Lipoprotein-cyclodextrin interaction

Interaction of cyclodextrins with native and isolated lipoproteins was studied by electrophoretic and spectroscopic means. Reaction between these two biomolecules resulted in the formation of soluble and insoluble complexes. Cyclodextrin-mediated precipitation of lipoproteins was strongly affected by the concentration of the oligosaccharide and the presence of guest molecules capable of being entrapped within the cyclodextrin cavity. Lipoprotein precipitation by cyclodextrins was observed under acidic, neutral as well as alkaline conditions. The ionic strength of the medium did not significantly affect this interaction. Under appropriate experimental conditions, most types of cyclodextrins were able to form complexes with the various lipoprotein classes. The ability of cyclodextrins to precipitate lipoproteins was in the order of β-cyclodextrin > α-cyclodextrin > γ-cyclodextrin and hydroxyalkylated β-cyclodextrin. Among the lipoproteins, the order of reactivity with a given cyclodextrin was: low density lipoproteins > high density lipoproteins > very low density lipoproteins. Competitive studies using L-phenylalanine and methanol, both of which form inclusion complexes with cyclodextrins, reveal that molecular encapsulation plays an important role in the stabilization of β-cyclodextrin-lipoprotein complexes. The present data also suggests that the binding of cyclodextrins to lipoproteins may involve the formation of exclusion complexes.