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A Desideri

Publications and source records attributed to A Desideri.

192 records · Page 11Linked to original sources
PubMed1981

X-ray absorption edge spectroscopy of Co(II)-binding sites of copper- and zinc-containing proteins.

X-ray absorption near-edge spectroscopy (XANES) of Co(II) in three derivatives of superoxide dismutase, namely [Cu(II)-Co(II)], [Cu(I)-Co(II)] and [...-Co(II)], suggests a tetrahedral coordination of the metal for all compounds. Significant differences, detected in the spectrum of the [Cu(II)-Co(II)] derivative as compared to the other species, indicate that a conformational change and/or a different charge of the imidazole bridging the two metal sites in superoxide dismutase occur in coincidence with the change of copper valence. The XANES spectra of the cobalt derivatives of alcohol dehydrogenase, carbonic anhydrase and stellacyanin show features that can be accounted for by an increasing degree of covalency in the metal first sphere of coordination, in the following order: alcohol dehydrogenase greater than stellacyanin greater than superoxide dismutase greater than or equal to carbonic anhydrase.

Alcohol Oxidoreductases↗
PubMed1981

Dependence on freezing of the geometry and redox potential of type 1 and type 2 copper sites of Japanese-lacquer-tree (Rhus vernicifera) laccase.

The room-temperature e.p.r. spectrum of the Japanese-lacquer-tree (Rhus vernicifera) laccase shows A parallel (the hyperfine splitting constant) and g parallel values of both the Type 1 and Type 2 Cu appreciably different from those measured at liquid-N2 temperature. The geometry of the sites, as inferred from the room-temperature e.p.r. parameters, is more consistent with their redox properties. A rough correlation is found between A parallel and g parallel values and redox potential of the blue copper in several enzymes.

Chemical Phenomena↗
PubMed1980

Titrations with ferrocyanide of japanese-lacquer-tree (Rhus vernicifera) laccase and of the type 2 copper-depleted enzyme. Interrelation of the copper sites.

1. Redox titrations are reported of the metal centres in Japanese-lacquer-tree (Rhus vernicifera) laccase with ferrocyanide. 2. The redox potential of Type 1 Cu was found to increase with ferrocyanide concentration up to a limiting value similar to that for the Type 1 Cu in Type 2 Cu-depleted enzyme (which is independent of ferrocyanide concentration). 3. The redox potential of the two-electron acceptor (Type 3 Cu) is also independent of ferrocyanide concentration in Type 2 Cu-depleted enzyme and lower than values reported for the native enzyme. 4. The two-electron acceptor is present in the oxidized state in the Type 2 Cu-depleted enzyme, though the latter lacks the 330 nm absorption band. 5. The redox potential of Type 2 Cu also depends on ferrocyanide concentration, at least in the presence of azide. 6. The redox potentials are affected by freezing the solutions and/or addition of azide, the latter binding to Type 2 Cu with affinity dependent on the redox state of the two-electron acceptor.

Binding Sites↗
PubMed1978

An electron spin resonance study of high spin forms of cobalt(II) bovine carbonic anhydrase.

The ESR spectra of bovine Co(II) carbonic anhydrase at 7 K at low and high pH and of the iodide derivative have been analyzed. The spectrum of the low pH form shows axial symmetry whilst that at high pH is rhombically distorted. This anisotropy is still more accentuated in the iodide derivative. The high pH (hydroxyl) form and the iodide derivative are thought to have a tetracoordinate trigonal pyramidal structure, with a fifth more distant axial ligand. The low pH form is consistent with a pseudotetrahedral geometry previously postulated.

Journal Article↗
PubMedDate not supplied

Membrane-perturbing activity of Viperidae myotoxins: an electrostatic surface potential approach to a puzzling problem.

Phospholipase-like myotoxins are a class of proteins present in Viperidae venom. Despite the high level of amino acid and structural homology with soluble phospholipases A(2), myotoxins are devoid of enzymatic activity and share cytolytic activity by means of a totally unknown mechanism involving the lipid bilayer perturbation. The distribution of electrostatic surface potentials of four myotoxins and seven phospholipases A(2) has been compared. The charge distribution is similar in all active non-cytolytic phospholipases with a strongly positive side corresponding to the domain interacting with the micellar substrate and with the opposite side negatively charged. In contrast, all myotoxins examined are positively charged on both sides. Myotoxin III, the only known example of a myotoxin sharing enzymatic activity, displays the same electrostatic surface potential as other related toxins. Using liposomes made with non-hydrolysable phospholipids, we demonstrate that myotoxin III perturbs the lipid bilayer like other myotoxins. Based on these results, a molecular model for myotoxin-membrane perturbing activity is proposed. In this model, potential double-face binding of myotoxic phospholipases A(2) to lipid surfaces could trigger a lipid bilayer destabilization and could generate a stable fusion pore, probably because of the presence of hydrophobic moieties that flank the cationic sites.

Cell Membrane Permeability↗
PubMedDate not supplied

A comparative study on liver ornithine carbamoyl transferase from a marine mammal Stenella and an elasmobranch Sphyrna zygaena.

1. Ornithine carbamoyl transferases from liver of the dolphin Stenella and the shark Sphyrna zygaena were purified to homogenity and compared for some kinetic and structural properties. 2. The two enzymes showed a specific activity of 211 and 115 respectively. 3. With respect to molecular weight, trimeric subunit structure and Km values, they were alike and similar to enzymes from other species. 4. Both enzymes were thermolable, but they were protected from thermal inactivation in a different way by ornithine and phosphate. 5. The two enzymes focused, respectively, at pH 8.6 and between pH 6.4 and 8.0, the former value being appreciably higher than those of enzymes from other species.

Animals↗
PubMedDate not supplied

Isotopic effect on the kinetic of thermal denaturation of ceruloplasmin.

The kinetics of thermal denaturation of ceruloplasmin in water and in water with different percentage of D2O in the temperature range 25-85 degrees C, following the optical density change of the 610 nm charge transfer band of the protein has been investigated. A temperature Tt approximately equal to 65 degrees C above which an irreversible denaturation process of the protein active site takes place has been found. The kinetics of the denaturation process of the protein are fitted by two first order reactions, which have been assigned to a different thermal denaturation behaviour of the two Cu2+ type I sites existing in the protein. Addition of D2O to the protein solution affects the two kinetics in a different way, i.e. the rate of one of them is increased whilst that of the other is decreased. The different effect of D2O on the kinetics of disruption of the two copper sites is discussed in terms of different location and degree of hydrophobicity of the two Cu2+ type I sites.

Ceruloplasmin↗
PubMedDate not supplied

Left ventricular function in thalassemia major: protective effect of deferoxamine.

OBJECTIVE: To test the hypothesis that chelation therapy with deferoxamine would prevent alterations in left ventricular systolic and diastolic function due to transfusional iron overload in patients with thalassemia major. DESIGN: A consecutive series of patients receiving chronic transfusional and chelation therapy were studied by two-dimensional and Doppler echocardiography. SETTING: Primary clinic. PATIENTS: Eight thalassemic patients (four men and four women), mean age 22 years (range 14 to 28) and seven age and sex matched control subjects. INTERVENTIONS: All patients had received transfusional therapy since birth, with mean annual load of red blood cells of 200 mL/kg. Iron chelation therapy with deferoxamine, using a subcutaneous infusion pump, was administered from age two years in the younger patients and from age 16 years in the two older cases. Doses were 25 mg/kg/day in children and 1.5 to 4 g per 12 h in adults to maintain ferritin blood levels at 1000 to 1500 ng/L. MAIN RESULTS: No significant differences were found in the following Doppler diastolic indexes: isovolumic relaxation time, early flow velocity (E wave), late flow velocity (A wave), E:A ratio, rate of deceleration of flow velocity in early diastole (EF slope), flow velocity deceleration time and end-diastolic volume. Ejection fraction was similar in the two groups (59 +/- 7 versus 64 +/- 5%), but contractility, expressed as end-systolic pressure/end-systolic volume index, appeared slightly depressed (4.6 +/- 1 versus 6.7 +/- 0.8) in the thalassemic group. CONCLUSIONS: Deferoxamine prevents alteration of left ventricular diastolic function in chronic transfusional therapy for thalassemia major. Depression of contractility, in spite of a normal ejection fraction, may be an early sign of worsening systolic performance, unavoidable even with chelation therapy.

Adolescent↗