Does agarose go bad?

[jlf]

I've started work in a new lab for a month or so now but I've not been getting good resolution of bands >3kb in the DNA ladder. The lower bands are defined but those above 3kb are thick and smear. I was using TAE and tried 90V-120V. Higher voltage seemed to improve the resolution but still nothing as good as what I used to get in my last lab. Using new TAE didn't improve the resolution. I thought it could be the buffer, since I used SB in my last lab. However, I still don't get good resolution. I tried new DNA ladder, still no difference. I'm now wondering if the agarose is old (based on the batch no., it's 2007) and has degraded or changed in some ways (absorption of moisture?) detrimental to resolution. How long is the shelf life of agarose? Does old agarose give poorer resolution?

[Muhammad Sufian]

Supplying 80V is moderate for Agarose gel to seperate the bands. Many other reasons may be interfering the protovol.

1. Either your DNA is not in pirified form, i.e. DNA isolation was not so accurate.
2. Shelf life of chemicals is also a major factor. Try to use a new batch.
3. I think, there are specific conc of agarose for specific DNA sizes. Try to check that.

And I hope other peptides should also reply.

Regards

[papay13]

Recently, I used old agarose (2006) and everything was ok.

[papay13]

Recently, I used old agarose (2006) and everything was ok.

[jlf]

For some strange reasons, everything's fine now. Still the same bottle but finishing. Could be that I'm using less of the ladder since the dye is much more sensitive than Ethidium bromide but it seems like there are some other factors 'cos the improvement is quite significant.