Hello everyone, I recently found an article showing that phosphatidylserine (PS) exposure occurring during platelet activation can be visualized by incubating blood platelets with unlabeled Annexin V, then with anti-Annexin V antibody and finally with protein A colloidal gold complex (uid=8560427). To read the abstract go to [http://www3.ncbi.nlm.nih.gov/Entrez/medline.html], paste the 9-digit code (uid) into the search field and hit <Enter>. I was wondering if anyone tried this method to count apoptotic cells by flow, i.e., using unlabeled Annexin V plus anti-Annexin V mAb-FITC? I think it would be much cheaper than Annexin-FITC. Let's do some calculations: Annexin V, biotin conjugate (SIGMA A-7810) 0.01 MG 145.60 US $. Number of tests - 50-100 Annexin V (33 kD) from human placenta (90% pure) (SIGMA A-9460) 0.1 MG 141.30 US $. Number of tests - 200? 300? 1000? Anti-Annexin V monoclonal antibody, FITC conjugate 0.1 MG 100-300 US $. Number of tests - 200? 300? Unfortunately, I didn't find any commercial source of anti-Annexin V antibody, although such antibodies do exist (see, for example, uid=10094941, 10203671, 9067499, 9731106). I spent some time at [www.abcam.com] and found a lot of anti-Annexin I, II, III, IV and VI, but NO anti-Annexin V. Coincidence? As I can understand, the main reason for not using this method may be the fact that Annexin V was found on the surface of certain cells (see, for example, uid=8495746, 9731106). Unfortunately, I didn't find any detailed information on how many cellular types express Annexin V normally. I spent a couple of hours on PubMed and found only one reference (uid=8422704) saying: "Although annexin-like molecules have been reported on the external plasma membranes of certain cells, in general they are considered to be cytoplasmic proteins". Can anyone tell me whether lymphocytes, thymocytes and other "cytes" popular in apoptosis research express Annexin V on their surface? Do they expose it upon activation? If they don't, then "Annexin-anti-Annexin" (AAA) method is worth trying (IMHO). Those who want to see prices on commercial kits go to [http://www.sciquest.com], type "annexin" and hit <Enter>. Thank you for your attention. Yuri Kudinov, postdoc SVMC, USC LA, CA 90057 PS. Did anybody see a TV ad about "Brain Gum", a chewing gum with phosphatidylserine? I wonder if chewing it too much may influence performance of Annexin-based kits :-) Wanna take a bite? Go to [http://www.freelit.com/1067/lit67.htm]
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