Information that could be of importance to the researcher contemplating the purchase of SPI-Mark Colloidal Gold products:

Protein Concentration

1nm gold conjugates, when available are always supplied at a specific protein concentration of 50ug/ml. However, because of some technical difficulties, we are presently unable to ship any 1 nm gold products. The protein concentration for the 5nm products will vary between batches, but here are example protein concentrations for some typical batches:

SPI #
04275-AB Goat anti Mouse 5 nm 28.2µg/ml
04791-AB Streptavidin 5 nm 25.7µg/ml


Labeling ratio (some typical examples): 
SPI #
04371-AB Goat anti Mouse 1 nm 1/3 protein molecules per colloid particle
04391-AB Streptavidin 1 nm 1/2 protein molecules per colloid particle
04771-AB Goat anti Mouse 5 nm 3 protein molecules per colloid particle
04791-AB Streptavidin 5 nm 5 protein molecules per colloid particle