Incorporation of fluorophore-cholesterol conjugates into liposomal and mycobacterial membranes

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• 作者：Ashley N. Wercholuk ; Jenna M. Thuman ; Jordan L. Stanley ; Andrew L. Sargent ; Eric S. Anderson ; William E. Allen ; ^{allenwi@ecu.edu" class="auth_mail" title="E-mail the corresponding author}
• 关键词：Fluorescence ; Cholesterol trafficking ; Membrane transport ; Tuberculosis
• 刊名：Bioorganic & Medicinal Chemistry
• 出版年：2016
• 出版时间：1 March 2016
• 年：2016
• 卷：24
• 期：5
• 页码：1045-1049
• 全文大小：554 K

文摘

Fluorescently-labeled steroids that emit intense blue light in nonpolar solvent (λ_em (CH₂Cl₂) ≈ 440 nm, Φ_F = 0.70) were prepared by treating cholesteryl chloroformate with 4-amino-1,8-naphthalimides. The lipid portion of the conjugates embeds into liposomal membrane bilayers in minutes, leaving the fluorophore exposed to the external aqueous environment. This causes a 40-nm red-shift in λ_em and significant quenching. DFT optimizations predict the conjugates to be about 30 Å long when fully extended, but rotation about the linker group can bring the compounds into an ‘L’-shape. Such a conformation would allow the cholesteryl anchor to remain parallel to the acyl chains of a membrane while the fluorescent group resides in the interfacial region, instead of extending beyond it. When incubated with Mycobacterium smegmatis mc2 155, a bacterial species known to use natural cholesterol, the labeled steroids support growth and can be found localized in the membrane fraction of the cells using HPLC. These findings demonstrate stable integration of fluorescent cholesterols into bacterial membranes in vivo, indicating that these compounds may be useful for evaluating cholesterol uptake in prokaryotic organisms.