Figure 4.

Correlation between reconstructed phase shift and projected atomic density. (a) Schematic of the orientation of the two β-galactosidase molecules in (b) with respect to the graphene substrate. The molecule on the left is in a flat orientation, whereas the molecule on the right is in an upright orientation; i.e., the molecules have different thicknesses as measured from the graphene. (b) Amplitude and phase reconstruction of a hologram featuring two β-galactosidase molecules in different orientations with respect to the substrate as schematically depicted in (a). (c) Projected atomic density of models of β-galactosidase (PDB: 6CVM) in orientations matching those in (b). Each pixel on the grid is colored according to the number of atoms projected into the pixel. The molecule in a flat orientation exhibits a lower overall projected atomic density than the molecule in upright orientation, which is reflected by the difference in overall phase shift generated by the two molecules. (d) Schematic of two β-galactosidase molecules in flat orientation. (e) Amplitude and phase reconstruction of a hologram featuring two β-galactosidase molecules in flat orientations with respect to the surface as sketched in (d). (f) Projected atomic density of the models corresponding to the orientations in (e). The overall projected atomic density as well as the overall phase shift of both molecules is similar. (g) Schematic of two β-galactosidase molecules in upright orientation. (h) Amplitude and phase reconstruction of a hologram featuring two β-galactosidase molecules in upright orientations with respect to the surface as sketched in (g). (i) Projected atomic density of the models corresponding to the orientations in (h). The overall projected atomic density as well as the overall phase shift of both molecules is similar, a slightly higher phase shift on the right can be correlated with an increased projected atomic density within the molecule on the right.