PubMed Health⌕ Search

Biomedical subjects

B Maggio

Publications and source records attributed to B Maggio.

At least 91 records · Page 5Linked to original sources
PubMed1978

Surface behaviour of gangliosides and related glycosphingolipids.

1. The surface behaviour of six different gangliosides and eight chemically related glycosphingolipids was investigated in monolayers at the air-water interface. 2. Mono-, di-, tri and tetra-hexosylceramides had force-area isotherms showing similar limiting molecular areas on 145 mM-NaCl, pH 5.6. The increasing number of negatively charged sialosyl residues in mono-, di- and tri-sialogangliosides induced a progressive increase in the liquid-expanded character of the films and in the limiting area occupied per molecule, owing to electrostatic repulsions. When the ganglioside monolayers were spread on subphases at pH 1.2, the limiting area per molecule was similar to that found for neutral glycosphingolipids. 3. The monolayer collapse pressure at pH 5.6 increased with the number of uncharged carbohydrate units up to when the polar head group contained 3-4 residues. For gangliosides the collapse pressures were lower and decreased from mono- to tri-sialogangliosides. Ganglioside monolayers on subphases at pH 1.2 showed increases in their collapse pressure. 4. The glycosphingolipid monolayers studied had various surface in their collapse pressure. 4. The glycosphingolipid monolayers studied had various surface potentials according to the complexity of the polar head group of the lipid. Attempts to calculate the dipolar contributions to the surface potential from each carbohydrate residue suggest that the second and third sialosyl residues in di- and tri-sialogangliosides contributed with a vertical dipole moment opposite to that of the first sialosyl residue.

Chemical Phenomena↗
PubMed1977

Interactions of tocopherols and ubiquinones with monolayers of phospholipids.

1. The penetration of alpha-tocopherol and seven of its derivatives, and five compounds in the ubiquinone series, having differing chain lengths, into monolayers at the air/water interface of 11 different synthetic phospholipids and cholesterol was investigated; the properties of mixed monolayers of the tocopherols and of ubiquinones with phospholipids were also studied. 2. Penetration of alpha-tocopherol into diarachidonylglycerylphosphorycholine was approximately constant for molar ratios of tocopherol/phospholipid ranging from 0.4:1.0 to 2.0:1.0. 3. Tocopherols with shorter or longer side chains than alpha-tocopherol had a lesser ability to penetrate monolayers of phospholipid molecules with 16 or more carbon atoms in their acyl chains. 4. All the tocopherols penetrated more readily as unsaturation in the phospholipids was increased, and their penetration into mixed monolayers of phospholipids was greatly facilitated by the presence of relatively small quantities of unsaturated phospholipid molecules. 5. There was relatively little interaction between the tocopherols and cholesterol, or between the ubiquinones and phospholipids. 6. The possible significance of the observed interactions between alpha-tocopherol and polyunsaturated phospholipids is discussed in relation to the biochemical actions of alpha-tocopherol in vivo. 7. It is suggested that fluidity of the lipid bilayer in membranes containing polyunsaturated phospholipids may allow alpha-tocopherol to interact in a dynamic manner with a number of phospholipid molecules.

Membranes↗
PubMed1976

Poly(ethylene glycol), surface potential and cell fusion.

Poly(ethylene glycol), glycerol and dimethyl sulphoxide markedly decrease the surface potentials of monolayers of phosphatidylcholine and phosphatidylethanolamine. This finding is discussed in relation to the properties of hen erythrocytes undergoing fusion induced by poly(ethylene glycol).

Animals↗
PubMed1976

Polar-group behaviour in mixed monolayers of phospholipids and fusogenic lipids.

1. The surface potentials of mixed monolayers of synthetic phospholipids with lipids that are fusogenic for hen erythrocytes were investigated. 2. At pH 5.6 and 10, but not at pH2, mixed monolayers of the fusogenic lipid, glycerol mono-oleate, with phosphatidylcholine exhibited negative deviations from the ideality rule in surface potential per molecule which were accompanied by negative deviations in mean molecular area. 3. Interactions of this type were not seen with chemically related but non-fusogenic lipids, nor were they found in mixed monolayers of any of the lipids with phosphatidylethanolamine. 4. Experiments with dihexadecyl phosphate and hexadecyltrimethyl-ammonium indicated that the complete head group of phosphatidylcholine is required for its observed behaviour with fusogenic lipids. 5. Bivalent cations (Ca2+, UO2(2+) or Zn2+) in the subphase at pH 5.6 significantly modified the behaviour of mixed monolayers of fusogenic lipids with phospholipids; there was a parallel perturbing effect of fusogenic lipids on interactions between monolayers of phospholipids and bivalent cations. 6. Possible molecular interactions of fusogenic lipids with membrane phospholipids, and the role of Ca2+, are discussed which may be relevant to cell fusion in erythrocytes induced by low-melting lipids in the presence of Ca2+.

Calcium↗
PubMed1975

Studies on mixed monolayers of phospholipids and fusogenic lipids.

1. The behaviour of mixed monolayers of 14 different lipids with preparations of erythrocyte lipids, purified natural and synthetic phospholipids, cholesterol and galactosylceramide was investigated. 2. The mean areas occupied per molecule in mixed films containing lipids that are fusogenic for hen erythrocytes were compared with those for corresponding films containing lipids that are inactive as fusogens. 3. Fusogenic lipids were found to exhibit interactions, which were not shown by non-fusogenic lipids, in mixed monolayers with several species of phospholipid, particularly those containing a choline head group. 4. Heterogeneity in the hydrophobic chains of phosphatidylcholine, their degree of unsaturation and the presence of cholesterol had little effect on the interaction of phosphatidylcholine with fusogenic lipids. 5. Fusogenic lipids showed little specific interaction with natural or synthetic preparations of phosphatidylethanolamine. 6. The possible significance of these observations in relation to the action of fusogenic lipids on biological membranes is discussed in the light of the asymmetrical distribution of phospholipids in erythrocyte membranes.

Cell Fusion↗
PubMedDate not supplied

Synthesis and antifungal activity of new N-isoxazolyl-2-iodobenzamides.

N-Isoxazolyl-2-iodobenzamides 3 and 9, with a benodanil-like structure, were synthesized by refluxing in acetic acid the corresponding benzotriazinones 2 and 8 with potassium iodide for 1 h with the aim to ascertain if they were active as fungicides against Phytophthora citricola Saw., Botrytis cinerea Pers., Rhizoctonia sp. and Alternaria sp. Among the tested iodo derivatives, compounds 3b and 9a possess interesting activities against the aforesaid fungal strains in several cases similar to that of benodanil I taken as reference drug.

Benzamides↗
PubMedDate not supplied

Modulation of phospholipases A2 and C activities against dilauroylphosphorylcholine in mixed monolayers with semisynthetic derivatives of ganglioside and sphingosine.

Most of the semisynthetic ganglioside and sphingosine derivatives studied here decreased the rate as well as the extent of hydrolysis of monomolecular layers of dilauroylphosphorylcholine (dlPC) by both phospholipase A2 (PLA2) and C (PLC). For PLA2, the rate of enzymatic activity was inversely correlated (p < 0.001) with the duration of the latency period of the enzymatic reaction. The correlation between the rate of activity and the latency period was not statistically significant for PLC. The potency to inhibit PLA2 and PLC was not significantly correlated with the presence of specific chemical groups. Also, the inhibitory effect is not correlated to changes of the substrate intermolecular spacing or surface potential caused by the sphingolipids (SLs). Conversely, for PLA2 the variation of the kinetic parameters of the reaction with the molecular polarization vector of the SLs are statistically significant (p < 0.01). The rate of phospholipid degradation by PLA2 decreased, and the lag times tended to become longer, with increasing values of the SLs' polarization vector. The kinetic parameters of the reaction with PLC did not show statistically significant correlation with the polarization vector of the SLs. Our results suggest that the configuration of the electrostatic field across the interface is more important than are formal charges or specific chemical moieties in modulating the activity of PLA2. Inhibition of phospholipase activities of these types by specific SLs or their metabolites may be important as supramolecular regulatory steps at the membrane level of the amplification of lipid-mediated signaling pathways.

Carbohydrate Sequence↗