Abstract:

We applied an atomic force microscopy（AFM）and a single molecular magnetic tweezer（MT）to the interaction between DNA and chitosan of different concentrations. We investigated their condensed morphologies and time dependent force curves. 0.2 to 0.5 μm steps and linear incremental area would appear from the DNA force curves for the MT experiment when the charge ratio of chitosan and DNA (k) is 3 and 4. The phenomenon may come from the circular, rod and spherical structures of DNAchitosan complexes. We also employed AFM to observe the condensed morphologies due to the interaction between λDNA or bpr322DNA and chitosan. The proportion of spherical and rod structures and the size of condensates significantly decreased with the increase of k. We eventully constructed a concrete model of DNA morphology variety caused by chitosan.

Key words: chitosan, magnetic tweezers (MT), DNA, atomic force microscopy(AFM)