A. Jancso et al., Potentiometric and spectroscopic evidence for coordination of dimehyltin(IV)(2+) to phosphate groups of DNA fragments and related ligands, MAGY KEM FO, 106(10), 2000, pp. 414-426
The co-ordination of dimethyltin(IV)(2+) to nucleic acid fragments (5'-GMP,
5'-ATP and 5'-d(CGCGCG)(2)) and their sugar constituents (D-ribose and 2-d
eoxy-D-ribose) as ligands was investigated in aqueous solution by means of
potentiometric titration and H-1 and P-31 NMR spectroscopic methods. The re
sults showed that in acidic medium the phosphate groups can provide suitabl
e sites for metal ion co-ordination, while the hydroxyl groups of the studi
ed sugars or the sugar moieties of the two nucleotides play a role in this
process in the higher pH range. The base moieties of 5'-GMP and 5'-ATP were
not co-ordinated to dimethyltin(IV)(2+). The stability constants of the co
mplexes formed in the above systems were determined by pH-metric titration.
The data revealed a stronger co-ordination ability of the triphosphate as
compared with that of the monophosphate. The comparison of the stability co
nstants of the D-ribose and 2-deoxy-D-ribose complexes showed that more sta
ble species were formed when neighbouring alcoholic hydroxy groups were ava
ilable for the co-ordination of metal ions. The observed chemical shift cha
nges of the P-31 NMR resonances, as compared with those measured for the me
tal-free systems, demonstrated that the phosphate groups of the DNA fragmen
t [5'-d(CGCGCG)(2)] chains act as binding sites for dimethyltin(IV)(2+) bet
ween pH 4.5 and 7. The 1D and 2D H-1 NMR spectra indicated that the base an
d sugar moieties do not participate in the coordination process under these
conditions.