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Dear List,

 I posted an example of N=1 experiment and N=1 information!!.. Sorry for that.
After Prof. George pointed out why Tetraspeck beads may not be QDs
(see below), I acquired spectrum again by lowering the excitation
wavelength a bit (740nm as compared to 760nm in earlier case).If they
are made up of QDs they will show roughly the same spectrum as in
earlier case - (of course, assuming newer tetraspeck beads may be made
up of QDs). This time instead of peaks with increasing intensity (from
blue to yellow to red) , I see plateu with small peaks in blue -
yellow and strong peak in red.

So Sarah,

 The emission of tetraspeck beads depends on excitation. You have got
to measure individually for each excitation. I think best people are
from Invitrogen if you want to see if the emission peaks of tetraspeck
will match the peaks of your fluorophores.

Thanks Prof. George!!

Regards
Shalin

On 7/27/07, George McNamara <[log in to unmask]> wrote:

    Hi Shalin,

    TetraSpeck beads predate fluorescent quantum dots by several years.

    I would not be suprised if some or all are BODIPY dyes. A paper on
the Transfluospheres 488/720 (
http://probes.invitrogen.com/media/pis/mp07186.pdf) listed the 6 dyes
used. Check the research literature for the paper (had to do with
spectral imaging).

    ***********


    The emission spectrum in 2-p case will be the same as 1-p case. I
am sending the TIFF to you. Interestingly, when I used the beads with
2-p excitation I found that they melted when I tried to acquire
experimental PSF in blue region. They seem to be poor emitters in blue
region. Additionally, they emit the signal in blue,green, red region
(with increasing intensity in that order) - it is a tell-tale sign
that they are made up of QDs.

    Regards,
    Shalin