New sample deposition technique for macromolecules: a puse injectionmethod

摘要

Using the pulse injection method[1]. single-stranded DNA, double-stranded plasmid DNA and porphyrin oligomer(Ni21mer) have been deoposited on well-defined Cu(111) surfaces under ultra-high vacuum (UHV) condition to obtain high resolution scanning tunneling microscopy (STM) images(fig.1). These particular UHV-STM images have revealed the DNA and porphyrin-Ni21 mer are adsorbed directly onto a clean Cu(111) surface, and exhibited the detailed structures of these macro-molecules which have not been resolved earlier. The single-stranded DNA oligomers have exhibited the images of individual internal base molecules(fig.2). For the double-stranded plasmid DNA(fig.3), the images has visualized Watson-Crick double-helix structures[2, 3]. And for the Ni21 mer, individual 21 units of prophyrinatonickel(II) are visualized(fig.4)[4].