PROBING OF B-Z JUNCTIONS IN RECOMBINANT PLASMIDS INVITRO AND IN THE CELL WITH DIFFERENT OSMIUM TETROXIDE COMPLEXES

Abstract

Complexes of OsO4 with 2,2''-bipyridine (Os,2,2''-bipy), 4,4''-bipyridine (Os,4,4''-bipy), 1,10-phenanthroline (Os,phe), bathophenanthroline disulfonic acid (Os,bpds) and OsO4, pyridine reagent (Os,py) were used to probe structural distortions at the junctions between right-handed B and left-handed Z DNA in supercoiled plasmids pRW751 and pPK1 (both containing (dC.sbd.dG)13 and (dC.sbd.dG)16 segments). With all five complexes the site-specific modification at the B.sbd.Z junctions was detected in vitro but only Os, 2,2''-bipy and Os,bpds produced strong site specific modification at submillimolar concentrations. In addition to the B.sbd.Z junctions, Os,phe also reacted at other sites. With the exception of Os,2,2''-bipy no one of the tested OsO4 complexes has proved to be suitable for probing structural distortions at the B.sbd.Z junctions in Escherichia coli cells.