(A) Structures of cholesterol (Chol) and eChol, a Chol analog in which a terminal alkyne group replaces the axial methyl at position C-19 of the sterol molecule. After labeling cells, eChol can be imaged by fluorescence microscopy, following copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC) with fluorescein-azide.
(B) Chol auxotrophic M19 CHO cells were grown for 4 days in media containing delipidated serum supplemented with oleic acid (35 μM), and in the presence or absence of Chol (10 μM) or eChol (35 μM), added as soluble methyl β-cyclodextrin (MCD) complexes. Representative fields of cells were photographed on days 1, 2 and 3 after plating. M19 CHO cells cannot proliferate in the absence of sterols; proliferation is completely rescued by eChol or Chol.