Abstract
Sphingomyelin (SM)–rich membrane domains, called lipid rafts, have been stimulating multi–disciplinary interests because they form signaling platforms. However, structure and physical property of lipid rafts are not sufficiently understood owing to two critical reasons. 1) Appropriate probes, which show similar behavior of raft lipids, have been lacking. 2) The size of lipid rafts is much smaller than the optical resolution and, thus, conventional light microscopy hardly visualizes lipid rafts. Recently, we developed fluorescent SM probes, which show the similar partition and dynamic behavior of native SMs. These probes disclosed transient assembly of putative raft–constituents such as SM, cholesterol and a glycophosphatidylinositol–anchored protein, in live cell membranes. Moreover, we examined distribution of two different types of SMs and found that a small structural difference of these SMs markedly affects their cluster formability.
