Alignment and Sensitive Detection of DNA by a Moving Interface

Abstract
In a process called "molecular combing," DNA molecules attached at one end to a solid surface were extended and aligned by a receding air-water interface and left to dry on the surface. Molecular combing was observed to extend the length of the bacteriophage λ DNA molecule to 21.5 ± 0.5 micrometers (unextended length, 16.2 micrometers). With the combing process, it was possible to (i) extend a chromosomal Escherichia coli DNA fragment (10 6 base pairs) and (ii) detect a minute quantity of DNA (10 3 molecules). These results open the way for a faster physical mapping of the genome and for the detection of small quantities of target DNA from a population of molecules.