Oligocholate Foldamers as Carriers for Hydrophilic Molecules across Lipid Bilayers

Three cholate foldamers were synthesized by the click reaction between an azide‐functionalized cholate trimer and different dialkynyl linkers. The foldamers were labeled with pyrene groups at the ends for their conformational study. The linkers between the two tricholate fragments were found to stro...

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Bibliographic Details
Published in:Chemistry : a European journal 2011-10, Vol.17 (44), p.12444-12451
Main Authors: Zhang, Shiyong, Zhao, Yan
Format: Article
Language:English
Subjects:
Biological Transport
Chemistry
Cholates - chemical synthesis
Cholates - chemistry
conformation analysis
foldamers
Hydrophobic and Hydrophilic Interactions
Lipid Bilayers - chemistry
Lipids
membranes
Models, Molecular
Molecular Conformation
oligocholates
Solutions - chemistry
transporters
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Summary:Three cholate foldamers were synthesized by the click reaction between an azide‐functionalized cholate trimer and different dialkynyl linkers. The foldamers were labeled with pyrene groups at the ends for their conformational study. The linkers between the two tricholate fragments were found to strongly influence the conformation of the foldamers in solution, as well as their ability to transport hydrophilic molecules across lipid bilayers. The folding of the oligocholates in mixed organic solvents was studied by fluorescence and UV/Vis spectroscopy. Although these molecules could not fold permanently in lipid bilayers, they were found to translocate carboxyfluorescein readily across by a carrier‐based mechanism. The transport is proposed to happen when the oligocholates adopt transiently folded structures with a hydrophobic exterior and a hydrophilic internal cavity. The transport rate strongly depended on the structure of the oligocholates and was sensitive even to the change of a single bond in a foldamer 3000 Da in MW. Better folded oligocholates in solution gave slower transport in the membranes. Shuttle launch: Oligocholate foldamers adopt helical conformations in nonpolar environments with a hydrophobic exterior and a hydrophilic internal cavity. By switching to such conformations transiently, they can traverse lipid bilayers (see picture) and shuttle hydrophilic guests across. The transport rate can be tuned over a broad range by the conformational properties of the foldamers.
ISSN:0947-6539
1521-3765
DOI:10.1002/chem.201101510