nuclear extract -- HEPES pH?! - (Aug/24/2009 )

I am trying to generate nuclear extracts from tissue. Most of the buffers for this protocol contain HEPES, and I have seen a variety of pHs listed: 7.6, 7.9, and 8.0, with 7.9 being by far the most common. Does anyone know how sensitive this protocol is to pH and how much variability it will tolerate?

I ask because I just made HEPES, aiming for pH 7.9 and resulting in pH 7.95, and I'm wondering if that's ok. If not, what acid should I use to adjst the pH down? I used KOH to increase it.

Also, if anyone has insight into why pH 7.9 is the most desired, I would like to know.

Thank you.

Different protocols use different pH because that is what is on their bench at the time.
I always use pH 7.4. I don't think it matters as long as you are within the 7.4 -8 range.