Scanning probe microscopy (STM/AFM) and applications in biology

In this paper, single-molecular imaging and manipulating are presented. By using STM, topographic features of single molecules including DNA and DNA-p rotein complex can be visualized with subnanometer resolution in air and in liquid. In this way, a new DNA;conformation, called parallel-stranded DNA, has been revealed. Conformation changes of DNA enzyme during the DNA repro duction procedure and loop structures of DNA in the process of some eukaryo tic gene regulation have also been found. With a modified "molecular-combin g'' technique and direct AFM imaging, DNA molecules can be aligned and then imaged on the surface of an APS mica film. The new approach could be used to improve present gene physical mapping.