Jim- >I feel that i must take issue with two parts of your email about the new >CalTech sorter. > >First, this is a late example, by no means the first example, of extending >"practical cytometry" in the direction of the analysis of smaller stuff. >Our first publication was in 1982 and we have been improving, evolving our >technology since that time. While you and I may argue over ther word >practical, our philosophy has been first do it and then make it parctical. No question you did it first (although I seem to remember that Tomas Hirschfeld's single molecule analysis in the mid-1970's and the slow-flow analyzer with which the Block group and I did virus analysis then provided some inspiration), and I am aware from Rob Habbersett's presentations at the Asilomar workshops that your systems get progressively more practical. But I think Steve Quake's instrument is more practical, and it does sort. And there's no question that it was easier for them to develop what they did after what had gone before. >The second item refers to your comment about our need to use an expensive >detector. While it is true that we use quenched APDs to do our photon >counting, PMT-based photon counting is more complex. The APD is a self >contained unit that you supply 5 volts and it cools itself and sends out a >pulse for each photon detected that is directly recorded in a multi channel >scaler, or equivalent. No preamps, amps, ADCs, etc. In the long run, >which appraoch is less expensive is not a simple answer. I believe that we >will be very competitive with the CalTech approach when the while system is >taken into account. While, as third parties (Bart De Grooth's group) seem to have shown, photon counting will give you the most sensitivity; the Caltech people do pretty well with linear fluorescence analysis. And their electronics are relatively simple. Where all this goes with the continuing miniaturization and larger scale integration of optoelectronics, I don't know. I guess the marketplace will tell us. >Have a good holiday You too - this year, I'm wishing everybody a bug-free Y2K instead of the standard Happy New Year... -Howard
This archive was generated by hypermail 2b29 : Wed Apr 03 2002 - 11:54:21 EST