[MTRAD1]

In an experiment, a homogenized myoglobin sample was centrifuged and subjected to salting out.

Sample A - just centrifugation, highest overall protein concentration
Sample B - centrifugation + 60% salting out (lower concentration)
Sample C - centrifugation + 100% salting out (even lower concentration)
Sample D - centrifugation + 100% salting out + dialysis (concentration suddenly shoots up to just under the highest here)

Why did the dialysis cause protein concentration to skyrocket? Doesn't it just remove the salt reagent and some other small molecules? I don't believe it is due to experimental error because several of my peers had the exact same pattern.

Thanks for your time.

EDIT: perhaps water molecules move through the pores as well, out of the initial solution thus concentrating the proteins?

[Arkcon]

Well, to start with, you'll have to identify how you quantitate the protein.  Once you tell us that, you can try to infer the effect dialysis can have on that assay.

EDIT: perhaps water molecules move through the pores as well, out of the initial solution thus concentrating the proteins?

That's not likely the reason, can you tell us why?

[Babcock_Hall]

I would have expected an increase in protein concentration; it makes perfect sense.  Can you define salting out for us?  The answer should jump out at you.

[MOTOBALL]

Why did the dialysis cause protein concentration to skyrocket? Doesn't it just remove the salt reagent and some other small molecules?

Yes, dialysis does just remove salt and other small inorganic/organic molecules; the protein is too large to pass through the pores of the membrane.  The amount of protein in the closed dialysis bag does not change; since the system tries to reach equal concentration of protein on both sides of the membrane (but the protein cannot escape) you might expect, if anything, the liquid volume inside the dialysis bag to increase slightly.  Protein concn. might therefore be expected to be lower, not higher. I have assumed that the protein is in a purely aqueous medium.

This makes sense to me, but have I missed something ?

[Babcock_Hall]

I suspect that the protein was salted out in the last fraction, then dialysis was used to remove the ammonium sulfate.  In other words, the protein was concentrated in the step that precipitated it, not the dialysis