title: The surface free energy of Leishmania mexicana amazonensis.
abstract: Surface charge of Leishmania mexicana amazonensis was investigated by direct zeta-potential determination and ultrastructural cytochemistry, and its surface tension was studied by measurements of the advancing contact angle formed by the parasite monolayers with drops of liquids of different polarities. Both virulent and avirulent promastigotes exhibited negatively charged surfaces with a zeta-potential of about -15 mV. Treatment of these cells with trypsin, alkaline phosphatase, or phospholipase C rendered their surfaces less negatively charged, whereas neuraminidase did not alter the parasite negativeness. Cytochemically, we could observe a reduction in the cationized ferritin binding after the parasite treatment with each of the former enzymes, but not with neuraminidase. The surface free energy of parasites was calculated by taken to account the London dispersion, the Keeson dipole-dipole, and the Debye dipole-induced forces, as well as the surface polarity of the parasites and their zeta-potentials, by considering their adhesion to polystyrene surfaces. The delta G values of -6.4 and -18.1 mJ.m-2 were obtained for avirulent and virulent promstigotes, respectively.
authors.affiliation: Departamento de Biofísica Celular e Parasitologia, Universidade Federal do Rio de Janeiro, Brazil.
authors.forename: F C
authors.initials: FC
authors.lastname: Silva Filho
authors.forename: E M
authors.initials: EM
authors.lastname: Saraiva
authors.forename: M A
authors.initials: MA
authors.lastname: Santos
authors.forename: W
authors.initials: W
authors.lastname: de Souza
mesh_terms: D000469:Alkaline Phosphatase / Q000494:pharmacology; D000818:Animals; D002448:Cell Adhesion / Q000187:drug effects / Q000502:physiology; D006001:Glycoconjugates / Q000502:physiology; D006651:Histocytochemistry; D007894:Leishmania mexicana / Q000166:cytology / Q000502:physiology* / Q000648:ultrastructure; D008564:Membrane Potentials / Q000187:drug effects / Q000502:physiology; D008854:Microscopy, Electron; D013499:Surface Properties; D013500:Surface Tension; D014357:Trypsin / Q000494:pharmacology; D010738:Type C Phospholipases / Q000494:pharmacology
chemical_list: D006001:Glycoconjugates; D000469:Alkaline Phosphatase; D010738:Type C Phospholipases; D014357:Trypsin