Tip to substrate distances in STM imaging of biomolecules

Electron tunneling properties of outer-membrane decaheme cytochromes from Shewanella oneidensis

“…4). The observed sizes of the cytochromes in the activated films are within the expected range for globular proteins of a similar molecular weight, as expected for ambient imaging of biomolecules (Alliata et al, 2004). The apparent sizes observed on the films, including the slight variation between OmcA and MtrC, may be a function of not only their molecular shapes, but whether or not the cytochromes are binding to the Au(111) surface in a preferred orientation.…”

“…Therefore, despite the numerous recent examples in the literature that have utilized STM on metalloproteins in air as an effective means of single-molecule analysis (e.g., Davis et al, 2000;Chi et al, 2001;Andolfi et al, 2003;Bonanni et al, 2003;Alliata et al, 2004;Andolfi et al, 2004a,b;Davis et al, 2004), there is always a concern regarding effects of the STM measurement itself on the proteins under study. However, it is clear from the high reproducibility of the STM images and TS data in this study that the electric fields associated with STM operation are not irreversibly altering the proteins.…”

Fast electron transfer through a single molecule natively structured redox protein

“…These conditions have only been partially fulfilled in previous attempts. [16][17][18][19][20][21][22][23][24][25][26] Conductance measurements on proteins by scanning probe techniques have nearly all involved a tunnelling barrier between tip and molecule, [20][21][22][23][24][25][26] or the application of mechanical force to improve the electrical contact between tip and molecule. 23 But recently, we have been able to measure STM conductance of protein molecules in air, 27,28 contacted to two metallic electrodes via chemical anchoring groups.…”

Topological and dynamical properties of Azurin anchored to a gold substrate as investigated by molecular dynamics simulation

“…AFM provides a good estimation for the height of a protein with respect to the substrate, while it markedly overestimates its lateral size; the latter effect being due to tip broadening effects [9]. On the other hand, STM gives a realistic estimation of the lateral size of a protein on gold; the corresponding macromolecular height being drastically reduced as due to a variety of effects still not well clarified [46]. To compare the MD simulated and scanning probe nanoscopy data, we have introduced a geometric quantity that could well represent the topological properties of a protein over a substrate.…”