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We have used quantum dots in widefield microscopy with a slow-scan CCD camera (single particle imaging: Hg lamp exc'n=488nm, em=660nm) and found them ~10x brighter than allophycocyanin.  This is not a fair comparison, as the lamp output is much greater at 488 than at 645nm, but we do not have a suitable power meter to normalise this.
An even longer excitation wavelength 530nm showed that they were still brighter than R-phycoerythrin under the same conditions. The single dot intensity is very variable though, in part I presume due to "blinking".  Ian

---------------Dr. I.E.G.Morrison       [log in to unmask]
               Dept.Biological Sciences, University of Essex
               Wivenhoe Park, Colchester, Essex CO4 3SQ
---------------Tel: 01206-872246           Fax: 01206-872592---------------



-----Original Message-----
From: Confocal Microscopy List [mailto:[log in to unmask]]On
Behalf Of Navara, Chris (PDC)
Sent: Friday, July 02, 2004 4:24 PM
To: [log in to unmask]
Subject: Quantum Dot conjugated secondary's

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I wanted to follow up on a previous thread on the archive.  Is anyone using
quantum dot conjugated secondary's with a non-uv laser on the confocal?  Are
they better, worse or the same as other fluorescent labels.  The excitation
spectra that I have seen shows a big fall off in intensity outside of the
optimal excitation (uv) and does this reduce their utility?

Chris

Christopher Navara Ph.D.
Assistant Professor
Obstetrics, Gynecology and Reprod. Sci. and
Pittsburgh Development Center
University of Pittsburgh
204 Craft Avenue
Pittsburgh, PA 15213
ph:412-641-2430
fax:412-641-2410