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Direct visualization of the alamethicin pore formed in a planar phospholipid matrix
Piotr Pieta, Jeff Mirza and Jacek Lipkowski
Proceedings of the National Academy of Sciences of the United States of America
Vol. 109, No. 52 (December 26, 2012), pp. 21223-21227
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/42553651
Page Count: 5
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We present direct visualization of pores formed by alamethicin (Aim) in a matrix of phospholipids using electrochemical scanning tunneling microscopy (EC-STM). High-resolution EC-STM images show individual peptide molecules forming channels. The channels are not dispersed randomly in the monolayer but agglomerate forming 2D nanocrystals with a hexagonal lattice in which the average channel-channel distance is 1.90 ± 0.1 nm. The STM images suggest that each Alm is shared between the two adjacent channels. Every channel consists of six Alm molecules. Three or four of these molecules have the hydrophilic group oriented toward the center of the channel allowing for water column formation inside the channel. The dimensions of the central pore in the images are consistent with the dimension of the water column in a model of hexameric pore proposed in the literature. The images obtained in this work validate the barrel-stave model of the pore formed in phospholipid membranes by amphiphatic peptides. They also provide direct evidence for cluster formation by such pores.
Proceedings of the National Academy of Sciences of the United States of America © 2012 National Academy of Sciences