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Qg buffer composition

wo hubahopp at gmx.de
Thu Feb 21 11:33:41 EST 2002

Hi Dima,

K+ and Cl- (as maybe phosphate, too) are easiest to determine by subjecting
a diluted aliquot to automated urine or serum analysis in the clinical
chemistry lab of a hospital. Hoping that Gu doesn't interfere though. Usually,
the machine will give you NH4+ and Na+ in the same run. But acetate? no idea.if
you'll get it there.

K+ also should be able to be determined gravimetrically using SDS :) if
there are lots present (add excess NaSDS, cool, filter through pre-weighted
or collect by centrifugation in pre weighted tube, wash precipitate with
NaSDS, allow to dry, weigh again)

Assuming all volatiles present are water and ipropOH, one might distill the
stuff and measure density of the condensate comparing against a standard
curve. Unless there is ammonia present (NH4Cl and NH4OAc are volatile). If GuX
is the same - no idea, but easily to be tested.

More thoughts about acetate? might be concluded from potassium and sodium...
does it form any insoluble precipitates making it accessible to gravimetry? I am
not aware of any.
There should be lots present and the buffer system is likely to be tris/acetate.
there might be sufficient data from the other analyses to calculate enough an
then just mix a lot of your own and thest the suitability.

Acetate might be determined indirectly by reducing to acetaldehyde / ethanol
with alcohol dehydrogenase and measuring NADH consumption, if the chemical
environment would permit it.

Maybe by some sort of quantitative FT-IR for the carboxylate (just guessing).
Thinking of more specialized physicochemical equipment like cyclovoltametry and
amperometry... but who has that kind of device in a biochem lab? for
refractometry, the mix is probably too complex...

tris - the amino group should react with sangers reagent (dansyl chloride),
determine fluorescence or absorbance against standard curve. no idea if it
interferes with guanidinium, though. negative control is easy, however :)

Any ideas of how to get rid of GuX? Can one sublimate it away? Or remove organic

hacking regards,

>- Ac-
>- K+
>- 2-propanol
>- GuCl (as it is bound to be present at high concentrations, just
>  Cl- or even conductivity will probably be good enough)
> - Tris (amine reaction?)


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