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Dear List

Does anyone have any information on the triplet state of Alexa488 or on how free
Alexa488 behaves in confocal FCS (1 species or 2 species)?

We are doing confocal fluorescence correlation spectroscopy (FCS) and we are
interested in answers to the following:
1.  What proportion of the dye might be expected to be in the triplet state
under "normal" conditions, eg in water/buffer/culture media of pH 7 to 8, under
non-saturating 488nm excitation.
2.  What is the expected triplet time (TauT) for the free (unconjugated)
Alexa488 dye?  (we are using the Alexa488 monosuccinimidyl ester)

I am also interested to know if anyone can comment on whether we can expect
Alexa488 to behave as "two species" for FCS.  It has been reported that
Alexa488 exists as two species for FLIM, ie. that it has two lifetimes (J Phys
Chem 2006 110(13):6973, but I understand that this different to the "species"
in FCS where separate species have a different diffusion time, mostly
representing a difference in mass.  (Please advise me if my understanding is
incorrect).

Thanks in advance
Jennifer Clarke

-- 
Jennifer Clarke BSc (Hons) PhD
Confocal Microscopy Facility Manager
Flinders Microscopy and Image Analysis Facility
(c/- Department of Anatomy and Histology, School of Medicine)
Flinders University
GPO Box 2100, Adelaide 5001
Phone: 6108 8204 6454
Email: [log in to unmask]