Objective: In this paper, we have introduced topoisomerase inhibitors, mechanism of action and types of them. DNA topoisomerases are ubiquitous enzymes that catalyze essential enzymes to solve the topological problems accompanying key nuclear processes such as DNA replication, transcription, repair and chromatin assembly by introducing temporary single or double strand breaks in the DNA. Result...

Dr Klaassen reported results of a recent study in which a novel mixed-format real-time polymerase chain reaction (PCR) assay was used to identify wild type cyp51A and point mutations conferring azole resistance in A. fumigatus isolates. Hybridisation of a single strand DNA detection probe with single strand target gene DNA enabled the researchers to differentiate between susceptible and resista...

A single strand of oligonucleotide can bind to double helical DNA under certain conditions. This must involve some unwinding of the original double helix in a process leading to the formation of a three-stranded region. The free energy for such an entropically unlikely reaction may come from a change in the degree of supercoiling of the original DNA. The conformation of the triple strand is inv...

We have devised a novel amplification strategy based on isothermal strand-displacement polymerization reaction, which was termed multiple cross displacement amplification (MCDA). The approach employed a set of ten specially designed primers spanning ten distinct regions of target sequence and was preceded at a constant temperature (61-65 °C). At the assay temperature, the double-stranded DNAs w...

Three-hundred ninety-two adult Dermacentor variabilis were collected from six Maryland counties during the spring, summer, and fall of 2002. Infection prevalence for spotted fever group Rickettsia was 3.8%, as determined by polymerase chain reaction. Single strand conformational polymorphism (SSCP) analysis followed by sequencing indicated that all infections represented a single rickettsial ta...

As an early step in DNA strand exchange reactions, the recA protein aligns homologous sequences within two DNA molecules to form a putative triple-stranded intermediate. In virtually all models for three-stranded DNA proposed to date, hydrogen bonds involving the N-7 position of guanine have played a prominent structural role. To determine whether the N-7 position of guanine is required for tri...

Following a DNA strand exchange reaction, RecA protein remains bound to the hybrid DNA product. DNA strand exchange reactions were carried out under optimal conditions in the presence of both RecA protein and SSB protein. As monitored by a sensitive DNA underwinding assay, all of the RecA protein present in the RecA nucleoprotein filament that initiates the strand exchange reaction can be accou...

In this study, a single-base change discrimination strategy was developed through enhanced DNA toehold exchange reaction on a chip surface. A DNA strand with single-base change (SNPs, insertion or deletion) at an arbitrary position was clearly discriminated with nucleic acid concentrations from 0.8 nM to 1 μM through this method.

The role of ATP hydrolysis in RecA protein-mediated DNA strand exchange reactions remains controversial. Competing models suggest that ATP hydrolysis is coupled either to a simple redistribution of RecA monomers within a filament to repair filament discontinuities, or more directly to rotation of the DNA substrates to drive branch movement unidirectionally. Here, we test key predictions of the ...

Single-stranded DNA oligonucleotides (ssODNs) can direct the repair of a single base mutation in human genes. While the regulation of this gene editing reaction has been partially elucidated, the low frequency with which repair occurs has hampered development toward clinical application. In this work a CRISPR/Cas9 complex is employed to induce double strand DNA breakage at specific sites surrou...