IMPROVED VISUALIZATION OF DNA IN AQUEOUS BUFFER WITH THE ATOMIC-FORCEMICROSCOPE

An improved method has been developed for imaging deoxyribonucleic aci d (DNA) in aqueous buffer with the atomic force microscope (AFM). DNA on untreated mica can be imaged in aqueous buffer with the AFM if the DNA is deposited onto the mica in a buffer with HEPES and MgCl2, if th e sample is rinsed thoroughly with high water pressure, and if the ima ging is done with an electron beam-deposited (EBD) tip that has been d eposited in the scanning electron microscope (SEM). The water rinse re moves DNA that is otherwise easily scraped off the substrate. There is evidence that sharper tips may be more damaging to DNA when imaged in aqueous buffer especially when the DNA is bound tightly to the mica. The ability to image DNA in nearly biological conditions has potential applications for imaging biomolecular processes with the AFM.