On antibody storage and ChIP - (Sep/17/2005 )
Have you ever experienced decline of antibody performance after long-term storage?
How do you store your antibodies?
I have been using this particular antibody for ChIP experiment, and it used to be working great about a year ago, just after it was purchased. I was getting very good enrichement of the target DNA sequences in ChIP and I was very happy about the results.
Now I'm repeating the same ChIP experiment using the same antibody and the same sample. However, enrichement this time is not nearly as good as a year ago, although it is still barely significant.
I can not rule out any other factors at this point, but I have always been concerned about the way I store the antibody.
When we purchased it, the antibody (in 100ul) was shipped frozen, so I thawed it, made 10ul aliquots, and stored them at -20c (-20c storage is recommended by the supplier).
One particular observation that bothers me is that, when you keep this small amount of liquid in a freezer, it sometimes "frosts" on the inside-wall of the tube, instead of staying frozen at the bottom of the tube. Call me paranoid, but this doesn't seem to be a good thing to me in terms of keeping the integrity of the antibody.
Maybe I'm getting too particular. My point really is the two questions I stated at the beginning.
our antibodies are normally stored at 4C with no problem at all, for long term storage (or if we have a big batch of a ChIP antibody) we store aliquots at -70C.
Our antibodies are stable when kept at 4C for upto one year and posed no problems for our immunflourescence and ChIP work.
Grateful to your reply, I am.
I have been doing ChIP using two unrelated antibodies, A and B.
Both are kept at -20c, but A gets frozen at this temerature and B is in some sort of anti-freeze formula and stays as liquid. Antibody B worked just fine after many months of storage, so it really looks like freezing of antibody A has been the source of my problem.
Notes to self
1. Don't make too small aliquots.
2. 4c storage is probably ok.
3. -70c is probably better than -20c.
Man, these antibodies are expensive...
but it;s these lessons that we will definitely learn from!!!