PI positive/Annexin V negative events are most likely mechanically damaged cells that lost most of its plasma membrane, or just isolated (naked) nuclei. Multiple centrifugations, especially at high rpm, and when cells are not suspended in media with serum or with serum albumin, may lead to mechanical striping of plasma membrane and nuclear isolation. Zbigniew Darzynkiewicz, M.D., Ph.D. Brander Cancer Research Institute at NYMC 19 Bradhurst Avenue, Suite 2400 Hawthorne, N.Y. 10532 darzynk@nymc.edu http://www.darzynkiewicz.com/zbigniew/ -----Original Message----- From: chen li [mailto:chen_li3@yahoo.com] Sent: Wednesday, January 25, 2006 7:19 PM To: cyto-inbox Subject: Annexin V and PI staining for apoptosis Dear Flowers, When Annexin V and PI are used for staining cells and subjected to FLOW there are 4 populations (sometimes 3), which are 1) Annexin V and PI both negative (alive cells), 2) Annexin V positive only (cells at early stage of apoptosis), 3)Annexin V and PI both positive (late apoptotic cells) and 4) PI positive only (???). I couldn't find the explanation for PI positive only. My questions are 1) what happens to PI positive only population? 2) Is this population included in the percentage of apoptosis cells? Thank you very much, Li __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.comReceived on Fri Jan 27 11:58:00 2006
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