Cytochrome c, aptamer binding

Figure 4.3 Standard curves for cytochrome c binding to immobilized aptamer CH6 (squares) and 37-lF (circles). The steady-state signals obtained during injection were corrected for the corresponding signal observed with the control flow cell containing immobilized streptavidin.

Figure 4.4 NaCl-dependent binding of cytochrome c to immobilized aptamers (steady-state signal for cnrve correction, see Figure 4.3).

Further control experiments were performed to find out if other proteins also bind to the DNA aptamers. All proteins used as controls—human serum albumin (p/ 4.9), bovine serum albumin (p7 4.7), myoglobin (p7 7.3), and mutarotase, 10 ftM each—showed negligible binding to the aptamer compared with cytochrome c (p7 10.65). At least by comparison with these few proteins, cytochrome c binding to DNA aptamers can be regarded as specific, although this specificity could simply reflect the p7 value of the protein. 

It can be concluded that CH6 as well as other aptamers bind cytochrome c rather unspeciflcally by ionic interactions of the polyanionic DNA and a protein containing a cationic cluster, at least when the aptamers are immobilized, as in SPR experiments. 

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