Fluorescently-labeled steroids that emit intense blue light in nonpolar solvent (CH2Cl2: λabs = 370 nm, λem = 440 nm, ΦF = 0.70) were prepared by treating cholesteryl chloroformate with N-alkyl-4-amino-1,8-naphthalimides. The lipid portion of the conjugates embeds into model membrane bilayers in minutes, with the fluorophore quenched by water in the interfacial region. DFT optimizations have identified low-energy conformations for the conjugates that would accommodate a “core-and-surface” binding mode. When incubated with a Mycobacterium tuberculosis model organism that uses natural cholesterol as a carbon source, the labeled steroids can be found in the membrane fraction of the cells using HPLC.

Incorporation of 3β-modified fluorescent cholesterols into liposomal and mycobacterial membranes

249th National Meeting (2015)

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