?Thiocyanate gold?: small (2?3 nm) colloidal gold for affinity cytochemical labeling in electron microscopy

Abstract

Reduction of HAuCl₄ by NaSCN or KSCN produces colloidal gold particles of 2.6 nm in diameter and homogeneous in size (coefficient of variation ∼15%). The Au_SCN sol forms protein-gold complexes. The amount of protein required to form an Au_SCN-protein complex is best determined in the electron microscope, where serial dilutions of protein with gold sol are inspected for the presence of aggregates. By immuno-electron microscopy SCN-gold complexed to protein A is active and visible as is shown by revealing α-amylase in rat pancreatic acinar cells.