Print Email Facebook Twitter Torsional sensing of small-molecule binding using magnetic tweezers Title Torsional sensing of small-molecule binding using magnetic tweezers Author Lipfert, J. Klijnhout, S. Dekker, N.H. Faculty Applied Sciences Department BN/Bionanoscience Date 2010-07-12 Abstract DNA-binding small molecules are widespread in the cell and heavily used in biological applications. Here, we use magnetic tweezers, which control the force and torque applied to single DNAs, to study three small molecules: ethidium bromide (EtBr), a well-known intercalator; netropsin, a minor-groove binding anti-microbial drug; and topotecan, a clinically used anti-tumor drug. In the low-force limit in which biologically relevant torques can be accessed (<10 pN), we show that ethidium intercalation lengthens DNA ~1.5-fold and decreases the persistence length, from which we extract binding constants. Using our control of supercoiling, we measure the decrease in DNA twist per intercalation to be 27.3 ± 1º and demonstrate that ethidium binding delays the accumulation of torsional stress in DNA, likely via direct reduction of the torsional modulus and torque-dependent binding. Furthermore, we observe that EtBr stabilizes the DNA duplex in regimes where bare DNA undergoes structural transitions. In contrast, minor groove binding by netropsin affects neither the contour nor persistence length significantly, yet increases the twist per base of DNA. Finally, we show that topotecan binding has consequences similar to those of EtBr, providing evidence for an intercalative binding mode. These insights into the torsional consequences of ligand binding can help elucidate the effects of small-molecule drugs in the cellular environment. To reference this document use: http://resolver.tudelft.nl/uuid:1e09fcf1-2147-4a23-a469-741d5a244bf5 DOI https://doi.org/10.1093/nar/gkq598 Publisher Oxford University Press ISSN 0305-1048 Source Nucleic Acids Research, July 12, 2010 Part of collection Institutional Repository Document type journal article Rights (c) 2010 The Author(s) ; Creative Commons 2.5 Files PDF Lipfert 2010.pdf 5.2 MB Close viewer /islandora/object/uuid:1e09fcf1-2147-4a23-a469-741d5a244bf5/datastream/OBJ/view