immunoelectron microscopy

[INSERM U189]

HI,
I am working on a protein, and I try to visualize it with immunoelectron
microscopy. I use a pre-embedding immunogold method. Analyzes were  not
simple, I think, because I use 5nm gold particles, and I see (in TEM)
electron dense particles in the cells, but the size of these seems to be
lightly different. Can someone explain me that ? perhaps because the
distribution of the protein in all the thickness of the section ?
Thanks in advance

Fabienne