Metal binding by thionucleosides

Metallointercalation Reagents. 2-Hydroxyethanethiolato(2,2′,2″-terpyridine)-platinum(II) Monocation Binds Strongly to DNA By Intercalation

“…During the course of this work, [(terpy)-PtCl]+, where terpy is 2,2',2V-terpyridine, (PtTC, Fig. 1) was found to shift the 335-nm band of 4-thiouridine in native Escherichia coli tRNA (K. W. Jennette, unpublished results), conditions under which the sterically less cumbersome mercury complex, p-chloromercuribenzoate (PCM11), does not bind (6). In view of the remarkable similarity between the molecular geometries of the PtTC cation and the acridine dyes, the result was rationalized by proposing that intercalation of the platinum complex sufficiently disturbed the tertiary structure of the tRNA in the region of the 4-thiouridine to permit the formation of a Pt-S bond.…”

“…In an attempt to achieve base specificity, several complexes of the polarizable class b (or "soft") metals (4,5) were used with the aim of providing fluorescent or heavy metal electron microscope labels for thiolated bases (6). During the course of this work, [(terpy)-PtCl]+, where terpy is 2,2',2V-terpyridine, (PtTC, Fig.…”

The reaction of an organomercury compound with a nucleoside phosphorothioate

“…K' = 1.6 X 10' l/mol f 0.4 X 10' l/mol This value IS shghtly larger than the highest binding constant reported [7 ] for the reaction of a thiobase with a mercurial. It may be appropriate to recall that our value, as well as other binding constants reported [7-lo] for reactions between nucleic acid thro-constituents and mercunals is not the equilibrium constant K of the reaction wrth (RSHgR') K = (RS-) (R'Hg+) but a condrtronal equilibrium constant [ 161. (RSHgR')…”

“…If such a reaction takes place, the obvrous criterion in deciding whether rt wrll be quantitative under given crrcumstances is the equihbrium constant. Although K, values can be found in the literature for the reactions of RHgX compounds with several thro-analogs of nucleic acid bases [7], nucleosrdes and polynucleotrdes [8], and with s4U-containing tRNAs [9,10], no such data are available for reactrons of heavy metal compounds with nucleoside phosphorothroates.…”

“…The choice of SAMP as the mercurral for examining the reaction with psA deserves some comment. Assocratron constants for bmdmg of mercurials to Theoanalogs of nucleic acid constrtuents [7,8] are usually computed by spectrophotometnc methods, the reaction causing a shift in the spectrum of the thiobase. Bindmg of a mercurial to a nucleosrde phosphorothroate does not affect the nucleotide spectrum.…”