Immunogold labeling of chromosomes for scanning electron microscopy: a closer look at phosphorylated histone H3 in mitotic metaphase chromosomes of Hordeum vulgare.

High-resolution detection of phosphorylated histone H3 at serine 10 in mitotic barley chromosomes for scanning electron microscopy was shown using a novel application of indirect immunogold labeling with Nanogold. This method permits localization and quantification of signals in a three-dimensional context. Because the chromosome structure is well preserved, characterization of binding sites (chromomeres, parallel matrix fibers, solenoids), currently in the realm of nanometer decades, is possible. Quantification and three-dimensional localization of labels is possible with stereoscopic analysis. Limitations of the method pertain to the challenges in preservation of chromosome ultrastructure, accessibility of immunoreactants into the fixed chromatin and unspecific labeling. The differences between silver and gold enhancement and the current status of labeling efficiency are addressed.