Many thanks to all of you who responded on my query about daily alignment particles suited for acquiring via a DAPI fluor channel. The answers break out as follows: Molecular Probes AlignFlow beads, cat # A-7305 (5 responses). I pulled out the catalog, and sure enough there's a 6 micron bead (A-7305) and a 2.5 micron bead (A-7304) both offered "for UV excitation". No info on CV, but they're marketed specifically for cytometer setup. There are also "DAPI-Like flow cytometry reference beads" offered in the same sizes (F-7310 and F-7311), but with slightly weaker and more variable signal meant to simulate DAPI stained cells. Anyone lacking contact info, try www.probes.com. Next most frequent (3 responses) were Polysciences BB beads. Their Cat #18340 was said to give good blue fluor (CV's approx 1.0) with UV excitation. Other Polysciences suggestions included a small (0.5um) bead with Ex(max) 365nm and Em(max) 468nm. Used as calibration for bacteria, but said to have a good strong signal. CV's well under 2.0 on a Facstar Plus and stable for at least a year for one user. Cat #23520. Bigger beads, apparently with same fluor, are Cat #19102 and Cat #19103. Contacts are: (email) polysci@tigger.jvnc.net, (www) http://www.polysciences.com. Three respondents prefer to stick with a biological standard, i.e. chick or trout erythrocytes or calf thymocyte nuclei, stained appropriately. One product is BDIS DNA QC kit (try via www.bdis.com, though I couldn't get through today, or contact tom_frey@bdis.com). Partec (via Cytomation, their U.S. distributor, www.cytomation.com or matto@cytomation.com) offers fixed stained (good for UV) trout cells (CV <= 1% and stable "long term" at room temp) and unfixed unstained thymocyte nuclei. Another user just fixes CRBC in glutaraldehyde and adds Hoechst dye for a homebrew reference. Two other suggestions were Coulter Immunobright beads, and multispectral beads from Spherotech (contact via email at jwsphero@aol.com). Thanks again for the help! Robert L. Becker, Jr. Col, USAF, MC Department of Cellular Pathology Armed Forces Institute of Pathology Washington, DC 20306-6000 202-782-1573
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