the interaction between isatin-β-thiosemicarbazone (ibt) and calf thymus dna (ct-dna) was investigated in physiological buffer (ph 7.4) using neutral red (nr) dye as a spectral probe by uv–vis absorption and fluorescence spectroscopy, as well as viscosity measurements. the ibt is stabilized by intercalation in the dna ( k [ibt –dna] =1.03×105 m−1), and displaces the nr dye from the nr–dna comple...

The interaction of brilliant green with herring sperm DNA was investigated in detail by spectrometric methods in γ-cyclodextrin systems. On the condition of physiological pH, brilliant green prefers to form the 1:1 inclusion complex with γ-cyclodextrin.All the evidences indicated that the binding modes between γ-cyclode...

The natural product jadomycin B, isolated from Streptomyces venezeulae ISP5230, has been found to cleave DNA in the presence of Cu(II) ions without the requirement for an external reducing agent. The efficiency of DNA cleavage was probed using supercoiled plasmid DNA in buffered solution as a model environment. EC₅₀ and t(½) values for cleavage were 1.7 μM and 0.75 h, respectively, and varied ±...

Type III restriction enzymes have been demonstrated to require two unmethylated asymmetric recognition sites oriented head-to-head to elicit double-strand break 25-27 bp downstream of one of the two sites. The proposed DNA cleavage mechanism involves ATP-dependent DNA translocation. The sequence context of the recognition site was suggested to influence the site of DNA cleavage by the enzyme. I...

The bleomycins (BLMs) are natural products that in the presence of iron and oxygen bind to and cause single-strand and double-strand cleavage of DNA. The mode(s) of binding of the FeBLMs that leads to sequence-specific cleavage at pyrimidines 3' to guanines and chemical-specific cleavage at the C-4' H of the deoxyribose of the pyrimidine has remained controversial. 2D NMR studies using the hydr...

Topoisomerase II catalyzes theATP-dependent transport of a DNAsegment (T-DNA) through a transient double strandbreak in another DNA segment (G-DNA). A fundamentalmechanistic question is how the individual steps in this process are coordinated. We probed communication between the DNA binding sites and the individual enzymatic activities, ATP hydrolysis, and DNA cleavage. We employed short DNA du...

EndoTT encoded by tte0829 of Thermoanaerobacter tengcongensis binds and cleaves single-stranded (ss) and damaged double-stranded (ds) DNA in vitro as well as binding dsDNA. In the presence of a low concentration of NaCl, EndoTT cleaved ss regions of damaged dsDNA efficiently but did not cleave DNA that was entirely ss or ds. At high concentrations of NaCl or MgCl(2) or ATP, there was also speci...

Site-specific recombinases of the lambda-integrase family recognize and cleave their cognate DNA sites through cooperative binding to opposite sides of the DNA substrate by a C-terminal catalytic domain and a flexibly linked "core-binding" domain; regulation of this cleavage is achieved via the formation of higher-order complexes. We report that the core-binding domain of lambda-integrase is ab...

A number of DNA minor groove-binding ligands (MGBLs) are known to exhibit antitumor and antimicrobial activities. We show that DNA topoisomerase (Topo) I may be a pharmacological target of MGBLs. In the presence of calf thymus Topo I, MGBLs induced limited but highly specific single-strand DNA breaks. The 3' ends of the broken DNA strands are covalently linked to Topo I polypeptides. Protein-li...