PE-Cy5.5 - PE compensation problem

I am having a problem on my MoFlo that I can not figure out. When I run 
PE-Cy5.5 I am getting a huge amount of signal in the PE channel (or maybe 
too little in the PE-CY5.5 channel). So much that I can not compensate 
properly - needs about 60-70% and then still doesn't look right. When I run 
the same sample on the FACSCalibur it looks great and only needs 12% 
compensation. Thus the problem is not the reagent. I have considered the 
filters as a problem but 2 different PE filters gave the same result. I 
have used a 580/30 and a 575/25. These filters in front of the PE detector 
in all other fluorochrome combos that I have tried give no problem.  Other 
parameters are 200mW 488nm, 685LP dichroic and a 700/50 filter in front of 
the PE-Cy5.5 detector.	I have not tried other filter combos in front of 
the PE-Cy5.5 detector.	Anybody have any ideas? Thanks

Larry


Larry W. Arnold, Ph.D.
Research Professor  and Director, Flow Cytometry Facility
Department of Microbiology and Immunology
Lineberger Comprehensive Cancer Center
CB# 7290
University of North Carolina at Chapel Hill
Chapel Hill, NC 27599
Phone: 919-966-1530
FAX: 919-962-8103