Subject: How to best freeze biological tissues without affect Caspase-3 activity?

Hello,
I want to study the caspase-3 level on renal tissues.  For logistic reasons, I 
need to freeze the tissues on several experiments and run the Caspase-3 assays 
on the tissues at the same time.  I was wondering if freezing affected the 
Caspase-3 activity as determined from flurimetric method?  If so, which method 
(shock freeze versus fresh freeze) has less effect?  Which temperature would 
be better?  How long can I store the tissues once frozen?

Re: How to best freeze biological tissues without affect Caspase-3 activity?