Nanostructural molecular films of two class II hydrophobins

Hydrophobins are a group of highly surface active, self-assembling fungal proteins. They function as coatings on various fungal structures, work as adhesive agents, and enable aerial growth of hyphae. In this work we have focussed on two class II hydrophobins from Trichoderma reesei, HFBI and HFBII [1]. Langmuir-Blodgett films of HFBI and HFBII analysed by atomic force microscopy (AFM) showed highly organised two-dimensional crystalline structures for both hydrophobins [2]. Comparison between AFM data of ordered films and small-angle X-ray scattering results of hydrophobin solutions [3] indicated that the unit cells in the films have dimensions similar to those of tetrameric aggregates found in solutions. The results also indicated functional and structural differences between HFBI and HFBII that help to explain differences in their properties. This detailed structural study of hydrophobin films brings the interest in new options for surface modification and nanostructured materials. [1] Linder, M., Selber, K., Nakari-Setälä, T., Qiao, M., Kula, M.-R., and Penttilä, M., The hydrophobins HFBI and HFBII from Trichoderma reesei showing efficient interactions with nonionic surfactants in aqueous two-phase systems, Biomacromolecules 2 (2001) 511-517. [2] Paananen, A., Vuorimaa, E., Torkkeli, M., Penttilä, M., Kauranen, M., Ikkala, O., Lemmetyinen, H., Serimaa, R., and Linder, M., Structural hierarchy in molecular films of two class II hydrophobins, Biochemistry 42 (2003) 5253-5258. [3] Torkkeli, M., Serimaa, R., Ikkala, O., and Linder, M., Aggregation and self-assembly of hydrophobins from Trichoderma reesei: Low-resolution structural models, Biophysical Journal 83 (2002) 2240-2247.