Dielectric spectroscopy of L-alpha-lysolecithin-packaged gramicidin A.
The complex permittivities of L-alpha-lysolecithin in the absence and presence of the gramicidin A ion channel were measured over the temperature range 0-60 degrees C and over the frequency range 1-1000 MHz. One dielectric relaxation/loss has been observed. It is located at 103.3 MHz (1.54 ns) for a micellar 0.4 M L-alpha-lysolecithin solution at 20 degrees C, whereas it is shifted to 71.7 MHz (2.22 ns) for a lamellar L-alpha-lysolecithin-gramicidin A aqueous solution (0.4 M L-alpha-lysolecithin, 0.0308 M gramicidin A) at 20 degrees C. The dielectric relaxation decreases and the relaxation time increases when gramicidin A is incorporated into L-alpha-lysolecithin. These dielectric changes are related, in part, to the micellar-to-lamellar lipid phase transition induced by the incorporation of gramicidin A into lysolecithin. We suggest that the diffuse rotational motion of the polar head group of L-alpha-lysolecithin contributes to the dielectric relaxation/loss at around 100 MHz.
Buchet
R
R
Department of Biochemistry and Molecular Biology State University of New York, Syracuse 13210.
Luan
C H
CH
D004563:Electrochemistry / Q000379:methods; D006096:Gramicidin; D007473:Ion Channels / Q000502:physiology*; D008244:Lysophosphatidylcholines; D008823:Micelles; D008962:Models, Theoretical; D013816:Thermodynamics
D007473:Ion Channels; D008244:Lysophosphatidylcholines; D008823:Micelles; D006096:Gramicidin