Intracellular staining with QuantumDots

Mario Roederer roederer at
Wed Mar 9 14:09:45 EST 2005

I want to correct one common misconception about QDots:  they are NOT 
very large particles.  In fact, QDots are smaller than PE.  Thus, any 
fixation/permeabilization procedure you use for PE-conjugates should 
in principle work for QDots.


At 4:42 PM -0800 3/7/05, Robert C. Leif wrote:
>    Since QDots are very large particles, you will have to permeabilize the
>cells. However, as a totally biased party, I suggest that you might try the
>europium Quantum Dye(R). The molecular weight of the monoisothiocyanate is
>674 daltons. The Quantum Dye molecular volume is approximately 0.45% that of
>a Qdot. The europium Quantum Dye is excited at 365 nm and emits at 619 nm.
>The emission width at half maximum, 5.2 nm, is approximately one fourth that
>of a Qdot. Because the lifetime of the europium Quantum Dye is approximately
>one millisecond, it is presently unsuited for flow cytometry and fast laser
>scanning systems.  More information including abstracts and papers can be
>found at
>	Bob Leif
>	rleif at
>	-----Original Message-----
>    From: Max Warncke [mailto:maxwarncke at]
>    Sent: Friday, March 04, 2005 1:47 PM
>    To: Cytometry Mailing List
>    Subject: Intracellular staining with QuantumDots
>	Do I have to use a very strong permeabilization protocol if I want to
>	intracellular antigens with QDots?
>	I tried to stain MHCII in and on murine (not fully matured) DC and
>	visiualized them on the confocal. Compared to FITC I get a brighter
>	extracellular fluorescence with QDots (525), but with the FITC
>antibody I
>	can see a bright signal inside the cell, which is totally absent with
>	For permeabilization I used Triton-X, counterstained with DAPI and
>	Phalloidin Alx594.
>	Many thanks
>	Max

Mario Roederer, Ph.D.
Chief, ImmunoTechnology Section and Flow Cytometry Core
Vaccine Research Center, NIAID, NIH
40 Convent Dr., Room 5509
Bethesda, MD 20892-3015
Phone: 301 594-8491
FAX: 301 480-2651

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