Shear-flow mediated changes in DNA morphology

1. Introduction The behavior of DNA molecules in liquid flow is of interest in many different fields, since many processes in medicine and technology involve the transport and manipulation of long polymers such as DNA. Furthermore, due to its variability in length, DNA is a useful target for verifying theoretical polymer models. In contrast to former experiments on similar issues [1-3], we do not stain the whole molecule with bis-intercalating fluorescent dyes in order to visualize the DNA, but we label exclusively the non-tethered end with a nanometer-sized quantum dot (Qdot). This end-specific labelling has the considerable advantage over common approaches not to modify the intrinsic mechanical properties of the DNA and to allow reasonably long observation times due to significantly reduced bleaching.