Michael Vork Michael.Vork at
Tue May 20 07:53:28 EST 1997

Hi there,

We have a serious problem in the lab. Two years ago we produced protein X in 
E. Coli, purified it and assessed its concentration by measuring the total 
nitrogen content instead of Lowry, Bradford or BCA. In short the method 
involves total protein destruction with perchloric acid at 180øC. Every 
nitrogen atom will be in the form of NH4+ after destruction. After 
destruction total NH4+ assessment is performed with the phenol/hypochorite 
assay (Berthelot reaction). We stored the protein at -20øC for two years in 
a concentration of approximately 0.5 g/l. Recently, we re-assessed its 
concentration with the above described assay and found only 20% of the 
original concentration. I can imagine that the protein decays in time, but 
then the nitrogen still has to be present in the vial in which we stored it.

Did we find a form of activity by which nitrogen is converted into e.g. 
gold, or is there a more plausible explanation ??

More information about the Proteins mailing list