Delynn, A common problem occurs with using log amplification of forward scatter if forward scatter is the trigger parameter and your cells are quite small. That problem is that the noise level of the log amplifier can be very close to the level of the forward scatter signal of the cells. You may not be able set the trigger to eliminate the noise, hence, you can't resolve cells from noise. As you note, the apparent spread of the forward scatter distribution is narrower with log amplification. This does make it easier to resolve several populations that have a broad size range. (I've seen this with things like trypanosomes that have different developmental states--even on a log scale the subpopulations overlap; on a linear scale, you can't resolve a single population much less several.) A way to get around the problem of resolving populations is to use another parameter that is common to all the cells of interest as a trigger such that you can identify cells and then look their forward scatter distribution. For example, if you can label DNA, trigger on the DNA signal. Alternatively, you might be able to use side scatter and adjust the trigger to eliminate log amp noise, but still resolve the cells from background. I'll be happy to give you more examples. Dave ---------------- David M. Coder, Ph.D. email: dcoder1@qwest.net tel./messages: 206-499-3446 ----- Original Message ----- From: "Moss, Delynn M." <dmm3@CDC.GOV> To: cyto-inbox Sent: Friday, July 20, 2001 5:42 AM Subject: Microsporidia > > Hi, > > I am interested in a response from anyone who has flow experience on > bacteria or microsporidia that measure one micron in size. We have > successfully performed flow (FACScan) on microsporidia that measure two > microns, but this was close to the minimum size limit on the FSC profiles > when using LOG mode. The purified populations become more dispersed when > LINEAR mode is used on the scatter profiles of which we prefer not to use. > Is it better to use LINEAR or LOG mode for scatter on one micron organisms > using a FACscan? > > Thanks in advance. > > Delynn Moss > Centers for Disease Control > Division of Parasitic Diseases >
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