Phenylgalactoside, quae p-nitrophenyl β-D-galactopyranoside (pNPG), synthetica subiecta est, saepe in experimentis biologiae biochemicis et hypotheticis adhibetur.Communiter adhibetur ad detectionem et modum actionis enzyme β-galactosidase.
Cum phenylgalactoside hydrolyzata ab β-galactosidase est, p-nitrophenolum emittit, quod mixtum luteum est.Liberatio p-nitrophenol utens spectrophotometris quantitatis mensurari potest, sicut absorbentia p-nitrophenol ad necem 405 um deprehendi potest.