David Haviland writes: >I once had a user that wanted to look at mitochondria and >examine the changes in size during apoptosis with time. On the Calibur, >with log FSC we were just at the edge outright machine noise but he was >able to discern changes in the mitochondria. However, when I was at BD >for training on the Vantage, I was told that getting a slightly larger FSC >obscuration bar would give us the sensitivity that was needed to look at >very small particles. Were you able to make such a change in the XL? Or >did you need to? How far away were you from machine noise? I wonder if >there may be a different FSC obscuration bar available for the Calibur as >well? > It should be noted that a wider obscuration bar increases the lower limit of the "forward" scatter collection angle, so, while you may be able to detect smaller stuff, you aren't measuring the same parameter with obscuration bars of different widths. I have always said that if two flow cytometers measure the same forward scatter signal, it's pretty much by accident. While I lament the commercial unavailability of the Steen [lately Bio-Rad] instrument, which was really good for scatter measurements, I expect that an instrument with much better forward scatter sensitivity than existing commercial systems will reach the market in mid-2000. Stay tuned. -Howard
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