Topoisomerase II resolves intrinsic topological problems of double-stranded DNA. As part of its essential cellular functions, the enzyme generates DNA breaks, but the regulation of this potentially dangerous process is not well understood. Here we report single-molecule fluorescence experiments that reveal a previously uncharacterized sequence of events during DNA cleavage by topoisomerase II: ...

the aggregation behavior of anionic cobalt(ii) 4,4′,4ʺ,4‴-tetrasulfonated phthalocyanine, [co(tspc)4-] was studied at its various concentrations and different ionic strengths using optical absorption and resonance light scattering (rls) spectroscopies in 5 mm phosphate buffer, ph 7.0 at 25 °c. the results show no aggregation behavior at concentration range of 5.1 × 10-6-7.5 × 10-5 m. also, the ...

Microcin B17 is a 3.1-kDa bactericidal peptide; the putative target of this antibiotic is DNA gyrase. Microcin B17 has no detectable effect on gyrase-catalysed DNA supercoiling or relaxation activities in vitro and is unable to stabilise DNA cleavage in the absence of nucleotides. However, in the presence of ATP, or the non-hydrolysable analogue 5'-adenylyl beta,gamma-imidodiphosphate, microcin...

Few new 4-aminoantipyrine based mixed ligand complexes having imidazole as a potential drug candidate, were designed, synthesized and characterized by analytical and spectral methods. The electronic absorption and electron paramagnetic resonance parameters of Cu(II) complex revealed that the Cu(II) ion exhibits a distorted octahedral geometry with the carbonyl oxygen atom of the 4-aminoantipyri...

Two copper(II) complexes, cluster 1, and mononuclear 2, have been synthesized by reacting acetylacetone and benzohydrazide (1:1 ratio for 1 and 1:2 ratio for 2) with CuCl(2) in a methanol solution. In 2, which is a new complex, the ligand acts as a tetradentate which binds the metal ion via two amide-O atoms and two imine-N atoms providing an N(2)O(2) square-planar around the copper(II) ion. Th...

Following V(D)J cleavage, the newly liberated DNA signal ends can be either fused together into a signal joint or used as donor DNA in RAG-mediated transposition. We find that both V(D)J cleavage and release of flanking coding DNA occur before the target capture step of transposition can proceed; no coding DNA is ever detected in the target capture complex. Separately from its role in V(D)J cle...

KpnI REase recognizes palindromic sequence, GGTACC, and forms complex in the absence of divalent metal ions, but requires the ions for DNA cleavage. Unlike most other REases, R.KpnI shows promiscuous DNA cleavage in the presence of Mg2+. Surprisingly, Ca2+ suppresses the Mg2+-mediated promiscuous activity and induces high fidelity cleavage. To further analyze these unique features of the enzyme...

Abstract Thermophilic Argonaute proteins (Agos) have been shown to utilize small DNA guides for cleaving complementary in vitro, which shows great potential nucleic acid detection. In this study, we explored mesophilic Agos the detection of molecule by cooperating with allosteric transcription factors (aTFs). Two from bacteria, Paenibacillus borealis ( Pb Ago) and Brevibacillus laterosporus Bl ...

Two acridine groups were successfully introduced into di-iron(III) complex. DNA cleavage experiments indicated that complex conjugating bisacridine groups can enhance 300-fold for the cleavage efficiency compared with complex lacking of acridine conjugation. Further ligation assay of DNA segments provided the evidence for hydrolytic mechanism of DNA cleavage.

The Type I restriction-modification enzymes comprise three protein subunits; HsdS and HsdM that form a methyltransferase (MTase) and HsdR that associates with the MTase and catalyses Adenosine-5'-triphosphate (ATP)-dependent DNA translocation and cleavage. Here, we examine whether the MTase and HsdR components can 'turnover' in vitro, i.e. whether they can catalyse translocation and cleavage ev...