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Record 37 of 201
Permeability of lipid bilayers to amino acids and phosphate
Author and Affiliation:
Chakrabarti, A. C.(University of British Columbia, Department of Biochemistry, Vancouver, Canada)
Deamer, D. W.
Abstract: Permeability coefficients for amino acid classes, including neutral, polar, hydrophobic, and charged species, were measured and compared with values for other ionic solutes such as phosphate. The rates of efflux of glycine, lysine, phenylalanine, serine and tryptophan were determined after they were passively entrapped in large unilamellar vesicles (LUVs) composed of egg phosphatidylcholine (EPC) or dimyristoylphosphatidylcholine (DMPC). The following permeability coefficients were obtained for: glycine, 5.7 x 10(-12) cm s-1 (EPC), 2.0 x 10(-11) cm s-1 (DMPC); serine, 5.5 x 10(-12) cm s-1 (EPC), 1.6 x 10(-11) cm s-1 (DMPC); lysine, 5.1 x 10(-12) cm s-1 (EPC), 1.9 x 10(-11) cm s-1 (DMPC); tryptophan, 4.1 x 10(-10) cm s-1 (EPC); and phenylalanine, 2.5 x 10(-10) cm s-1 (EPC). Decreasing lipid chain length increased permeability slightly, while variations in pH had only minor effects on the permeability coefficients of the amino acids tested. Phosphate permeability was in the range of 10(-12)-10(-13) cm s-1 depending on the pH of the medium. The values for the polar and charged amino acids were surprisingly similar to those previously measured for monovalent cations such as sodium and potassium, which are in the range of 10(-12)-10(-13) cm s-1, depending on conditions and the lipid species used. This observation suggests that the permeation rates for the neutral, polar and charged amino acids are controlled by bilayer fluctuations and transient defects, rather than partition coefficients and Born energy barriers. The results are relevant to the permeation of certain peptides into lipid bilayers during protein translocation and membrane biogenesis.
Publication Date: Nov 09, 1992
Document ID:
20050000568
(Acquired Jan 06, 2005)
Subject Category: EXOBIOLOGY
Document Type: Journal Article
Publication Information: Biochimica et biophysica acta; p. 171-7; (ISSN 0006-3002); Volume 1111; 2
Publisher Information: Netherlands
Description: In English
Distribution Limits: Unclassified; Publicly available; Unlimited
Rights: Copyright
NASA Terms: AMINO ACIDS; LIPIDS; MEMBRANES; PERMEABILITY; PHOSPHATES; CHLORIDES; EXOBIOLOGY; ION CONCENTRATION; POTASSIUM
Other Descriptors: AMINO ACIDS/METABOLISM; LIPID BILAYERS/METABOLISM; PHOSPHATES/METABOLISM; CHLORIDES/METABOLISM; DIMYRISTOYLPHOSPHATIDYLCHOLINE; FLUORESCAMINE; HYDROGEN-ION CONCENTRATION; LIPOSOMES; PERMEABILITY; PHOSPHOLIPIDS; POTASSIUM/METABOLISM; SUPPORT, NON-U.S. GOV'T; SUPPORT, U.S. GOV'T, NON-P.H.S; NASA DISCIPLINE EXOBIOLOGY; NON-NASA CENTER
Availability Source: Other Sources
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