Alan Saluk writes- >I had a researcher come into the lab with a Eu-chelate as the >fluorochrome. He came without literature and said it had an excitation >peak around 345nm (I used the relatively weak 351nm line from an >Enterprise) and a very narrow emission at 615nm (I used a 610/20 to >collect). I was unable to see any kind of signal although his controls >using a FITC-conjugate worked fine. I was a little suspicious when he >said it was "quantumly inefficient" and he had never seen it tried on a >flow cytometer (I'm betting it might need a little more time in the >beam). Do any of the gurus out there have any wisdom to share. Eu-chelates have fluorescence lifetimes of about 1 millisecond. They have been measured by flow cytometry using relatively slow flow and a measurement station well downstream from the excitation beam. The references are: Condrau MA, Schwendener RA, Niederer P, Anliker M: Time-resolved flow cytometry for the measurement of lanthanide chelate fluorescence: I. Concept and theoretical evaluation. Cytometry 16:187-94, 1994 Condrau MA, Schwendener RA, Zimmermann M, Muser MH, Graf U, Niederer P, Anliker M: Time-resolved flow cytometry for the measurement of lanthanide chelate fluorescence: II. Instrument design and experimental results. Cytometry 16:195-205, 1994 A commercial instrument would have to be modified substantially to do this trick... -Howard
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