IC3 and IC5 are indocyanine dyes that can react with aminegroups on proteins, peptides, and amine-modified oligonucleotides. Because neither IC3 nor IC5 has a sulfonate group in its structure, water solubility of the molecules is very low. An organic solvent is required to dissolve the compound. Over-labeling of proteins with these compounds may precipitate the labeled protein from aqueous solutions as a result of the poor water solubility. However, because no negative charge is added to the protein, the total number of charges of the modified protein is the same before and after labeling with these compounds. The IC dye package contains 100 μg dye. This amount is sufficient to modify 1-2 mg proteins or more depending on the purpose of the downstream experiment.