Formation of stable vesicles from N- or 3-alkylindoles: possible evidence for tryptophan as a membrane anchor in proteins.
Twelve indole derivatives have been prepared and studied. Five were 1-substituted: 1, methyl; 2, n-hexyl; 3, n-octyl; 4, n-octadecyl; and 5, cholestanyloxycarbonylmethyl. Four were 3-substituted: 6, methyl; 7, n-hexyl; 8, n-octyl; and 9, n-octadecyl. Three were disubstituted as follows: 10, 1-n-decyl-3- n-decyl; 11, 1-methyl-3-n-decyl; and 12, 1,3-bis(n-octadecyl)indole. Sonication of aqueous suspensions afforded stable aggregates from 3-5 and 8-12. Laser light scattering, dye entrapment, and electron microscopy were used to characterize the aggregates. Aggregates formed from N-substituted indoles proved to be more robust than those formed from 3-alkylindoles. A stable monolayer formed from 3-n-octadecylindole but not from N- or 1,3-disubstituted analogues by using a Langmuir-Blodgett trough. The formation of aggregates was explained in terms of stacking by the relatively polar indole headgroup. In the monolayer experiment, this force was apparently overwhelmed by H-bonding interactions with the aqueous phase.
Abel
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E
Bioorganic Chemistry Program, Washington University School of Medicine, 660 South Euclid Avenue, Campus Box 8103, St. Louis, Missouri 63110, USA.
De Wall
S L
SL
Edwards
W B
WB
Lalitha
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S
Covey
D F
DF
Gokel
G W
GW
D002850:Chromatography, Gel; D020285:Cryoelectron Microscopy; D005456:Fluorescent Dyes / Q000737:chemistry; D007211:Indoles / Q000138:chemical synthesis / Q000737:chemistry*; D009682:Magnetic Resonance Spectroscopy; D008567:Membranes, Artificial; D008854:Microscopy, Electron; D008956:Models, Chemical; D008958:Models, Molecular; D011506:Proteins / Q000737:chemistry*; D014364:Tryptophan / Q000737:chemistry*
D005456:Fluorescent Dyes; D007211:Indoles; D008567:Membranes, Artificial; D011506:Proteins; D014364:Tryptophan