- Email: [email protected]
Site-selective cleavage of tRNAPhe by metal complexes
288
Abstracts
5024
METAL ION MOVEMENTS IN [(NH&R@] COMPLEXES OF ADENOSINE AND RELATED LIGANDS BY SQUARE-WAVE VOLTAMMETRY R.D. Galang, A. Prock and M.J. Clarke, Departments of Chemistry, Boston College, Chesmut Hill, MA 02167 and Boston University, Boston, MA 02215 USA Square-wave voltammetry (SWV) provides the required sensitivity and resolution to separate electrochemical waveforms arising from rotational isomers in which the metal swings around the C-N bond on exocyclic ammine nitrogens of nucleoside ligands. SWV generated Eh vs. pH diagrams yield both the E“ and pKa values for the individual rotamers, which agree well with those determined by lH-NMR and the average values measured by spectrophotometry. A linkage isomerization reaction also occurs upon reduction whereby Ru(I1) moves to a ring nitrogen. The reverse reaction occurs on re-oxidation. Computer simulations of SWV scans of these complexes yield the rate constants for both the rotameric and isomerization reactions. Analogous reactions can also be monitored on nucleic acids with coordinted [(NH,),Ru].
THE INTERACTION OF TRANSITION METAL IONS WITH DNA. N. Katsaros, A. Koutsodimou and E. Tselepi, "Demokritos" N.R.C., Institute of Physical Chemistry, 153 10 Ag. Paraskevi, Athens, Greece. The interaction of [Ru(NH3)gCl12+, Rh2(OCOCH3)4, [Rh(en)2C121+ and Me2Sn2+ with calf thymus DNA have been examined at various metal:DNA ratios. Electronic spectra of metal-DNA solutions and melting curves have been taken for the determination of DNA melting temperature (T,) in the presence of the above complex ions. Except for Rh2(OCOCH3)4 that does not appreciably interact with DNA all other complex ions interact with DNA so as to stabilize the double helix thus indicating interaction of the complex ions with the phosphate moieties of the DNA. The experimental results also showed biphasic melting for the ruthenium complex ions.
JO25
CLEAVAGE OF tFtNAPhe BY METAL COMPLEXES JO26SITE-SELECTIVE Christine S. Chow and Jacqueline K. Barton, Columbia University
Deptartment of Chemistry, New York, NY, 10027. Photoactivated cleaving agents have recently been employed to probe local variations in RNA structure. A variety of metal complexes, namely Ru(TMP)$+, Rh(DIP)$+, and Rh(phen)z(phi) 3+, have been found to cleave tRNA. In particular, Rh(phen)z(phi)3+ recognizes and cleaves at conformationally distinct sites on tRNAPhe which are characterized by tertiary junctions and an opening of the major groove in helical regions. These molecules may be useful to explore the tertiary structure of RNA and the variations in RNA structure which may demarcate biologically important regions in the RNA .
Abstracts
5024
METAL ION MOVEMENTS IN [(NH&R@] COMPLEXES OF ADENOSINE AND RELATED LIGANDS BY SQUARE-WAVE VOLTAMMETRY R.D. Galang, A. Prock and M.J. Clarke, Departments of Chemistry, Boston College, Chesmut Hill, MA 02167 and Boston University, Boston, MA 02215 USA Square-wave voltammetry (SWV) provides the required sensitivity and resolution to separate electrochemical waveforms arising from rotational isomers in which the metal swings around the C-N bond on exocyclic ammine nitrogens of nucleoside ligands. SWV generated Eh vs. pH diagrams yield both the E“ and pKa values for the individual rotamers, which agree well with those determined by lH-NMR and the average values measured by spectrophotometry. A linkage isomerization reaction also occurs upon reduction whereby Ru(I1) moves to a ring nitrogen. The reverse reaction occurs on re-oxidation. Computer simulations of SWV scans of these complexes yield the rate constants for both the rotameric and isomerization reactions. Analogous reactions can also be monitored on nucleic acids with coordinted [(NH,),Ru].
THE INTERACTION OF TRANSITION METAL IONS WITH DNA. N. Katsaros, A. Koutsodimou and E. Tselepi, "Demokritos" N.R.C., Institute of Physical Chemistry, 153 10 Ag. Paraskevi, Athens, Greece. The interaction of [Ru(NH3)gCl12+, Rh2(OCOCH3)4, [Rh(en)2C121+ and Me2Sn2+ with calf thymus DNA have been examined at various metal:DNA ratios. Electronic spectra of metal-DNA solutions and melting curves have been taken for the determination of DNA melting temperature (T,) in the presence of the above complex ions. Except for Rh2(OCOCH3)4 that does not appreciably interact with DNA all other complex ions interact with DNA so as to stabilize the double helix thus indicating interaction of the complex ions with the phosphate moieties of the DNA. The experimental results also showed biphasic melting for the ruthenium complex ions.
JO25
CLEAVAGE OF tFtNAPhe BY METAL COMPLEXES JO26SITE-SELECTIVE Christine S. Chow and Jacqueline K. Barton, Columbia University
Deptartment of Chemistry, New York, NY, 10027. Photoactivated cleaving agents have recently been employed to probe local variations in RNA structure. A variety of metal complexes, namely Ru(TMP)$+, Rh(DIP)$+, and Rh(phen)z(phi) 3+, have been found to cleave tRNA. In particular, Rh(phen)z(phi)3+ recognizes and cleaves at conformationally distinct sites on tRNAPhe which are characterized by tertiary junctions and an opening of the major groove in helical regions. These molecules may be useful to explore the tertiary structure of RNA and the variations in RNA structure which may demarcate biologically important regions in the RNA .