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CONSTRUCTION OF A RAMAN TWEEZER SYSTEM
FOR INVESTIGATION OF BIOLOGICAL MOLECULES
Günay Başar
İstanbul Teknik Ü[email protected]
International Symposium on Molecular Spectroscopy 62nd Meeting - June 18-22, 2007
• Basic principles of optical tweezers• Experimental set-up• Advantages of Raman Tweezer set-up• Test measurements on micro particles
and living cells
Outline
Basic Principles of Optical Tweezers
Light besides energy carries
Lineer momentum Force Classical : EM theory, Radiation pressure
Quantum : Photon momentum,
Angular momentum Torque
dP Fdt
hpc
dLdt
Radiation Presure→ Optical Trapping
1 mW
1μm F ~10 pNm ~pg
F ~ 10 pN
a ~105 g
a b
Fb Fa
F
b a
a b
b a
a b
FFa Fb
f
f
fFa
Fb
F
b
a
La se r Be a m
M ic . O b je c tive
PinP o ut
(A. Ashkin, Biophys. J. (61), 1992)
21
2
21
2
cos(2 2 ) cos 21 cos 2
1 2 cos 2
sin(2 2 ) sin 2sin 2
1 2 cos 2
z scat
y grad
T r Rn PF F Rc R R r
T r Rn PF F Rc R R r
Single Ray SolutionP : PowerMomentum per unit time:
1n Pc
P
r
O
y
zPT2
PTR2
PTR2 2
PRn1
n2
Be a m
f
r
m a x
S
rm a x
x
y
z z
y
w
O
Be a mr rm a x
w
z
f
Be a m a xis
n̂
Fg S
Fs
O
M ic .o b je c tiveb a c k a p e rture
Extended Laser Beam
• Large NA objectives• Overfilling• n2 > n1 • Power ~1mW is enough to trap
Critical Points for Optical Trapping
Experimental setup
1µm trapped polystyrene particle
4.6 µm trapped polystyrene particle
~ 5 µm trapped yeast cell
~ 5 µm trapped yeast cell
• The ability to get Raman Spectrum of a single living object in their natural environment.
• Decreasing of background signals from cover slip.
• No mechanical immobilization of living cells.
Advantages of Raman Tweezer Set-up
Excitation wavelength: 780 nmPower: 6 mW on the sampleAccumulation: 100 s
Raman spectrum of trapped polystyrene particle
Raman spectrum of trapped yeast cell
C. Xie et al. Opt. Exp. 25, 6208-6214 2004
Collaboration
Istanbul University
Physics Department
Prof.Dr. Sevim Akyuz
• Optimizing Laser Tweezer Raman Spectrometer• Investigation of interaction between cell membranes and their environment
Future Work
Support by the Scientific and Technological Research Council of Turkey under the project number 105T482 is gratefully acknowledged.
Our Laser Spectroscopy Groupat Istanbul Technical UniversityPhysics Engineering Department
PhD studentSeda Kin
MsC studentUğur Parlatan
BsC studentsOnur PusulukBerkin Malkoç
Group leaderAssoc.Prof. Dr. Gunay Basar
Thank You!