Biology Reference
In-Depth Information
4
Notes
1. It is important that the coverslip surface is fl at. This can be
achieved by fi xing the coverslip with super glue or vacuum
grease on a metal frame.
2. Safety considerations: a 3,000 mW infrared laser beam is both
invisible and very dangerous; especially exposure to the eyes
should be avoided at all times. Although most optical trapping
systems require the use of infrared-blocking safety goggles, we
have equipped our system with safety detectors that automati-
cally switch off the infrared laser when the appropriate fi lters
are not in place, when the trapping laser is not properly con-
nected to the back port, or when the arm of the microscope is
tilted backwards.
3. If desired, the output intensity of the trapping laser can be
measured by placing a photon fl ux sensor, adjusted to sensitiv-
ity at 1,064 nm, in a fl at position in the focal plane of an objec-
tive lens. The output intensity should be linear in a large
output range of the laser (25-100 % output).
4. If the trap does not appear to trap anything in plant samples, a
slide with fl uorescent beads can be prepared to further test the
tweezers. Freshly prepared fl uorescent, polystyrene beads of
0.5-5
m should be easy to trap. Freshly prepare a dilution of
1 drop polystyrene beads (Polysciences, carboxylate fl uores-
cent microspheres) in 5 ml water. Prepare a slide with diluted
beads. A fraction of the beads will attach to the charged glass
surface and cannot be trapped.
μ
References
1. Neumann KC, Block SM (2004) Optical trap-
ping. Rev Sci Instrum 75:2787-2810
2. Grabski S, Xie XG, Holland JF et al (1994)
Lipids trigger changes in the elasticity of the
cytoskeleton in plant cells: a cell optical dis-
placement assay for live cell measurements.
J Cell Biol 126:713-726
3. Grabski S, Arnoys E, Busch B et al (1998)
Regulation of actin tension in plant cells by kinases
and phosphatases. Plant Physiol 116:279-290
4. Sparkes IA, Ketelaar T, de Ruijter NC et al
(2010) Grab a Golgi: laser trapping of Golgi
bodies reveals in vivo interactions with the
endoplasmic reticulum. Traffi c 10:567-571
5. van der Honing HS, de Ruijter NC, Emons
AM et al (2010) Actin and myosin regulate
cytoplasm stiffness in plant cells: a study using
optical tweezers. New Phytol 185:90-102
6. Vos JW, Dogterom M, Emons AMC (2004)
Microtubules become more dynamic but not
shorter during preprophase band formation: a
possible 'search-and-capture' mechanism for
microtubule
translocation.
Cell
Motil
Cytoskeleton 57:246-258
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