Ultrasound enhanced the binding ability of chitinase onto chitin: From an AFM insight

In order to evaluate the effect of ultrasound to chitinase from a molecular level, atomic force microscopy (AFM) was employed to investigate the interaction force of chitinase binding onto chitin surface. In the measurement of force-distance curve, a series of pull-off events were discovered using the immobilized AFM tips with chitinase either treated by ultrasound or not, whereas no interaction peak was observed by the AFM tips without chitinase, indicating that the obtained adhesion forces were coming from the binding functions between chitinase and chitin. Through the analysis of these force curves, at the loading velocity of 0.3 mu m/s, the maximum binding force of the chitinase treated by ultrasound for 20 min onto chitin was measured to be 105.33 +/- 23.51 pN, while the untreated onto chitin was 71.05 +/- 12.73 pN, suggesting the stronger binding force between ultrasonic treated chitinase and chitin substrate. Therefore, AFM has provided a useful method to directly and quantitatively characterize the interactions between chitinase and chitin, and successfully proved that ultrasound could activate chitinase by enhancing the binding ability of chitinase onto chitin.