[3dem] UA stock powder - age a factor?

[Cornelia Cazey]

Dear 3DEM list,

I have up until now not had any major issues with making 2% UA negative stain. I am used to making stain and I used to be fairly consistent in getting good results. I am also making UFo, 0.75% which has no issues at all. 

In the past few months, however, the results of making UA stain have varied greatly and I am unable to figure out why. In order to find out, what might be the issue, I have tried a few variations in protocol (cooler water- longer mixing, different filter sizes).. 

I have just found out that the UA stock powder we use is roughly 14 years old... could this contribute to inconsistent results?

Thanks for any help and best wishes,

Cornelia Cazey
TEM Technician
OPIC - Oxford Particle Imaging Centre
The Division of Structural Biology
The Wellcome Trust Centre for Human Genetics
University of Oxford
Roosevelt Drive
Oxford
OX3 7BN
Office:01865287843
Mob:07981959647