Experiments are described, showing that DNA solutions with lithium chloride present a hypochromicity, which increases with the molarity of the salt. Different absorbancy versus temperature curves are obtained for different solutions, and it is found that the melting point (Tm) increases with the lithium chloride concentration. When cooling the samples, the absorbancy decreases in a symmetric wa...

A novel DNA damage detection technique based on the characteristic fluorescence lifetimes exhibited by Pico-Green-single-stranded DNA and -double-stranded DNA complexes is employed to establish the damage produced on DNA isolated from sheep white blood cells following gamma radiation. This technique, which incorporates key concepts such as alkaline unwinding buffers and higher unwinding rates o...

In vertebrates, MCM2-7 and Cdc45 are required for DNA replication initiation, but it is unknown whether they are also required for elongation, as in yeast. Moreover, although MCM2-7 is a prime candidate for the eukaryotic replicative DNA helicase, a demonstration that MCM2-7 unwinds DNA during replication is lacking. Here, we use Xenopus egg extracts to investigate the roles of MCM7 and Cdc45 i...

The simian virus 40 (SV40) large T antigen (large tumor antigen), in conjunction with a topoisomerase, a DNA binding protein, and ATP, catalyzed the conversion of a circular duplex DNA molecule containing the SV40 origin of replication to a form with unusual electrophoretic mobility that we have named form U. Analysis of this molecule revealed it to be a highly underwound covalently closed circ...

The reaction of aged carboplatin (reaction of carboplatin in 24 mM NaHCO(3) for 45 h, 37 degrees, pH 8.6) with pBR322 DNA at 0 < r < 2.8, where r = [drug]/[DNA-bp], in 24 mM HEPES buffer, pH 7.4, for 24 h, followed by agarose gel electrophoresis showed DNA mobility changes consistent with unwinding closed circular DNA. However, identical experiments conducted in a two-buffer system, 24 mM HEPES...

Mini-chromosome maintenance (Mcm) is a central component for DNA unwinding reaction during eukaryotic DNA replication. Mcm2∼7, each containing a conserved ATPase motif, form a six subunit-heterohexamer. Although the reconstituted Mcm2∼7-Cdc45-GINS (CMG) complex displays DNA unwinding activity, the Mcm2∼7 complex does not generally exhibit helicase activity under a normal assay condition. We det...