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Biomedical subjects

M Fasano

Publications and source records attributed to M Fasano.

At least 37 records · Page 2Linked to original sources
PubMed1996

Azide, cyanide, fluoride, imidazole and pyridine binding to ferric and ferrous native horse heart cytochrome c and to its carboxymethylated derivative: a comparative study.

Azide, cyanide, fluoride, imidazole, and pyridine binding to ferric and ferrous native horse heart cytochrome c and to its carboxymethylated derivative has been investigated, from the thermodynamic viewpoint, at pH 7.5 and 25.0 degrees C. Ligand affinity for ferric and ferrous carboxymethylated cytochrome c is higher by about 30- and 400-fold, respectively, than that observed for the native protein. The results here reported: (i) allow the estimation, for the first time, of the ligand-independent free energy associated with the heme-iron sixth coordination bond in ferric and ferrous native cytochrome c, which turns out to be +8.4 kJ mol-1 and +14.6 kJ mol-1, at 25.0 degrees C, respectively, and (ii) suggest an interplay between redox, structural, ligand binding, and recognition properties of cytochrome c.

Animals↗
PubMed1996

A new ytterbium chelate as contrast agent in chemical shift imaging and temperature sensitive probe for MR spectroscopy.

A paramagnetic Yb(III) complex that is the prototype of a novel class of probes for MRI and MRS has been developed. The complex displays highly shifted 1H resonances that are characterized by short relaxation times and, as such, may prove to be a valuable alternative in applications that currently require fluorine-containing probes. Selective excitation of the paramagnetically shifted resonances allows the spatial distribution of the complex to be mapped. This communication reports the images that were obtained by selectively exciting the most intense methyl group (-14.2 ppm at 27 degrees C) for complex concentrations ranging from 0.003-0.1 M. Spectroscopically, the complex may be used as a temperature probe since the proton chemical shifts exhibit a strong temperature dependence. In human serum the chemical shift difference of a selected pair of proton resonances was observed to follow a gradient of -0.42 +/- 0.01 ppm/degrees C. Furthermore, since the chemical shift of the methyl resonance displays a temperature coefficient of -0.04 +/- 0.01 ppm/degrees C, it should be possible to use the image phase for thermal mapping.

Contrast Media↗
PubMed1996

Structural determinants of fluoride and formate binding to hemoglobin and myoglobin: crystallographic and 1H-NMR relaxometric study.

The x-ray crystal structure of the fluoride derivative of ferric sperm whale (Physeter catodon) myoglobin (Mb) has been determined at 2.5 A resolution (R = 0.187) by difference Fourier techniques. The fluoride anion, sitting in the central part of the heme distal site and coordinated to the heme iron, is hydrogen bonded to the distal His(64)E7 NE2 atom and to the W195 solvent water molecule. This water molecule also significantly interacts with the same HisE7 residue, which stabilizes the coordinated fluoride ion. Moreover, fluoride and formate binding to ferric Aplysia limacina Mb, sperm whale (Physeter catodon) Mb, horse (Caballus caballus) Mb, loggerhead sea turtle (Caretta caretta) Mb, and human hemoglobin has been investigated by 1H-NMR relaxometry. A strong solvent proton relaxation enhancement is observed for the fluoride derivatives of hemoproteins containing HisE7. Conversely, only a small outer-sphere contribution to the solvent relaxation rate has been observed for all of the formate derivatives considered and for the A. limacina Mb:fluoride derivative, where HisE7 is replaced by Val.

Animals↗
PubMed1996

1H-NMR relaxometric study of pancreatic serine (pro)enzyme inhibition by a Gd(III) chelate bearing boronic functionalities.

Binding of the paramagnetic N,N"-bis(m-boroxyphenylcarbamoylmethyl)-diethylenetriamine-N,N', N"-triacetic acid Gd(III) [sequence: see text] complex (GdBB) to chymotrypsin, chymotrypsinogen, trypsin, trypsinogen and pancreatic elastase has been investigated by 1H-NMR relaxometry, between pH 6.0 and 8.5, at 25.0 degrees C. Values of Ki for the competitive inhibition of serine proteinases by GdBB are in excellent agreement with values of Kd obtained by 1H-NMR relaxometry, suggesting that the substrate and the paramagnetic complex bind to the same region. Moreover, 1H-NMR relaxometry allowed to determine values of Kd for GdBB binding to chymotrypsinogen and trypsinogen, both devoid of catalytic activity. The increase of the water proton relaxation rate upon GdBB binding to serine (pro)enzymes may be useful in the design of novel functional contrast agents for magnetic resonance imaging.

Boron↗
PubMed1995

NMR relaxometric investigation on human methemoglobin and fluoromethemoglobin. An improved quantitative in vitro assay of human methemoglobin.

Longitudinal water proton relaxation rates of methemoglobin solutions show a strong dependence on temperature and pH. The increase of the relaxation rates with temperature is associated with shortened exchange lifetime of the coordinated water molecule. An accurate measurement of the relaxation rate of methemoglobin solutions thus requires careful control of the experimental temperature. This observation prompted the authors to look for an improved version of the relaxometric in vitro determination of methemoglobin. The method is based on transforming methemoglobin into the corresponding fluoromethemoglobin derivative, which shows both a higher relaxivity and a negligible dependence on temperature. The proposed method has been found to be in good agreement with data from spectrophotometric assays.

Humans↗
PubMed1995

Inhibition of bovine beta-trypsin, human alpha-thrombin and porcine pancreatic beta-kallikrein-B by 4',6-diamidino-2-phenylindole, 6-amidinoindole and benzamidine: a comparative thermodynamic and X-ray structural study.

The inhibitory effect of 4',6-diamidino-2-phenylindole (DAPI) and 6-amidinoindole on the catalytic properties of bovine beta-trypsin (trypsin), human alpha-thrombin (thrombin) and porcine pancreatic beta-kallikrein-B (kallikrein) was investigated (between pH 3.0 and 7.0, I = 0.1 M; T = 30.0 +/- 0.5 degrees C), and analyzed in parallel with that of benzamidine, commonly taken as a molecular inhibitor model of serine proteinases. Next, the X-ray crystal structure of the trypsin:DAPI complex was solved at 1.9 A resolution (R = 0.161). Over the whole pH range explored, values of the association inhibition constant (Ki) for DAPI and 6-amidinoindole binding to trypsin, thrombin and kallikrein are higher than those found for benzamidine association, suggesting a binding mode of DAPI to the enzyme primary specificity pocket-based on the indole moiety of the inhibitor. On lowering the pH from 5.5 to 3.0, the decrease in affinity for DAPI, 6-amidinoindole and benzamidine binding to trypsin, thrombin and kallikrein reflects the acidic pK shift of the Asp189 invariant residue, present at the bottom of the primary specificity subsite of the serine proteinases considered, from 4.5, in the free enzyme, to 3.7, in the proteinase:inhibitor complexes. Inspection of the refined crystal structure of the trypsin:DAPI complex, however, does not allow a unique interpretation of the inhibitor binding mode. The present data were analysed in parallel with those reported for related serine (pro)enzyme/inhibitor systems.

Animals↗
PubMed1994

Structure of the sulfide-reactive hemoglobin from the clam Lucina pectinata. Crystallographic analysis at 1.5 A resolution.

The crystal structure of the aquo-met form of the sulfide-reactive hemoglobin (component I) from the gill of the symbiont-harboring mollusc, Lucina pectinata, has been solved and refined at 1.5 A resolution, based on synchrotron radiation X-ray diffraction data, and employing molecular replacement techniques. The crystallographic R-factor, calculated for the data in the 15.0 to 1.5 A resolution range, is 0.170, with highly regular stereochemical parameters for the protein model, and including 131 water molecules. The monomeric hemoglobin I chain consists of 142 amino acid residues, which have been partly identified on the basis of the crystallographic analysis. The molecule is characterized by an unusual distribution of aromatic residues, particularly in the region surrounding the distal site in the heme pocket. The heme distal residue is Gln(64)E7, while other notable amino acid substitutions include Trp(21)B2, Phe(29)B10, Leu(46)CD3, Phe(68)E11 and Trp(75)E18. An amino acid insertion (Ser44) is observed between sites CD1 and CD2. In the aquo-met protein, a water molecule is present at the sixth coordination position of the heme iron, and hydrogen bonded to Gln(64)E7. Simple model building shows that a dioxygen molecule, bound to ferrous protein, would contact with its free atom the ring edge of Phe(29)B10, being thus stabilized at the coordination site by an aromatic-electrostatic interaction. Similarly, the unique packing and organization of aromatic residues in the surroundings of the heme distal site is proposed as the molecular basis of the very high affinity of Lucina pectinata hemoglobin I for hydrogen sulfide, considered as one of the two physiological ligands of the protein.

Amino Acid Sequence↗
PubMed1994

Evidence for a glycidic-lipidic matrix in human neuromelanin, potentially responsible for the enhanced iron sequestering ability of substantia nigra.

The high-resolution solid-state 13C-NMR spectrum of a neuromelanin specimen (from patients dying from nonneurological diseases) is compared with that obtained from enzymatically prepared dopamine-melanin. The main differences between the two spectra suggest the occurrence in neuromelanin of a glycidic/lipidic matrix tightly associated with the melanin macromolecule. Atomic emission spectroscopy revealed high iron content (1.5%) in the neuromelanin specimen, in full agreement with previous reports. These observations support the view that neuromelanin acts as a strong chelating (and insolubilizing) system for iron ions and further suggest that the attack to this compact composite substrate may be an important step to allow the release of iron ions responsible for the increased lipid peroxidation reported in the pathogenesis of Parkinson's disease.

Carbon Isotopes↗
PubMed1993

Inhibition of serine proteinases belonging to the chymotrypsin superfamily by the cyclic thiolic compound YS3025: a comparative crystallographic study.

The synthetic cyclic thiolic compound 3-[2-(2-thiophencarboxythio)]-propanoyl-4-thiazolidin carboxylic acid (YS3025) acts as an effective inhibitor of bovine alpha-chymotrypsin. In the present communication YS3025 binding studies are extended to bovine beta-trypsin and porcine pancreatic elastase, by means of crystallographic difference Fourier techniques. For all the enzymes considered, the thiopencarbonyl moiety of YS3025 is located at the entrance of the inhibited proteinase primary specificity pocket (S1), covalently linked to the catalytic Ser195 OG atom, and forming an acyl-enzyme complex. These observations allow to select between alternative binding (and inhibition) mechanisms for YS3025 and related molecules to serine proteinases belonging to the chymotrypsin superfamily.

Animals↗
PubMed1992

Paramagnetic water proton relaxation enhancement: from contrast agents in MRI to reagents for quantitative "in vitro" assays.

The use of stable complexes of paramagnetic metal ions as probes in analytical applications of the NMR technique is discussed. Two examples are given that involve the determination of the total Fe3+ content of human serum transferrin (Tf) and the extent of glycation of human serum albumin (HSA). The method is based on the measurement of the longitudinal water proton relaxation times, conveniently altered following a selective chemical interaction between the substrate and the paramagnetic probe.

Contrast Media↗
PubMed1992

Quantitative determination of methemoglobin by measuring the solvent-water proton-nuclear magnetic resonance relaxation rate.

We report a new method for the quantitative determination of human methemoglobin (metHb) based on the measurement of the solvent-water proton-nuclear magnetic resonance (NMR) relaxation rate R1 [normalized to 1 mmol/L hemoglobin (Hb) concentration]. MetHb (%) is estimated from the linear dependence of R1 on the metHb concentration, taking into account the simple relationship [MetHb] = [(R1 - R1HbO2)/(R1metHb - R1HbO2)].100, where R1HbO2 and R1metHb are values for the solvent-water relaxation rate of standard 1.0 mmol/L solutions of the oxygenated derivative of human hemoglobin (HbO2) and of metHb, respectively. The minimum metHb that may be determined from the analysis of the experimental data is 0.5 +/- 0.4%.

Cytochrome-B(5) Reductase↗
PubMed1991

An NMR study of the interaction between melanin free acid and Mn2+ ions as a model to mimic the enhanced proton relaxation rates in melanotic melanoma.

The interaction of a soluble Melanin Free Acid (MFA) from Sepia melanin with Mn2+ ions is investigated by measuring the proton water relaxation rates. The similarity between MFA and the parent melanin is assessed by means of their high resolution 13C cross polarization magic angle spinning NMR spectra. The observed marked increase in longitudinal proton relaxation rates and the characteristic 1/T1 NMRD profile are associated to the formation of a macromolecular metal complex. The presence of similar paramagnetic species is expected to cause the high contrast shown by melanotic tissues in MRI.

Animals↗
PubMed1991

NMR studies of melanins: characterization of a soluble melanin free acid from Sepia ink.

This paper deals with the nuclear magnetic resonance characterization of a soluble derivative (melanin free acid) of Sepia melanin obtained by a peroxidative treatment of the parent (insoluble) species. High resolution 13C and 15N solid state NMR spectroscopies allow the assessment of the chemical changes occurring in the macromolecule upon solubilization. 1H and 13C NMR solution spectra are discussed in light of the results obtained from the solid state spectra. Furthermore, the coordination properties of melanin have been investigated through 27Al NMR spectroscopy and proton relaxation enhancement studies of the paramagnetic gadolinium complex of melanin free acid. Through these experiments it has been possible to evaluate the molecular reorientational time tau R (and from it an estimated molecular weight close to 20 KDa) and the strength of the metal-macromolecule interaction.

Aluminum↗
PubMed1990

Breast and soy-formula feedings in early infancy and the prevalence of autoimmune thyroid disease in children.

It has been suggested that feeding practices in infancy may affect the development of various autoimmune diseases later in life. Since thyroid alterations are among the most frequently encountered autoimmune conditions in children, we studied whether breast and soy-containing formula feedings in early life were associated with the subsequent development of autoimmune thyroid disease. A detailed history of feeding practices was obtained in 59 children with autoimmune thyroid disease, their 76 healthy siblings, and 54 healthy nonrelated control children. There was no difference in the frequency and duration of breast feeding in early life among the three groups of children. However, the frequency of feedings with soy-based milk formulas in early life was significantly higher in children with autoimmune thyroid disease (prevalence 31%) as compared with their siblings (prevalence 12%; chi 2 = 7.22 with continuity factor; p less than 0.01), and healthy nonrelated control children (prevalence 13%, chi 2 = 5.03 with continuity factor; p less than 0.02). Therefore, this retrospective analysis documents the association of soy formula feedings in infancy and autoimmune thyroid disease.

Adolescent↗
PubMed1986

[Diabetes and surgical interventions].

Due to the ways their disease develops diabetics are more likely to require surgery than the rest of the population and operations constitute a stress factor with high rates of morbidity and post-operative mortality due essentially to cardiovascular and infectious complications. In normal subjects the stimulation of the hypothalamohypophyseal axis and the suprarenal marrow induced by surgical stress mobilizes energy substrates that provoke the secretion of insulin that prevents their accumulation and improves their utilization. In diabetics the inadequacy or lack of insulin secretion unbalances these mechanisms to the great danger of the patients themselves. For this reason patients' pre-operative conditions must be very carefully assessed and treatment designed to prevent the increase of catabolic ways due to the lack of insulin must be given. Some of the many treatment protocols proposed are described and discussed, a distinction being made between diet, non insulin and insulin dependent diabetics. The post-operative risk constituted by the onset of non-ketoacidotic hyperosmolar coma, as occurs in other severe stress situations should also be remembered.

Anesthesia↗