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Difference between revisions of "Talk:Calculation of mitochondrial membrane potential from measurements with a TPP electrode"

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== Pmt, PC from literature? ==
'''Question:'''Ā  Ā  (1) With the TPP spreadsheets, Pmt and Pc values are the values that we use literature values for (that actually measured membrane content), and not actually measured protein (mg/mL) off the sample that is being run? and Vmt I think we also used published values for?
'''Answer:'''Ā  No, Pmt and Pc describe how much sample you put into your chamber andĀ  therefore can not be taken from literature. If you use twice the amountĀ  of sample these values will have to double. For isolated mitochondriaĀ  Pmt =Ā  Pc.
Please see also the Rottenberg paper cited.
Vmt can be taken from literature, especially as the TPP method is very insensitive against errors in Vmt.
Similarly we take Kin and Kout from literature. Vmt, Kin , and Kout areĀ  all SPECIFIC values,Ā  that is values per amount of mitochondrial /Ā  cellular protein.Ā  But to use these specific values you needĀ  theĀ  absolute values of mitochondrial cellular protein- ideally from anĀ  assay or at least some rough estimation from the respiration itself (ifĀ  you know the typical respiration of your sample per mg mitochondrialĀ  protein). In the sheet "external input" you see a very rough templateĀ  for this respiration approach, but a proper assay is of course the wayĀ  to go.
SomeĀ  background information :-) :Ā  Actually the choice ofĀ  mitochondrial protein as the marker the specific valuesĀ  Kin andĀ  KoutĀ  is a bit arbitrary /Ā  counter intuitive: The unspecific binding,Ā  described by Kin and Kout, actually will take place mainly in theĀ  mitochondrial lipids not in the proteins. But since mitochondrialĀ  protein is easy to measure and the ratio lipid to protein is hopefullyĀ  constant all the initial developers of the method used mitochondrialĀ  protein as a marker for the amount of mitochondria. For samples beyondĀ  isolated mitochondria (permeabilized cells,..) the assumption of aĀ  constant lipid to protein ration of course brakes down, maybe one reasonĀ  why there are no good values for Kout in "cellular samples". [[User:Fasching Mario|Fasching Mario]] 09:41, 17 April 2015 (CEST)
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Latest revision as of 08:41, 5 August 2015