title: Electrochemistry of nano-scale bacterial surface protein layers on gold.
abstract: The mechanism of the recrystallization of nano-scale bacterial surface protein layers (S-layers) on solid substrates is of fundamental interest in the understanding and engineering of biomembranes and e.g. biosensors. In this context, the influence of the charging state of the substrate had to be clarified. Therefore, the electrochemical behaviour of the S-layers on gold electrodes has been investigated by in-situ electrochemical quartz microbalance (EQMB) measurements, scanning force microscopy (SFM) and small-spot X-ray photoelectron spectroscopy (SS-XPS) of potentiostatically emersed substrates. It was shown that the negatively charged bonding sites of the S-layer units (e.g. carboxylates) can bond with positively charged Au surface atoms in the positively charged electrochemical double layer region positive of the point of zero charge ( approximately -0.8 V vs. saturated mercury-mercurous sulphate electrode). Surface conditions in other potential regions decelerated the recrystallization and fixation of S-layers. Time-resolved in-situ and ex-situ measurements demonstrated that two-dimensional S-layer crystal formation on gold electrodes can occur within few minutes in contrast to hours common in self-assembled monolayer (SAM) generation. These results proved that the recrystallization and fixation of 2D-crystalline S-layers on an electronic conductor can be influenced and controlled by direct electrochemical manipulation.
authors.affiliation: Laboratory for Thin Film Technology, Federal Institute for Materials Research and Testing, Unter den Eichen 87, Berlin D-12205, Germany.
authors.forename: Marlene
authors.initials: M
authors.lastname: Handrea
authors.forename: Mario
authors.initials: M
authors.lastname: Sahre
authors.forename: Angela
authors.initials: A
authors.lastname: Neubauer
authors.forename: Uwe B
authors.initials: UB
authors.lastname: Sleytr
authors.forename: Wolfgang
authors.initials: W
authors.lastname: Kautek
mesh_terms: D001425:Bacterial Outer Membrane Proteins / Q000737:chemistry* / Q000378:metabolism; D015374:Biosensing Techniques / Q000379:methods*; D002462:Cell Membrane / Q000737:chemistry / Q000378:metabolism; D003460:Crystallization; D004563:Electrochemistry; D004566:Electrodes; D004577:Electron Probe Microanalysis; D006046:Gold / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D036103:Nanotechnology; D011791:Quartz
chemical_list: D001425:Bacterial Outer Membrane Proteins; D011791:Quartz; D006046:Gold