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Biomedical subjects

S Poli

Publications and source records attributed to S Poli.

At least 19 recordsLinked to original sources
PubMed1992

Mechanism of enantioselective oxygenation of sulfides catalyzed by chloroperoxidase and horseradish peroxidase. Spectral studies and characterization of enzyme-substrate complexes.

The binding of a series of alkyl aryl sulfides to chloroperoxidase (CPO) and horseradish peroxidase (HRP) has been investigated by optical difference spectroscopy, circular dichroism, paramagnetic NMR spectroscopy, and NMR relaxation measurements. The data are consistent with binding of the sulfides in the distal side of the heme pocket with CPO and near the heme edge with HRP. A linear correlation between the binding constants of para-substituted sulfides to CPO and the Taft sigma I parameter suggests that these substrates act as donors in donor-acceptor complexes involving some residue of the protein chain. Spectral studies during turnover show that high enantioselectivity in the CPO-catalyzed oxidation of sulfides results from a reaction pathway that does not involve the accumulation of compound II enzyme intermediate.

Catalysis↗
PubMed1991

Spectroscopic and binding studies on the stereoselective interaction of tyrosine with horseradish peroxidase and lactoperoxidase.

The interaction of a series of derivatives of tyrosine with horseradish peroxidase (HRP) and lactoperoxidase (LPO) was studied by using optical difference spectroscopy, c.d. and proton n.m.r. spectroscopy in order to reveal differences in the mode of binding of L-tyrosine and D-tyrosine, which are substrates of but react at different rates with the two peroxidases, to HRP and LPO. All the donor molecules form 1:1 complexes with HRP and LPO, but they display a range of affinities for the enzymes. Whereas D-tyrosine binds to HRP more strongly than does L-tyrosine, the opposite holds for the binding to LPO. The distances of the protons of bound tyrosine molecules from the haem iron atoms of HRP and LPO indicate that the site of binding of these substrates is the same as that of simple phenols. This involves the interaction of the phenol nucleus with a protein tyrosine residue [Sakurada, Takahashi & Hosoya (1986) J. Biol. Chem. 261, 9657-9662; Modi, Behere & Mitra (1989) Biochim. Biophys. Acta 996, 214-225]. However, for the present substrates the additional interaction of the carboxylate group with a protein residue (probably an arginine residue) provides further stabilization for the adducts HRP-D-tyrosine and LPO-L-tyrosine with respect to the corresponding complexes with the opposite enantiomers. The differences in the mode of binding of L-tyrosine and D-tyrosine to HRP and LPO is thus determined by the fact that the spatial arrangement of the interacting protein residues can recognize the chirality of the C(alpha)-CO2- and C(beta)-C6H4OH attachment bonds of the substrates.

Animals↗
PubMed1984

Diagnostic approach to pulmonary embolism: our strategy.

The nonspecificity and variety of clinical features in acute pulmonary embolism account for a high suspicion rate, with a further exclusion of the diagnosis in up to 80% of cases. Arterial blood gas analysis and other laboratory tests are highly non-specific, and suggestive signs on the electrocardiogram are uncommon. The plain chest X-ray often yields valuable information. Lung scan, when normal, has the great advantage of excluding pulmonary embolism. At present, no procedure has superseded pulmonary angiography to attest the presence of emboli. Angiography will probably gain widespread acceptance with the larger use of thrombolysis.

Acute Disease↗
PubMed1983

[Streptococcus (S. pyogenes) group A septicemia. Analysis of 20 cases in adults].

From 1976 to 1981, 25 cases of S. pyogenes septicemia were diagnosed at the University Medical Center, Lausanne, Switzerland, in 5 children and 20 adults. The twenty adult patients are described. The age range was from 24 to 94 years. The portal of entry was the skin (erysipelas, skin ulcers, surgical wounds) in 12 cases, the respiratory tract (upper 3, lower 3) in 6 cases, and the vagina in 2 cases. All except 3 patients were acutely ill with high temperature (39 degrees C) and toxic appearance. None had an underlying malignancy. The clinical course was complicated in 5 patients, i.e. septic arthritis (2), pulmonary abscess (1), endocarditis (1) and acute rheumatic fever (1). After initiation of penicillin therapy, temperature and symptoms resolved only slowly (mean 11 days). Four patients died from infection. In 2 of them the antibiotic treatment had been delayed. When a patient exhibits clinical signs of septicemia and muco-cutaneous lesions suggestive of a portal of entry, S. pyogenes septicemia should be suspected. Complications are frequent and the prognosis remains poor despite early adequate antibiotic treatment.

Adult↗