We ran amino acid analysis of some whey samples using our Beckman 6300,
Sodium method, found 20% cysteine (ususal for this lot), but there was a
lot of noise, so we decided to rerun the samples. A machine breakdown
later, we rehydrolyze, on the assurance that our Ninhydrin is on the truck.
The truck was slower than usual, so the samples and standards sat in the
refrigerator dissolved in Na-S for five days. The latest analysis has no
noise, nice baselines, but _no_ cysteine, and threonine levels had doubled
from earlier. All the other results were within the range I might expect,
considering that we were not happy with the earlier analysis.
My question: Does cysteine break down in the fridge in Na-S? Does it
break down into something that elutes with threonine?
-laurey
Weather Inconsequential: It was gorgeous yesterday, but the clouds have
moved in today and the temperature is dropping. It seems like March again
instead of May.
Laurey Steinke
Protein Structure Core Facility
University of Nebraska Medical Center
Omaha Nebraska, 68198-4525
Phone (402) 559-6647
FAX (402) 559-6650
lsteinke@molbio.unmc.edu