Abstract:
:We study DNA supercoiling in a quantitative fashion by micromanipulating single linear DNA molecules with a magnetic field gradient. By anchoring one end of the DNA to multiple sites on a magnetic bead and the other end to multiple sites on a glass surface, we were able to exert torsional control on the DNA. A rotating magnetic field was used to induce rotation of the magnetic bead, and reversibly over- and underwind the molecule. The magnetic field was also used to increase or decrease the stretching force exerted by the magnetic bead on the DNA. The molecule's degree of supercoiling could therefore be quantitatively controlled and monitored, and tethered-particle motion analysis allowed us to measure the stretching force acting on the DNA. Experimental results indicate that this is a very powerful technique for measuring forces at the picoscale. We studied the effect of stretching forces ranging from 0.01 pN to 100 pN on supercoiled DNA (-0.1 < sigma < 0.2) in a variety of ionic conditions. Other effects, such as stretching-relaxing hysteresis and the braiding of two DNA molecules, are discussed.
journal_name
Biophys Jjournal_title
Biophysical journalauthors
Strick TR,Allemand JF,Bensimon D,Croquette Vdoi
10.1016/S0006-3495(98)77908-1subject
Has Abstractpub_date
1998-04-01 00:00:00pages
2016-28issue
4eissn
0006-3495issn
1542-0086pii
S0006-3495(98)77908-1journal_volume
74pub_type
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