Tina, The way the omnicomp is designed, you can only subtract laser 1 (488) signals from laser 2, not the other way around. This is because the laser 1 signal (PE-Cy5 in your case) is delayed, by putting it through an electronic delay module, to match up with the laser 2 pulse that is generated when, say your PE-Cy5 control is excited by the HeNe. Once matched, you then subtract out that pulse. However, you cannot subtract an APC pulse from the PE-Cy5 detector, since that signal has already gone. For bright APC stains, you may see excitation by the argon, that you cannot compensate out. For duller APC stains, you will see very little 488 excitation of APC. Hope this helps. Kevin L. Holmes, Ph.D. Head, Flow Cytometry Section Research Technologies Branch Bldg. 7, Room 01 NIAID, NIH Phone: 301-496-9071 FAX: 301-402-4532 Email: kholmes@atlas.niaid.nih.gov -----Original Message----- From: Tina Rogers [mailto:Tina.Rogers@ccc.uab.edu] Sent: Wednesday, July 07, 1999 5:38 PM To: cyto-inbox Subject: FACS Vantage SE /Omnicomp Greetings! I am now trying to figure out how to use Omnicomp for an 8 parameter/3 laser analysis. I have been told by BD that Omnicomp can only be used to subtract primary (488) laser signals from secondary laser (HeNe) detectors. At issue is cychrome vs. APC and PharRed. Does anyone have a problem without the ability to subtract HeNe signals from 488 detectors? Thanks in advance for any help TIna S. Rogers, Ph.D. Manager, MAMDC FACS Core Facility Division of Rheumatology University of Alabama at Birmingham 1900 University Blvd. THT 405 Birmingham, AL 35294-0006 205-934-1362
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