Labelling proteins in plant protoplasts

[c515455 at mizzou1.missouri.edu]

Does anyone have any suggestions for labelling proteins in plant protoplasts?  
I've been trying to label a transiently expressed protein for the purpose of 
measuring its half-life.  Currently, I am pulsing the cells with 35-S 
methionine (100-200 micro Ci) for 1 hr in a volume of 0.5 ml.  I don't see 
much incorporation following Immunoprecipitation.  Are there conditions which 
would allow more effectient uptake of the label?

Michael Curtin
Univ. of Missouri- Columbia