BINDING OF TRIVALINE TO SINGLE-STRAND POLYRIBONUCLEOTIDES

Binding of dansyl hydrazide trivaline (DHTV) with poly(U) was studied with fluorometric titration circular and flow linear dichroism, equili brium dialysis and electron microscopy. With poly(U), DHTV forms monom er cooperative dimer and tetramer complexes with binding constants of 100, 40, and 18.10(4) M-1 respectively and with a cooperativity parame ter omega = 2000. Poly(U) molecules at a concentration greater than 4. 10(-5) M phosphates are filled with peptide tetramers capable of bindi ng with each other, producing several types of compact structures that differ in morphology and in number of molecules of poly(U) that const itute them (hypothetically from two to several dozen). The formation o f tetramer complexes of DHTV with poly(U), poly(G), poly(A) and poly(C ) is accompanied by a substantial increase in intensity of fluorescenc e. When DHTV dimers bind cooperatively to poly(A), poly(C), and poly(U ) molecules, their rigidity increases, but that of poly(G) molecules d oes not. The hypothesis is that the observed similarity in thermodynam ic, hydrodynamic and optical properties of the DHTV complex with the d ouble- and single-helix deoxy- and ribonucleic acids and the similarit y between their electron microphotographs may reflect a similarity in structure of the respective complexes.