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Related Concept Videos

DNA Packaging00:58

DNA Packaging

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Overview
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Chromatin Packaging01:32

Chromatin Packaging

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Each human somatic cell contains 6 billion base pairs of DNA. Each base pair is 0.34 nm long, meaning each diploid cell contains a staggering 2 meters of DNA. This long DNA strand is packed inside a nucleus measuring only 10-20 microns in diameter with the help of specialized DNA-binding proteins called histones. Together they form a compact DNA-protein complex called chromatin. The chromatin is further compacted into higher-order structures. The highest level of compaction is achieved during...
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Chromatin Packaging02:21

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Each human somatic cell contains 6 billion base-pairs of DNA. Each base-pair is 0.34 nm long, which means that each diploid cell contains a staggering 2 meters of DNA. How is such a long DNA strand packed inside a nucleus measuring only 10 - 20 microns in diameter? 
The chromatin
In combination with specialized DNA binding protein called Histones, the DNA double helix forms a compact DNA: protein complex called chromatin. The chromatin itself is further compacted into higher-order...
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DNA Topoisomerases02:02

DNA Topoisomerases

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Topoisomerases are enzymes that relax overwound DNA molecules during various cell processes, including DNA replication and transcription. These enzymes regulate positive and negative DNA supercoiling without changing the nucleotide sequence. DNA overwinding in a clockwise direction results in positively supercoiled DNA, whereas underwinding in a counterclockwise direction produces negatively supercoiled DNA.
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Topoisomerases are divided into two main types. ...
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Fixing Double-strand Breaks02:04

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The double-stranded structure of DNA has two major advantages. First, it serves as a safe repository of genetic information where one strand serves as the back-up in case the other strand is damaged. Second, the double-helical structure can be wrapped around proteins called histones to form nucleosomes, which can then be tightly wound to form chromosomes. This way, DNA chains up to 2 inches long can be contained within microscopic structures in a cell. A double-stranded break not only damages...
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DNA Helicases00:55

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DNA unwinding helicase enzymes are a type of motor protein. Motor proteins can translocate along filaments or polymers using energy generated from ATP hydrolysis. Helicases are involved in all the important cellular processes where DNA unwinding is required, such as DNA replication, repair, recombination, and transcription. They are present in all living organisms, but vary in their structure, function, and mechanism of action. For example, in prokaryotes, DnaB helicase binds and translocates...
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Related Experiment Video

Updated: Feb 16, 2026

Stretching Short Sequences of DNA with Constant Force Axial Optical Tweezers
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Stretching Short Sequences of DNA with Constant Force Axial Optical Tweezers

Published on: October 13, 2011

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Hyperstretching DNA.

Koen Schakenraad1,2, Andreas S Biebricher3, Maarten Sebregts4

  • 1Department of Applied Physics, Eindhoven University of Technology, P.O. Box 513, 5600 MB, Eindhoven, The Netherlands. schakenraad@lorentz.leidenuniv.nl.

Nature Communications
|December 21, 2017
PubMed
Summary
This summary is machine-generated.

Mechanical forces and compounds can alter DNA structure, leading to overstretching. This study confirms a hyperstretched DNA state, twice the length of B-DNA, revealing sequence dependence and physical principles for DNA applications.

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Area of Science:

  • Biophysics
  • Molecular Biology
  • Materials Science

Background:

  • DNA's three-dimensional structure is sensitive to mechanical and biochemical factors.
  • Mechanical overstretching and compound intercalation significantly increase DNA base pair spacing beyond regular B-DNA.

Purpose of the Study:

  • To quantitatively understand the interplay between B-DNA, overstretched DNA, and intercalated DNA.
  • To investigate the physical principles governing DNA mechanics under tension and biochemical influence.

Main Methods:

  • Single-molecule force-fluorescence experiments.
  • Development and application of a three-state statistical mechanical model.

Main Results:

  • Confirmation of a previously unconfirmed hyperstretched DNA state, approximately twice the length of B-DNA.
  • Demonstration of sequence-dependent variations in this hyperstretched state.
  • Quantitative model predictions align with experimental observations.

Conclusions:

  • The study elucidates the physical principles governing DNA mechanics under mechanical and biochemical stimuli.
  • Findings provide a predictive framework for DNA extension possibilities and limitations.
  • Results can guide the use of DNA in advanced applications like programmable soft materials and DNA origami.