cell surface biotinylation

[uvsbgsm at Msu.oscs.montana.edu]

I have been trying to cell surface biotinylate membrane proteins with very
little efficiency.  Radiolabeled monoclonals bound to surface proteins give a
higher signal, so I really think I have an efficiency problem.  The protein is
a highly glycosylated type I protein expressed in CHO cells.  Any
methods/advice would be welcome.  

Thanks!