... or, is the grass greener on the other side of the picket fence? I have learned that some instrument sales representatives are making claims and misrepresentations about whether or not we are satisfied with our high end sorter (BD DiVa), of course without my permission. These claims are uninformed, and should be taken with less than a grain of salt. While I am sure that most readers of this list are savvy enough not to believe most of what sales reps say, there are also plenty that don't have the necessary expertise to judge the veracity of such statements. First of all, a disclosure: in the last 14 years, I have neither consulted for any instrument manufacturer, received any financial remuneration from any, or hold financial interest in any. In fact, as a government employee, we can't even receive discounts below standard GSA pricing on anything we buy from them, no matter how many sorters we buy. Finally, my laboratory is not under nondisclosure agreement with BD; however, federal law prevents us from disclosing private corporate information. That said, we have had a BD Digital Vantage (DiVa) for nearly one year. We have extensive experience with it now, and have tested it for sensitivity, sorting capabilities, stability, etc. As we published in a poster at CAC (the contents of which are therefore in the public domain), we find the sensitivity of the digital electronics on this DiVa to be at least as good as the analog electronics on the same instrument for individual channel measurements. However, it is with multi-color applications that the advantage of the digital electronics becomes apparent: the lack of log amplifiers combined with high resolution A/D conversion leads to more accurate compensated data (for explanations, see my recent paper in November Cytometry). In particular, compensating digital data across lasers does not require the careful pulse matching (and delay timing) that is so problematic on analog systems--i.e., we don't need to look at pulse traces anymore. (A real bonus, given that we have a fully-utilized 14-parameter system!) As predicted, we found the sorting performance to be better than analog, in terms of speed, given the essentially zero dead time. Purity in 1-way, 2-way, or 4-way sorting was identical to analog in 1- or 2-way sorting. We have successfully single-cell cloned, purity sorted, yield sorted, etc. We have long since abandoned the analog electronics in favor of the digital electronics. Nonetheless, I think the biggest advantage of digital electronics is still in the future. I firmly believe that once manufacturers develop some sophisticated signal processing of the digital waveforms (probably with relatively straightforward firmware upgrades to current digital systems), we will achieve considerably better sensitivity. And maybe even learn something about the subcellular distribution of the fluorescence signals! If you are considering a high end sorter, please disregard any claims made by sales reps of any company about our level of satisfaction or dissatisfaction with our instrument (and I've heard about both types of claims, obviously from reps of different companies). If you are in the market and care to discuss our experience with the DiVa, then feel free to call me and we can talk candidly. mr (PS, one more disclosure: the content of this email represent my views, and do not necessarily state or reflect those of the US Government.)
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