Nanometer-scale direct observation of the receptor for the leaf-movement factor in plant cell by a novel TEM probe

Electron microscopy is a useful method for observing localization of some proteins in a cell. In this Letter, we report a nanometer-scale direct observation of the receptor for a bioactive substance of small molecular weight by using TEM (transmission electron microscopy). We developed a novel TEM probe compound (1) that is a modified leaf-movement factor with benzophenone as a photoaffinity group and FITC as an antigen that is recognized by a nano-gold bound anti-FITC antibody. By using probe 1, we revealed that the receptor for the leaf-movement factor of Cassia mimosoides is localized in the plasma membrane of the plant motor cell.