Thermal noise in liquid

Slawek Kulesza posted on Fri, Jul 11 2014 6:12 AM

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Hello all,

This is my first post. although I read this forum for a long time. I have MM8 with nanoscope V instrument and now I'm trying to image lipase on the mica substrate using PF QNM in liquid and SNL probes (A or C). To this end I first determine the deflection sensitivity (ramp in air on silicon substrate), and then estimate the spring constant (thermal tune in air). Then I switch to liquid and try to image the enzymes. I spotted, however, that although the amplitude of thermal cantilever vibrations in air is very small (ca. 10 pN), it increases up to 100 pN once the cantilever is put into liquid (even after thermalization). From other works I know that the max force should not exceed 100 pN in order to prevent proteins from being damaged, and I am curious, if such a noise in liquid is normal or not. Thanks in advance for any suggestions. Best greetings.