The Mosquito measures muscle contraction

posted Jan 29, 2013, 11:56 AM by Tiberius Brastaviceanu   [ updated Feb 13, 2013, 6:44 PM ]
During the night between Jan 28 and 29 Ivan, Tibi and Daniel obtained the first biological results with the Mosquito Scientific Instrument at Phil's lab. They used the Mosquito V3 made by Jonathan, equipped with a Joint-type transducer (the C6, see in this doc) fabricated by Francois. A new bath was used, specially designed by Ivan and Daniel for chemical activation of skinned muscle cells. The bath parts were received the same day and it was assembled by Ivan right before the experiment. 

Experimental parameters
  • Sample: wild type mouse, skinned psoas muscle cells (bundle of 4-5)
  • Room temperature
  • Activating solution: pCa = 4.5
  • Relaxing solution: regular 
  • Cantilever stiffness 1138.78 nN/microns (open spreadsheet)

The video below shows Mosquito displacement/force data (on the right) in sync with video recording (on the left) during the experiment. The resolution of the original video is much better. Due to computer memory problems the original video is 30 frames/second, Phil's CCD camera can go up to 300 frames/sec. The acquisition rate was only 1K. Averaging was performed on the data after the acquisition. 

The chemical solutions were exchanged manually by Ivan during the experiment, using a pipette to suck and inject them into the bath through a small orifice, specially designed for this purpose. In the video above we can clearly see when solutions are changed. Changing solutions generates a signal before the activation and relaxation, because the sample is perturbed by capillary forces as the solution exits and enters the small chamber. This is not so bad, compared to other systems that are used to study muscle contraction, like for example Aurora's system.

Chemical activation bath with sample in it

Before the experiment we had some problems with signal fluctuation, which was coming from a damaged delivery fiber. Damaged optical fibers become bend sensitive, and any mechanical vibration generates a signal. Tibi found a way to hold the fiber and to reduce the fluctuations. 

See discussion about this experiment during our weekly meeting the next day