Membrane permeation of a peptide: it is better to be positive.
A joint experimental and computational study investigates the translocation of a tryptophan molecule through a phospholipid membrane. Time dependent spectroscopy of the tryptophan side chain determines the rate of permeation into 150 nm phospholipid vesicles. Atomically detailed simulations are conducted to calculate the free energy profiles and the permeation coefficient. Different charging conditions of the peptide (positive, negative, or zwitterion) are considered. Both experiment and simulation reproduce the qualitative trend and suggest that the fastest permeation is when the tryptophan is positively charged. The permeation mechanism, which is revealed by molecular dynamics simulations, is of a translocation assisted by a local defect. The influence of long-range electrostatic interactions, such as the membrane dipole potential on the permeation process, is not significant.
†Institute for Computational Engineering and Sciences and ‡Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States.
Alfredo E
AE
Cardenas
†Institute for Computational Engineering and Sciences and ‡Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States.
Rebika
R
Shrestha
†Institute for Computational Engineering and Sciences and ‡Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States.
Lauren J
LJ
Webb
†Institute for Computational Engineering and Sciences and ‡Department of Chemistry, University of Texas at Austin, Austin, Texas 78712, United States.
Ron
R
Elber
D002462:Cell Membrane / Q000737:chemistry*; D017136:Ion Transport; D008051:Lipid Bilayers; D056004:Molecular Dynamics Simulation; D010455:Peptides / Q000737:chemistry*; D014364:Tryptophan / Q000737:chemistry
D008051:Lipid Bilayers; D010455:Peptides; D014364:Tryptophan