I produce nuclei for chromatin preps.  When I started my advisor told
that nuclei could be sticky, and that a good way to prevent or
decrease aggregation was to bring to -20C in 50% glycerol.  This
technique is used quite succesfully for HL60 cells.
  I was working in fresh human blood monocytes and figured they should
work similarily.  However, I have found to interest things.  1)
Monocytes lyse extremely easily (incubating in hypotonic %0.5 tween
20) compared to HL60 cells. 2)  Monocyte nuclei stick like mad crazy. 
After douncing and spinning down I'm left with a small white pellet
which is about as easy to resuspend as rubber cement.  I've tried
EDTA/EGTA and other obvious solutions, but none seem to help.  Any
suggestions?

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Clarification of Question by nickct-ga on 16 May 2004 11:34 PDT

- You might try detergents such as SDS or dodecyl maltoside. -

Thanks for the suggestion.  Indeed detergents due work well for
disrupting membrane mebrane aggregation.  Unfortunately though I'm
preparing chromatin for Immunopercipition.  Most detergents and
certainly SDS interfere with the protein protein binding in IPs. 
Hence the use of detergents is undesirable.  However, I may consider
washing my nuclei with SDS.  Any idea on concentrations?  0.1% or so?

You might try detergents such as SDS or dodecyl maltoside. They should
help with membranes. Where'd I get this info? No, I'm not a
biochemist, but someone close to me is. This is my friend's
suggestion.

Hope it helps,
dtc

I have a little more info for you from my biochemist friend: "You can
tell him that we typically used 0.1% dodecyl maltoside for a poorly
soluble protein. But other than that, it is outside my area of
expertise. The problem with detergents is that it is very difficult to
get rid of them. They form large molecular weight micelles that are
retained by dialysis and ultrafiltration membranes."

G'luck,
dtc

A cursory literature search suggets that Nonidet P-40 (somewhere
between 0.5-5.0% v/v) or 1% v/v of IgePal CA-360 is commonly used in
nuclear preps.  I have no idea whether or not this is specifically
used because it discourages nuclear aggregation, or if it's just
supposed to be for removing as much junk as possible.  Also, it might
be too much detergent for your IP- though it might be worth trying to
resuspend your nuclei in the detergent buffer (a la one of the
published nuclei isolation buffer recipes), spin down again, and then
see if the nuclei are now less sticky and can be resuspended in
something without detergent.  If they can take the extra step.

Just a thought from a bacteria guy.