Preparation of Mono-Disperse Gold Suspensions for Protein Labeling

Preparation of Mono-Disperse Gold Suspensions for Protein Labeling 

Prepare 1ml of a 4 percent HAuC14 solution in deionized water. 

Add 375 pi of the chloroauric acid solution plus 500pi of 0.2M K2CO3 to 100ml deionized water, cooled on ice to 4°C. Mix well. 

Dissolve sodium borohydride (NaBH4) in 5 ml of water at a concentration of 0.5mg/ml. Prepare fresh. 

Add five 1-ml aliquots of the sodium borohydride solution to the chloroauric acid/ carbonate suspension with rapid stirring. A color change from bluish-purple to reddish-orange will be noted as the additions take place. 

The following sections discuss the preparation of colloidal gold suspensions of various particle sizes and their use in labeling proteins for detection purposes. Gold-labeled molecules and proteins are available from a number of manufacturers (Janssen, E-Y Labs, and Nanoprobes). 

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