A novel supramolecular [Au6Cu2(C2C6H4-4-COONC4H4O2)6(Ph2PC6H4PPh2)3](PF6)2 complex functionalized with succinimide alkynyl substituent has been synthesized and characterized using X-ray crystallography, mass spectrometry and NMR spectroscopy. Like the other complexes of this class demonstrates bright emission in acetone and dichloromethane solutions with the excited state lifetime in microsecond domain. This complex readily reacts with surface amine group of proteins/enzymes (human serum albumin, rabbit anti-HSA antibodies, α-chymotrypsin) to give covalent conjugates, which contain up to five molecules of the luminescent label bound to the biomolecule. The conjugates keep high level of the phosphorescent label emission but in contrast to the parent complex molecule display excellent solubility and high stability in physiological media. Investigation of biological activity of the conjugates also showed that specific structure of the biomolecules remains nearly unchanged upon bonding with the label that is indi