Thanks for you comments, Mario. When we prepare "tetramers", we most often use SA-PE or SA-APC from Molecular Probes, and they tell me that their material is size-selected to be 1:1. I haven't verified this myself, although we have been planning to take a better look at that issue. Incidentally, we have prepared "tetramers" in the past using SA-FITC, and SA-TR, and Letvin's group has published using SA-Alexa488 "tetramers". As you know, preparations shouldn't have the same higher order aggregates that are seen in the phycobili conjugates, because the chemistry is different. Another complication, of course, is that almost no one really knows the "specific activity" of any of the SA conjugates, so some of our reagents may actually be "trimers", or complicated mixtures. For most of what we do, I don't care too much -- I'm mostly concerned that the reagents are specific! John on 2/28/2000 2:04 PM, Mario Roederer at Roederer@DrMR.com wrote: > (Incidentally, this is why the name "tetramer" for the MHC-HLA > complexes first made at Stanford is a misnomer. These "tetramers" > are probably complexes that include as many as a dozen > HLA-molecules--"MHC Multimer" is a far more accurate term. > Unfortunately, the term "tetramer" has become so common as to be > irreplaceable... however, it is important to realize that these are > large-order complexes, because binding studies that purport to > measure affinity become far less meaningful (if any meaning is left) > due to the high order valency of these complexes). *************************************************************************** John D. Altman, Ph.D. Emory University Vaccine Center at Yerkes 954 Gatewood Road Atlanta, GA 30329 Office: (404) 727-5981 FAX: (404) 727-9005 FAX2: (404) 727-8199 Lab: (404) 727-8914 email: altman@microbio.emory.edu *************************************************************************** Tetramer Core Facility: http://www.niaid.nih.gov/reposit/tetramer/index.html ***************************************************************************
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