Comparison between HPLC and Capillary Electrophoresis for the Separation and Identification of the Platination Products of Oligonucleotides withcis-[Pt(NH3)2(H2O)2]2+and [Pt(NH3)3(H2O)]2+

Abstract

HPLC and capillary electrophoresis (CE) were compared in order to separate the platinum adducts formed upon reaction of the double-stranded 18-mer d(AACGGTTAACCGTTAATT)2I with the two complexescis-[Pt(NH3)2(H2O)2]2+1 and [Pt(NH3)3(H2O)]2+2 and of the single-stranded octamer d(CTGGCTCA) II with complex 2. The GG sequence in both oligonucleotides is the only site of platination giving monoadducts on either of the two guanines or the diadduct which is theN7,N7chelate of the Pt(NH3)22+moiety. The HPLC separation of the adducts was performed with a reverse-phase technique similar to that previously used for platinated oligonucleotides up to octamers. The adducts were identified by enzymatic digestion followed by mass spectrometry characterization of the digests collected at the outlet of the column. The CE separation of the platination products of I with 2 and 1 was performed using respectively a simple capillary zone electrophoresis technique and a micellar electrokinetic capillary chromatography technique. For the more difficult separation of the platination products of II with 2, a capillary gel electrophoresis technique was required. In contrast to HPLC, CE gives better resolution the longer the oligonucleotide. Moreover, the separations are run with higher efficiency and time saving. However, with the present machines, CE precludes the recovery of sufficient amounts of material required by product identification.