Surface functionalization for protein arrays

FIGURE 4.3 The variety of ProteinChip arrays available for sample preparation. (A) The upper arrays represent chemically modified chromatographic surfaces, while the bottom arrays are biochemically modified surfaces. Chemically modified surfaces are used to retain a group of proteins, while biochemically modified surfaces are typically used to isolate a specific protein or functional class of proteins. (B) Protein profile of a cell lysate on different ProteinChip surfaces. As shown in the figure for a selection of protein chips, the individual surfaces retain different groups of proteins, depending on their physiochemical properties. The proteins retained are also dependent on the pH of the sample for the cation and anion exchange surfaces. 

Heterobifunctional cross-linkers have been used to attach activated biomolecules on surfaces functionalized with either aminosilane [27] or mercaptopropylsi-lane [28]. These strategies have resulted in up to fourfold higher signal-to-noise ratios compared with the polylysine surface for arrayed antibodies [29]. Specific immobilization via interaction of surfaces functionalized with salicylhydroxamic acid derivatives and phenyldiboronic acid-labeled nucleic acids and proteins has also been demonstrated [30]. 

Surface Viscosity of Protein Monolayers. Figure 2 shows the surface viscosity ( H g) of a number of proteins and one polyamino acid as a function of H ( ), The extremely high surface viscoelasticity of protein monolayers appears to be more characteristic of an interacting random chain system than an array of rigid helices. The theory of surface viscosity of Moore and Eyring ), based on the Theory of Absolute Reaction Rates, postulates that the flow of a monolayer consists of movements of flow units, normally molecules, from one equilibrium position to another, over an intermediate activation energy barrier. The equation derived for the coefficient of surface viscosity ( g)... 

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