How much protein is required for efficient labeling?
• The manufacturer’s published protocol for Cy3/Cy5 labeling describes using 1 mg of total protein. • For low abundance proteins, and if quantity of sample permits, it is highly recommended to label concentrated protein samples (5-10 mg/mL) and then dilute appropriately for the assay. • Reaction volumes for the labeling procedure may be scaled down by maintaining the molar ratios of the reagents as described in the original protocol. It is advised, however, to conduct initial array experiments according to published protocols to ensure a valid result is obtained and allow a baseline to be determined.
