[Histonet] Thermal polymerisation of LR gold resin for electron microscopy

[Peter Bannister]

Hello Histonetters,

Does anyone have a method for the thermal polymerisation of LR gold resin 
for electron microscopy?
I am trying to produce blocks of cultured cell pellets fixed in para/glut, 
post fixed in Osmium tetroxide, dehydrated in ethanol, infiltrated with the 
resin and cured.
I have tried polymerisation using light with mixed results - non osmium 
treated blocks polymerise okay and are just about suitable for sectioning. 
However, osmium treated blocks will only polymerise down as far as the cell 
pellet (I understand that the dark colour absorbs light and therefore 
interferes with the polymerisation). I have tried to keep exposure to oxygen 
during polymerisation to a minimum by using closed BEEM capsules or snap fit 
gelatin capsules. I would therefore like to try the more classical thermal 
polymerisation at +60°C.
The problem is that when I add the initiator (benzoyl peroxide) to the pure 
resin I end up with a solid mass of resin even before the peroxide is fully 
dissolved, at room temperature -so i can't use it on my samples.
If anyone can help me out with a protocol that will ensure the resin only 
polymerises quickly when at heated to +60°C it would be very much 
appreciated.
Many thanks for your time,
Peter Bannister.

Dr. Peter Bannister,
Thrombosis Research Institute,
Histopathology,
Emmanuel Kaye Building,
Manresa Road,
London SW3 6LR. UK.

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