TEM MOIRE PATTERNS EXPLAIN STM IMAGES OF BACTERIOPHAGE-T5 TAILS

A subtle combination of constant current and constant height modes in scanning tunnelling microscopy allowed the imaging of a non-flat uncoa ted biological specimen, namely the tail of the bacteriophage T5. In p arallel, a reference three-dimensional structure of the T5 tail was ca lculated from cryo-transmission electron microscopy images, based on i ts helical symmetry. This three dimensional reconstruction was compare d with scanning tunnelling microscopy data. The images of the tail obt ained by transmission electron microscopy, as well as projections of t he reconstructed model, show similar moire patterns. Here we show that scanning tunnelling microscopy performed in an aqueous environment pr ovides direct images which are remarkably similar to the projection of the three dimensional model obtained by transmission electron microsc opy. We deduce that our scanning tunnelling microscopy images are the result of a transmission of electrons through the gap between the scan ning tip and the conductive support across the biological specimen.