Manipulating DNA

This chapter describes the various methods used to manipulate single DNA molecules and the considerations in the choice of one particular method. It starts with a description of DNA end-labelling, necessary to anchor the molecule to surfaces or beads that can be manipulated. A particular application of DNA anchoring is molecular combing, whereby the molecule is stretched on a surface by a receding meniscus. DNA rearrangements and replication bubbles can then be observed by fluorescence on these straightened molecules. It then looks at the forces at the molecular scale, which range from the smallest one due to thermal agitation, to the largest associated with breaking a covalent bond, via entropic and non-covalent bonding forces. It describes the tools used to manipulate single molecules (micro-needles, AFM cantilevers, optical, magnetic, and acoustic tweezers and traps, etc.), comparing their performances in terms of bandwidth and signal to noise (i.e., force and extension resolutions).