Relaxation kinetics of the interaction between RNA and metal-intercalators: the Poly(A).Poly(U)/platinum-proflavine system.
The interactions of Poly(A).Poly(U) with the cis-platinum derivative of proflavine [{PtCl(tmen)}(2){HNC(13)H(7)(NHCH(2)CH(2))(2)}](+) (PRPt) and proflavine (PR) are investigated by spectrophotometry, spectrofluorimetry and T-jump relaxation at I=0.2M, pH 7.0, and T=25 degrees C. Base-dye interactions prevail at high RNA/dye ratio and binding isotherms analysis reveals that both dyes bind to Poly(A).Poly(U) according to the excluded site model (n=2). Only one relaxation effect is observed for the Poly(A).Poly(U)/PRPt system, whereas two effects are observed with Poly(A).Poly(U)/PR. The results agree with the sequence D+S <==> D, S <==> DS(I) <==> DS(II), where D,S is an external complex, DS(I) is a partially intercalated species, and DS(II) is the fully intercalated complex. Formation of DS(II) could be observed in the case of proflavine only. This result is interpreted by assuming that the platinum-containing residue of PRPt hinders the full intercalation of the acridine residue.
Biver
Tarita
T
Dipartimento di Chimica e Chimica Industriale, Università di Pisa, Via Risorgimento 35, 56126 Pisa, Italy.
Secco
Fernando
F
Venturini
Marcella
M
D002942:Circular Dichroism; D006863:Hydrogen-Ion Concentration; D007364:Intercalating Agents / Q000737:chemistry*; D007700:Kinetics; D009994:Osmolar Concentration; D010984:Platinum / Q000737:chemistry*; D011061:Poly A / Q000737:chemistry; D011063:Poly A-U / Q000737:chemistry*; D011370:Proflavine / Q000737:chemistry*; D012313:RNA / Q000737:chemistry*; D012492:Salts / Q000494:pharmacology; D013057:Spectrum Analysis; D013816:Thermodynamics; D017186:Titrimetry
D007364:Intercalating Agents; D012492:Salts; D011063:Poly A-U; D011061:Poly A; D010984:Platinum; D012313:RNA; D011370:Proflavine