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Related Concept Videos

Complex Numbers01:29

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The real number system cannot represent the square root of a negative number, which restricts solutions for certain equations, such as quadratics with negative discriminants. To address this, the complex number system was developed, introducing the imaginary unit i, where i = √(-1). This extension allows for the representation of all roots, including those involving negative radicands.A complex number is written in the form x + yi, where x and y are real numbers. Here, x represents the...
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Updated: Feb 1, 2026

Self-assembly of Complex Two-dimensional Shapes from Single-stranded DNA Tiles
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Fluoroquinolone-Gyrase-DNA Cleaved Complexes.

Gan Luan1, Karl Drlica2

  • 1Department of Microbiology, Biochemistry & Molecular Genetics, Public Health Research Institute, New Jersey Medical School, Rutgers Biomedical and Health Sciences, Rutgers University, 225 Warren St, Newark, NJ, 07103, USA.

Methods in Molecular Biology (Clifton, N.J.)
|November 28, 2017
PubMed
Summary
This summary is machine-generated.

Quinolone antibacterials form complexes with DNA and bacterial enzymes, blocking DNA replication and cell growth. Studying these "cleaved complexes" helps improve drug design and understand resistance mechanisms.

Keywords:
Cleaved complexesDNA gyraseDNA topoisomeraseFluoroquinolonePlasmid DNA isolationQuinolone

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Area of Science:

  • Biochemistry
  • Microbiology
  • Molecular Biology

Background:

  • Quinolones are critical antibacterial agents targeting bacterial DNA gyrase and topoisomerase IV.
  • These drugs function by forming stable ternary complexes with DNA and the target enzymes, leading to DNA breakage.
  • Understanding these interactions is key to developing new antibiotics and combating resistance.

Purpose of the Study:

  • To investigate the formation, stability, and properties of quinolone-DNA-topoisomerase cleaved complexes.
  • To explore the utility of studying cleaved complexes for improving quinolone structure and understanding resistance.
  • To correlate in vitro findings with in vivo observations in bacterial cells.

Main Methods:

  • In vitro formation and detection of cleaved complexes using purified gyrase, topoisomerase IV, plasmid DNA, and quinolones.
  • Assessing complex stability through EDTA treatment, heat, or dilution, and analyzing DNA by gel electrophoresis.
  • Detecting cleaved complexes in vivo in quinolone-treated bacterial cells via DNA replication inhibition and chromosome fragmentation assays, including CsCl density-gradient centrifugation.

Main Results:

  • Cleaved complexes readily form in vitro, causing DNA linearization detectable by gel electrophoresis.
  • Complex stability is influenced by quinolone structure and specific topoisomerase mutations conferring resistance.
  • In vivo studies confirmed that cleaved complexes rapidly inhibit DNA replication and cause chromosome fragmentation in treated bacteria.

Conclusions:

  • Studying quinolone-DNA-topoisomerase cleaved complexes provides valuable insights into antibacterial mechanisms.
  • These studies can guide the development of novel quinolone antibiotics with enhanced efficacy.
  • Understanding cleaved complex properties is crucial for elucidating the biochemical basis of quinolone resistance.