β-D-Galactopyranosylphenyl isothiocyanate is a specialty chemical used in biochemical research, particularly in glycobiology for studying glycoproteins, carbohydrates, and carbohydrate-protein interactions. It functions as a labeling reagent by reacting with primary amino groups (e.g., on lysine residues) of proteins or peptides, attaching a galactose-containing moiety to form thiourea linkages. This enables the creation of neoglycoproteins or labeled conjugates for detecting and analyzing glycoconjugates via techniques such as fluorescence microscopy, chromatography, or immunoassays like ELISA. It is valuable for developing probes to investigate cellular processes including signaling, immune responses, and lectin-carbohydrate binding.