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CHMC21 Topics in Biophysical Chemistry Fall 2025 Problem Set 2

1. Consider the QCM-D data in Figure 1 below, obtained from a quartz crystal with a resonant frequency of 5MHz. Mefp-1 is a mussel adhesive protein while NalO4 is an agent that facilitates protein cross-linking.

Figure 1

(i) What gives rise to the profile (in terms of decreasing/increasing △fand △D) of the curves at different time points-exposure to Mefp-1, rinsing, and upon exposure to NalO4. The three different curves are responses at different harmonics, normalized to make the comparison easier.

(ii) For all harmonics, estimate the amount of mass adsorbed before and after exposure to the cross-linking agent. Use a mass sensitivity constant of 17.7 ngcm 2· Hz'. At which time point is the Sauerbrey relation most suitable? Explain your answer.

2. Surface Plasmon Resonance:

(i) What physical quantity does a surface plasmon resonance (SPR) measure? In wbiol unit is it commonly given in?

(ii) Provide a dlearly labelled diagram of the expected data output, indicating where required to extract the kinetic rate constants kon and kof from the resulting data external interventions (e.g. changes in buffer composition) take place. What steps are without curve-fitting? Provide an equation and an explanation for each step.

3. Supposed you performed an SPR experiment looking at the binding of a growth factor and its antagonist to produce the sensorgram below (Figure 2).

(i) Label the axes with appropriate units.

(ii) There are three distinct experimental phases in this sensorgram. Label each phase and explain what is happening during that part of the experiment.