RESUMO
A new class of amphiphilic peptidolipidyl-cyclodextrins is reported. The derivatives are chiral due to the presence of an L-leucine in the spacer arm that links a saccharide moiety and a grafted, saturated hydrocarbon chain. Self-assembly properties of the peptidolipidyl-cyclodextrins are characterized by quasi-elastic light scattering, turbidity and UV-visible absorption measurements. NMR experiments give insight into the intermolecular dipolar interactions as a function of temperature and concentration. N-dodecyl-N alpha-(6 I-amidosuccinyl-6 1-deoxy-cyclomaltoheptaose)-L-leucine (1) is poorly soluble in aqueous media. N-dodecyl-N(alpha)-(6 I-amidosuccinyl-6 I-deoxy-2 I,3 I-di-O-methyl-hexakis-(2 II-VII,3 II-VII,6 II-VII-tri-O-methyl)-cyclomaltoheptaose)-L-leucine (2) is found to be more soluble and self-assembles into stable supramolecular colloidal aggregates with nanometric dimensions above a critical aggregation concentration (CAC). It has a propensity for solubilization of hydrophobic species revealing a micellar-like behavior, which is compared to that of the non-ionic detergent octyl glucoside. On the contrary, compound 1 precipitates in a crystalline phase beyond its water solubility limit, and it does not display any solubilizing capacity. The observed behavior corroborates at the molecular level with the NMR results.
Assuntos
Ciclodextrinas/química , Detergentes/química , Lipídeos/química , Micelas , Peptídeos/química , Absorção , Coloides/química , Glucosídeos/química , Interações Hidrofóbicas e Hidrofílicas , Leucina/análogos & derivados , Espectroscopia de Ressonância Magnética , Nefelometria e Turbidimetria , Espalhamento de Radiação , Solubilidade , Espectrofotometria Ultravioleta , Temperatura , Água/químicaRESUMO
Using per(3,6-anhydro)cyclodextrin derivatives [per(3,6-anhydro)CD], it was possible to produce new lanthanide chelates by careful choice of the size and functional groups. Heptakis(3,6-anhydro-2-O-methyl)cyclomaltoheptaose fulfils the best criteria for complexation of lanthanide ions. Nuclear magnetic resonance was used to derive the association constants and the stoichiometries of these new complexes. Finally, a three-dimensional structure of these complexes consistent with the NMR data is proposed, to ascertain the position of lanthanide in the cavity of the per(3,6-anhydro)CD. For the present purposes, heptakis(2-O-acetyl-3,6-anhydro)cyclomaltoheptaose, octakis(2-O-acetyl-3,6-anhydro)cyclomaltooctaose, heptakis(3,6-anhydro-2-O-methyl)cyclomaltoheptaose and octakis(3,6-anhydro-2-O-methyl)cyclomaltooctaose have been synthesized and purified.
