From Nano to Subnano Resolution: Reconstitution of Hydrofobin Structure from a SPM Scan of HFBI Layer

Applying Scanning Probe Microscopy (SPM) methods to determine structural details of biomolecules (e.g. proteins) is one of the key trends in nanotechnology. Here we present the analysis of a Langmuir-Blodgett film of hydrofobin HFBI. The statistical analysis is based on an accurate procedure of data detrending to study the quasi-crystalline clusters of the HFBI layer. A statistical improvement method of signal to noise ratio was used. It relies on the variation of the crystallographic lattice superimposed on a quasi-periodical data set. The procedure produces optimal values of crystallographic periods and orientations of the symmetry axes. This information is used for selecting coherent data sets within a crystallographic cluster. Superposition of cells from the same cluster and calculation of an average periodical structure improves the signal to noise ratio, which leads from nano to subnano resolution of the protein structure. The number of superimposed cells N defines the resolution gain factor N 1/2 . In the case of hydrofobin, the value of N lies in the range of 25-100. This allows for the determination of fine structural details of HFBI. Average structures obtained from different domains of the protein layer also show a high degree of reproducibility.