Analysis for the molecular motion of phospholipid bilayer with picosecond fluorometry

Issue title: Proceedings of the Seventh International Congress of Biorheology. Part I. Palais des Congrès, Nancy, France, 18–23 June 1989. Dedicated to Richard Skalak

Guest editors: Alfred L. Copley and Jean-François Stoltz

Article type: Research Article

Authors: Araiso, T.^a | Saito, H.^b | Shirahama, H.^b | Koyama, T.^a

Affiliations: [a] Section of Physiology, Research Institute of Applied Electricity, Hokkaido Univ. Sapporo, 060, Japan | [b] Dept. Chem., Facul. Sci., Hokkaido Univ., Sapporo, 060, Japan

Note: [] Accepted by: Guest Editor M. Donner

Abstract: The viscosity and the molecular motion of phospholipid molecule in biological and artificial phospholipid bilayers were studied using picosecond fluorescence depolarization method with rod-like fluorophore, DPH. From the relationship between the viscosity in the lipid bilayer and the free space of phospholipid acyl-chain, it is concluded that the viscosity is determined mainly by the range of wobbling motion of the acyl-chain. Motion of polar head group was also measured by the same method with a newly synthesized fluorescent phospholipid, dipalmitoyl-phosphatidylumbelliferone. The rate and the range in the motion of head group were faster and larger than those of acyl-chain and gave the viscosity of head group layer to be 0.03 poise, which was about one tenth of that of acyl-chain layer in the liquid crystalline phase. This fact indicates that the head group layer would not resist the lateral diffusion of molecules in membrane and that the lateral diffusion rate of molecules could be estimated from the viscosity in the acyl-chain layer.

Keywords: membrane fluidity, picosecond fluorometry, molecular motion of phospholipid, viscosity in membrane surface, free-space model, lateral diffusion

DOI: 10.3233/BIR-1990-273-414

Journal: Biorheology, vol. 27, no. 3-4, pp. 375-387, 1990