I don't think storage matters. I doubt Hampton stores their PEG stock solutions at -80 before they ship out to customers.

I've solved tons of structures leaving my PEGS and PEG screens at RT in the light.

Nick

On Mon, Jul 14, 2014 at 12:32 PM, Chris Fage <[log in to unmask]> wrote:

Hi Jerome,

-I have heard that PEG solutions can become unstable in light. We usually store our block in the fridge, where photons are scant anyway. For any stocks that I prepare, I wrap the tube/bottle in aluminum foil. I'm not sure about freezing them.

-Some labs (not ours) evidently prepare buffered stocks of PEG solutions, as their pHs tend to shift with time. This is something I've been meaning to try. Of course, you may need to worry about buffer components that are incompatible with crystal hits.

Hope this helps,
Chris

On Mon, Jul 14, 2014 at 9:33 AM, Jerome Nwachukwu <[log in to unmask]> wrote:

Dear all,
I have 3 short questions about PEG solutions:
Does anyone know the best way to store crystallization screening blocks that contain PEG 3350?
Is it a good idea to freeze the PEG solutions at -80°C and thaw them before use?
Would the freeze-thaw process considerably alter the PEG chain lengths?

Thank you,
-Jerome

Jerome Nwachukwu

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