The study of the mechanism of action of an antitumor active drug is essential for
improving the efficacy and reducing the side effects of the drug as well as for developing
better alternatives. In this vein, reactions of dirhodium compounds with DNA
oligonucleotides were investigated by the techniques of mass spectrometry, HPLC, and
NMR spectroscopic analytical methods.
The relative reactivities of three dirhodium compounds, namely Rh2(O2CCH3)4,
Rh2(O2CCF3)4, and [Rh2(O2CCH3)2(CH3CN)6](BF4)2, with DNA oligonucleotides were
studied and compared to the clinically used anticancer drugs cisplatin and carboplatin
using both MALDI and ESI mass spectrometric methods. The compound Rh2(O2CCF3)4
exhibits the highest reactivity among the dirhodium compounds, which is comparable to
cisplatin, followed by [Rh2(O2CCH3)2(CH3CN)6](BF4)2, and finally Rh2(O2CCH3)4
which is the least reactive.
Various dirhodium-oligonucleotide adducts were detected with both MALDI and
ESI methods, which involve substitution of different numbers of the original ligands of the given dirhodium compound. ESI MS was found to be a sufficiently soft ionization
method for detecting intact metal adducts, and CID MS-MS was useful for detecting
weakly bound species such as axial adducts [M+Rh2(O2CCH3)4] and for comparing the
relative bond strength between ligands in the metal adduct.
A combination of anion exchange HPLC purification and enzymatic digestion
studies of the adducts of Rh2(O2CCH3)4 with the 5'-CCTTCAACTCTC oligonucleotide
revealed that Rh2(O2CCH3)4 binds to the center or to the ends of the oligonucleotide
sequence by displacement of one or two acetate groups.
Kinetic products of the type [M+Rh2(O2CCH3)3] obtained from the reaction of
Rh2(O2CCH3)4 with 5'-CTCTCAACTTCC were separated by employing both reverse
phase and anion exchange HPLC methods. The adduct that involves binding of the
dirhodium unit to the exocyclic N4 atom of C5 and the N7 of A6 was found to be most
stable whereas other adducts involving binding of C3 or C12 residues are clearly less
stable.
Reaction of cis-[Rh2(DAP)(O2CCH3)3(CH3OH)](O2CCH3) (DAP = 1,12-
diazaperylene) with 5'-CTCTCAACTTCC produced a major adduct in which DAP
group intercalates between 6A and 7A in the double stranded adduct with the rhodium
atom that is not coordinated to the DAP group forming a covalent bond to the N7 atom
of 6A which lends stability to the adduct.
| Identifer | oai:union.ndltd.org:tamu.edu/oai:repository.tamu.edu:1969.1/4767 |
| Date | 25 April 2007 |
| Creators | Kang, Mijeong |
| Contributors | Dunbar, Kim R. |
| Publisher | Texas A&M University |
| Source Sets | Texas A and M University |
| Language | en_US |
| Detected Language | English |
| Type | Book, Thesis, Electronic Dissertation, text |
| Format | 7200823 bytes, electronic, application/pdf, born digital |
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