Protein-aptamer interactions techniques

Label-free detection of ligand-aptamer interaction was also demonstrated by means of impedance spectroscopy technique [52,53]. Simultaneously, Radi et al. [52] and Rodriguez et al. [53] reported application of Faradaic impedance spectroscopy (FIS) in detection of interaction of proteins with DNA aptamers. The detection method is based on the measurement of resistance in presence of redox mediator Fe(CN)6-In absence of target protein, the negatively charged aptamer repulse the redox mediator molecules from the sensor surface. In a paper by... 

Antibody fragment libraries from immunized and nonimmunized sources can be used in phage display and peptide libraries are commercially available. An alternative technique is to design protein aptamers that consist of a stable protein scaffold on which random peptides are displayed. An example of protein aptamers are affibodies, which present a library of 13 randomized amino acids on the Z domain of Staphylococcus aureus protein A. Crystal structure studies indicate similarity in the binding of an affibody to its target to protein-antibody interactions. However, affibodies have a dissociation constant of approximately 1 /.tM compared to antibody-antigen complexes ofl nM orless(H3, Rl, Wl). 

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