Misfolding and self assembly of proteins in nano-aggregates of different sizes and morphologies (nano-ensembles, primarily nanofilaments and nano-rings) is a complex phenomenon that can be facilitated, impeded, or prevented, by interactions with various intracellular metabolites, intracellular nanomachines controlling protein folding and interactions with other proteins. A fundamental understanding of molecular processes leading to misfolding and self-aggregation of proteins involved in various neurodegenerative diseases will provide critical information to help identify appropriate therapeutic routes to control these processes. An elevated propensity of misfolded protein conformation in solution to aggregate with the formation of various morphologies impedes the use of traditional physical chemical approaches for studies of misfolded conformations of proteins. In our recent alternative approach, the protein molecules were tethered to surfaces to prevent aggregation and AFM force spectroscopy was used to probe the interaction between protein molecules depending on their conformations. It was shown that formation of filamentous aggregates is facilitated at pH values corresponding to the maximum of rupture forces. In this paper, a novel surface chemistry was developed for anchoring of amyloid β (Aβ) peptides at their N-terminal moieties. The use of the site specific immobilization procedure allowed to measure the rupture of Aβ -Aβ contacts at single molecule level. The rupture of these contacts is accompanied by the extension of the peptide chain detected by a characteristic elasto-mechanical component of the forcedistance curves. Potential applications of the nanomechanical studies to understanding the mechanisms of development of protein misfolding diseases are discussed.

Microscopic chemical patterning of diamond surfaces by hydrogen and oxygen surface atoms is used for self-assembly of human osteoblastic cells into micro-arrays. The cell adhesion and assembly is further controlled by concentration of cells (2,500-10,000 cells/cm2) and fetal bovine serum (0-15%). The cells are characterized by fluorescence microscopy of actin fibers and nuclei. The serum protein adsorption is studied by atomic force microscopy (AFM). The cells are arranged selectively on O-terminated patterns into 30-200 μm wide arrays. Higher cell concentrations allow colonization of unfavorable H-terminated regions due to mutual cell communication. There is no cell selectivity without the proteins in the medium. Based on the AFM, the proteins are present on both H- and O-terminated surfaces. Pronounced differences in their thickness, surface roughness, morphology, and phase images indicate different conformation of the proteins and explain the cell selectivity.

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We investigate adhesion of fetal bovine serum (FBS) on diamond surfaces which have alternating H/O-terminated surface patterns of 30 mm width prepared by hydrogen and oxygen plasma. The samples are immersed into 15% FBS in McCoy's 5A supporting medium and characterized by in situ atomic force microscopy (AFM) during 6 days of adsorption. Within the first day, 2-4 nm primary layer is formed on both H-/O-terminated surfaces. After 6 days, we observe 17 AE 5 nm FBS layer on O-terminated surface and 35 AE 5 nm layer on H-terminated surface. Adhesion of the primary and secondary layer is weaker on H-terminated surface. We present a model of FBS protein layers on H-/O-terminated diamond and we discuss implications for a preferential cell growth on O-terminated diamond. We also show that the preferential cell growth is not affected by the long-term FBS pre-adsorption.

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