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Electric field and ionic strength effects!!!


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#1 Prep!

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Posted 03 March 2010 - 01:15 AM

Hi folks... I wanted to know what exactly is the relation between ionic strength of a solution and high voltage. I ask this specifically cause at higher voltages, I get current fluctuations in the vertical gel IEF tat i run, I use 500 V to focus the protein. At lower voltages say till 250 V i dont get any current fluctuations but as i go upto 500V, i see the current is neither constant nor is it decreasing as it should, but fluctuates between a wide range. Any ideas or suggestions?

P.S> I use 500 mM NaOH and 500 mM Ortho Phosphoric acid as catholyte and anolyte. I will be trying a 25 mM solutions to check if buffer ionic strength has a role to play in the current fluctuations at higher voltages.

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#2 mdfenko

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Posted 03 March 2010 - 08:43 AM

voltage reduces as ionic strength increases if you hold current constant.

if you are seeing current fluctuation at high voltage then you are probably experiencing arcing. you may have a dry spot or a crack in your gel.

reducing the ionic strength of your electrolytes may make matters worse. you should not change the tried and true procedure (especially if you are using prepared gels or a kit).

inspect your gel prior to and during the run to see if there is a flaw where arcing can occur or is occurring.
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#3 Prep!

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Posted 04 March 2010 - 02:01 AM

thanx md.. i m not using any precast gels or kits.. everything is manual here!!! and i l get back to you about the results of the blot wen done with lower ionic strength b uffers... the fluctuation in current was not seen though!!!

i tried doing a step voltage increase with time so as to control the current... seems to have worked.. thanx again!!

Edited by Pradeep Iyer, 04 March 2010 - 02:02 AM.

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