Nanoscale Science Department

We discover that landing macromolecules on an one-atom-thick membrane, like graphene, preserves the gas-phase 3D-structure of the molecules at the surface. By exploiting this dynamics for proteins landing on graphene, we are able to land folded proteins on surface and see them one-at-a-time by low-energy electron holography technique. Our approach opens new opportunities to visualize 3D-structures of many proteins, nucleic acids, and carbohydrates at the single molecule level.

Interference requires coherence, which is usually hard to come by in condensed matter environments. However, sometimes even short coherence times are suffcient to reveal most peculiar phenomena such as making it look like a supercurrent reverses its flow, which can be exploited for quantum sensing. An  international collaboration of scientists between the Max Planck Institute for Solid State Research in Stuttgart, Ulm University, the Autonomous University of Madrid, and the University of Uppsala has now used such a supercurrent reversal to detect the ground state of a magnetic impurity coupled to a superconductor. Using a scanning tunneling microscope, they detect the interference in the Josephson current thereby creating a rudimentary phase sensitivity like in a superconducting quantum interference device (SQUID).

To better understand and possibly control fast chemical reactions, it is necessary to study the behavior of electrons as precisely as possible - at their intrinsic length and time scales. Until now, however, microscopy techniques have only provided sharp images in either space or time. Using a unique combination of tunneling microscopy and attosecond technology, we have managed to overcome these difficulties. Our atomic quantum microscope can visualize the movement of electrons in individual molecules, simultaneously at picometer length and attosecond time scales.

Molecular imaging at the single-molecule level of large and flexible proteins such as monoclonal IgG antibodies is possible by low-energy electron holography after chemically selective sample preparation by native electrospray ion beam deposition (ES-IBD) from native solution conditions. The single-molecule nature of the measurement with a spatial resolution down to 5 Å allows the mapping of the structural variability of the protein molecules that originates from their intrinsic flexibility and from different adsorption geometries.