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AG Dietzel-Meyer
Elektrobiochemistry of neural cells
Schülerpraktika Patch-Clamp III - Die Uni entdecken V - Die Uni entdecken
 
    Biochemie II | Faculty | e-learning  |  

SICM

 

Scanning ion- conductance microscopy (SICM)

The SICM was developed by Hansma et al. (1) and used to monitor pores of 800 nm diameter in nucleopor membrane filters in aqueous solution. The method uses a feedback-system which keeps the conductance between an electrolyte-filled glass micoelectrode and a reference electrode in the bath solution constant. Keeping the conductance constant the topography of an insulator in an electrolyte solution can be traced. Korchev et al. (2) were the first to succeed in visualizing surfaces of living epithelial and muscle cells using this method. It can also be combined with patch-clamp techniques to localize K+channels in membranes (3) and to measure cellular volume changes (4). A remarkable advantage of this method is, that cellular surfaces can be traced in a "safe distance" from the cellular glycocalix, thus promissing to prevent destructions of the membrane during repeated scannings. We have developed a novel type of an SICM which deviates from the original method of Hansma et al. (1) in several respects: The stability of the system against DC shifts was improved by controlling the approximation of the electrode to the membrane surface by using short current pulses to the monitor resistance changes which indicate a close approximation of the electrode tip to the insulating membrane. Furthermore, we introduced a "backstep"-mode, which retracts the electrode before lateral movements, thus preventing the electrode tip from running into possibly overhanging parts of membrane, especially at the interfaces between culture dishes and cells (5). The pulse-mode SICM can now be applied to study movements and volume changes of complete nerve and glial cells in the range of 20 minutes to hours with lateral step sizes of 0.5 µm and vertical step sizes of 0.1 nm (6).

    Principle
    SICM
    Laboratory courses

sicm_principle


Fig. 1: Principle of operation of the pulse-mode scanning ion conductance microscope (SICM): An electrode tip is continuously approached to a nonconducting surface in an electrolyte-filled bath solution until the electrical resistance change reaches a pre-set value.

Setting up a SICM

ZelleA_1001


Fig. 2: Example of a scanned cell from pig white matter. (lateral resolution: 0,5 µm, vertical resolution: 0,1 µm).
To learn the SICM technique we offer laboratory courses Bachelorprojects and Masterthesis projects.



    Literatur

 
 
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Letzte Änderung: 24.07.2006 | Ansprechpartner/in: Inhalt & Technik
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