>
> >Question:
> >Is dark red (~670-810nm) visible for human eye?
> >If yes, is there a filter set recommended?
>
> If it's very brightly stained and you have excellent red vision, you might
> see it very faintly.  Otherwise, you have to use a mechanical detector
> (e.g. your confocal or a video camera) to see it.  Cy5 and Cy7 are awesome
> dyes.  They are very bright and photostabile.
>

670nm ought to be visible (this is the wavelength of many laser pointers,
although now 637-650nm is more common). If you cannot see it at all then
either the staining is bad or you are not exciting it efficiently).
With our confocal I use 514nm to excite Cy5, because that is what I have.
Not great, but it can work. I also see by eye it with our TRITC cube
(green excitation, orange-red low pass filter).

Concerning photostability, in general the shorter cyanine dyes are more stable
than the longer ones, so for stability Cy3 > Cy5 > Cy7. There are some
papers by Alan  Waggoner which have extensive characterizations of this
family of dyes, including indo, thio, and oxa cyanines. This includes
excitation and emission peaks in various solvents, and also stability data.
I may be able to find them in my files if you want them. I think that they
are from the '70s.

--aryeh
Aryeh Weiss                          | email: [log in to unmask]
Department of Electronics            | URL:   http://optics.jct.ac.il/~aryeh
Jerusalem College of Technology      | phone: 972-2-6751146
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