Protein adsorption atomic force microscopy

The shift of the amide I mode (FTIR spectra) from 1657 to 1646 cm-1 was attributed to a change in the a-helix native structure to fl-sheets, secondary structure conformations. Atomic Force Microscopy (AFM) images display the coating of the manganese oxide surface as well as the unfolding in a ellipsoidal chain of the protein molecules after adsorption and immobilization on the surface. 

The stmctural and conformational analysis of proteins adsorbed to solid surfaces is difficult because most common analytical methods are not compatible with the presence of the interacting solids. With recent developments in instrumentation and techniques, our understanding of protein adsorption behavior has improved considerably [4, 14]. The most commonly used techniques include attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR), radiolabeling techniques, immunofluorescence enzyme-linked immunosorbent assay (ELISA), ellipsometry, circular dichroism (CD) spectroscopy, surface plasmon resonance (SPR), and amide HX with nuclear magnetic resonance (NMR). Atomic force microscopy (AFM) and scanning... 

Measurement of interfacial forces thus offers the potential to study the factors involved in protein repellence or adsorption. Force measurements on adsorbed and grafted PEG layers have been reported, using both the surface forces apparatus (SFA) and the colloid-probe atomic force microscopy (AFM) technique. - Adsorbed PEG layers show responses due to relaxation processes,... 

Subsequent adsorption of the micelles to an interface can lead to two different modes of adsorption, as shown in Figure 7.5. If the core of the micelle is fluid enough, the micelle can unfold on the interface to form a continuously flat layer as confirmed by atomic force microscopy (AFM) data [30], but also by other techniques, such as neutron reflection [29]. In the other mode of adsorption the micelle does not unfold, and thus the surface is covered by complete micelles, as shown from the AFM data in the right-hand part of Figure 7.5. The planar, spread-out, adsorption is most desired, as this gives a uniform brush across the whole surface. Still, for both the planar adsorption [30] and the adsorption of complete micelles [49,53], significant reductions were observed in the subsequent adsorption of model proteins to the coated surface. 

Figure 4.1 The biomimetic advantages of nanomaterials. (a) The nanostructuied hierarchical self-assembly of bone, (b) Nanophase titanium (top, atomic force microscopy image) and nanocrystalline HA/ helical rosette nanombe (HRN) hydrogel scaffold (bottom, scanning electron microscopy (SEM) image), (c) Schematic illustration of the mechanism by which nanomaterials may be superior to conventional materials for bone regeneration. The bioactive surfaces of nanomaterials mimic those of natural bones to promote greater amounts of protein adsorption and efficiently stimulate more new bone formation than conventional materials. Zhang, L., Webster, T.J., 2009. Nanotechnology and nanomaterials promises for improved tissue regeneration. Nano Today 4, 66-80.

Kennedy et al. reported [79,80] that the amphiphilic materials consisting of hydrophic polyisobutylene (PIB) and hydrophilic poly(, V-dimethylac-rylamide) showed lower human blood monocyte adhesion than that of PIB and hydrophilic poly(2-hydroxyethyl methacrylate), for which the weight fractions between hydrophobic and hydrophilic components were identical. However, the amounts of various adsorbed proteins onto these samples were similar [79,80]. The relation between protein adsorption and cell adhesion has not yet been elucidated. The surface characterization methods that we employ were contact angle measurements, XPS, and SEM. There must be some structural differences among these samples of PAS that we could not detect using the aforementioned apparatus. Further studies on the surface structure of PAS by TEM and atomic force microscopy (AFM) in dry and wet conditions are now in progress. 

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