moiety of piroxicam was carried out. Selective proton-carbon nuclear Overhauser effect (NOE) measurements were made in order to determine the solution structure of piroxicam. The effect of indirect NOE arising from exchangeable protons has been analyzed and considered.

Thermodynamic Analysis of Ceramics Production in Sassuolo (Italy) from a Sustainability Viewpoint

We present a thermodynamic analysis of the sustainable use of resources in the province of Modena, focusing the attention on the district of Sassuolo. The methodology that is used is the emergy evaluation. The analysis shows that the Sassuolo district represents the peak of non-sustainability of the whole area, with a huge consumption of non-renewable primary resources, both imported and local. The role of the ceramic tile industry is relevant in the consumption of energy and materials. Different types of factories for ceramics production are compared, representing a good sample of different methods of production. Emergy analysis shows which of these has higher levels of sustainability with respect to the others.

Purine nucleotide-copper(II) binary and ternary complexes. Synthesis, electron paramagnetic resonance and infrared investigation

Abstract An X-band EPR and IR investigation was carried out on Cu(II) binary and ternary complexes involving ATP (adenosine 5′-triphosphate) or IMP (inosine 5′- monophosphate) and an aromatic base such as 2,2′- dipyridylamine (DPA), 2,2′-bipyridyl (BIPY) or 1,10- phenanthroline (PHEN) in the microcrystalline state or in aqueous solution. The measurements were performed at room temperature and at 100 K. A new ternary complex containing Cu(II), IMP and DPA in a 1:1:1 molar ratio was prepared and characterized. The compound crystallizes as thin green plates in the monoclinic P21 space group with a = 7.828(2), b = 18.552(3), c = 17.378(3) A and β = 91.16(2)°. The Cu(II) ion interacts with phosphate oxygen atoms from IMP and with nitrogen atoms from DPA. The interpretation of out data on the basis of the coordination sphere geometries suggests that EPR is a useful tool in investigating the structure and the nature of the close-lying donors of the Cu(II) ions. The EPR and IR data show that in the ternary complexes the aromatic bases BIPY, PHEN and DPA are bound to the Cu(II) centre, probably acting as bidentate ligands both in the solid state and in aqueous solution at pH = 7.

Complexity at the Molecular Level : A Dynamic View of Biomolecules Obtained by NMR

Dominant processes in natural systems are usually controlled by feedback mechanisms that are directly related to self-organization and complex behavior. Much work has been done to understand the biophysical basis of complexity in ecology and biology. Information at the molecular level, such as macromolecular flexibility, is fundamental for understanding this feedback regulation.1 Conformational changes can cause variations in the activity of enzymes by interaction with reaction products at the regulating site. Here we analyze the problem of molecular flexibility in order to understand how it affects the activity of biomolecules from another point of view. The molecule studied was the pain-producing nonapeptide hormone bradykinin (Arg1-Pro2-Pro3-Gly4-Phe5-Ser6-Pro7-Phe8-Arg9), which is formed by proteolysis of kininogen during inflammation.2 Small peptides, like bradykinin, usually do not have any single stable conformation in solution. The conformation that causes the biological effect is adopted only at the active site. Also in this case the flexibility of the biomolecule determines the mechanism of action. We are interested in studying whether the molecule has a random-coil behavior in solution and adopts the active conformation only when the interaction occurs at the active site, or whether the molecule rapidly exchanges between a few low-energy conformations and the interaction just stabilizes one of them. We have determined the conformation of bradykinin in solution by nuclear magnetic resonance (NMR) coupled with theoretical calculations based on dipolar relaxation theory and molecular mechanics. The experimental results are compatible neither with a single static conformation nor with a “random-coil” molecule in solution.

Nuclear Relaxation Analysis of the Xenobiotic- Receptor (DNA Or Plasmatic Protein) Recognition Process

Abstract The study of interactions of xenobiotics with macromolecular receptors is very important for understanding the chemical behaviour of xenobiotic compounds in the biological organisms. The xenobiotic molecules are able to affect the natural activities of biological receptor such as DNA or plasmatic protein. In fact the modification of the conformation of DNA or plasmatic protein, induced by interaction with xenobiotic molecules, can determine profound alterations of the normal biochemical activity. In this study a method based on proton NMR selective and non-selective spin-lattice relaxation rate measurements and their dependence on temperature for analyzing the ability of ligand to interact with receptor is used. The NMR parameters are a weighted average between the free and bound to xenobiotic environments.

THE EXCRETION OF OXALIC ACID IN GOUTY PATIENTS: 121

Utilizing the very satisfactory HPLC procedure recently reported by Hughes et al. (1), we have determined the urinary excretion of oxalic acid in control subjects (aged 20 to 70 years) and in gouty patients (from 35 to 73 years), before and after allopurinol treatment. The urinary excretion in normal subjects was 27.5±1.89 mg/24h, in gouty patients 31.3±3.08 mg/24h before allopurinol, and 43.22±4.66 mg/24h after treatment. It is evident that there is no substantial difference between normal subjects and gouty patients, while allopurinol significantly increases (p<0.05) the urinary excretion of oxalic acid. Since allopurinol inhibits the incorporation of glycine into purine ribonucleotides, this increase suggests that the glycine might be channeled toward the formation of glyoxylate and oxalic acid in gouty patients (2).Results suggest that the behavior of urinary oxalic acid should be under constant control during allopurinol treatment.(1) Hughes H. et al. (1982) Anal. Biochem. 119, 1-3(2) Dean D.M. et al. (1968) Clin. Sci. 35, 325-335