Hi Heba,

This is very simple and you do not need to do any special caution with brain tissues.

i. Take 550 μl of your sample lysate, mix with 100 μl of ice cold PCA 4M in 1.5 ml microcentrifuge tubes, vortex briefly and incubate on ice for 5 minutes.

ii. Centrifuge at 13,000g for 2 min at 4°C and transfer supernatant to a fresh tube. Measure volume of supernatant!

iii. Precipitate excess PCA by adding an equal volume of ice- cold 2M KOH (to supernatant obtained in Step 1e-ii) and vortexing briefly. This step called neutralization is very important to keep samples at pH = 6.8 – 7.2 to occur TOTAL PCA precipitation (any left over PCA will interfere with the assay).

iv. Centrifuge at 13,000g 15 min at 4°C and collect supernatant.

There is a very similar protocol at

http://www.google.com.br/url?sa=t&rct=j&q=&esrc=s&source=web&cd=2&cad=rja&uact=8&ved=0CDQQFjAB&url=http%3A%2F%2Fdocs.abcam.com%2Fpdf%2Fcancer%2Fdeproteinization_protocol.pdf&ei=5PA_U6XeIZSqsATntoD4DA&usg=AFQjCNFtah8xo_JrlYnNC8OF0p0QK3MZiQ&sig2=WY0jAdb_g-MoXcCj45EZXw&bvm=bv.64125504,d.cWc

Thanks alot..you have been a great help...:)