Applied Surface Science 258 (2012) 4383–4390 Contents lists available at SciVerse ScienceDirect Applied Surface Science journal homepage: www.elsevier.com/locate/apsusc Solid surface dependent layering of self-arranged structures with fibril-like assemblies of alpha-synuclein V. Bukauskas a,∗ , A. ˇ Setkus a , I. ˇ Simkien ˙ e a , S. Tum ˙ enas a , I. Kaˇ salynas a , A. R ˙ eza a , J. Babonas a , V. ˇ Casait ˙ e b , S. Povilonien ˙ e b , R. Meˇ skys b a Center for Physical Sciences and Technology, Goˇ stauto 11, LT-01108 Vilnius, Lithuania b Institute of Biochemistry, Vilnius University, Mokslinink ˛ u 12, LT-08662 Vilnius, Lithuania article info Article history: Received 21 October 2011 Received in revised form 22 December 2011 Accepted 29 December 2011 Available online 5 January 2012 Keywords: Biomolecular structures Scanning probe microscopy Optical properties abstract In present work the formation of hybrid constructions composed of alpha-synuclein-based colloidal solu- tions on various solid surfaces (silica coated Si, mica, CaF 2 and KBr) is investigated by scanning probe microscopy, spectrocopic ellipsometry, Fourier transformed infrared spectroscopy and vibrational cir- cular dichroism. Prior to the modification of the solids, the proteins were intentionally fibrilled under special conditions. It is proved that the multi-component coatings are self-arranged on the solid sub- strates. Depending on the substrate material, the interface films consisting of individual biomolecules can be detected on the solid surfaces. The coatings with fibril-like alpha-synuclein objects can be obtained on solid surfaces with negligible or comparatively thick interface films. The results are interpreted in terms of the charged surface-controlled electrostatic interaction between the substrate and the biomolecules. Solubility of solids is considered in this interpretation. © 2012 Elsevier B.V. All rights reserved. 1. Introduction Combination of supramolecular and nanostructured solid struc- tures on the surfaces of electronic systems offers highly promising opportunities in creating unique technologies for multicomponent and multifunctional assemblies acceptable for detection of chang- ing environment, transfer of signals and a response generation [1]. Advances in the technology of the hybrid materials are still hindered by a lack of detailed understanding about adsorption of supramolecules and multimolecular arrangements (e.g., pro- tein fibrils) on the solid surfaces. Large biomolecular objects do not simply attach to or detach from the surfaces but are involved in complex phenomena such as re-arrangement [2], cooperative effects [3] and surface aggregation [4]. There is a huge interest in elucidation of various aspects of these phenomena. Alpha-synuclein (-syn) is normally an unstructured soluble protein, which can aggregate forming insoluble fibrils [5].  -syn is the primary structural component of Lewy body fibrils related to disorders which are known as synucleinopathies [6]. The structural rearragements of -syn both in solution and in solid state have been investigated in a series of works [7–10]. Various structural studies including analysis by circular dichroism (CD) spectroscopy have ∗ Corresponding author. E-mail address: virgis@pfi.lt (V. Bukauskas). suggested a structural transformation of -syn from a random coil to a -sheet structure when the protein is transferred from solution to solid state surfaces [11,12]. In this work, the influence of surface on the secondary struc- ture of -syn deposited on substrates was investigated. For this, we experimentally compared the properties of biomolecular coat- ings on the several types of solid surfaces and analyzed the results in the terms of structures of the coatings and the interface arrange- ments. 2. Experimental 2.1. Sample preparation The samples with thin biomolecular films were prepared by a deposition of -syn fibrils from the colloidal solutions on vari- ous solid substrates, namely, mica, Si, CaF 2 , and KBr. The solutions typically contained the fibrilized -syn protein of concentration 10–30 mg/mL. The concentration of fibrils was reduced by dilut- ing the initial solution with 100 mM glycine–HCl buffer containing 0.01% NaN 3 , if necessary. The fixed volume of the solution (from 1 L to 6 L) was casted on the clean surface of solid substrates. After the incubation at room temperature in the clean air for 18 h, the samples were washed with distilled water and dried at 30 ◦ C in an oven with the clean air flow for 2–3 h. 0169-4332/$ – see front matter © 2012 Elsevier B.V. All rights reserved. doi:10.1016/j.apsusc.2011.12.120