Carmichael’s Concise Review
Using Quantum Dots to Demonstrate
Coming Events
Kiss-and-Run
2009
Stephen W. Carmichael
Advanced Electron Microscopy
Mayo Clinic, Rochester, MN 55905
in NanoMedicine
October 2–3, 2009, Los Angeles, CA
carmichael.stephen@
mayo.edu
www.cnsi.ucla.edu/electron-microscopy
Society for Histochemistry
October 7–10, 2009, Fulpmes, Austria
www.histochemistry.eu
Secretion is a basic biologic phenomenon. Although most mammalian cells are
capable of secreting, neurons are of particular importance because the exchange of
Neuroscience 2009
information throughout the nervous system usually involves secretion of transmitters
October 17–21, 2009, Chicago, IL
from synaptic vesicles. Two mechanisms have been proposed, but the prevalence of
www.sfn.org
one over the other has not been clear. One is called full-collapse fusion (FCF) whereby
American Society of Human Genetics
the membrane of the synaptic vesicle fuses with the plasma membrane by exocytosis,
October 20-24, 2009, Honolulu, HI
all of the contents of the vesicle are unloaded into the synaptic cleft , and a new vesicle
www.ashg.org
is generated de novo. Th e other mechanism is oft en referred to as kiss-and-run (K&R)
CIASEM 2009 and is characterized by the transient fusion and retrieval of the vesicle membrane with
October 25–28, 2009, Rosario, Argentina
a subtotal release of vesicular content. Recently, Qi Zhang, Yulong Li and Richard
www.cab.cnea.gov.ar/ciasem2009
Tsien have developed an ingenious technique to clearly distinguish between these two
AVS 56th Int. Symposium & Exhibition mechanisms [2].
November. 8–13, 2009, San Jose, CA
Th e key is the use of single quantum dots (Qdots). Zhang et al. found that Qdots
www2.avs.org/symposium
with a peak emission at 605 nm and a diameter of about 15 nm were most suitable
2009 MRS Fall Meeting
for their purposes. A single Qdot is small enough to fi t inside the lumen of a synaptic
November 30–December 4, Boston, MA
vesicle (about 24 nm in diameter) yet too large to move through a putative K&R fusion
www.mrs.org
pore (1 to 5 nm). Th ey mildly stimulated neurons in the presence of these Qdots and
American Society of Cell Biology
determined that the dots were taken up in almost half of the synapses. Further tests
December 5–9, 2009, San Diego, CA determined that many of the nerve terminals contained a single Qdot. Probably the
www.ascb.org
big step forward in this study was to demonstrate that they could select terminals with
2010
only one Qdot and thereby track only one vesicle. Th e pH-dependence of the Qdot
Multiphoton Microscopy at SPIE
photoluminescence indicated that the dots were in an environment of about pH 5.5,
Photonics West
which is thought to be the acidity of synaptic vesicles.
January 23-28, 2010, San Francisco, CA Th e pH dependence of Qdot photoluminescence predicted that K&R would
www.spie.org
allow protons to escape the vesicle (and pH to rise) but retain the Qdot, which would
PITTCON 2010
get brighter, whereas FCF would show the same brightening but then lose signal
February 28–March 5, 2010, Orlando, FL as the Qdot departs (see Figure 1). By examining Qdot-loaded synapses during
www.pittcon.org
stimulation and manipulation of the vesicular pH with a proton blocker, Zhang et al.
Microscopy & Microanalysis 2010
found they could reliably distinguish between K&R and FCF mechanisms. Additional
August 1–5, 2010, Portland, OR
experiments where the external pH was manipulated and studies tracking the motion
www.microscopy.org
of single Qdots confi rmed this.
2011
Interestingly, Zhang et al. found that K&R was predominant during early phases
Microscopy & Microanalysis 2011
of stimulation but became less prevalent as stimulation continued. Th rough a series of
August 7–11, 2011, Nashville, TN
K&R
2012
Microscopy & Microanalysis 2012
July 29–August 2, Phoenix, AZ
2013
Microscopy & Microanalysis 2013
August 4-8, Indianapolis, IN
FCF
Please check the “Calendar of
Meetings and Courses in the MSA
journal Microscopy and Microanalysis
for more details and a much longer list
of meetings and courses.
Figure 1: Cartoon of the basic mechanisms of K&R and FCF release during secretion. The red circle
represents a Qdot.
6
doi: 10.1017/S1551929509000297
www.microscopy-today.com • 2009 July
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