IC3 and IC5 are indocyanine dyes which can react with aminegroups on proteins, peptides, and amine-modified oligonucleotides. Since both IC3 and IC5 do not have a sulfonate group in the 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 due to the poor water-solubility. However, since no negative charge is added to the protein, the total number of charges of the modified protein is the same before and after the labeling with these compounds. The IC dye package contains 100 ug dye. This amount is sufficient to modify 1-2 mg proteins or more depending on the purpose of the downstream experiment.