Antibiotic G-418 Sulfate is an aminoglycosidic antibiotic toxic to both prokaryotic and eukaryotic cells. It acts by interfering with protein synthesis and is used as an agent for selection of cultured cells expressing a gene (i.e., aminoglycoside 3´ phosphotransferase [APH 3´]) that confers resistance to G-418. The liquid form of the product is in distilled water and aseptically filtered.