Search PubMed⌕ Search

Biomedical subjects

F M Veronese

Publications and source records attributed to F M Veronese.

At least 73 records · Page 4Linked to original sources
PubMed1984

Enzymatically active subunits of Bacillus stearothermophilus enolase bound to Sepharose.

The octameric enolase from Bacillus stearothermophilus was immobilized onto Sepharose 4B activated by the cyanogen bromide reaction under conditions for achieving essentially a single-point attachment. The immobilized enzyme was dissociated with guanidine hydrochloride to yield bound monomeric enolase. The Sepharose-bound subunit regained activity upon removal of the denaturant. It was also possible to rehydribize immobilized monomers to native octamers. Of note, the thermal stability of the immobilized enolase subunit does not appreciably differ from that of the parent soluble octameric enzyme. Thus, these results indicate that single subunits of thermophilic enolase are active and that oligomerization is not a prerequisite for the enzymic activity as well as for thermal stability.

Enzymes, Immobilized↗
PubMed1981

Drug protein interaction: displacement of albumin bound 8-methoxypsoralen by drugs.

The displacement of 8-methoxypsoralen (8-MOP) bound to albumin by a number of drugs commonly used in therapy was investigated by equilibrium dialysis, using tritium labelled furocoumarin. Furocoumarin binding was found to be influenced by several compounds. However because of the concentrations of furocoumarin and displacers reached in plasma, only tolbutamide could modify the 8-MOP binding to a pharmacokinetically significant extent.

Binding, Competitive↗
PubMed1979

Drug-protein interaction: plasma protein binding of furocoumarins.

The binding of six furocoumarins (angelicin, psoralen, 8-methoxypsoralen, 5-methoxypsoralen, 8-methylpsoralen, 4,5'8-trimethylpsoralen) to human serum and human serum albumin was studied by equilibrium dialysis using tritium labelled compounds. The results indicated that in serum all furocoumarins are bound mostly by albumin, the extent of binding being related to the structure of the furocoumarins; at any rate, high values of the bound drug, ranging from 84 to 97% were observed. The percentage of binding is strictly related to the water solubility of the compounds. A limited number of binding sites, n = 1-2.4, were detected in the albumin molecule, indicating a high specificity in the binding process. The association constants of the furocoumarins to albumin. Ka, ranged from 1.2 X 10(4) M-1 (8-methoxypsoralen) to 1.9 X 10(5) M-1 (4,5'8-trimethylpsoralen).

Biological Availability↗
PubMed1978

The binding of 8-methoxypsoralen by human serum albumin.

The ability of 8-methoxypsoralen (8-MOP) to bind human serum albumin has been investigated in vitro through equilibrium dialysis and fluorescence quenching. By means of the first technique it was observed that, at concentrations presumably close to those obtainable in vivo following its administration in the photochemotherapy of psoriasis, over 80% of 8-MOP was bound to serum albumin. In human serum albumin fluorescence techniques revealed a preferential site of binding for 8-MOP with a high binding constant (Ka = 0.7 X 10(5) M-1) and precise steric requirements, since small conformational variations of the protein molecule were able to abolish its affinity for furocoumarin.

Dialysis↗
PubMed1977

A fluorimetric study of the role of calcium ions in the stability of thermolysin.

1. Fluorimetric techniques were used to characterize the environment of tryptophan residues in thermolysin and apo-thermolysin. The apo-thermolysin was obtained by dissolving the enzyme in the presence of 10mm-EDTA, which removed the functional Zn(2+) ion and the four Ca(2+) ions/molecule from the enzyme. 2. At 25 degrees C in aqueous solution the fluorescence-emission spectrum of the native holoenzyme, on excitation at 290nm, was essentially characteristic of tryptophan, with an emission maximum at 333nm. The emission maximum of the apoenzyme is red-shifted to 338nm and the relative intensity of fluorescence is decreased by 10%, both effects indicating some unfolding of the protein molecule, with the indole groups being transferred to a more hydrophilic environment. 3. Fluorescence quenching studies using KI, N'-methylnicotinamide hydrochloride and acrylamide indicated a more open structure in the apoenzyme, with the tryptophan residues located in a negatively charged environment. 4. The thermal properties of the apoenzyme, as monitored by fluorescence-emission measurements, are dramatically changed with respect to the native holoenzyme. In fact, whereas the native enzyme is heat-stable up to about 80 degrees C, for the apoenzyme a thermal transition is observed near 48 degrees C. The apoenzyme is also unstable to the action of unfolding agents such as urea and guanidinium chloride, much as for other globular proteins from mesophilic organisms. 5. The functional Zn(2+) ion does not contribute noticeably to the stability of thermolysin. 6. It is concluded that a major role in the structural stability of thermolysin is played by the Ca(2+) ions, which have a bridging function within this disulphide-free protein molecule.

Calcium↗
PubMed1977

Fluorescent labelling of 6-phosphogluconate dehydrogenase from Bacillus stearothermophilus.

The thermophilic 6-phosphogluconate dehydrogenase from Bacillus stearothermophilus was inhibited upon specific modification of the -SH group of cysteine residues by 7-chloro-4-nitrobenzo-2-oxa-1, 3-diazole (NBD-Cl) at pH 7.0. By using 20-100-fold molar excess of NBD-CL the reaction occurs slowly at pH 7.0 as a first order process. Partial protection from inactivation was observed when the substrate 6-phosphogluconate or the coenzyme NADP was added to the reaction mixture. Complete inactivation was achieved upon modification of 1.9 of the six cysteine residues per mole of enzyme, which corresponds to nearly one residue per enzyme subunit. Circular dichroism measurements suggest that the gross structure of the protein molecule is practically unchanged upon reaction of the enzyme with NBD-Cl. Melting profile experiments revealed a single transition occurring at about 65 degrees C. Analogously, the profile of intensity of the fluorescence emission at 520 nm of the enzyme-bound S-NBD groups versus temperature indicated a midpoint of transition near 65 degrees C. Since this melting temperature corresponds closely to that observed with the native enzyme, these results would indicate that the molecular organizations of the native and modified enzyme are similar and stabilized by similar interactions within the polypeptide chain.

4-Chloro-7-nitrobenzofurazan↗
PubMed1977

Drug-protein interaction: the binding of cephalosporins to albumins.

The binding of some cephalosporin antibiotics, namely cephalothin, cephaloridine and cephalexin, to serum albumins was quantitized using a fluorescence probe technique. The results suggest that these drugs bind to hydrophobic sites on serum albumins. The association constants of the three drugs with bovine serum albumin showed the strongest binding for cephalothin (Ka 1.2 x 10(3) M(1)) and weaker ones for cephaloridine and cephalexin (Ka 0.59 and 0.4 x 10(3) M(-1)). Serum albumin from different species was also investigated, only minor variations in the binding properties being found.

Animals↗