SCANNING-TUNNELING-MICROSCOPY OBSERVATIONS OF BIOMOLECULES ON LAYEREDMATERIALS

Scanning tunnelling microscopy (STM) has been performed on the reverse transcriptases of the human immunodeficiency virus (HIV-1) and the mo loney murine leukaemia virus (MuLV). The biological molecules are adso rbed on n-type semiconducting MoTe2. The p66 (66 kD) subunit of the RT of HIV-1 is imaged by STM. Both STM and processed transmission electr on microscopy (TEM) data show a spherical and horseshoe-like shape of external diameter ca. 65 angstrom, depending on the angle of observati on. The STM results show a larger diameter which is related to the cur vature radius of the tip of the probing needle. The RTs of HIV-1 and M uLV exhibit a circular hole of ca. 20 angstrom diameter in accordance with structure predictions and functioning considerations. The surface -molecule interaction is discussed in terms of the electronic properti es of the semiconductor surface including the influence of small defec t sites at the layered crystal surface.