DETECTION OF PROTEIN A GOLD 15 NM MARKED SURFACE-ANTIGENS BY BACKSCATTERED ELECTRONS

  • 1 January 1984
    • journal article
    • research article
    • p. 1257-1266
Abstract
Colloidal Au has become an important marker in EM. Due to its scattering properties colloidal Au is easily detected in TEM [transmission electron microscopy]. Because of the material dependent signal, preferentially backscattered electrons are used in the SEM [scanning electron microscopy]. A YAG (cerium dotted yttrim aluminum garnet) single crystal annular scintillator mounted directly below the objective pole piece. The secondary (SE) and backscattered (BSE) images of protein A Au marked cell surface proteins on 2 test specimens were compared: Red blood cells with a smooth and yeasts with a highly structured surface. After freeze-drying, the specimens were coated with a layer of C (5-10 nm) to enhance conductivity. The specimens were observed in a field emission SEM. In the SE mode a distinction between the Au particles and organic structures was hardly possible; this mode gave good surface information. In the BSE mode, individual Au particles of 10-15 nm were easily detected. The combination of the high resolution surface image and the material dependent BSE image provides an accurate localization of the surface antigens.

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