inside the cardiac troponin complex the strongest interaction between molecules has been demonstrated for ctni – tnc binary complex especially in the presence of ca ( ka = 1.5x10 m). tnc, forming a complex with ctni, changes the conformation of ctni molecule and shields part of its surface. according to the latest data ctni is released in the blood stream of the patient in the form of binary complex with tnc or ternary complex with ctnt and tnc. ctni-tnc complex formation plays an important positive role in improving the stability of ctni molecule. ctni, which is extremely unstable in its free form, demonstrates significantly better stability in complex with tnc or in ternary ctni-ctnt-tnc complex. it has been demonstrated that stability of ctni in native complex is significantly better than stability of the purified form of the protein or the stability of ctni in artificial troponin complexes combined from purified proteins.