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Biomedical subjects

M Deleers

Publications and source records attributed to M Deleers.

67 records · Page 4Linked to original sources
PubMed1979

The effect of surface charge density on valinomycin-K+ complex formation in model membranes.

The model membrane approach was used to investigate the surface charge effect on the ion-antibiotic complexation process. Mixed monolayers of valinomycin and lipids were spread on subphases containing K+ or Na+. The surface charge density was modified by spreading ionizable valinomycin analogs on aqueous subphases of different pH or by changing the nature of the lipid (neutral, negatively charged) in the mixed film. Surface pressure and surface potential measurements demonstrated that a neutral lipid (phosphatidylcholine) or positively charged valinomycin analogs didn't enhance the anti-biotic complexing capacity. However, a maximal complexation is reached for a critical lipid concentration in the valinomycin-phosphatidylserine mixed film. The role of the surface charge on the valinomycin complexing properties was examined in terms of the Gouy-Chapman theory. As a consequence of the negative charge of the lipid monolayer, the K+ concentration near the surface is larger than the bulk concentration, by a Boltzmann factor. A good agreement was observed between the experimental results and the theoretical predictions. Conductance measurements of asymmetric bilayers containing a neutral lipid (egg lecithin) on one side and a negatively charged lipid (phosphatidyl-serine) on the other, confirm the role of the surface charge. Indeed, addition of K+ to the neutral side of the bilayer containing valinomycin had no effect on the conductance whereas addition of K+ to the charged side of the bilayer caused a 80-fold conductance increase.

Kinetics↗
PubMedDate not supplied

Binding of tumor-promoting and biologically inactive phorbol esters to artificial membranes.

Multilamellar liposomes formed of phospholipids bind [20-3H(N)]-phorbol 12,13-dibutyrate, the dissociation constant and maximal binding being comparable to those found in fibroblasts or epidermal cells. The relative capacity of distinct phorbol esters to compete with the labeled ligand was similar to their relative tumor-promoting capacity. It is proposed that the specific binding of phorbol esters to biological material may be accounted for by their insertion in the phospholipid domain of membranes.

Dimyristoylphosphatidylcholine↗