Figure 6
Monitoring individual mucin–protein interactions and their effects on the layer properties using quartz crystal mass detection with dissipation (QCM-D): the frequency shift one of the three of the overtones (F7, blue) and the dissipation shift for one of the three overtones (D7, red) were monitored using MUC5B+BSA+GST (a). The Sauerbrey model calculated an absorbed mucin layer of 1,600±5 ng cm−2. The addition of BSA did not affect the properties of the layer. After the addition of GST, the frequency decreased to ΔF=−87 IE-6, which was equal to an additional mass of 233±7 ng cm−2 and dissipation has significantly increased up to ΔD7=12,14 IE-6. The graphics in the right panel show the viscosity, shear and layer thickness comparisons before and after GST binding. The means and s.e.m. values are indicated by the major and minor horizontal bars, respectively. A paired samples t-test was used to determine changes in before/after values (*P=0.04, **P=0.015, and ***P=0.005). (b) Effect of galectin-3 on the mucin layer. The model calculated an absorbed mucin layer of 1,300±50 ng cm−2. Unlike GST, the addition of galectin-3 decreased the dissipation from 11.2 to 10.6, suggesting that galectin-3 has a stiffening effect on the layer. There is a sharp decrease in the frequency and subsequent reorganization of the layer (broken arrow) from the galectin-3 addition until the buffer wash (W) at the end which significantly decreased the layer thickness. The graphics in the right panel show the viscosity, shear, and layer thickness comparisons before and after galectin-3 binding. The means and s.e.m. values are indicated by the major and minor horizontal bars, respectively. A paired samples t-test was used to determine the changes in the before and after values (*P=0.0025, **P=0.008, and ***P=0.005). BSA, bovine serum albumin; GST, glutathione S-transferase.
