[Spm] baseline slope in force curves

[Olivier Arnould]

Hi,

Thank you for the article. I've never recommanded to remove the baseline "blindly" too but by using the baseline obtain on silicon substrate for example (i.e., a stiff sample). This is only for removing the part of the Z-displacement due to the cantilever deflection and you have to do it anyway. If an other effect due to an other interaction with your sample occurs, it will remain even with this (necessary) correction !

Best regards,

Olivier Arnould
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  ----- Original Message ----- 
  From: Igor Sokolov 
  To: 'Olivier Arnould' ; spm at spmlist.di.com 
  Cc: schille at uni-muenster.de 
  Sent: Tuesday, October 07, 2008 6:47 PM
  Subject: RE: [Spm] baseline slope in force curves


  Hi there,
  It seems I missed the original question. However, the question was clear, and important. 
  I would not recommend just subtract the base line blindly. We saw a similar phenomenon on epithelial cells, and initially thought that it was artifact. But when we got a scanner with larger Z-range, we found that was a real signal from cell microvilli etc. (cell brush). As a result we developed a bit more complicated model. This is described in a paper: 
  Igor Sokolov, Swaminathan Iyer, Venkatesh Subba-Rao, Ravi M. Gaikwad, and Craig D. Woodworth, "Atomic Force Microscopy Detects Surface Brush on Cells In-Vitro", Applied Physics Letters, 91, 023902 _2007.
  Best regards,
  Igor

  _____________________________________
  Igor Sokolov, Ph.D.
  Director of Nano-Bio Laboratory (NABLAB), Clarkson University,
  Professor,
  Department of Physics, 
  Department of Chemical and Biomolecular Science,
  Clarkson University,
  NY Center for Advanced Materials Processing,
  Potsdam, NY 13699-5820, USA

  office:        315-268-2375
  fax:            315-268-6610
  E-mail:       isokolov at clarkson.edu
  Web:         http://www.clarkson.edu/~isokolov/
  ______________________________________




------------------------------------------------------------------------------
  From: Olivier Arnould [mailto:arnould at lmgc.univ-montp2.fr] 
  Sent: Thursday, September 18, 2008 8:16 AM
  To: spm at spmlist.di.com
  Cc: schille at uni-muenster.de
  Subject: [Spm] baseline slope in force curves


  Hi,

  If I have well understood, I think that this baseline slope is due to the cantilever deflection that must be substract to the z-displacement to obtain the indentation depth. This is usually done by doing a force-distance curve on a stiff material that will give you the baseline slope due to the cantilever deflection only, i.e., only a negligible indentation occurs so z-displacement ~ cantilever deflection. You have then to substract this displacement to the one you obtain on your cell.

  Best regards,

  Olivier Arnould
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