RECENT ADVANCES IN ATOMIC-FORCE MICROSCOPY OF DNA

Three advances involving DNA in atomic force microscopy (AFM) are repo rted here. First a HEPES-Mg buffer has been used that improves the spr eading of DNA and provides good DNA coverage with as little as 200-500 picograms per sample. Second, the new ''tapping'' mode has been used to improve the ease and resolution of AFM-imaging of DNA in air. Final ly, AFM images are presented of single-stranded Phi Chi-174 virion DNA with the gene 32 single-stranded binding protein. A summary of the cu rrent state of the field and of the methods for preparing and imaging DNA in the AFM is also presented.