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. Author manuscript; available in PMC: 2011 Nov 1.
Published in final edited form as: Nat Nanotechnol. 2011 Apr 10;6(5):314–320. doi: 10.1038/nnano.2011.45

Figure 3. The kinetic model can predict the number of protein binding events.

Figure 3

By fitting real-time binding curves to the model, it is possible to convert the signal generated from the GMR sensor into an absolute number of magnetic tags bound to the sensor surface. Here, EpCAM protein was loaded onto the sensors at a mass of 2.5 attomoles (nmax) and at masses serially diluted in twofold increments down to 78 zeptomoles (nmax/64). At least three replica sensors were used for each dilution. After 20 mins incubation with the 20-fold diluted solution of MNP-anti-EpCAM antibody (C0/20), the solution was washed away to terminate the binding reaction. Subsequently, a small section of the sensors was imaged with SEM (right panel; colour-coded boxes represent the different loading masses) to compare the number of MNPs bound in the experiment with that predicted by the model (left panel). The number of MNPs presented above each binding curve in the left panel represents the number of MNPs predicted to have bound to each corresponding sensor. Dotted lines are predictions using the analytical model in equation 2 (•••) and full lines are experimental data (–). SEM image of nmax/64 was not shown due to the low surface coverage of MNPs.