Non-detergent Isolation of Membrane Structures from Beet Plasmalemma and Tonoplast Having Lipid Composition Characteristic of Rafts.

ABSTRACT

Vacuolar and plasma membranes were isolated by a detergent-free method from beet roots (Beta vulgaris L.), and were fractionated in a sucrose density gradient of 15-60% by high-speed centrifugation at 200,000×g during 18 h. The membrane material distributed over the sucrose density gradient was analyzed for the presence of lipids characteristic of raft structures in different zones of the gradient. The quantitative and qualitative content of lipids and sterols, and the composition of fatty acids were analyzed. Some membrane structures differing in their biochemical characteristics were revealed to be located in different zones of the sucrose gradient. The results of the analysis allowed us to identify three zones in the sucrose gradient after the vacuolar membrane fractionation and two zones in the plasma membrane where membrane structures, which may be defined as rafts for their lipid composition, were presented.